Experimental Radiation Oncology is a Division of the Department of Radiation Oncology. The goal of the Division is to advance the treatment of cancer by ionizing radiation, alone or in combination with other therapeutic agents, through modern basic and translational research on related topics. Ongoing research in the Division covers the areas of DNA damage response, hyperthermia, interactions between chemotherapeutics and radiation, angiogenesis, and the genetics of human cancer. The Division is also responsible for resident/fellow education in the radiobiology.

Tumor Sensitization to Thermo-radiotherapy by Intracellular Acidification

The importance of future research in hyperthermic oncology is underscored by the positive results of seven prospective, randomized trials that demonstrate a substantial benefit of thermo-radiotherapy versus radiotherapy alone. There was approximately a doubling of complete response and local control in all sites and an improvement in survival after thermo-radiotherapy in some. There was not an increase in complication rates. The sites included head and neck, melanoma, recurrent breast, focal glioblastoma multiforme, esophagus, bladder and cervix cancer. Therefore, efforts to sensitize tumor cells to hyperthermia are justified. While different approaches can be used to sensitize tumor cells to hyperthermia, the program exploits the uniquely acidic environment of the tumor for this purpose.

Most human tumors are acidic relative to normal tissues because of their higher glycolytic metabolic potential leading to an accumulation of lactic acid. However, NMR spectroscopy shows that this acidification mainly reflects the extracellular environment (pHe), as the intracellular pH (pHi) is in the normal range. This observation indicates that human tumor cells adapt to low extracellular pH by regulating the intracellular pHi to normal levels.

While acutely acidified cells are sensitized to hyperthermia, cells adapted to low pH may be more resistant to heat than cells at normal pH. The theme of this program is to reverse the effect of low pH adaptation in tumor cells by exploiting fundamental aspects of tumor physiology, metabolism and signal transduction pathways. The focus of the program is on human melanoma and the long-term goal is to clinically sensitize these tumors to hyperthermia and/or chemotherapy by acute tumor acidification induced by hyperglycemia combined with respiratory inhibitors and/or membrane proton pump inhibitors.

Impressive prelinical results with human melanoma xenografts in immune suppressed mice and rats show that combining the mitochondrial respiratory inhibitor, meta-iodobenzylguanidine (MIBG), with clinically attainable hyperglycemia greatly enhances tumor acidification by as much as a full pH unit. Furthermore, significant tumor oxygenation into the radiosensitizing range occurs during exposure to inhibitors of mitochondrial respiration and inhibition of oxygen consumption. There is only a transient and modest effect on normal tissues. Recent experiments also suggest that inhibition of the membrane H+-linked monocarboxylate acid transporter in melanoma by alpha-cyano-4-hydroxy cinnamic acid or lonidamine combined with hyperglycemia to fuel lactate production lead to tumor acidification and sensitization to hyperthermia and alkylating agent chemotherapy.

A Program Project Grant from the National Cancer Institute supports this research program. It has four components supported by three Cores that address fundamental and translational aspects of acute acidification in hyperthermia and chemotherapy response. The first component of the project, directed by Drs. Dennis Leeper and Randy Burd, investigates the response, in vivo, of early passage human melanoma xenografts and bone marrow in Nude mice to test the hypothesis that hyperglycemia combined with the respiratory inhibitor, MIBG, or with inhibitors of the monocarboxylate pump will lead to acute and selective tumor acidification and oxygenation, which will lead to selective tumor sensitization to thermo-radiotherapy or chemotherapy. NMR techniques are used to non-invasively measure pHi and by-products of glucose metabolism.

This component uses a unique fluorescence system that allows pHi to be monitored during the actual heating of cells in the presence or absence of inhibitors while adherent to a growth substrate. These measurements confirm acidification under various conditions, and are crucial as they provide critical insight into the nature of proton extrusion mechanisms in human melanoma. It is recognized that only by monitoring pHi as a function of time and temperature will it be possible to understand the mechanism(s) by which reduced pHi, associated with acute extracellular acidification, affects cell survival during hyperthermia.

The second component directed by Dr. Jerry Glickson, University of Pennsylvania, uses non-invasive NMR spectroscopy and NIR techniques to understand the mechanisms of tumor acidification and oxygenation and to determine strategies to optimize treatment protocols. The technology will be developed to heat tumors while in the magnet. The second component also uses inhibition of respiration to study tumor oxygenation, which will sensitize tumors to radiation. The assays used will determine pHi and pHe, pO², ²³Na_i, lactate production, blood flow, glucose metabolism, nuclear phosphates and phospholipids, and oxygen consumption (reduction of ¹⁷O₂→H₂¹⁷O). In this way, components one and two test the global hypothesis and provide a strategy for tailoring a protocol for acidification to an individual melanoma’s metabolic properties.

The third component, directed by Dr. Ronald Coss, evaluates the effect of acute acidification on the downregulation of the heat-shock proteins, HSP27, 70 or 90, when acidification occurs before or during hyperthermia in melanoma cells growing at pH 6.7 or 7.3. The heat shock proteins induced during exposure to hyperthermia are chaperones involved not only in heat-resistance but also inhibition of apoptosis proteins that inhibit apoptotic signal transduction pathways. Downregulation of the heat shock proteins triggers the incidence of apoptosis. The effect of pH on heat shock gene activation is determined by antisense oligonucleotide strategies against hsp27 and transfection with an HSP70 promoter-GFP construct. The endpoints are apoptosis and clonal survival as they relate to tumor response in vivo.

The fourth component, directed by Dr. George Iliakis, University of Essen, Germany, elucidates molecular mechanisms underlying checkpoint activation in cells exposed to heat shock, acute acidification as a strategy to abrogate the heat-induced checkpoint response, and the molecular predictors of response. The project is based on discoveries that heat-induced inhibition of DNA replication has a trans-acting component equivalent to checkpoint activation operating through regulation of the activity of replication protein A (RPA) by nucleolin, a key component of the nucleolus. The observation that inhibitors of casein kinase II (CK2) cause a similar intranuclear translocation of nucleolin as heat allows the development of mechanistic models that can be tested. The effects of pH on heat shock protein levels will also be directly incorporated into fourth component since the nucleolar localization of nucleolin depends on HSP90 and perhaps other HSP chaperones (e.g. HSP 110).

The clinical benefit of this line of investigation will be to support a phase I/II clinical trial to demonstrate enhanced acidification of human tumors by combining respiratory inhibitors or proton pump inhibitors with hyperglycemia and to demonstrate enhancement of the response of melanoma to thermoradiotherapy or chemotherapy.

Cancer Research Training in the Science of DNA Damage Response

This postdoctoral training program is in the funding cycle that spans years 22-26 and supports five postdoctoral fellows. Dr. Dennis Leeper directs the training program with a training faculty of 17 funded investigators representing five academic departments. The goal is the training of independent investigators on the molecular basis of DNA damage response and on the ways this knowledge can be translated to new cancer therapies. It emphasizes direct research experience in the laboratory and is supplemented by formal courses, seminars and conferences, as well as by exposure in the clinical environment. The revised program offers training adapted to the emerging requirements of Cancer Research and takes full advantage of the available resources within the Jefferson Campus. It includes training on the essential aspects of DNA damage response such as signal transduction, DNA repair, checkpoint activation, apoptosis and response modifiers. A unique feature of the program is the potential exposure of trainees to the clinical environment and the possibility to assign them to clinician scientists working at the forefront of clinical cancer research. The training program provides research training essential to the academic and research base of DNA damage response. The training emphasizes hypothesis-oriented research, the development of an appropriate experimental design and the use of modern techniques to address pertinent issues of cancer research. Following completion of the program trainees will be prepared to enter independent research careers in modern aspects of cancer research in a university, government laboratory or industrial research setting

Randy Burd:

Manipulation of Tumor Metabolism

Dr. Burd recently joined the faculty as an Assistant Professor. Dr. Burd received his Ph.D. in Molecular and Cellular Biophysics from Roswell Park Cancer Inst. He was trained in the laboratory of Dr. Elizabeth Repasky, who pioneered a technique for growing human breast tumor xenografts derived from patient surgical specimens. He now directs an experimental tumor program at Thomas Jefferson University and maintains several human tumor xenografts in SCID and Nude mice. He and Dr. Dicker co-direct the New Drug Development Program Core (NDDPC) for the Radiation Therapy Oncology Group.

Dr. Burd’s research focuses on manipulating tumor metabolism to improve tumor oxygenation. Oxygen is a potent radiation sensitizer and can increase the effectiveness of radiation up to 3 fold. However, because of the high rate of oxygen consumption by tumor cells and poor tumor blood flow, many tumors are hypoxic. Therefore, decreasing oxygen consumption in tumors or improving tumor blood flow can improve tumor oxygenation and reduce hypoxia. Studies have shown that patients treated with radiation or surgery whose tumors are oxygenated have a better treatment outcome than patients with hypoxic tumors.

In non-malignant tissue the blood supply is organized and efficient. Perfusion and oxygen consumption are balanced so that the tissue is in an oxygenated steady state. In contrast, malignant tissue contains dividing tumor cells that outgrow their blood supply, which limits oxygen availability. Tumor cells located at a distance greater than 70 um from a blood vessel are hypoxic because oxygen delivery is diffusion limited. (Figure A). Additionally, the emergence of tumor hypoxia induces angiogenesis. The newly formed blood vessels are torturous and inefficient, which further comprises perfusion. The hypoxic environment of the tumor is problematic because hypoxic cells are resistant to radiation.

Oxygen consumption can be inhibited in tumor cells by various cellular respiratory inhibitors, including glucose, insulin, guanidine compounds and some cytotoxic drugs. Not all mechanisms of inhibition are the same, but many drugs, such as quanidine compounds and some cytotoxic drugs work by interfering with the respiratory chain of the mitochondria. Blocking electron transport results in decreased oxygen consumption (Figure B) and increased glycolysis to maintain ATP levels. If perfusion is sufficient, the reduced demand for oxygen by inhibited tumor cells should lead to an improved oxygenated state (Figure C). The respiratory inhibitor meta-iodobenzylgauidine for example inhibits respiration at complex I of the electron transport chain. This compound is selectively taken-up by catecholamine receptors which allows it to accumulate in tumors such as neuroblastoma and melanoma.

Adam P. Dicker:

Use of novel drugs in combination with radiation therapy.
Role of extracellular matrix in radiation response.
Clinical drug development with radiation therapy.

Radiation therapy is an effective modality for the treatment of a number of tumors. It is one of the most widely used treatments for cancer, with over half of all cancer patients receiving radiation therapy during their course of treatment for cancer. There remains a need to improve the cure rate by radiation therapy alone. The most common approach is to use a radiosensitizer, a drug that will sensitize tumor cells to radiation. This has traditionally been done through the combined use of chemotherapy and radiation.

The goal of traditional chemotherapy is to destroy tumor cells with a cytotoxic agent. The cytotoxicity of these agents is not limited to tumor cells, and treatment of tumors with chemotherapy can result in normal tissue toxicity. Recently, there has been a rapid development of rational drug therapy targeting specific receptors on tumor cells or tumor associated stromal cells. The foundation for use of these agents is that tumor growth is dependent on specific signaling pathways that can be selectively inhibited. This represents a powerful and novel approach to combined modality treatment with the goal of greater tumor local control and possibly a reduction of total radiation dose, resulting in reduced side effects in surrounding normal tissue. Studies that relate to these goals can be read in more detail in the program that Drs. Burd and Dicker co-direct (New Drug Development Program Core (NDDPC) for the Radiation Therapy Oncology Group).

The work in the laboratory is divided into two aspects. The first is a basic science understanding of how inhibitors of the epidermal growth factor receptor may work with radiation therapy. Forty years ago the study of retroviral transformation revolutionized our understanding of malignant transformation. The discovery of virally transmitted oncogenes was closely followed by the realization that they were homologues of mammalian genes, thus leading to the term proto-oncogenes. The epidermal growth factor receptor (EGFR; HER1; erbB1) is a prominent example for this sequence of events. First cloned in 1984, it was immediately recognized to be the counterpart of a viral oncogene, v-erbB. In keeping with its oncogenic potential, the EGFR is molecularly altered and deregulated in many 'spontaneous' tumors with no apparent viral etiology. The EGFR is one of many receptor tyrosine kinases with transforming potential. Yet, it is believed to contribute to the malignant phenotype of a broad spectrum of neoplasms primarily affecting epithelial tissues. Almost twenty years after its discovery, the EGFR has emerged as a prominent target for therapeutic intervention.

EGFR antagonists have recently been shown to be highly effective as components of adjuvant radio-/chemotherapy regimes in various epithelial malignancies including squamous cell carcinoma (SCC). It is surprising that tumor cells are highly susceptible to radiosensitization through EGFR blockade whereas normal tissues appear to be more resistant.

Our previous work has shown that EGFR blockade enhances apoptosis susceptibility of normal as well as transformed keratinocytes in conditions of cellular stress including ionizing radiation. However, this effect is ‘conditional’, i.e. EGFR activation is critical for cell survival in conditions of suboptimal extracellular matrix (ECM) attachment whereas it is not essential for cells receiving appropriate matrix-derived signals.

Based on these findings we hypothesize that transformed cells are more susceptible to radiosensitization by EGFR blockade because they lack appropriate survival signals derived from ECM. Using specific inhibitors of EGFR allows us to better understand why cells become radiosensitized and may enhance our use of this class of drugs in the clinic. This work is integrated with other projects related to EGFR in the Departmental of Radiation Oncology.

Another example of developing the use of novel drugs is the area that our Study of Platelet-Derived Growth Factor and c-Kit in collaboration with the laboratory of Dr. Uli Rodeck. Platelet-derived growth factor (PDGF) was one of the first polypeptide growth factors identified that signals through a cell surface tyrosine kinase receptor (PDGF-R) to stimulate various cellular functions including growth, proliferation, and differentiation. A family of ligands (primarily PDGF A and B) and their cognate receptors (PDGF-R a and b) have been identified. To date, PDGF expression has been shown in a number of different solid tumors, from glioblastoma to prostate carcinomas. In other tumor types, the biologic role of PDGF signaling can vary from autocrine stimulation of cancer cell growth to more subtle paracrine interactions involving adjacent stroma and even angiogenesis. c-Kit expression has also been identified in some solid tumors.

Work from our laboratory has demonstrated that, c-kit and SCF are coexpressed in colorectal cancer (CRC) cells, raising the question of whether c-kit serves an autocrine role in normal or malignant epithelial tissues. Furthermore, we demonstrated that human colorectal carcinomas, but not normal colorectal mucosa cells, coexpress SCF and c-kit in situ. Expression of c-kit was also observed in mucosa adjacent to colorectal tumor tissue. Consistent with a growth-regulatory role of SCF in CRC cells, exogenous SCF stimulated anchorage-dependent and anchorage-independent growth in four out of five CRC cell lines. In other work we have investigated possible roles of the c-kit/SCF autocrine/paracrine system in survival and invasive capacity of DLD-1 colon carcinoma cells. We reported that SCF was required for migration and invasion of DLD-1 cells through reconstituted basement membranes (Matrigel) and up-regulated gelatinase (matrix metalloproteinase-9) activity in DLD-1 cells. Furthermore, we describe that SCF supported survival of DLD-1 cells in growth factor-deprived conditions. These results suggest multiple roles of c-kit activation in support of the malignant phenotype of DLD-1 cells related to growth, survival, migration, and invasive potential. We are studying both in preclinical models as well as on the molecular level how inhibition of PDGF / cKit Activity affects tumor growth in conjunction with radiation.

Ya Wang:

The Molecular Base of Cell Response to DNA Damage

This program focuses on the elucidation of the mechanism of DNA double strand break repair, as well as on mechanisms of activation and regulation of the S- and G2-checkpoints in response to DNA damage.

Double strand breaks (DSB) are induced in the DNA of human cells as a result of intrinsic metabolic processes and exposure to DNA damaging agents such as ionizing radiation (IR). If left unrepaired, or if misrepaired, DSB will lead to reproductive cell death, and to transformation or mutation events. It is now widely recognized that homologous recombination (HR) and non-homologous endjoining (NHEJ) contribute to repair DSB and thus to the restoration of genomic integrity in various organisms from bacteria to man, but the relative importance of each process varies among different organisms. HRR is the main DSB repair pathway in yeast but both HRR and NHEJ are the main DSB repair pathways in mammalian cells. Studies from yeast revealed that DNA damage-induced cell cycle checkpoints (especially S and G2 checkpoints) provide time for DNA repair. However, the results from mammalian cells were not in line with that from yeast. It was not clear whether DNA damage-induced checkpoints facilitate DNA repair in mammalian cells. The long-term objective of our program is to contribute to the elucidation of the mechanism(s) by which checkpoints affect DNA DSB repair in mammalian cells. We have published data to address this question and have hypothesized that IR-induced checkpoint activation regulated mainly by ATM and ATR pathways only facilitates HRR but not NHEJ (Fig. 1). It is anticipated that information on clarifying the relationships among the processes involved in checkpoints, HRR and NHEJ as well as on elucidating the pathways of checkpoints, HRR and NHEJ enzymatic processes will be helpful in the development of new drugs for the treatment of human tumors, alone or in combination with IR.

Fig. 1. The central hypothesis. IR-induced DNA DSBs activate checkpoint response via the ATM-dependent and the ATR/CHK1 dependent pathways, which facilitate only HRR and have no direct relationship with NHEJ, therefore affect radiosensitivity of mammalian cells.

Camptothecin (CPT), an inhibitor of DNA topoisomerase I (Topo I), is one of the most promising broad-spectrum anticancer drugs in development today. However, the mechanism by which cells respond to CPT-treatment remains unclear. The cytotoxicity of CPT is S phase specific because the collision between advancing replication forks and CPT-Topo I-DNA complexes results in DNA DSB. One apparent phenotype of CPT-treated mammalian cells is the strong inhibition of DNA replication. After DNA damage, proliferating cells slow down cell cycle progression by activating checkpoints that provide time for repair and therefore reduce the cytotoxicity. Now we know that the strong inhibition of DNA replication in CPT-treated cells reflects the S phase (S) checkpoint response. We have demonstrated that the S checkpoint in CPT-treated cells is mainly regulated by the ATR/CHK1 pathway, which is different from the S checkpoint in IR-irradiated cells that is regulated by both ATM and ATR pathways. We have also demonstrated that the S checkpoint protects cells from CPT-induced killing. Therefore to elucidate the mechanism by which CPT-induced checkpoint promote DNA repair will provide new ways to modify the cytotoxicity of CPT, which will potentially benefit for chemotherapy in the near future.

Phyllis R. Wachsberger:

Tumor Sensitization to Radiation by Anti-angiogenic Mechanisms.

This research focuses on understanding mechanisms of interaction between tumor response to ionizing radiation and antiangiogenic/vascular targeting agents with the goal of improving radiotherapy.

Recent preclinical studies have suggested that radiotherapy in combination with antiangiogenic/vasculature targeting agents enhances the therapeutic ratio of  ionizing radiation alone. Since radiotherapy is one of the most widely used treatments for cancer, it is important to understand how best to use these two modalities in order to aid in the design of rational patient protocols.

The mechanisms of interaction between antiangiogenic/vasculature targeting agents and ionizing radiation are complex and involve interactions between the tumor stroma and vasculature and the tumor cells themselves. Vascular targeting agents are aimed specifically at the existing tumor vasculature. Antiangiogenic agents target angiogenesis or the new growth of tumor vessels. These agents can decrease overall tumor resistance to radiation by affecting both tumor cells and tumor vasculature, thereby breaking the co-dependent cycle of tumor growth and angiogenesis. The hypoxic microenvironment of the tumor also contributes to the mechanisms of interactions between antiangiogenic/vasculature targeting agents and ionizing radiation. Hypoxia stimulates upregulation of angiogenic and tumor cell survival factors giving rise to tumor proliferation, apoptosis resistance, radioresistance and angiogenesis. Preclinical evidence suggests that antiangiogenic agents reduce tumor hypoxia and provides a rationale for combining these agents with ionizing radiation. Optimal scheduling of combined treatment with these agents and ionizing radiation will ultimately depend on understanding how tumor oxygenation changes as tumors regress and regrow during exposure to these agents.

Signaling mechanisms involved in VEGF-induced tumor angiogenesis.

Endothelial cell survival and neovascular processes are induced by VEGF/VEGFReceptor –2 signaling via the PI3K/Akt signaling axis. VEGF is upregulated by external environmental stress (i.e., ionizing radiation) and internal tumor microenvironmental stress (i.e., hypoxia).

Model of tumor oxygen tension, pH, and radioresistance as a function of size.

As a tumor grows larger the demand for oxygen increases. However, the vascular network is unable to supply the tumor with enough oxygen to maintain an oxygenated state and the tumor becomes hypoxic. To produce sufficient energy for cell survival, the rate of glycolysis and nutrient consumption is increased and the pH becomes acidic through lactic acidosis. The lack of oxygen and nutrients and state of chronic low pH eventually leads to necrosis and pH may increase. The increase in tumor burden and hypoxic low pH environment results in tumor radioresistance. The theoretical curves are based on pO2 and pH data obtained in our laboratory using U87 glioma and DB-1 melanoma xenografts.

Kulbir (Kolby) Sidhu:

Dr. Sidhu received her BSc in the physical sciences in 1991 from the University of Western Ontario in London, Ontario. She graduated in 1995 from McMaster University Medical School in Hamilton, Ontario. In June 2000, Dr. Sidhu completed her radiation oncology residency at Princess Margaret Hospital/University of Toronto in Toronto, Ontario. She then spent a fellowship year conducting research at Memorial Sloan-Kettering Cancer Center in New York City. She is currently an attending physician at the Bodine Cancer Center - Thomas Jefferson University Hospital. She has an interest in the treatment of head & neck and breast cancers. In addition to an active clinical research program, Dr. Sidhu has recently started her laboratory science program. She has identified a unique nontoxic agent that has intrinsic anticancer properties and may enhance conventional cytotoxic therapy. She is working with Drs. Dicker and Burd to further this work to the point of starting a clinical trial.

Division of Experimental Radiation Oncology Publications 2001-2003

Adam Dicker, MD, PhD

Manuscripts

1. Cvetkovic D, Movsas B, Dicker AP, Hanlon AL, Greenberg RE, Chapman JD, Hanks GE, Tricoli JV. Increasing hypoxia correlates with increased expression of the angiogenesis markervascular endothelial growth factor in human prostate cancer. Urology 2001;57:821-825.

2. Gaffney DK, Holden J, Zempolich K, Murphy KJ, Dicker AP, Dodson M. Elevated COX-2 expression in cervical carcinoma: reduced cause-specific survival and pelvic control. Am J Clin Oncol 2001;24:443-446.

3. Dicker AP, Williams TL, Grant DS. Targeting angiogenic processes by combination rofecoxib and ionizing radiation. Am J Clin Oncol 2001;24:438-442.

4. Butzbach D, Waterman FM, Dicker AP. Can extraprostatic extension be treated by prostate brachytherapy? An analysis based on postimplant dosimetry. Int J Radiat Oncol Biol Phys 2001;51:1196-1199.

5. Chen CT, Waterman FM, Valicenti RK, Gomella LG, Strup SE, Dicker AP. Dosimetric analysis of urinary morbidity following prostate brachytherapy (125I vs. 103Pd) combined with external beam radiation therapy. Int J Cancer 2001;96:83-88.

6. Kaminski JM, Kaminski RJ, Dicker AP, Urbain JL. Defining a future role for radiogenic therapy. Cancer Treat Rev 2002;27:289-294.

7. Forsberg F, Dicker AP, Thakur ML, Rawool NM, Liu JB, Shi WT, Nazarian LN. Comparing contrast enhanced ultrasound to immunohistochemical markers of angiogenesis in a human melanoma xenograft model; preliminary results. Ultrasound Med Biol 2002;28:445-451.

8. Waterman FM, Dicker AP. Impact of postimplant edema on V100 and D90 in prostate brachytherapy: can implant quality be predicted on day 0?, Int J Radiat Oncol Biol Phys 2002;610-621.

9. Waterman FM, Dicker AP. The probability of late rectal morbidity in 125I prostate brachytherapy. Int J Radiat Oncol Biol Phys, 2003;55:342-353.

10. Grant DS, Williams, TL, Michael Zahaczewsky, M and Dicker AP. Comparison of Antiangiogenic Activities using two Taxanes; Paclitaxel (Taxol) and Docetaxel (Taxotere). Int J Cancer 2003;104:121-129.

11. Gaffney DK, Haslam D, Tsodikov A, Hammond E, Seaman J, Holden J, Lee J, Dicker AP. Epidermal growth factor receptor (EGFR) expression as a prognostic factor in carcinoma of the cervix treated with radiotherapy. Accepted, Int J Radiat Oncol Biol Phys, 2003.

12. Chakravarti, A, Dicker, A, Mehta M. The Contribution of Epidermal Growth Factor Receptor (EGFR) Signaling Pathway to Radioresistance in Human Gliomas: A Review of Preclinical and Correlative Clinical Data. Accepted, Int J Radiat Oncol Biol Phys, 2003

13. Waterman FM, and Dicker AP. Is it necessary to eliminate the posterior dose margin in prostate brachytherapy to achieve an acceptably low risk of late rectal morbidity? Submitted, Int J Radiat Oncol Biol Phys, 2003.

14. Wachsberger, P. Burd, R, Dicker AP. Ionizing Radiation and Anti-Vascular Therapy: Exploring Mechanisms of Tumor Response. Accepted, Clinical Cancer Research.

15. Patel AB, Waterman FM, Dicker AP. Can a 5 mm planning margin provide adequate treatment of extraprostatic extension of prostate adenocarcinoma in prostate brachytherapy? An Analysis of I-125 Prostate Post-Implant Dosimetry. Accepted for publication, Int J Radiat Oncol Biol Phys,2003

16. Bloomer CW, Kenyon L, Hammond E, Hyslop T, Andrews DW, Curran WJ, Dicker AP. Cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) expression in human Pituitary Macroadenomas. In press, American Journal of Clinical Oncology.

17. Debbie Lin C-CD, Kenyon L, Hyslop, T, Hammond E, Andrews DW, Curran WJ Jr., Dicker AP. Ph.D. Cyclooxygenase-2 (COX-2) expression in human meningioma as a function of malignant progression. Accepted, American Journal of Clinical Oncology.

18. Dicker AP, Rodeck U. Targeting the epidermal growth factor receptor in cancer-rationale for therapeutic ratio. Accepted, Int J Radiat Oncol Biol Phys, 2003

Randy Burd, PhD

Manuscripts

1. Evans, S.S., Wang, W.C., Burd, R., Bain, M.D., Schleider, D.M., Ostberg, J.R. and Repasky, E.A. Fever-range hyperthermia dynamically regulates lymphocyte delivery to high endothelial venules. Blood. 97: 2727-2733, 2001

2. Lee, I., Glickson, G., Dewhirst, M.W., Leeper, D.B., Burd, R., Poptani, H., Nadal, L., Mc Kenna, W.G. and Biaglow, J. E. Effect of glucose ± MIBG on the radiation response of R3230 AC tumors. “Oxygen to tissue XXII”. Edited by Dunn, J.F. and Swartz, H.M. Pabst Science Publishers, Germany, 2001

 3. Burd, R., Wachsberger, P.R., Biaglow, J.E., Wahl, M., Lee, I. and Leeper, D.B. Absence of crabtree effect in human melanoma cells adapted to low pH: reversal by respiratory inhibitors. Cancer Res., 61: 5630-5635, 2001.

4. Wachsberger, P.R., Burd, R., Wahl, M. and Leeper, D.B. Effect of betulinic acid on hyperthermia-induced cell killing in low pH adapted cells. Int. J. Hyperthermia. 18:153-64, 2002.

5. Wahl, M.L., Owen, J. A., Burd, R., Herlands, R.A., Nogami, S.S., Rodeck, U., Berd, D., Leeper, D.B. and Owen, C. S. Regulation of intracellular pH in human melanoma: Potential therapeutic implications. Mol. Cancer Ther., 1:617-628, 2002.

6. Burd, R., Lavorgna, S. N. Wachsberger, P.R., Biaglow, J.E., Stephens, C., Wahl, M. and Leeper, D.B. Tumor oxygenation and acidification are increased in melanoma after exposure to meta-iodo-benzylguanidine. Rad. Res., 159:328-335, 2003.

7. Wachsberger, P.R., Burd, R., Bhala, A., Bobyock, S.B., Wahl, M.L., Owen, C.S., Rifat, S.B. and Leeper, D.B. Quercetin Sensitizes Cells in a Tumor-Like Low pH Environment to Hyperthermia (Int., J. Hyperthermia, In Press 2002).

8. Pritchard, M.T., Ostberg, J.R., Evans, S.S., Burd, R., Kraybill, W., Bull, J.M., Repasky, E.A. Protocols for simulating the thermal component of fever: Preclinical and clinical experience. (Submitted to Methods, July 2002).

9. Wachsberger, P.R., Burd R. and Dicker, A.P. Ionizing radiation and anti-vascular therapy: Exploring mechanisms of tumor response. (In Press, Cancer Res., Dec. 2002).

Invited Book Chapter

1. Burd R., Choy H. and Dicker A. Targeting Angiogenic Processes by Combination COX-2 inhibition and Ionizing Radiation. “Cyclooxygenase 2 (COX-2) Blockade in Cancer Prevention and Therapy. Series in Cancer Drug Discovery and Development.” Edited by Randall E. Harris. Humana Press, Totowa NJ, 2002

Ronald Coss, PhD

1. Rambhatla L., Bohn SA., Stadler PB., Boyd JT., Coss RA. and Sherley L. Cellular Senescence: ex vivo p53-Dependent Asymmetric Cell Kinetics. J. of Biomed. and Biotech. 1:28-37, 2001.

2. Wachsberger PR., Gressen EL., Bhala A., Bobyock SB., Storck C., Coss RA., Berd D. and Leeper DB. Variability in glucose transporter-1 levels and hexokinase activity in human melanoma. Melanoma Res. 12:35-43, 2002.

3. Coss RA., Sedar AW., Sistrun SS., Storck CW., Wang PH., and Wachsberger PR. Hsp27 protects the cytoskeleton and nucleus from the effects of 42°C at pH 6.7 in CHO cells adapted to growth at pH 6.7. Intl. J. of Hyperthermia 18:216-232, 2002.

4. Han J.-S., Storck CW., Wachsberger PR., Leeper DB., Berd D., Wahl M.L. and Coss, R.A. Acute extracellular acidification increases nuclear associated protein levels in human melanoma cells during 42°C hyperthermia and enhances cell killing. Intl. J. of Hyperthermia 18: 404-415, 2002.

5. Coss RA., Storck CW., Daskalakis C., Berd D., and Wahl ML. Intracellular acidification abrogates the heat shock response and compromises survival of human melanoma cells. Mol. Cancer Therapeutics ( In Press).

6. Thakur ML., Coss R., Howell R., Vassileva-Belnikolovska D., Liu J., Rao P.S., Spana G., Wachsberger P., and Leeper DL. Role of lipid soluble complexes in targeted tumor therapy. The J. of Nuclear Med. (In Press).

7. Coss RA., Storck CW., Reilly J., Wachsberger PW., Leeper DB., Berd D., and Wahl ML. Acute extracellular acidification reduces intracellular pH, 42°C-induction of heat shock proteins and clonal survival of human melanoma cells grown at low pH. Intl. J. of Hyperthermia. (Accepted with revisions yet to be submitted).

8. Hargis MT., Wickstrom E., Yakubov LA., Leeper DB., and Coss R.A. Hsp27 antisense oligonucleotides sensitize Chinese hamster ovary cells grown at low pH to 42°C-induced cytoskeletal reorganization. Intl. J. of Hyperthermia (Submitted, resubmission in preparation).

Phyllis Wachsberger, PhD

1. Wachsberger, P.R. Variability in glucose transporter 1 levels and hexokinase activity in human melanoma. Melanoma Res. 12:35-43, 2002.

2. Coss, R.A, Sedar, A.W., Sistrum, S.S., Storck, C.W., Wang, P.H., and Wachsberger, P.R. Hsp27 protects the cytoskeleton and nucleus from the effects of 42oC at pH 6.7 in CHO cells adapted to growth at pH 6.7. Int. J Hyperthermia, 18:216-232, 2002.

3. Wachsberger, P.R, Burd, R., Wahl, M.L. and Leeper, D.B. Betulinic acid sensitization of low pH adapted human melanoma cells to hyperthermia. Int. J Hyperthermia,18:153-164, 2002.

4. Han, J.S., Storck, C.W., Wachsberger, P.R., Leeper, D.B., Berd, D., Wahl, M.L. and Coss, R.A. Acute extracellular acidification increases nuclear associated protein levels in human melanoma cells during 42 degrees C hyperthermia and enhances cell killing. Int. J Hyperthermia, 18:404-415, 2002.

5. Burd, R, Lavorgna, S.N., Daskalakis, C., Wachsberger, P.R. Wahl, M., Biaglow, J., Stevens, C., and Leeper, D.B. Tumor oxygenation and acidification are increased in melanoma after exposure to hyperglycemia and meta-iodo-benzylguanidine. Radiat. Res. In Press, 2002.

6. Wachsberger, P., Bhala, A., Bobyock, S., Wahl, M., Owen, C. Rifat, S. and Leeper, D. Hyperthermia sensitization by quercetin of cells in a tumor-like low pH environment. In Press, Int. J. Hypert., 2002.

7. Wachsberger, P., Burd, R., and Dicker, A.P. Tumor response to ionizing radiation and anti-angiogenesis/anti-vasculartherapy: exploring mechanisms of interaction. Clinical Cancer Research, June, 2002 In press.

8. Wachsberger P. Burd R, Dicker AP. Improving tumor response to radiotherapy by targeting angiogenesis signaling pathways. Hematol Onc Clin North Am, 18:1039-1057, 2004.

9. Wachsberger PR, Burd R, Marero N, Daskalakis C, Ryan A, McCue P, Dicker AP. Effect of the tumor vascular damaging agent, ZD6126 on the radioresponse of U87 glioblastoma. Clin.Cancer Res. 11:835-42, 2005.

10. Woodward WA, Wachsberger P, Burd R, Dicker AP. Effects of androgen suppression and radiation on prostate cancer suggest a role for angiogenesis blockade. Prostate Cancer and Prostatic Disease, 8:127-32, 2005.

11. Wachsberger PR, Burd R, Cardi C Thakur M, Daskalakis C, Holash J, Yancopoulos GD, Dicker AP. VEGF trap in combination with radiotherapy improves tumor control in U87 Glioblastoma. Int.J.Radiat Oncol Biol Phys 67:1526-37, 2007.

12. Cantor JP, Iliopoulos D, Rao AS, Druck T, Semba S, Han SY, McCorkell KA, Lakshman TV, Collins JE, Wachsberger P, Friedberg JS, Huebner K. Epigenetic modulation of endogenous tumor suppressor expression in lung cancer xenografts suppresses tumorigenicity. Int J Cancer, 120:24-31, 2007.

Ya Wang, Ph.D.

1. Hu B., Zhou XY., Wang X., Zeng ZC., Iliakis G. and Wang Y. The radioresistance to killing of A1-5 cells derives from activation of the Chk1 Pathway. J Biol. Chem. 276:17693-17698, 2001.

2. Cheong N., Zeng Z.-C., Wang Y., and Iliakis G. Evidence for factors modulating radiation-induced G2-delay: potential application as radioprotectors. Physica Medica 17, Suppl. 1: 205-209, 2001.

3. Wang YZ., Guan J., Wang H., Wang Y., Leeper D., and Iliakis G. Regulation of DNA replication after heat shock by RPA-nucleolin interactions. J Biol. Chem., 276: 20579-20588, 2001.

4. Wang H., Guan J., Wang HC., Perrault A., Wang Y., and Iliakis G. RPA2 phosphorylation after DNA damage by the coordinated action of ATM and DNA-PK. Cancer Res. 61: 8554-8563, 2001.

5. Zhou X-Y., Wang X., Hu B., Guan J., Iliakis G., and Wang Y. An ATM-independent S phase checkpoint response involves CHK1 pathway. Cancer Res. 62: 1598-1603, 2002.

6. Wang H., Wang X., Zhou X-Y., Chen DJ., Li GC., Iliakis G., and Wang Y. Ku affects the ataxia and Rad 3-related/CHK1-dependent S phase checkpoint response after camptothecin treatment. Cancer Res. 62: 2483-2487, 2002.

7. Zhou X-Y., Wang X., Wang H., Chen DJ., Li GC., Iliakis G., and Wang Y. Ku affects the ATM-dependent S-phase checkpoint following ionizing radiation. Oncogene, 21: 6377-6381, 2002.

8. Wang J-L, Wang X., Wang H., Iliakis G. and Wang Y. CHK1-regulated S-phase checkpoint response reduces camptothecin cytotoxity. Cell Cycle, 1: 267-272, 2002.

9. Wang X., Li GC., Iliakis G. and Wang Y. Ku affects the CHK1-dependent G2 checkpoint following ionizing radiation. Cancer Res. 62: 6031-6034, 2002.

10. Wang H., Wang X., Iliakis G., and Wang Y. Caffeine could not efficiently sensitize homologous recombination repair deficient cells to ionizing radiation-induced killing. Radiat. Res. 159: 420-425, 2003.

11. Wang X., Wang H., Iliakis G., and Wang Y. Caffeine-induced radiosensitization is independent of non-homologous end joining of DNA double strand breaks. Radiat. Res. 159: 426-432, 2003.

12. Iliakis G., Wang Y., Guan J. and Wang H. DNA damage checkpoint control in cells exposed to ionizing radiation. (Review) Oncogene (In Press), 2003.

Invited Book Chapter:

1. Wang Y. and Wang,H., “CHK1 kinase activity assay” in the Book (Checkpoint Controls and Cancer: Methods and Protocols) 2003.

Dennis B. Leeper, PhD

1. Burd R, Wachsberger PR, Biaglow JE, Wahl ML, Lee I & Leeper DB (2001) Absence of Crabtree effect in human melanoma cells adapted to growth at low pH: reversal by respiratory inhibitors. Cancer Res. 61:5630-5635.

2. Wang YS, Guan J, Wang HY, Wang Y, Leeper, DB & Iliakis G. (2001) Regulation of DNA replication after heat shock by replication protein A-nucleolin interactions. J. Biol. Chem. 276: 20579-88.

3. Zhou R, Bansal N, Leeper DB, Pickup S & Glickson JD (2001) Enhancement of hyperglycemia-induced acidification of human melanoma xenografts with inhibitors of respiration and ion transport. Acad. Radiol. 8:571-82.

4. Wachsberger PR, Gressen EL, Bhala A, Bobyock SB, Storck C, Coss RA, Berd D & Leeper DB (2001) Variability in glucose transporter-1 levels and hexokinase activity in human melanoma. Melanoma Res., 11:1-9.

5. Wahl ML, Owen JA, Burd R, Heralds RA, Nogami SS, Rodeck U, Berd D, Leeper DB & Owen CS (2002) Regulation of intracellular pH in human melanoma: Potential therapeutic implications. Molec. Cancer Therap. 1:617-28.

6. Lee I, Glickson, JD, Dewhirst MW, Leeper DB, Burd R, Poptani H, Nadal L, McKenna WG, and Biaglow JE (2002) Effect of glucose ± meta-iodobenzylguanidine (MIBG) on the radiation response of R3230 AC tumors. Ed. J.E. Dunn and A.M. Swartz, Oxygen Transport to Tissues XXII, Pabst Scientific Publishers, Germany, in press.

7. Wachsberger PR, Burd R, Wahl ML & Leeper DB (2002) Effect of betulinic acid on hyperthermia-induced cell killing in low pH adapted melanoma cells. Int. J. Hyperthermia, 18:153-164.

8. Guan J, Stavridi E, Leeper DB & Iliakis G (2002) Effects of hyperthermia on p53 protein expression and activity. J. Cell. Physiol. 190:365-374.

9. Hekmatyar SK, Poptani H, Babsky A, Leeper DB & Bansal N (2002) Noninvasive magnetic resonance thermometry using thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA-) complex. Int. J. Hypertherm. 18:165-179.

10. Han J-S, Storck CW, Wachsberger PR, Leeper DB, Berd D, Wahl ML & Coss RA (2002) Acute extracellular acidification increases nuclear associated protein levels in human melanoma cells during 42°C hyperthermia and enhances cell killing. Int. J. Hypertherm. 18:404-415.

11. Wahl ML, Owen JA, Burd R, Herlands RA, Nogami SS, Rodeck U, Berd D, Leeper DB & Owen CS (2002) Regulation of intracellular pH in human melanoma: Potential therapeutic implications. Molec. Cancer Therap. 1:617-628.

12. Burd R, Zalipsky U, Pollard MD, Wachsberger PR, O'Hara MD, Berd D & Leeper DB (2003) Acidification and oxygenation of human melanoma xenografts during exposure to MIBG and hyperglycemia. Radiat. Res. 159:328-335.

13. Coss RA, Owen CS, Wahl ML, Storck CS, Bobyock SB, Wachsberger PR & Leeper DB (2003) Acute acidification differentially inhibits 42°C-induction of Hsp27 and Hsp70 in human melanoma cells adapted to growth at low pH. Int. J. Hypertherm. (in press).

14. Wachsberger, PR, Bhala A, Bobyock SB, Wahl ML, Owen CS, Rifat SB & Leeper DB (2003) Quercetin inhibits thermotolerance development in Chinese hamster ovarian carcinoma cells adapted to growth at low pH. Int. J. Hypertherm. (in press).

15. Hargis M, Wickstrom E, Yakubov L, Leeper DB & Coss RA (2003) Antisense hsp27 oligonucleotides sensitize low pH adapted CHO cells to hyperthermia. Int. J. Hypertherm. (in press).

16. Coss RA, Storck CW, Reilly J, Wachsberger PW, Leeper DB, Berd D & Wahl ML (2003) Acute extracellular acidification reduces intracellular pH, 42°C-induction of heat shock proteins and clonal survival of human melanoma cells grown at low pH. Int. J. Hypertherm. (in press).

17. Leeper DB, Engin K, Dover JD, Wang J & Li DJ (2003) Effect of insulin on human tumor extracellular pH during hyperglycemia. Int. J. Hyperthermia (accepted).

18. Leeper DB, Engin K, Dover JD, Wang J & Li DJ (2002) Effect of 200 gm oral glucose on extracellular pH in human tumors. Int. J. Radiat. Oncol. Biol. Phys. (accepted).

Kulbir Sidhu, M.D.

1. Sidhu K, Ford EC, Spirou S, Yorke E, Chang J, Mueller K, Todor D, Rosenzweig K, Mageras G, Chui C, Ling CC, Amols H. Optimization of conformal thoracic radiotherapy using cone-beam CT imaging for treatment verification. Int J Radiat Oncol Biol Phys 2003 Mar 1;55(3):757-67

2. Ford EC, Chang J, Mueller K, Sidhu K, Todor D, Mageras G, Yorke E, Ling CC, Amols H. Cone-beam CT with megavoltage beams and an amorphous silicon electronic portal imaging device: potential for verification of radiotherapy of lung cancer. Med Phys 2002 Dec;29(12):2913-24.