|
|
|
|
Studies in Tumor Angiogenesis Antiogenesis, Antiangiogenic Therapy, and Drug Resistance Professor Robert S. Kerbel, Ph.D., Queen's University, Kingston. Key Words: anti-angiogenic therapy; metronomic chemotherapy; acquired drug resistance; vascular endothelial cell growth factor; apoptosis; oncogenes; EGF receptor; cell adhesion and multicellular resistance; clinical trials The overall goal of Dr. Kerbel’s research program is to devise innovative treatment strategies for the treatment of metastatic cancer which can be moved rapidly into the clinic. The innovation stems from the potential of the therapies to circumvent two of the most difficult problems faced by oncologists and cancer patients: the tendency of cancers to develop drug resistance and the harsh side effects caused by anti-cancer drugs. Dr. Kerbel’s laboratory is at the forefront of tumor angiogenesis research. His current major interests in this area include the following: i) investigating the contribution of various oncogenes and tumor suppressor genes to tumor angiogenesis: for example, previous studies in his lab, and now others, have shown that activation of certain common oncogenes, e.g. ras, erbB2/neu/Her-2, BCR-ABL, and the EGF receptor can induce the expression of molecular stimulators of angiogenesis such as vascular endothelial cell growth factor (VEGF). How this happens and the relative importance of such functional changes to tumor growth by oncogenes are subjects of major interest in the lab ii) the anti-angiogenic effects of anti-oncogene signal transduction inhibitors: the work described above has implicated the idea that signal transduction inhibitory drugs designed to block oncogenic proteins may function in vivo, in part, by suppression of tumor angiogenesis. Dr. Kerbel’s group is studying the impact of drugs which block the epidermal growth factor (EGF) receptor (e.g. Cetuximab/C225), the erbB2 receptor tyrosine kinase (e.g. Herceptin), and Bcr-Abl (e.g. Gleevec/STI571) on tumor angiogenesis. These studies have revealed evidence of anti-angiogenic activity and, for the first time, of acquired resistance to such drugs. At least one of the mechanisms involves altered angiogenesis, which may define a new form of microenvironment-mediated drug resistance. iii) the low-dose metronomic/anti-angiogenic chemotherapy concept: similar to the signal transduction inhibitors, Dr. Kerbel’s group has been studying the potential of conventional anti-cancer cytotoxic drugs such as taxol, vinblastine and cyclophosphamide as “accidental?anti-angiogenic agents. The rationale for these studies stems from the possibility that dividing endothelial cells - which are present in newly forming tumor blood vessels - should be sensitive to such drugs as they target any rapidly dividing cells. This could lead to very durable anti-tumor effects, i.e., no, or delayed, drug resistance since, unlike tumor cells which are genetically unstable and therefore highly mutable, normal host cells are not. By giving chemotherapy drugs at low doses in a continuous or very frequent manner (“metronomic?dosing) the anti-angiogenic effects of such drugs can be heightened without inflicting severe toxic side effects. This anti-angiogenic/anti-tumor treatment strategy can be made significantly more potent by combination with a new investigational molecular targeted anti-angiogenic drug such as monoclonal anti-VEGF receptor antibodies. The rationale for this type of combination “one-two punch?treatment approach is based on the property of VEGF to function as a potent, and highly specific, pro-survival/anti-apoptotic for activated endothelial cells. The specificity derives from the highly restricted expression of several VEGF receptor tyrosine kinases (called flk-1/KDR and flt-1) to activated endothelial cells. How low-dose chemotherapy works as an anti-angiogenic targeting strategy, and the signalling mechanisms by which VEGF functions as an endothelial cell survival factor, are areas of ongoing investigation in Dr. Kerbel’s laboratory. These preclinical concepts have resulted in the initiation of several phase II clinical trials recently, which are designed to evaluate the treatment concepts coming out of Dr. Kerbel’s laboratory utilizing combination continuous low-dose chemotherapy and commercially available drugs which have anti-angiogenic activity. Dr. Kerbel is collaborating in some of these clinical trials which represent an example of “translational?(i.e., from the lab to the clinic) research underway in his laboratory. iv) studies on resistance mechanisms to anti-angiogenic drugs/therapies: Dr. Kerbel’s drug resistance studies began with chemotherapeutic agents (see below) and then moved to signal transduction inhibitors, as described above. More recently, he has begun to study whether, and how, resistance may develop to certain anti-angiogenic drugs, either by epigenetic or genetic mechanisms. The former may occur by such processes as VEGF-mediated transient induction of pro-survival/anti-apoptotic genes, such as bcl-2 or “survivin?in activated endothelial cells, whereas the latter may result from genetic mutations such as p53 inactivation which make tumor cells more adept at surviving in hypoxic microenvironments created by anti-angiogenic therapies. This could result in the selection of mutant tumor cells which are less vascular dependent. Heterogeneous tumor cell vascular dependence is being actively studied in Dr. Kerbel’s laboratory at the present time. v) cell adhesion and multicellular drug resistance: Dr. Kerbel’s laboratory is also involved in a major program to investigate an unusual concept by which solid tumors may clinically acquire resistance to chemotherapeutic drugs, designated "multicellular drug resistance." It is generally believed that many cancers develop resistance to drugs as a result of the selection of rare mutant cells which, one for one reason or another, are resistant to the toxic action of certain drugs. These are known as "(uni)cellular resistance" mechanisms. They are based almost entirely on the isolation and study of drug resistant mutant tumor cells in monolayer tissue culture systems. However Dr. Kerbel has obtained evidence which suggests that tumor cells may respond as an organized (multicellular) mass in order to express resistance. This would appear to be a form of "group protection" or "safety in numbers". It was discovered on the basis of isolating certain drug resistant sublines in vivo (not in vitro), which do not express their resistance in vitro unless grown as three-dimensional multicellular aggregates or "spheroids." The expression of this type of drug resistance is also accompanied by striking changes in tumor spheroid morphology, something which is not seen in conventional two-dimensional monolayer cell cultures. As such, the results could implicate the involvement of molecules such as integrins, extracellular matrix components or cell adhesion molecules as indirect mediators of acquired drug resistance in cancer. This is also implied by the fact that the ability of various anti-cancer agents to spontaneously kill tumor cells in tissue culture is significantly suppressed when the cells are grown three-dimensionally as multicellular spheroids, i.e., "intrinsic" drug resistance may also be regulated by cell adhesion. Many questions raised by this new paradigm are being explored in Dr. Kerbel's laboratory, including its relevance to human cancer drug resistance in the clinical setting, and whether so-called "anti-adhesive" agents can be used as chemosensitizers to reverse the expression of intrinsic or acquired multicellular drug resistance. For example, Dr. Kerbel's laboratory is studying the impact of monoclonal neutralizing antibodies to an adhesion molecule called E-cadherin ("E" stands for epithelial) on reversing forms of intrinsic or acquired drug resistance. In addition, gene profiling techniques are being used to investigate the contribution of various known, or new, genes to multicellular drug resistance. * * * * * Dr. Kerbel’s laboratory utilizes both cellular and molecular techniques, as well as in vitro cell culture and various mouse tumor model in vivo systems. The approach encompasses both basic and applied research. The research is supported by large, long standing (17 - 25 years) grants from the National Cancer Institute of Canada, the Canadian Institutes of Health Research and the National Institutes of Health, USA awarded to Dr. Kerbel, as well as some contracts with industry. Selected References: Okada, F., Rak, J., St. Croix, B., Lieubeau, B., Kaya, M., Roncari, L., Sasazuki, S. and Kerbel, R.S. (1998) Impact of oncogenes on tumor angiogenesis: mutant K-ras upregulation of VEGF/VPF is necessary but not sufficient for tumorigenicity of human colorectal carcinoma cells. Proc. Natl. Acad. Sci. (USA), 95: 3609-3614. Kerbel, R.S., Viloria-Petit, A., Okada, F., and Rak, J. (1998) Establishing a link between oncogenes and tumor angiogenesis. Molecular Medicine 4:286-295. St. Croix, B., Sheehan, C., Rak, J., Florenes, V.A., Slingerland, J.M. and Kerbel, R.S. (1998) E-cadherin-dependent growth suppression is mediated by the cyclin-dependent kinase inhibitor p27KIP1. J. Cell. Biol., 142: 557-571.
Lieubeau-Teillet,
B., Rak, J., Jothy, S., Iliopoulos, O., Kaelin, W. and Kerbel, R.S. (1998) von
Hippel-Lindau gene-mediated growth suppression and induction of differentiation
in renal cell carcinoma cells grown as multicellular tumor spheroids. Cancer
Res., 58: 4957-4962. Kerbel, R.S. (1999) What is the optimal rodent model for anti-tumor drug testing? Cancer & Metastasis Rev., 17: 301-304. Krestow J.K., Rak, J., Filmus, J. and Kerbel, R.S. (1999) Functional dissociation of anoikis-like cell death and activity of stress activated protein kinase. Biochemical and Biophysical Research Communications, 260: 48-53. Green, S.K., Frankel, A. and Kerbel, R.S. (1999) Adhesion-Dependent Multicellular Drug Resistance. Anti-Cancer Drug Design, 14: 153-168. Tran, J., Rak, J., Sheehan, C., Saibil, S.D., LaCasse, E., Korneluk, R.G., and Kerbel, R.S. (1999) Marked induction of the IAP family anti-apoptotic proteins survivin and XIAP by VEGF in vascular endothelial cells. Biochemical and Biophysical Research Communication, 264: 781-788. Goertz, D.E., Christopher, D.A., Yu, J.L., Kerbel, R.S., Burns, P.N., and Foster F.S. (2000) High-frequency color flow imaging of the microcirculation. Ultrasound Med. Biol. 26: 63-71.
Kerbel, R.S. (2000)
Tumor angiogenesis: past, present and the near future. In: Carcinogenesis, 21:
505-515. Kerbel, R.S., Viloria-Petit, A., Klement, G., and Rak, J. (2000) “Accidental?anti-angiogenic drugs: anti-oncogene directed signal transduction inhibitors and conventional chemotherapeutic agents as examples. Eur. J. Cancer, 36: 1248-1257.
López-Ocejo, O.,
Bequet-Romero, M., Viloria Petit, A., Rak, J., Mukhopadhyay, D., and Kerbel, R.S.
(2000) Oncogenes and tumor angiogenesis: the HPV-16 E6 oncoprotein activates the
vascular endothelial growth factor (VEGF) gene promoter in a p53 independent
manner. Oncogene, 19: 4611-4620. Yu, J.L., Rak, J.W., Carmeliet, P., Kerbel, R.S., and Coomber, B.L. (2001) Heterogeneous vascular dependence of tumor cell populations. Am. J. Path., 158: 1325-1334. Frankel, A., Rosen, K., Filmus, J. and Kerbel, R.S. (2001) Induction of Anoikis and Suppression of Human Ovarian Tumor Growth In Vivo by Downregulation of Bcl-XL. Cancer Res. 61: 4837-4841. Viloria-Petit, A., Crombet, T., Jothy, S., Hicklin, D., Bohlen, P., Rak, J., Schlaeppi, J.-M., and Kerbel, R.S. (2001) Acquired resistance to the anti-tumor effect of epidermal growth factor receptor-blocking antibodies in vivo: a role for altered tumor angiogenesis. Cancer Res. 61: 5090-5101. Kerbel, R.S. (2001) Clinical trials of anti-angiogenic drugs: opportunities, problems and assessment of initial results. Journal of Clinical Oncology, 19 (Suppl 1): 45S?51S. Gately, S. and Kerbel, R. (2001) Antiangiogenic scheduling of lower dose cancer chemotherapy. Cancer Journal, 7: 427-436. Mayer, B., Kaneko, M., Man, S., Jothy, S., Rak, J. and Kerbel, R.S. (2001) Differentiated tumor architecture is lost in gastric cancer xenografts but maintained in spheroid culture. Gastroenterology, 121: 839-852. Kerbel, R.S. and Folkman, J. (2002) Clinical translation of angiogenesis inhibitors. Nature Reviews Cancer, 2: 727-739. Klement, G., Mayer, B., Huang, P., Bohlen, P., Hicklin, D. and Kerbel, R.S. (2001) Differences in therapeutic indexes of combination metronomic chemotherapy and an anti-VEGFR-2 antibody in multidrug resistant human breast cancer xenograft . Clin. Cancer Res., 8: 221-232. Yu, J.L., Rak, J.W., Klement, G., and Kerbel, R.S. (2002) VEGF isoform expression as a determinant of blood vessel patterning in human melanoma xenografts. Cancer Res., 62: 1838-1846. Yu, J.L., Rak, J.W., Coomber, B.L., Hicklin, D.J., and Kerbel, R.S. (2002) Effect of p53 status on tumor response to antiangiogenic therapy. Science, 295: 1526-1528.
Kerbel, R.S.,
Klement, G., Pritchard, K.I., and Kamen, B. (2002) Continuous low dose
anti-angiogenic/metronomic chemotherapy: from the research laboratory into the
oncology clinic. Annals of Oncology, 13: 12-15. Man, S., Bocci, G., Francia, G., Green, S., Jothy, S., Bergers, G., Hanahan, D., Bohlen, P., Hicklin, D., and Kerbel, R. (2002) Anti-tumor and anti-angiogenic effects in mice of low-dose (metronomic) cyclophosphamide administered continuously through the drinking water. Cancer Res., 62: 2731-2735. Rak, J., Yu, J.L., Kerbel, R.S. and Coomber, B.L. (2002) Review: What do oncogenic mutations have to do with angiogenesis/vascular dependence of tumors? Cancer Res., 62:1931-1934. Bocci, G., Nicolaou, K.C., and Kerbel, R. (2002) Protracted low-dose effects on human endothelial cell proliferation, adhesion and migration in vitro reveals a potential "antiangiogenic window" for chemotherapeutic drugs. Cancer Res., 62: 6938-6943. Goertz, D.E., Yu, J.L., Kerbel, R.S., Burns, P.N., and Foster, F.S. (2002) High frequency doppler ultrasound monitors the effects of antivascular therapy on tumor blood flow. Cancer Res., 62: 6371-6375. Green, S.K., Karlsson, M.C.I., Ravetch, J.V., and Kerbel, R.S. (2002) Disruption of cell-cell adhsion enhances antibody-dependet cellular cytotoxicity: Implications for antibody-based therapeutics of cancer. Cancer Res., 62: 6891-6900. Kerbel, R.S. and Klement, G. (2002) Low-dose metronomic antiangiogenic chemotherapy: preclinical and clinical applications in breast cancer. In: Breast Cancer Management: Application of Clinical and Translation Evidence to Patient Care. Ed: Nabholtz, J.-M., Tonkin, K., Reese, D., Aapro, M., and Buzdar, A. Lippincott, in press. Gesundheit, B., Klement, G., Senger, C., Becker, L., Kerbel, R.S., and Baruchel, S. (2002) Marked differences between vascularity and angiogenesis in childhood pilocytic and anaplastic astrocytomas. Medical Pediatric Oncology, in press. Ebos, J., Tran, J., Master, Z., Dumont, D., Melo, J.V., Buchdunger, E. and Kerbel, R.S. (2002) Imatinib mesylate (STI 571) reduces Bcr-Abl mediated VEGF secretion in chronic myelogenous leukemia. Molecular Cancer Res., in press. Yu, J.L., Coomber, B.L., and Kerbel, R.S. (2002) A paradigm for therapy-induced microenvironmental changes in solid tumors leading to drug resistance. Differentiation, in press. Jones, N., Chen, S., Sturk, C., Master, Z., Tran, J., Kerbel, R.S. and Daniel J. Dumont "A unique consensus sequence on Tie2/Tek mediates Dok-R PTB domain binding and function" Molecular & Cellular Biology, in press. Viloria-Petit, A., Miguerol, L., Gertenstein, M., Sheehan, C., May, L., Hicklin, D.L., Lobe. C., Nagy, A., Kerbel, R.S., and Rak, J. (2002) Contrasting effects of VEGF gene disruption in embryonic stem cells derived teratoma versus adult fibrosarcoma cells. EMBO J., submitted. Francia, G., Man, S., Teicher, B., and Kerbel, R.S. (2002) Gene expression analysis of tumor spheroids reveals a role for suppressed DNA mismatch repair in multicellular resistance to alkylating agents. Molecular and Cellular Biology, submitted. Glode, M., Crighton, F., Barqawi, A., Johnson, A., Kerbel, R.S., Berman, C., and Crawford, D. (2002) Metronomic Therapy with Cyclophosphamide and Dexamethasone for Prostate Cancer. Cancer, submitted.
|
|
Send mail to
webmaster@yatai.com with
questions or comments about this web site.
|
