"Tumor Vaccines" TUMOR TIDBITS, A BIWEEKLY EMAIL NEWSLETTER FROM GULF COAST VETERINARY ONCOLOGY Number 99; May 9, 2003. ======================================================================= ANNOUNCEMENTS: Free Cancer Therapy for 4 months! Dogs without lymphoma having a hematocrit between 19% and 37% and a creatinine <1.8 may be eligible for this anemia study. The qualification examination is provided at no cost and eligible dogs may have all services provided at no charge (including any appropriate surgery, radiation, or chemotherapy) for 4 months. Call our offices in Houston (713.693.1166, Ms. Kelly Griffice) or San Antonio (210.822.1913, Ms. Waynette Wheeler) for additional information. Want a copy of our latest Oncology Handbook? A download is available at: http://www.gcvs.com/oncology/download.htm We support research! Visit our Foundation web site at: http://www.gcvs.com/gcvef/index.htm ======================================================================= THIS WEEK'S TUMOR TIDBIT: Tumor Vaccines ======================================================================= TUMOR VACCINES In previous Tidbits, we've talked about measures to improve the immune response against cancer cells (Piroxicam for example). Tumor vaccines represent another example of the potential of immunotherapy for treating cancer. Unlike the traditional vaccine, they are used to treat an established disease, rather than to prophylactically prevent the development of a specific infection. The theoretical intent of this form of cancer therapy is to present the patients immune system with its own tumor in such a way as to elicit an immune response capable of destroying the cancer. That is, the tumor will no longer escape normal immune surveillance and be destroyed. Various methods have been applied to make the tumor cell more immunogenic, including transfecting the cells with genes resulting in the production of immunogenic cytokines or co-stimulatory molecules, or enhanced major histocompatibility complex (MHC) expression. This actually represents a combination of immunotherapy and gene therapy. One approach taken at the University of Wisconsin Veterinary School is to transfect (inject) tumor cells with the gene for the cytokine GM-CSF (granulocyte/monocyte-colony stimulating factor). This cytokine is a pluripotent immunomodulator that activates neutrophils, eosinophils and macrophages to lyse tumor cells directly or to mediate antibody-dependent cellular cytotoxicity (ADCC). It also results in enhanced MHC expression, which theoretically results in enhanced recognition of the tumor by the immune system. Simply put, tumors are excised surgically, and then dissociated to a single cell suspension. The cells are irradiated so they are still living but not capable of dividing (i.e. you obviously don’t want to inject a dog with tumor capable of growing) then transfected mechanically with the GM-CSF gene. These cells are then injected intradermally back into the patient; in essence vaccinating the patient with its own tumor cells that will now produce GM-CSF to enhance the immune response. This entire process takes 4 hours from the time of surgery to the time of vaccination, making it a clinically feasible method. Vaccine trials in dogs with malignant melanoma and lymphosarcoma have been initiated at the University of Wisconsin Veterinary School. This form of treatment is virtually devoid of systemic toxicity. Other approaches currently under study at the UW include allogeneic tumor vaccines for malignant melanoma in dogs that have been genetically modified to co- express GM-CSF and gp-100, an antigen expressed on the surface of virtually all melanoma cells. This is currently under trial in dogs with malignant melanoma. WHAT DO WE DO AT GULF COAST VETERINARY ONCOLOGY? We are currently collaborating with UW on use of the melanoma vaccine following conventional chemoradiation for oral melanoma in dogs. Our conventional approach (weekly radiation and low-dose carboplatin for 6 weeks) results in a 50% 1-year survival rate and 40% 2-year survival rate in dogs with incompletely removed oral melanomas. To date we have treated 6 dogs with the UW melanoma vaccine following chemoradiation (range 3 to 18 months) and have detected metastatic disease in 1 of those dogs. ======================================================================= As always, we hope this info helps and don't hesitate to call or email us Gulf Coast Veterinary Oncology! Kevin A. Hahn, DVM, PhD, Diplomate ACVIM (Oncology), drhahn@gcvs.com Janet K. Carreras, VMD, Diplomate ACVIM (Oncology), drcarreras@gcvs.com Glen K. King, DVM, MS, Diplomate ACVR (Radiology & Radiation Therapy), drking@gcvs.com Gulf Coast Veterinary Diagnostic Imaging & Oncology 1111 West Loop South, Suite 150, Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 W: www.gcvs.com ======================================================================= Copyright © 2003, Gulf Coast Veterinary Oncology