"Chemotherapy Drug Resistance" TUMOR TIDBITS, A BIWEEKLY VETERINARY ONCOLOGY E-LETTER Volume 3; Number 6; February 15, 2002. Editor: Kevin A. Hahn, DVM, PhD, Dipl - ACVIM (Oncology) & Overall Nice Guy! ANNOUNCEMENTS 1 - Come Celebrate! We're having a Celebration of Life reception Saturday March 23rd at Gulf Coast Veterinary Oncology from 2-5 pm. Bring a picture of your pet to place in our new display case. Sorry, no pets allowed since we will be celebrating in our Deli. 2 - Free chemotherapy for lymphoma! Beginning April 15th, we will be offering a free chemotherapy trial for dogs diagnosed but previously untreated lymphoma at our Houston Office. 3 - Free chemotherapy for relapse lymphoma! Beginning June 1st, we will be offering a free chemotherapy trial for dogs with previously treated lymphoma at our Houston Office. 4 - Are you an RVT living in the Houston area and want to work for us! Call Dr. Hahn or Ms. Rhonda Dailey (713-693-1166) for more information. Great Benefits, 4 day workweek, travel to a National Meeting every other year, and more! These are exciting times for us at Gulf Coast Veterinary Oncology - Please call us (Drs. King, Hahn, Cerraras, Freeman & Turner) at any time and check our web site regulary for more information! THIS WEEK'S TUMOR TIDBIT: CHEMOTHERAPY DRUG RESISTANCE Some chemotherapy patients have been shown to develop a resistance to therapeutic drugs. The genes responsible for this resistance may also 'drive' tumor growth. A study conducted in 1995 found that drug resistant cancer tissue contained an over abundance of two enzymes which protect cancer cells from death. Drug resistance can be induced by the drug itself or acquired without prior induction. Susceptible cancer patients run the risk of tumor promotion within drug resistant tissues when undergoing chemotherapy. There are various mechanisms known to convey drug resistance in the chemotherapy patient: 7 Specific resistance to a selected drug can occur by deletion of the necessary activation enzyme for that drug such as deoxycitidine kinase for the drug cytosine arabinoside. 7 A general type of resistance is the over-expression of a drug efflux pump in the cell such as P-glycoprotein (pump) which, conveys resistance to a broad array of natural products used in cancer treatment. 7 Mutations in genes such as, the p53 suppressor oncogene may lead to drug resistance. A suppressor gene is necessary for controlling the proliferation of normal cells; it controls their life cycle, including reproduction. The loss or mutation of this type of gene allows cells to undergo malignant transformation and can inactivate programmed cell death (apoptosis). This leads to the continuous proliferation and survival of highly mutated cells (3). Current research is focusing on the restoration of apoptosis, which is correlated to the cell's sensitivity to drugs. Furthermore, it has been shown that combining drug therapies which have different mechanisms for fighting cancer is the more effective method for fighting cancer. WHAT DO WE DO AT GULF COAST? * We are investigating new agents that reverse the mechanisms of drug resistance. One clinical trial that begins in late April will be looking at an agent that not only inhibits drug resistance but new blood vessel growth around tumor regions. * We are investigating novel approaches to older drugs such as Tamoxifen for use in the reversal of clinical drug resistance. * We are using radiation therapy in a novel way to prime drug resistant cells to become chemotherapy sensitive again. FOR MORE INFORMATION ON CHEMOTHERAPY RESISTANCE, PLEASE CHECK OUT OUR WEB PAGE AT: * http://www.gcvs.com/oncology/pwc/chemoinformation.htm#_Toc521211091 Don't hesitate to call or email us at Gulf Coast Veterinary Oncology! ALL THE BEST, Kevin A. Hahn, DVM, PhD Diplomate ACVIM (Oncology) & Overall Nice Guy Gulf Coast Veterinary Specialists 1111 West Loop South, Suite 150 Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 http://www.gcvs.com mailto:drhahn@gulfcoastvetspec.com