logical to assume that agents that inhibit telomerase activity may be effective and selectively cytotoxic to tumor cells. Hsp90 inhibitors, such as7-allylamino-17 demethoxygeldanamycin (17-AAG), have previously been shown to enhance the cytotoxic effects of several anticancer agents, including irradiation. The mechanism appears to involve the ability to associate with and interfere with Hsp90 stabilization of several Rosuvastatin pro-survival signaling factors/pathways including HIF-1 , Akt, Erk, Raf, Lyn, CK2, and HER-2/neu. However, the speci ?c molecular target(s) and the tumor types most susceptible to the cytotoxic and sensitizing effects of7-AAG remains to be fully determined. To address this, we examined whether7-AAG could differentially enhance cytotoxicity without or with radiation in a telomerase expressing transformed human ?broblast cell line compared to an isogenic control. Materials/Methods: The established human ?broblast cell lines CCR (normal human ?broblasts) and BJ1 (telomerase expressing transformed human ?broblasts) were obtained from Dr. Tej Pandita. Cell cultures were exposed to0 ?1000 nM of7-AAG and cell growth and drug induced cytotoxicity were determined.
Analysis of cell cycle aberrations and induction of apoptosis were determined via PI and Annexin staining with FACS. Radiation was given using an orthovoltage unit without Rosuvastatin Crestor and with pre-exposure to7-AAG. Telomerase activity was assessed with TRAP assay. Dose response curves and time to recover to baseline telomerase activity were assessed and compared with isogenic control. Gene expression analysis of differential response to7-AAG without and with radiation will be performed and selected targets con ?rmed with real-time PCR. Results: CCR and BJ1 human isogenic ?broblasts show minimal differences in growth rate and plating ef ?ciency as well as several other biological endpoints. Following extended exposure (6 days) to7-AAG CCR cells were more sensitive to drug-induced cytotoxicity than BJ1 in a dose dependent manner up to000nM. Pretreatment for 24hrs with nontoxic doses of7-AAG (100nM) markedly sensitized BJ1 telomerase expressing cells to a single dose of radiation (8Gy) compared to CCR cells. At this concentration7-AAG reduced telomerase activity in BJ1 cells to 60 percent of baseline following 24 hr exposure. In addition,7-AAG induced reduction in intracellular protein levels were con ?rmed via western and RT-PCR. Finally, FACS analysis revealed a signi ?cant shift into G2 following7-AAG exposure to BJ1 that was not observed in CCR. Conclusions: Since telomerase activity and expression are upregulated in a variety of tumor cells it seems logical to determine if telomerase may be a molecular target to sensitize tumor cells to the cytotoxicity of irradiation.
In this study we have determined that7-AAG down regulates expression and function of telomerase. In addition,7-AAG preferentially radiosen- sitizes transformed telomerase expressing cells versus wild type human ?broblasts that coincided with the Rosuvastatin RAAS inhibitor inhibition of telomerase activity. This differential effect, using non-cytotoxic doses, suggests a favorable therapeutic index in vivo. 2032 Inhibition of DNA Mismatch Repair by Cadmium and Oxidative Damage 1 1 Radiation Oncology, University of Maryland Medical System, Baltimore, MD, 2 Molecular and Cellular Biology Program, University of Maryland Medical System, Baltimore, MD Purpose/Objective: The goal of this study was to examine the combined effect of cadmium and oxidative damage on DNA mismatch repair (MMR) activities. De ?ciencies in MMR activity result in hypermutability of microsatellite sequences (MSI) in DNA and have been linked to the inherited cancer syndrome hereditary nonpolyposis colorectal cancer.
Cadmium is one of the most serious environmental pollutants and has been linked to an increased risk for cancer of the prostate, lung, nose and nasal sinus. Currently, the Rocky Mountains most signi ?cant source of cadmium exposure to humans is through cigarette smoking.