Effects of p300 inhibition on prostate cancer cell growth

Background: Radiation is a central component of many anti-cancer therapy regimens, utilized for more than half of all cancer patients. Despite advances in the delivery and success of radiation treatment, many individuals express, or will develop, radioresistance, a major contributor to treatment failure and malignant progression. While the etiology of radioresistance is complex, it may be mediated in part by expression of p300, a histone acetyltransferase known to facilitate DNA repair. We hypothesized that inhibition of p300 would increase radiosensitivity of prostate cancer cells in vitro. Methods: Human prostate adenocarcinoma (PC-3) cells were grown in tissue culture flasks incubated at 37° C with 5% CO 2 . Cells were randomized to receive 1 μM CCS 1477, a selective inhibitor of p300, or vehicle for 1 hour prior to a single treatment of 0 Gy (NR+ or NR-, respectively) or 2 Gy radiation (R+ or R-, respectively). Four hours after radiation, cells were seeded into 100 mm diameter tissue culture dishes and incubated for 10 days. Cells were then stained, and colonies > 50 cells were counted to determine clonogenic survival. Cell survival was corrected for plating effciency and group comparisons were made using a two-way ANOVA. Results: Results were determined from the average of 3 separate experiments. Compared to non-radiated controls (NR-), survival of R- was reduced to 47%, while survival of R+ was reduced to 32%. However, there was no significant difference between % survival of R- and R+. Conclusions: In vitro, 1 μM exposure to CCS 1477 does not reduce clonogenic survival in PC-3 cells subjected to 2 Gy radiation. The duration of exposure and concentration of CCS 1477 may not be adequate to elicit significant improvements in radiosensitivity of PC-3 cells to 2 Gy radiation. Future experiments will explore the effects of varying durations of exposure and concentrations of CCS 1477. Additionally, it remains to be determined whether CCS 1477 improves radiosensitivity in other cancer cell lines (e.g., breast cancer). Johnson Cancer Research Center. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.