Farnesyltransferase inhibitor effects on prostate tumor micro-environment and radiation survival

Ras activation by mutation, overexpression, or receptor signaling can increase tumor cell survival after irradiation.

We examined whether inhibiting Ras activity with farnesyltransferase inhibitors (FTI) altered the radiosensitivity and tumor micro-environment in prostate tumors.

Treatment with FTIs L-744,832 or FTI-277 reduced clonogenic survival of prostate tumor cells expressing oncogenic H-ras after irradiation. PI3-kinase/Akt and MAPK signaling pathways were downregulated by FTIs in these cells. FTI treatment reduced tumor hypoxia and also reduced MMP-9 expression in tumors with activated mutant H-ras. FTI treatment did not, however, increase apoptosis in irradiated intestine, demonstrating that acute radiation injury of this normal tissue was not enhanced by FTIs.

FTIs can enhance the killing of prostate tumors with activated H-Ras. Together with the absence of increased acute toxicity to normal bowel, these results imply that FTI treatment should be further studied as a possible adjuvant to radiotherapy in the treatment of abdominal cancers with activated Ras signaling.