Since farnesylation by
farnesyltransferase (FTase) is the first obligatory step in the signaling transduction pathway of ras p21, FTase has been the target of new anticancer treatment modalities. Famesyl
transferase inhibitors (FTIs), a novel class of
antitumor drugs that blocks the oncogenic activity of ras, were first developed as
therapy for ras-mutated human
tumors. FTIs are also capable of inhibiting
tumors without ras mutations, while different mechanisms of cell growth inhibition by FTI have been proposed. In cell culture and in animal models, FTIs have been shown to be potent inhibitors of
cancer cell growth. We showed that
manumycin, a farnesyl pyrophosphate competitive inhibitor, inhibits ovarian and
mesothelioma cancer cell growth. To examine the molecular changes after exposure to
manumycin, total
proteins from treated and untreated 2774 cell line were extracted and separated by two dimensional gel electrophoresis (2-DE) and detected by colloidal
coomassie blue staining. The 2-DE was found reliable for comparison of
protein profiles before and after
manumycin treatment. Two
protein spots (spot 1 and 2) appeared after
manumycin treatment. Generated
peptide peaks were matched by database query (
prowl.rockefeller.edu/cgi-bin/ProFound) to a
heat shock protein (HSP) and a modified HSP, both with MW 70 KD. The expression status of HSP 70 was confirmed by Western blot and HSP 70 ELISA using an antibody against HSP 70. The expression of HSP70 increased with the length of exposure to, and the dose of
manumycin as demonstrated by ELISA. Increase in HSP70 expression was also observed by Western blot after a 48-hour treatment with
manumycin in
ovarian cancer cell line OVCAR3 and three other cell cultures derived from samples of patients diagnosed with
ovarian cancer and
mesothelioma. Our study is the first report demonstrating an up-regulation of HSP 70 in
ovarian cancer cell lines and
mesothelioma cell cultures
after treatment with the FTI,
manumycin. This up-regulation of HSP 70 may be a cellular mechanism of cell self-protection against the apoptotic process and cell death, and it may enhance resistance and account for the altered sensitivity of certain
cancers to FTIs agents. HSPs may therefore be an important molecular target for
drug intervention strategies.