Growth-suppressive effect of suberoylanilide hydroxamic acid (SAHA) on human oral cancer cells

Purpose: The histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) has been reported to exhibit anticancer activities in various cancer cell types, but as yet there are few reports on the anticancer effects of SAHA in oral squamous cell carcinoma (OSCC)-derived cells and xenograft models. Methods: The anti-proliferative and apoptotic activities of SAHA were assessed in human HSC-3 and HSC-4 (OSCC)-derived cell lines and JB6 normal mouse skin-derived epidermal cells using histone acetylation, soft agar colony formation, trypan blue exclusion, 4′-6-diamidino-2-phenylindole (DAPI) staining, Live/Dead viability/cytotoxicity and Western blot analyses. Results: We found that SAHA treatment resulted in hyperacetylation of histones H2A and H3 and a concomitant decrease in the viability of HSC-3 and HSC-4 cells. SAHA also significantly inhibited the neoplastic transformation of JB6 cells treated with TPA, whereas the viability of these cells was not affected by this treatment. Additionally, we found that SAHA suppressed the anchorage-independent growth (colony forming capacity in soft agar) of HSC-3 and HSC-4 cells. DAPI staining, Live/Dead and Western blot analyses revealed that SAHA can induce caspase-dependent apoptosis in HSC-3 and HSC-4 cells. We also found that SAHA treatment led to inhibition of ERK phosphorylation, and that two MEK inhibitors potentiated SAHA-mediated apoptosis. Okadaic acid treatment inhibited SAHA-mediated apoptosis in both the HSC-3 and HSC-4 cell lines, wheras SAHA induced a profound in vivo inhibition of tumor growth in HSC-3 xenografts. Conclusions: Our results indicate that the ERK signaling pathway may constitute a critical denominator of SAHA-induced apoptosis in OSCC-derived cells and that SAHA may have therapeutic potential for OSCC.