Chemo-sensitivity of a human salivary adenocarcinoma cell line to several anti-cancer drugs and enhancement of the antitumor effects by combination with filipin or verapamil

A human salivary adenocarcinoma cell line, HSGc, was tested for the chemosensitivity and compared with a human squamous cell carcinoma cell line, KB. From IC50 values of anti-cancer drugs on the cells, it was found that HSGc was sensitive to CDDP, 5-FU and DTIC but resistant to ADM, MTX, VCR, PEP and MMC as compared to KB. The chemosensitivity of HSGc was in agreement with previously reported clinical data on the therapeutic results of salivary gland tumors. This suggests that HSGc may be an useful model for understanding the biological response of salivary adenocarcinoma cells to anti-cancer drugs. We further examined the combined effects of filipin and verapamil with these anti-cancer drugs. Filipin was found to enhance cell-killing effect of 5-FU and PEP on HSGc, while the combination of filipin with either DTIC or PEP was also effective on KB. Verapamil was effective in combination with 5-FU, VCR or PEP on HSGc and with DTIC, VCR or PEP on KB. Especially the most predominant enhancement on HSGc was observed in combination of filipin or verapamil with PEP. These findings suggest that even low-sensitive drug, PEP, is also useful when combined with either filipin or verapamil.