Cytotoxic activity of deferiprone, maltol and related hydroxyketones against human tumor cell lines

Hydroxyketone chelators, deferiprone (HK1), maltol (HK3) and their related compounds (HK2, 4-8), were characterized for their cytotoxic profiles against oral human normal and tumor cells. Most hydroxyketones except HK6 showed relatively higher tumor-specific cytotoxicity. Deferiprone (HK1), which showed the highest tumor specificity, had 10 times higher cytotoxicity than maltol (HK3) in both human promyelocytic leukemia HL-60 and human oral squamous cell carcinoma HSC-2 cell lines. The cytotoxic activity of HK1 against HL-60 and HSC-2 cells was reduced in the presence of FeCl3, while that of HK3 was significantly increased by FeCl3. Agarose gel electrophoresis showed that HK1 induced internucleosomal DNA fragmentation in HL-60 cells, but the addition of FeCl3 inhibited the DNA fragmentation. HK3 did not induce DNA fragmentation in HL-60 cells, regardless of the presence or absence of FeCl3. In HSC-2 cells, HK1 and 3 did not induce DNA fragmentation in the presence or absence of FeCl3. Colorimetric protease assay showed that HK1 activated the caspase 3, 8 and 9 in HL-60 cells. On the other hand, HK3 did not activate the caspase 3, 8 and 9 in HL-60 cells, but activated the caspase 3 only slightly in the presence of FeCl3. HK1 and 3 also activated the caspase 3, 8 and 9 in HSC-2 cells, but to a lesser extent. The present study suggested that the antitumor activity of hydroxyketones may be modified by Fe3+ concentration.