Involvement of Akt in mitomycin C and its analog triggered cytotoxicity in MCF-7 and K562 cancer cells.

Mitomycin C (MC) is a well-known DNA alkylating agent. MC analog, 10-decarbamoyl mitomycin C (DMC), unlike MC, has stronger effects on cancer with p53 mutation. We previously demonstrated that MC/DMC could activate p21WAF 1/ CIP 1 in MCF-7 (p53-proficient) and K562 (p53-deficient) cells in a p53-independent mode. This study aimed to elucidate the upstream signaling pathway of p21WAF 1/ CIP 1 activation triggered by MC/DMC. Besides p53, Akt plays an important role on deactivating p21WAF 1/ CIP 1 . The results showed that MC/DMC inhibited Akt in MCF-7 cells, but not in K562 cells. By knocking down p53, the Akt inhibition in MCF-7 cells was alleviated. This implied that the deactivated Akt caused by MC/DMC was p53-dependent. With Akt activator (SC79), p21WAF 1/ CIP 1 activation triggered by MC/DMC in MCF-7 cells was not reduced. This indicated that Akt inhibition triggered by MC/DMC was not associated with MC/DMC-induced p21WAF 1/ CIP 1 activation. Label-free quantitative proteomic profiling analysis revealed that DMC has a stronger effect on down-regulating the PI3K/Akt signaling pathway in MCF-7 cells as compared to MC. No significant effect of MC/DMC on PI3K/Akt in K562 cells was observed. In summary, MC/DMC regulate Akt activation in a p53-dependent manner. This Akt deactivation is not associated with p21WAF 1/ CIP 1 activation in response to MC/DMC.