Anticancer drug cytotoxicity assessed using controllable HELA TET-ON/HCYP1 cell lines

Objective: P450 enzymes have a key role in the metabolism of a many anticancer drugs. Metabolism via CYP1s in a variety of solid tumours is thought to aid tumour avoidance of chemotherapeutic induced cytotoxicity. The objective of the present research was to establish the influence of CYP1 mediated metabolism of three anticancer drugs (baicalein, resveratrol, doxorubicin) on their cytotoxicity, using a series of HeLa Tet-ON/hCYP1 cell lines controllably expressing CYP1 enzymes. Methods: The full length genes coding human CYP1A1, CYP1A2 and CYP1B1 were cloned from human liver cDNA library by PCR into the cloning plasmid pBluescriptKS(+) and expressed in different mammalian vectors, with subsequent DNA sequencing of the cloned CYP1 genes. The cytotoxicity of the anticancer drugs (baicalein, resveratrol, doxorubicin) by CYP1 cells was investigated in the presence and absence of α-naphthoflavone (ANF; potent inhibitor of CYP1 family). Cell survival was assessed by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results:
CYP1A1 was found to be the most potent enzyme for conversion of the anticancer drugs to more cytotoxic metabolites. CYP1A1, but not CYP1B1 or CYP1A2, enhanced cytotoxicity of resveratrol. Doxorubicin was found to have highest increase (53-fold) in cytotoxicity mediated by CYP1A1 (Table 1 and Fig. 1). Conclusion: Tumours expressing CYP1A1 would respond more favourably to doxorubicin and could be treated effectively with lower doses of the anticancer agent, thus reducing harm to normal tissue. The double stable cell lines expressing CYP1 enzymes were effective cellular systems for assessing cytotoxicity profiles of candidate anticancer agents.