Modulation of "orphan" cytochromes by selected phytochemicals and their combination in HepG2 cells

The “orphan” cytochromes P450 (CYPs), although still not well characterized, may be involved in the metabolism of several hepatocarcinogens. There are also a piece of evidence of their possible role in the stimulation of cancer cell proliferation and metastasis. Our earlier studies showed that naturally occurring phytochemicals and mainly their combinations can induce apoptosis and limit the proliferation of human hepatocellular carcinoma cells, HepG2. The aim of this study was to evaluate their effect on the expression of “orphan" CYPs, 2S1, 2W1, and 2U1 in the hepatic cancer cell line. HepG2 cells were treated with xanthohumol (X), phenethyl isothiocyanate (PEITC), resveratrol (RES), or indole-3-carbinol (I3C) and their combinations for 24 h. The expression of CYP genes was assessed by r-t PCR and Western blot. Generally, a moderate effect of the tested phytochemicals on the expression at the evaluated CYP protein level was found. More significant changes were detected at the mRNA level. X and RES were the most efficient reducers of CYP2S1 and CYP2W1 expression. This effect was confirmed by treatment with a mixture of these compounds as well. CYP2U1 expression was diminished as a result of treatment with X and PEITC and their combination. The above mentioned results indicate that tested phytochemicals, particularly X, may reduce the expression of “orphan" CYPs and, in this way, diminish the activation of hepatocarcinogens and possibly limit the proliferation of HCC cells.