Modulations of benzo[a]pyrene-induced DNA adduct, cyclin D1 and PCNA in oral tissue by 1,4-phenylenebis(methylene)selenocyanate

Abstract

Tobacco smoking is an important cause of human oral squamous cell carcinoma (SCC). Tobacco smoke contains multiple carcinogens include polycyclic aromatic hydrocarbons typified by benzo[a]pyrene (B[a]P). Surgery is the conventional treatment approach for SCC, but it remains imperfect. However, chemoprevention is a plausible strategy and we had previously demonstrated that 1,4-phenylenebis(methylene)selenocyanate (p-XSC) significantly inhibited tongue tumors-induced by the synthetic 4-nitroquinoline-N-oxide (not present in tobacco smoke). In this study, we demonstrated that p-XSC is capable of inhibiting B[a]P-DNA adduct formation, cell proliferation, cyclin D1 expression in human oral cells in vitro. In addition, we showed that dietary p-XSC inhibits B[a]P-DNA adduct formation, cell proliferation and cyclin D1 protein expression in the mouse tongue in vivo. The results of this study are encouraging to further evaluate the chemopreventive efficacy of p-XSC initially against B[a]P-induced tongue tumors in mice and ultimately in the clinic.

Fig. 1

The effect of p-XSC on cell survival and induction of apoptosis in oral cell lines. SCC 1483 (A) or MSK Leuk1 cells (B) were incubated with p-XSC for 24 hours and cell survival was determined by the MTT assay. (C) SCC 1483 Cells were incubated with p-XSC for 24 hours and apoptitic cell cell-death was determined by ELISA. Results were quantitated from three independent experiments. Data are presented as means ± S.D. *, statistically significant (P < 0.01) as compared with untreated controls.

Fig. 2

The effect of p-XSC on cyclin D1 expression in squamous cell carcinoma SCC1483 cells. A representative illustration of (A) the western blot analysis, and a comparison between various doses of p-XSC of (B) is provided. Levels of protein expression were quantified from three independent experiments. Results are presented as means ± S.D. *, statistically significant (P < 0.05) and **, statistically significant (P < 0.01) as compared with untreated controls.

Fig. 3

Inhibition of B[a]P-induced cell proliferation and cyclin D1 by p-XSC in the mouse tongue. Cell proliferation (PCNA) (A) and cyclin D1 (B) were measured by immunohistochemistry. Data are presented as percentage relative to the effect of B[a]P treatment. Data are presented as means ± S.D. *, statistically significant (P < 0.01) as compared with B[a]P-treated controls.

Fig. 4

The effects of p-XSC on the BPDE-DNA adduct formation. (A) BPDE-DNA isolated from Squamous cell carcinomas SCC1483 cells. (B) Representative Autoradiographic profiles are presented for tongues from untreated mice, and mice treated with p-XSC (C), B[a]P (D), and B[a]P and p-XSC (E). The spot in the upper right of panels D and E coelute with standard N²-BPDE-dG. A comparison of N²-BPDE-dG adduct formation between groups of mice fed control and p-XSC supplemented diets (n = 3/group) is provided in panel E. Levels of BPDE-DNA adducts were quantitated from three independent experiments. Results are the means ± S.D. of three separate experiments. *, statistically significant (P < 0.05) as compared with untreated controls.