Antitumor and normal cell protective effect of PKC412 in the athymic mouse model of ovarian cancer

N-benzoyl-staurosporine (PKC412) is a selective inhibitor of protein kinase C, and it inhibits the growth of human cancer cells. In this study, we examined the antitumor effect of PKC412, given singly and in combination with paclitaxel, on tumor regression and chemotherapeutic side effects by assessing tumor burden and cytokine production responses in vivo. Twenty-six nude mice intraperitoneally inoculated with SKOV3 cells were treated differently in 4 treatment groups: PKC412 plus paclitaxel (n = 7), paclitaxel-only (n = 6), PKC412-only (n = 6), and controls (n = 7). At autopsy, we found that PKC412 itself slightly reduced the mass of tumor but did not fully inhibit tumor formation. The incidence of evident disease was decreased when PKC412 was combined with paclitaxel (43%). From the body weight of the tumor-bearing mice, we observed that PKC412 plus paclitaxel treated mice were less wasted than paclitaxel-only treated mice (18.1 g vs 22.4 g, p = 0.001). We measured intracellular TNFalpha, IFNgamma, IL-4, and IL-10 in stimulated mouse splenocytes using flow cytometry to determine if PKC412 inhibited cytokine production in T cells. TNFalpha, IFNgamma, and IL-10 production were all significantly inhibited in the paclitaxel-treated mice. The inhibitory effects on cytokine production by paclitaxel were compensated with PKC412 combination (p = 0.008, 0.035, 0.014, respectively). From this study, we deduce that PKC412 may have clinical applications in promoting tumor regression in ovarian cancer when combined with paclitaxel. Moreover, PKC412 is able to prevent weight loss and immunosuppression induced by paclitaxel because it rescues normal proliferating cells from cytotoxic effects.