Enhancement of antitumor activity of mitomycin C in vitro and in vivo by UCN-01, a selective inhibitor of protein kinase C

Abstract

UCN-01 (7-hydroxy-staurosporine) is a potent and selective inhibitor of protein kinase C (PKC), one of several protein kinases examined. UCN-01 itself was shown to exhibit antitumor activity in vitro and in vivo in oncogene-activated human and murine tumor cell lines. Since the mechanism(s) of action of UCN-01 is thought to be different from those of alkylating agents, including mitomycin C (MMC), we tested the combined effect of UCN-01 with MMC on human epidermoid carcinoma A431 cells. UCN-01 potentiated the antiproliferative activity of MMC and yet it did not affect the growth of the cells in vitro. However, other nonselective protein kinase inhibitors, such as staurosporine, K-252a, KT6124 (a derivative of K-252a) and H7, did not enhance the activity of MMC. Isobologram analysis revealed that the interaction of UCN-01 with MMC was synergistic in its antiproliferative activity. A DNA histogram of A431 cells treated with both UCN-01 and MMC showed a block in the cell cycle at the G1/S phase. However, a histogram of cells treated with UCN-01 or MMC alone showed a G1 or a G2M block, respectively. The combined effect of UCN-01 with MMC was further examined in vivo in xenografted A431 cells in nude mice. The combination of both drugs in a single i.v. injection exhibited greater antitumor activity than MMC and UCN-01 alone (P < 0.01). This synergistic antitumor effect was also confirmed in two other solid tumor cell lines, i.e. human xenografted colon carcinoma Co-3 and murine sarcoma 180. The same was observed in the i.v.-inoculated P388 leukemia model, in which we saw an increased lifespan of mice when UCN-01 was combined with MMC. These results suggests the feasibility of using UCN-01 in clinical oncology, especially in combination with alkylating agents such as MMC. In addition, this combination therapy might be a novel chemotherapeutic approach to MMC-insensitive tumors in clinical trials.

The broad-range cyclin-dependent kinase inhibitor UCN-01 induces apoptosis in colon carcinoma cells through transcriptional suppression of the Bcl-xL protein

“…As a modulator, UCN-01 enhances the antitumour activity of several antitumour agents, including mitomycin C (Akinaga et al, 1993), cisplatin (Bunch and Eastman, 1996;Husain et al, 1997) and 5-FU both in vitro (Abe et al, 2000) and in vivo (Koh et al, 2002). The potentiation of cytotoxicity by UCN-01 is ascribed to its ability to abrogate the G2/M checkpoint Wang et al, 1996), as previously reported for caffeine (Powell et al, 1995;Fan et al, 1997).…”

Small molecule modulators of cyclin-dependent kinases for cancer therapy

“…Moreover, MCF-7 cell lines harboring no endogenous p53 due to ectopic expression of the human papillomavirus type-16 E6 protein, showed enhanced cytotoxicity with the combination between DNA-damaging agents, such as cisplatin and UCN-01, compared with the isogenic wild type MCF-7 cell line. This synergistic e ect of UCN-01 was also observed with mitomycin C, 5-¯uoruracil, BCNU, camptothecin, among others (Akinaga et al, 1993;Bunch and Eastman, 1996;Hsueh et al, 1998;Husain et al, 1997;Pollack et al, 1996;Shao et al, 1997;Tsuchida and Urano, 1997). Therefore, it is likely that this preclinical information may guide us in the clinical development of UCN-01 as a modulator of standard chemotherapy in the clinic Wilson et al, 2000).…”

Differential response of normal and malignant urothelial cells to CHK1 and ATM inhibitors

“…The potent Chk1/Chk2 inhibitor AZD7762 is under phase I, dose-escalation study to evaluate the safety, pharmacokinetics (PK) and preliminary efficacy alone or in combination with gemcitabine in Japanese patients with advanced solid malignancies (Seto et al, 2013). Similarly, other CHK1 inhibitors including PF-477736 (Pfizer) and SCH900776 (Schering Plough) are also under Phase I or II clinical evaluation in patients (Ashwell et al, 2008;Karp et al, 2012 (Mizuno et al, 1995) Chk1 (Busby et al, 2000) Mytomycin C (Akinaga et al, 1993) Cisplatin (Bunch and Eastman, 1996) Topoisomerase I poisons (Tse et al, 2007a) Gemcitabine (Shi et al, 2001) Phase I/ II Gö6976 PKC(Martiny-Baron et al, 1993…”