In vitro cytotoxicity on human ovarian cancer cells by T-type calcium channel blockers.

The growth inhibition of human cancer cells via T-type Ca(2+) channel blockade has been well known. Herein, a series of new 3,4-dihydroquinazoline derivatives were synthesized via a brief SAR study on KYS05090 template and evaluated for both T-type Ca(2+) channel (Cav3.1) blockade and cytotoxicity on three human ovarian cancer cells (SK-OV-3, A2780 and A2780-T). Most of compounds except 6i generally exhibited more potent cytotoxicity on SK-OV-3 than mibefradil as a positive control regardless of the degree of T-type channel blockade. In particular, eight compounds (KYS05090, 6a and 6c-6h) showing strong channel blockade exhibited almost equal and more potent cytotoxicity on A2780 when compared to mibefradil. On A2780-T paclitaxel-resistant human ovarian carcinoma, two compounds (KYS05090 and 6d) were 20-fold more active than mibefradil. With respect to cell cycle arrest effect on A2780 and A2780-T cells, KYS05090 induced large proportion of sub-G1 phase in the cell cycle progression of A2780 and A2780-T, meaning the induction of cancer cell death instead of cell cycle arrest via blocking T-type Ca(2+) channel. Among new analogues, compounds 6g and 6h induced cell cycle arrest at G1 phase of A2780 and A2780-T cells in dose-dependent manner and exhibited strong anti-proliferation effects of ovarian cancer cells by blocking T-type Ca(2+) channel. Furthermore, 6g and 6h possessing strong cytotoxic effects could induce apoptosis of A2780 cells, which was detected by confocal micrographs using DAPI staining.

T-type Ca2+ channel blocker, KYS05047 induces G1 phase cell cycle arrest by decreasing intracellular Ca2+ levels in human lung adenocarcinoma A549 cells.

In a previous study, we found that the 3,4-dihydroquinazoline derivative, 4-(Benzylcarbamoylmethyl)-2-(biphenyl-4-ylamino)-3-(5-tert-butyloxycarbamoyl-1-pentyl)-3,4-dihydroquinazoline (KYS05047), was a selective T-type Ca(2+) channel blocker with anti-proliferative effects against various cancer cells. However, the mechanism responsible for its effects has not been studied. In this study, we investigated the effect of KYS05047 on cell cycle arrest and the mechanisms involved in human lung adenocarcinoma A549 cells. Among the G(1) phase cell cycle-related proteins examined, the levels of cyclin-dependent protein kinase (Cdk2) and Cdk4 were reduced by KYS05047 (7 µM), whereas the steady-state levels of cyclin D1 and E were unaffected. In addition, KYS05047 increased the protein level of p27(KIP1) and suppressed the kinase activities of Cdk2 and Cdk4. In addition, pretreatment with KCl, which increases intracellular Ca(2+) levels, prevented KYS05047-induced intracellular Ca(2+) decreases and cell cycle arrest. Furthermore, the administration of KYS05047 (2 or 10 mg/kg, po) for 21 days was also found to significantly inhibit tumor growth in an A549 xenograft nude mice model. In conclusion, our results suggested that KYS05047 induced G(1) phase cell cycle arrest in A549 cells associated with a decrease in intracellular Ca(2+) concentrations and inhibited the in vivo tumor growth of A549 xenograft mice.

In vivo evaluation of oral anti-tumoral effect of 3,4-dihydroquinazoline derivative on solid tumor.

An extension of our previously reported 3,4-dihydroquinazoline derivative is investigated. Oral anti-tumoral activity of 3,4-dihydroquinazoline derivative (KYS05090) as potent and selective T-type calcium channel blocker was in vivo evaluated against A549 xenograft in BALB/c(nu/nu) nude mice. The rate of tumor volume increment in mouse model with KYS05090-treated group was remarkably slower than that of control group. With respect to tumor weight, it exhibited 60% and 67% tumor growth inhibition through oral administration of 1 and 5mg/kg of bodyweight, respectively, compared to control and was more potent than paclitaxel (53%). In addition, KYS05090 (10 and 50mg/kg, po) was found to have a marked analgesic effect in acetic acid-induced writhing test, whereas it did not show any effect on hot plate test.