Exploring the anticancer potential of pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-one derivatives: the effect on apoptosis induction, cell cycle and proliferation.

In order to investigate their anticancer potential, four new pyrazolo[1,2-a]benzo[1,2,3,4]tetrazinone derivatives, designed through the chemometric protocol VLAK, and three of the most active compounds of the previous series have been evaluated on some cellular events including proliferation, apoptosis induction, and cell cycle. The NCI one dose (10 μM) screening revealed that the 8,9-di-methyl derivative showed activity against Leukemia (CCRF-CEM) and Colon cancer cell line (COLO 205), reaching 81% and 45% of growth inhibition (GI), respectively. Replacement of the two methyl groups with two chlorine atoms maintained the activity toward Leukemia cell (CCRF-CEM, GI 77%) and selectively enhanced the activity against COLO 205 attaining a LD50 in the μM range and against SW-620 a GI of 77%. Interestingly, an appreciable growth inhibition of 47% against therapeutically "refractory" Non-Small Cell Lung Cancer (NCI-H522) was observed. Moreover, the apoptosis induction, based on mitochondrial membrane depolarization, was found in the range EC50 3-5 μM on HeLa cell, evidencing a well defined relationship with the related in vitro cell growth inhibitory assays (MTT) performed against other selected tumor cell lines not included in the NCI tumor panel (HeLa, cervix; H292, lung; LAN-5, CNS; CaCo-2, colon; 16HBE, normal human cell lung) and against MCF-7 tumor cell line (breast). Only for the most active compounds, further cell cycle tests on HeLa displayed a cell arrest on S phase. Thus, a promising new class of anticancer candidates, acting as valuable apoptotic inductors, is proposed.