In this study cytotoxicity of organotin(IV) compounds with 1,2,4-triazolo[1,5-a]pyrimidines, Me₃Sn(5tpO) (1), n-Bu₃Sn(5tpO) (2), Me₃Sn(mtpO) (3), n-Bu₃Sn(mtpO) (4), n-Bu₃Sn(HtpO₂) (5), Ph₃Sn(HtpO₂) (6) where 5HtpO = 4,5-dihydro-5-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, HmtpO = 4,7-dihydro-5-methyl-7-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, and H₂tpO₂ = 4,5,6,7-tetrahydro-5,7- dioxo-[1,2,4]triazolo-[1,5-a]-pyrimidine, was assessed on three different human tumor cell lines: HCT-116 (colorectal carcinoma), HepG2 (hepatocarcinoma) and MCF-7 (breast cancer). While 1 and 3 were inactive, compounds 2, 4, 5 and 6 inhibited the growth of the three tumor cell lines with IC₅₀ values in the submicromolar range and showed high selectivity indexes towards the tumor cells (SI > 90). The mechanism of cell death triggered by the organotin(IV) derivatives, investigated on HCT-116 cells, was apoptotic, as evident from the externalization of phosphatidylserine to the cell surface, and occurred via the intrinsic pathway with fall of mitochondrial inner membrane potential and production of reactive oxygen species. While compound 6 arrested the cell progression in the G2/M cell cycle phase and increased p53 and p21 levels, compounds 2, 4 and 5 blocked cell duplication in the G1 phase without affecting the expression of either of the two tumor suppressor proteins. Compounds 1 and 2 were also investigated using single crystal X-ray diffraction and found to be, in both cases, coordination polymers forming 1 D chains based on metal-ligand interactions. Interestingly, for n-Bu₃Sn(5tpO)(2) H-bonding interactions between 5tpO⁻ ligands belonging to adjacent chains were also detected that resemble the “base-pairing” assembly and could be responsible for the higher biological activity compared to compound 1. In addition, they are the first example of bidentate N(3), O coordination for the 5HtpO ligand on two adjacent metal atoms.

Combining phytochemicals with chemotherapics is an emerging strategy to treat cancer to overcome drug toxicity and resistance with natural compounds. We assessed the effects of indicaxanthin (Ind), a pigment obtained from Opuntia ficus-indica (L. Mill) fruit, combined with cisplatin (CDDP) against cervical cancer cells (HeLa). Measured cell viability via Trypan blue assay; cell morphology via fluorescence microscopy; apoptosis, cell cycle, mitochondrial membrane potential (MMP) and cell redox balance via flow-cytometry; expression levels of apoptosis-related proteins via western blot. Cell viability assays and Chou-Talalay plot demonstrated that the combination of CDDP and Ind had synergistic cytotoxic effects. Combined treatment had significant effects (p < 0.05) on phosphatidylserine externalization, cell morphological changes, cell cycle arrest, fall in MMP, ROS production and GSH decay compared with the individual treatment groups. Bax, cytochrome c, p53 and p21^waf1 were over-expressed, while Bcl-2 was downregulated. Pre-treatment with N-acetyl-l-cysteine abolished the observed synergistic effects. We also demonstrated potentiation of CDDP anticancer activity by nutritionally relevant concentrations of Ind. Oxidative stress-dependent mitochondrial cell death is the basis of the chemosensitizing effect of Ind combined with CDDP against HeLa cancer cells. ROS act as upstream signaling molecules to initiate apoptosis via p53/p21^waf1 axis. Ind can be a phytochemical of interest in combo-therapy.

Manna is produced from the spontaneous solidification of the sap of some Fraxinus species, and, owing its content in mannitol, is used in medicine as a mild laxative. Manna is also a rich source of characteristic bio-phenols with reducing, antioxidant and anti-inflammatory properties. This study assesses the activity of a hydrophilic extract of manna (HME) on cellular and molecular events in human colon-rectal cancer cells. HME showed a time- and concentration-dependent anti-proliferative activity, measured by MTT assay, in all the cell lines examined, namely Caco-2, HCT-116 and HT-29. The amounts of HME that caused 50% of cell death after a 24 h treatment were 8.51 ± 0.77, 10.73 ± 1.22 and 28.92 ± 1.99 mg manna equivalents/mL, respectively; no toxicity was observed in normally differentiated Caco-2 intestinal cells. Hydroxytyrosol, a component of HME known for its cytotoxic effects on colon cancer cells, was ineffective, at least at the concentration occurring in the extract. Through flow-cytometric techniques and Western blot analysis, we show that HME treatment causes apoptosis, assessed by phosphatidylserine exposure, as well as a loss of mitochondrial membrane potential, an intracellular formation of reactive oxygen species (ROS), increases in the levels of cleaved PARP-1, caspase 3 and Bax, and a decrease in Bcl-2 expression. Moreover, HME interferes with cell cycle progression, with a block at the G1/S transition. In conclusion, the phytocomplex extracted from manna exerts an anti-proliferative activity on human colon cancer cells through the activation of mitochondrial pathway-mediated apoptosis and cell cycle arrest. Our data may suggest that manna could have the potential to exert chemo-preventive effects for the intestine.