Acetyl-11-keto-ß-boswellic acid triggers premature senescence via induction of DNA damage accompanied by impairment of DNA repair genes in hepatocellular carcinoma cells in vitro and in vivo.

Cellular senescence, a state of irreversible growth arrest, occurs in all somatic cells and causes the cells to exhaust replicative capacity. Recently, cellular senescence has been emerging as one of the principal mechanisms of tumor suppression, which can be induced by low doses of therapeutic drugs in cancer cells. Acetyl-11-keto-ß-boswellic acid (AKBA), an active ingredient isolated from the plant Boswellia serrata, has been identified to induce apoptosis in hepatocellular carcinoma (HCC) cells. In this study, we found that low concentrations of AKBA treatment triggered cell growth arrest at G0/G1 phase with features of premature cellular senescence phenotype in both HCC cell lines HepG2 and SMMC7721, as observed by enlarged and flattened morphology, significant increase in cells with senescence-associated ß-galactosidase staining, and decrease in cell proliferation and DNA synthesis. Furthermore, cellular senescence induced by AKBA occurred via activation of DNA damage response and impairment of DNA repair, as evidenced by strong induction of γH2AX and p53, and downregulated expressions of multiple DNA repair associated genes. Induction of p53 by AKBA caused a significant increase in p21CIP1 , which had a critical involvement in the induction of cellular senescence. Additionally, in vivo study demonstrated that induction of senescence contributed to the anticancer efficacy of AKBA. Therefore, our findings suggested that induction of premature senescence by AKBA through DNA damage response accompanied by impairment of DNA repair genes defines a novel mechanism contributing to its growth suppression in HCC cells.

Short-chain C6 ceramide sensitizes AT406-induced anti-pancreatic cancer cell activity.

Our previous study has shown that AT406, a first-in-class small molecular antagonist of IAPs (inhibitor of apoptosis proteins), inhibits pancreatic cancer cell proliferation in vitro and in vivo. The aim of this research is to increase AT406's sensitivity by adding short-chain C6 ceramide. We show that co-treatment of C6 ceramide dramatically potentiated AT406-induced caspase/apoptosis activation and cytotoxicity in established (Panc-1 and Mia-PaCa-2 lines) and primary human pancreatic cancer cells. Reversely, caspase inhibitors largely attenuated C6 ceramide plus AT406-induced above cancer cell death. Molecularly, C6 ceramide downregulated Bcl-2 to increase AT406's sensitivity in pancreatic cancer cells. Intriguingly, C6 ceramide-mediated AT406 sensitization was nullified with Bcl-2 shRNA knockdown or pretreatment of the Bcl-2 inhibitor ABT-737. In vivo, liposomal C6 ceramide plus AT406 co-administration dramatically inhibited Panc-1 xenograft tumor growth in severe combined immunodeficient (SCID) mice. The combined anti-tumor activity was significantly more potent than either single treatment. Expressions of IAPs (cIAP1/XIAP) and Bcl-2 were downregulated in Panc-1 xenografts with the co-administration. Together, we demonstrate that C6 ceramide sensitizes AT406-mediated anti-pancreatic cancer cell activity possibly via downregulating Bcl-2.

The small-molecule IAP antagonist AT406 inhibits pancreatic cancer cells in vitro and in vivo.

In the present study, we tested the anti-pancreatic cancer activity by AT406, a small-molecule antagonist of IAP (inhibitor of apoptosis proteins). In established (Panc-1 and Mia-PaCa-2 lines) and primary human pancreatic cancer cells, treatment of AT406 significantly inhibited cell survival and proliferation. Yet, same AT406 treatment was non-cytotoxic to pancreatic epithelial HPDE6c7 cells. AT406 increased caspase-3/-9 activity and provoked apoptosis in the pancreatic cancer cells. Reversely, AT406' cytotoxicity in these cells was largely attenuated with pre-treatment of caspase inhibitors. AT406 treatment caused degradation of IAP family proteins (cIAP1 and XIAP) and release of cytochrome C, leaving Bcl-2 unaffected in pancreatic cancer cells. Bcl-2 inhibition (by ABT-737) or shRNA knockdown dramatically sensitized Panc-1 cells to AT406. In vivo, oral administration of AT406 at well-tolerated doses downregulated IAPs (cIAP1/XIAP) and inhibited Panc-1 xenograft tumor growth in severe combined immunodeficient (SCID) nude mice. Together, our preclinical results suggest that AT406 could be further evaluated as a promising anti-pancreatic cancer agent.

MiR-130b inhibits proliferation and induces apoptosis of gastric cancer cells via CYLD.

A role of microRNA-130b (miR-130b) in the carcinogenesis of gastric cancer remains undetermined. In this study, we studied the effects and mechanism of miR-130b to the gastric cell proliferation and apoptosis. We found that the levels of miR-130b significantly up-regulated in gastric cancer tissue, compared to the paired adjacent non-tumor gastric tissue. The miR-130b levels in gastric cancer cell lines were significantly higher than those in control normal gastric tissues. Transfection with the miR-130b mimic enhanced the cell proliferation and suppressed cell apoptosis in gastric cancer cells, while transfection with the anti-sense of miR-130b (anti-miR-130b) suppressed cell proliferation and induced cell apoptosis in gastric cancer cells. Bioinformatics analyses showed that cylindromatosis gene (CYLD) was a potential target gene of miR-130b. The luciferase activity assay and western blot verified that miR-130b targeted CYLD messenger RNA (mRNA) to modulate its protein levels. Together, our study suggests that aberrantly expressed miR-130b may regulate cell apoptosis and proliferation of human gastric cancer cells via CYLD, which appears to be a promising therapeutic target for gastric cancer.