Pre-clinical characterization of PKC412, a multi-kinase inhibitor, against colorectal cancer cells.

The potential effect of PKC412, a small molecular multi-kinase inhibitor, in colorectal cancer (CRC) cells was evaluated here. We showed that PKC412 was cytotoxic and anti-proliferative against CRC cell lines (HT-29, HCT-116, HT-15 and DLD-1) and primary CRC cells. PKC412 provoked caspase-dependent apoptotic death, and induced G2-M arrest in the CRC cells. AKT activation was inhibited by PKC412 in CRC cells. Reversely, expression of constitutively-active AKT1 (CA-AKT1) decreased the PKC412's cytotoxicity against HT-29 cells. We propose that Bcl-2 could be a primary resistance factor of PKC412. ABT-737, a Bcl-2 inhibitor, or Bcl-2 siRNA knockdown, dramatically potentiated PKC412's lethality against CRC cells. Forced Bcl-2 over-expression, on the other hand, attenuated PKC412's cytotoxicity. Significantly, PKC412 oral administration suppressed AKT activation and inhibited HT-29 tumor growth in nude mice. Mice survival was also improved with PKC412 administration. These results indicate that PKC412 may have potential value for CRC treatment.

ROS-p53-cyclophilin-D signaling mediates salinomycin-induced glioma cell necrosis.

BACKGROUND: The primary glioblastoma multiforme (GBM) is the most malignant form of astrocytic tumor with an average survival of approximately 12-14 months. The search for novel and more efficient chemo-agents against this disease is urgent. Salinomycin induces broad anti-cancer effects; however, its role in GBM and the underlying mechanism are not clear. RESULTS: Here we found that salinomycin induced both apoptosis and necrosis in cultured glioma cells, and necrosis played a major role in contributing salinomycin's cytotoxicity. Salinomycin induced p53 translocation to mitochondria, where it formed a complex with cyclophilin-D (CyPD). This complexation was required for mitochondrial permeability transition pore (mPTP) opening and subsequent programmed necrosis. Blockade of Cyp-D by siRNA-mediated depletion or pharmacological inhibitors (cyclosporin A and sanglifehrin A) significantly suppressed salinomycin-induced glioma cell necrosis. Meanwhile, p53 stable knockdown alleviated salinomycin-induced necrosis in glioma cells. Reactive oxygen species (ROS) production was required for salinomycin-induced p53 mitochondrial translocation, mPTP opening and necrosis, and anti-oxidants n-acetylcysteine (NAC) and pyrrolidine dithiocarbamate (PDTC) inhibited p53 translocation, mPTP opening and glioma cell death. CONCLUSIONS: Thus, salinomycin mainly induces programmed necrosis in cultured glioma cells.

The short chain cell-permeable ceramide (C6) restores cell apoptosis and perifosine sensitivity in cultured glioblastoma cells.

Primary glioblastoma multiforme is the most malignant form of astrocytic tumor with an average survival of approximately 12-14 months. The combination of novel Akt inhibitors with anti-cancer therapeutics has achieved improved anti-tumor efficiency. In the current study, we examined the synergistic anti-cancer ability of Akt inhibitor perifosine in combination with short-chain ceramide (C6) against glioblastoma cells (U87MG and U251MG), and studied the underlying mechanisms. We found that perifosine, which blocked Akt/mammalian target of rapamycin activation, only induced moderate cell death and few cell apoptosis in cultured glioblastoma cells. On the other hand, perifosine administration induced significant protective autophagy, which inhibited cell apoptosis induction. Inhibition of autophagy by 3-methyaldenine or by autophagy-related gene-5 RNA interference significantly enhanced perifosine-induced apoptosis and cytotoxicity. We found that the short chain cell-permeable ceramide (C6) significantly enhanced cytotoxic effects of perifosine in cultured glioblastoma cells. For mechanism study, we observed that ceramide (C6) inhibited autophagy induction to restore cell apoptosis and perifosine sensitivity. In conclusion, our study suggests that autophagy inhibition by ceramide (C6) restores perifosine-induced apoptosis and cytotoxicity in glioblastoma cells.