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Curcumin has been shown to exert potential antitumor activity in vitro and in vivo involved in multiple signaling pathways. However, the application of curcumin is still limited because of its poor hydrophilicity and low bio-availability. In the present study, we investigated the therapeutic effects of a novel and water soluble bis(hydroxymethyl) alkanoate curcuminoid derivative, MTH-3, on human breast adenocarcinoma MDA-MB-231 cells. This study investigated the effect of MTH-3 on cell viability, cell cycle and induction of autophagy and apoptosis in MDA-MB-231 cells. After 24-h treatment with MTH-3, a concentration-dependent decrease in MDA-MB-231 cell viability was observed, and the IC50 value was 5.37±1.22 μM. MTH-3 significantly triggered G2/M phase arrest and apoptosis in MDA-MB-231 cells. Within a 24-h treatment, MTH-3 decreased the CDK1 activity by decreasing CDK1 and cyclin B1 protein levels. MTH-3-induced apoptosis was further confirmed by morphological assessment and Annexin V/PI staining assay. Induction of apoptosis caused by MTH-3 was accompanied by an apparent increase of DR3, DR5 and FADD and, as well as a marked decrease of Bcl-2 and Bcl-xL protein expression. MTH-3 also decreased the protein levels of Ero1, PDI, PERK and calnexin, as well as increased the expression of IRE1α, CHOP and Bip that consequently led to ER stress and MDA-MB-231 cell apoptosis. In addition, MTH-3-treated cells were involved in the autophagic process and cleavage of LC3B was observed. MTH-3 enhanced the protein levels of LC3B, Atg5, Atg7, Atg12, p62 and Beclin-1 in MDA-MB-231 cells. Finally, DNA microarray was carried out to investigate the level changes of gene expression modulated by MTH-3 in MDA-MB-231 cells. Taken together, our results suggest that MTH-3 might be a novel therapeutic agent for the treatment of triple-negative breast cancer in the near future.

Pterostilbene is an effective chemopreventive agent against multiple types of cancer cells. A novel pterostilbene derivative, ANK-199, was designed and synthesized by our group. Its antitumor activity and mechanism in cisplatin-resistant CAR human oral cancer cells were investigated in this study. Our results show that ANK-199 has an extremely low toxicity in normal oral cell lines. The formation of autophagic vacuoles and acidic vesicular organelles (AVOs) was observed in the ANK-199-treated CAR cells by monodansylcadaverine (MDC) and acridine orange (AO) staining, suggesting that ANK-199 is able to induce autophagic cell death in CAR cells. Neither DNA fragmentation nor DNA condensation was observed, which means that ANK-199-induced cell death is not triggered by apoptosis. In accordance with morphological observation, 3-MA, a specific inhibitor of PI3K kinase class III, can inhibit the autophagic vesicle formation induced by ANK-199. In addition, ANK-199 is also able to enhance the protein levels of autophagic proteins, Atg complex, beclin 1, PI3K class III and LC3-II, and mRNA expression of autophagic genes Atg7, Atg12, beclin 1 and LC3-II in the ANK-199-treated CAR cells. A molecular signaling pathway induced by ANK-199 was therefore summarized. Results presented in this study show that ANK-199 may become a novel therapeutic reagent for the treatment of oral cancer in the near future (patent pending).

Background and PurposeYC‐1 exhibits potent anticancer activity via numerous actions in many cancer cell lines. Hence, we investigated the in vivo antitumour efficacy of YC‐1 in an MDA‐MB‐468 xenograft model and elucidated the mechanism of down‐regulation of enhancer of zeste homology 2 (EZH2) by YC‐1 in breast cancer cells.Experimental ApproachIn YC–1‐treated breast cancer cells and tumour specimens from YC–1‐treated MDA‐MB‐468 xenografts, EZH2 expression was analysed by Western blotting. Pharmacological inhibitors and short hairpin RNA‐mediated knockdown were applied to identify possible signalling pathways involved in EZH2 down‐regulation by YC‐1.Key ResultsYC‐1 reduced the viability of breast cancer cells and tumour growth in MDA‐MB‐468 xenografts. In breast cancer cells, YC‐1 down‐regulated EZH2 expression in a concentration‐ and time‐dependent manner. Depletion of EZH2 reduced the proliferation and susceptibility of breast cancer cells to YC–1‐induced apoptosis. EZH2 expression was suppressed in tumour specimens from YC–1‐treated MDA‐MB‐468 xenograft mice. YC‐1 enhanced both the degradation rate and ubiquitination of EZH2. The down‐regulation of EZH2 by YC‐1 was associated with activation of PKA and Src–Raf–ERK‐mediated signalling pathways. Furthermore, depletion of Casitas B‐lineage lymphoma (c‐Cbl), an E3 ubiquitin ligase, abolished YC–1‐induced apoptosis and suppression of EZH2. YC‐1 rapidly activated c‐Cbl to induce signalling associated with ERK and EZH2.Conclusion and ImplicationsWe discovered that YC‐1 induces apoptosis and inhibits tumour growth of breast cancer cells via down‐regulation of EZH2 by activating c‐Cbl and ERK. These data suggest that YC‐1 is a potential anticancer drug candidate for triple‐negative breast cancer.

Our results reveal the cellular events in which CSC-3436 induces tumor cell death and demonstrate that CSC-3436 is a potential tubulin-disrupting agent for antitumor therapy against NSCLC.