Alternative Pathways of Cancer Cell Death by Rottlerin: Apoptosis versus Autophagy

Abstract

Since the ability of cancer cells to evade apoptosis often limits the efficacy of radiotherapy and chemotherapy, autophagy is emerging as an alternative target to promote cell death. Therefore, we wondered whether Rottlerin, a natural polyphenolic compound with antiproliferative effects in several cell types, can induce cell death in MCF-7 breast cancer cells. The MCF-7 cell line is a good model of chemo/radio resistance, being both apoptosis and autophagy resistant, due to deletion of caspase 3 gene, high expression of the antiapoptotic protein Bcl-2, and low expression of the autophagic Beclin-1 protein. The contribution of autophagy and apoptosis to the cytotoxic effects of Rottlerin was examined by light, fluorescence, and electron microscopic examination and by western blotting analysis of apoptotic and autophagic markers. By comparing caspases-3-deficient (MCF-73def) and caspases-3-transfected MCF-7 cells (MCF-73trans), we found that Rottlerin induced a noncanonical, Bcl-2-, Beclin 1-, Akt-, and ERK-independent autophagic death in the former- and the caspases-mediated apoptosis in the latter, in not starved conditions and in the absence of any other treatment. These findings suggest that Rottlerin could be cytotoxic for different cancer cell types, both apoptosis competent and apoptosis resistant.

Knockdown of the M2 Isoform of Pyruvate Kinase (PKM2) with shRNA Enhances the Effect of Docetaxel in Human NSCLC Cell LinesIn Vitro

“…Cyclin, cyclin dependent kinase (CDK) and CKI together regulate the cell cycle 34. CDK1 regulates the G2/M phase with specificity, and p21 may cause G2/M phase arrest by inhibiting the functions of CDK1 35. And, p21 may induce apoptosis under certain conditions, but sometimes does not.…”

Artesunate induces G2/M cell cycle arrest through autophagy induction in breast cancer cells

“…Cell culture MCF-7 cells, which have a low level of Beclin1 expression [29,30], and MDA-MB-231 cells were obtained from the American Type Culture Collection (Manassas, Virginia, USA) and maintained in RPMI-1640 (Gibco, Grand Island, New York, USA) medium supplemented with 10% fetal calf serum (Hyclone, Logan, Utah, USA), 100 U/ml penicillin, and 100 mg/ml streptomycin at 371C in a humidified atmosphere with 5% CO 2 . The cells were passaged every 2-3 days to maintain exponential growth.…”

Inhibitions of mTORC1 and 4EBP-1 are key events orchestrated by Rottlerin in SK-Mel-28 cell killing

“…Although Rottlerin may exert its anticancer effect by inducing apoptosis in apoptosis-competent cells [1], it did not induce morphological (condensed chromatin) and biochemical (PARP and caspases cleavage, increased caspase 3/7 activity) traits typical of an apoptotic form of cell death in SK-Mel-28 cells. Consistently, a pan-caspase inhibitor did not rescue cells from death.…”

“…In apoptosis-resistant MCF-7 breast cancer cells, the treatment, at cytotoxic doses, led to autophagic cell death [1]. Autophagy induction was AMPK-and Beclin-1-independent and mediated by direct inhibition of mTORC1 [2], a central controller of several essential cellular functions, the best understood of these being the inhibition of autophagy and the positive regulation of protein synthesis [3].…”