benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and Pheochromocytoma

Furanodiene is a natural product isolated from Rhizoma curcumae, and exhibits broad-spectrum anti-cancer activities in vitro and in vivo. Our previous study proved that furanodiene could increase growth inhibition of steroidal agent in ERα-positive breast cancer cells, but whether furanodiene can influence ER status is not clear. In this study, we confirmed that furanodiene down-regulated the ERα protein expression level and inhibited E2-induced estrogen response element (ERE)-driven reporter plasmid activity in ERα-positive MCF-7 cells. Actually, ERα-knockdown cells were more sensitive than ERα positive cells to furanodiene on the cytotoxicity effect. So the anti-cancer effects of furanodiene and non-steroidal agent in breast cancer cells still requires further investigation. Our results showed that furanodiene exposure could enhance growth inhibitory effects of doxorubicin in ERα-negative MDA-MB-231 cells and ERα-low expression 4T1 cells. However, furanodiene did not increase the cytotoxicity of doxorubicin in ERα-positive breast cancer cells, non-tumorigenic breast epithelial cells, macrophage cells, hepatocytes cells, pheochromocytoma cells and cardiac myoblasts cells. Furanodiene enhances the anti-cancer effects of doxorubicin in ERα-negative breast cancer cells through suppressing cell viability via inducing apoptosis in mitochondria-caspases-dependent and reactive oxygen species-independent manners. These results indicate that furanodiene may be a promising and safety natural agent for cancer adjuvant therapy in the future.

Topics: Amino Acid Chloromethyl Ketones; Antineoplastic Agents; Apoptosis; Breast; Breast Neoplasms; Doxorubicin; Drug Synergism; Epithelial Cells; Estrogen Receptor alpha; Furans; Gene Expression Regulation, Neoplastic; Hepatocytes; Heterocyclic Compounds, 2-Ring; Humans; Macrophages; MCF-7 Cells; Myoblasts; Pheochromocytoma; Reactive Oxygen Species

Telomerase is a protein-RNA enzyme complex that adds a six-base DNA sequence (TTAGGG) to the ends of chromosomes and thereby prevents their shortening. Reduced telomerase activity is associated with cell differentiation and accelerated cellular senescence, whereas increased telomerase activity is associated with cell transformation and immortalization. Because many types of cancer have been associated with reduced apoptosis, whereas cell differentiation and senescence have been associated with increased apoptosis, we tested the hypothesis that telomerase activity is mechanistically involved in the regulation of apoptosis. Levels of telomerase activity in cultured pheochromocytoma cells decreased prior to cell death in cells undergoing apoptosis. Treatment of cells with the oligodeoxynucleotide TTAGGG or with 3,3'-diethyloxadicarbocyanine, agents that inhibit telomerase activity in a concentration-dependent manner, significantly enhanced mitochondrial dysfunction and apoptosis induced by staurosporine, Fe2+ (an oxidative insult), and amyloid beta-peptide (a cytotoxic peptide linked to neuronal apoptosis in Alzheimer's disease). Overexpression of Bcl-2 and the caspase inhibitor zVAD-fmk protected cells against apoptosis in the presence of telomerase inhibitors, suggesting a site of action of telomerase prior to caspase activation and mitochondrial dysfunction. Telomerase activity decreased in cells during the process of nerve growth factor-induced differentiation, and such differentiated cells exhibited increased sensitivity to apoptosis. Our data establish a role for telomerase in suppressing apoptotic signaling cascades and suggest a mechanism whereby telomerase may suppress cellular senescence and promote tumor formation.

Topics: Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Base Sequence; Cell Differentiation; DNA Primers; Enzyme Inhibitors; PC12 Cells; Pheochromocytoma; Proto-Oncogene Proteins c-bcl-2; Rats; Telomerase