RESUMO
Metastatic melanoma is the most aggressive of all skin cancers and is associated with poor prognosis owing to lack of effective treatments. 25-epi Ritterostatin GN1N is a novel antitumor agent with yet undefined mechanisms of action. We sought to delineate the antitumor mechanisms of 25-epi Ritterostatin GN1N in melanoma cells to determine the potential of this compound as a treatment for melanoma. Activation of the endoplasmic reticulum (ER) stress protein glucose-regulated protein 78 (GRP78) has been associated with increased melanoma progression, oncogenic signaling, drug resistance, and suppression of cell death. We found that 25-epi Ritterostatin GN1N induced cell death in melanoma cells at nanomolar concentrations, and this cell death was characterized by inhibition of GRP78 expression, increased expression of the ER stress marker CHOP, loss of mitochondrial membrane potential, and lipidation of the autophagy marker protein LC3B. Importantly, normal melanocytes exhibited limited sensitivity to 25-epi Ritterostatin GN1N. Subsequent in vivo results demonstrated that 25-epi Ritterostatin GN1N reduced melanoma growth in mouse tumor xenografts and did not affect body weight, suggesting minimal toxicity. In summary, our findings indicate that 25-epi Ritterostatin GN1N causes ER stress and massive autophagy, leading to collapse of mitochondrial membrane potential and cell death in melanoma cells, with minimal effects in normal melanocytes. Thus, 25-epi Ritterostatin GN1N is a promising anticancer agent that warrants further investigation.
Assuntos
Proteínas de Choque Térmico/genética , Melanoma/tratamento farmacológico , Proteínas Associadas aos Microtúbulos/biossíntese , Compostos de Espiro/administração & dosagem , Esteroides/administração & dosagem , Fator de Transcrição CHOP/biossíntese , Animais , Antineoplásicos/administração & dosagem , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Linhagem Celular Tumoral , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Retículo Endoplasmático/efeitos dos fármacos , Chaperona BiP do Retículo Endoplasmático , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Proteínas de Choque Térmico/biossíntese , Humanos , Melanoma/genética , Melanoma/patologia , Camundongos , Proteínas Associadas aos Microtúbulos/genética , Fator de Transcrição CHOP/genética , Ensaios Antitumorais Modelo de XenoenxertoAssuntos
Antineoplásicos/síntese química , Macrolídeos/síntese química , Tetra-Hidronaftalenos/síntese química , Antineoplásicos/química , Antineoplásicos/toxicidade , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Desenho de Fármacos , Células HCT116 , Células HL-60 , Células HT29 , Humanos , Macrolídeos/química , Macrolídeos/toxicidade , Tetra-Hidronaftalenos/química , Tetra-Hidronaftalenos/toxicidadeRESUMO
3ß,16ß,17α-Trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-ß-D-xylopyranosyl)-(1â3)-2-O-acetyl-α-L-arabinopyranoside (OSW-1) is a natural product with potent antitumor activity against various types of cancer cells, but the exact mechanisms of action remain to be defined. In this study, we showed that OSW-1 effectively killed leukemia cells at subnanomolar concentrations through a unique mechanism by causing a time-dependent elevation of cytosolic Ca(2+) prior to induction of apoptosis. A mechanistic study revealed that this compound inhibited the sodium-calcium exchanger 1 on the plasma membrane, leading to an increase in cytosolic Ca(2+) and a decrease in cytosolic Na(+). The elevated cytosolic Ca(2+) caused mitochondrial calcium overload and resulted in a loss of mitochondrial membrane potential, release of cytochrome c, and activation of caspase-3. Furthermore, OSW-1 also caused a Ca(2+)-dependent cleavage of the survival factor GRP78. Inhibition of Ca(2+) entry into the mitochondria by the uniporter inhibitor RU360 or by cyclosporin A significantly prevented the OSW-1-induced cell death, indicating the important role of mitochondria in mediating the cytotoxic activity. The extremely potent activity of OSW-1 against leukemia cells and its unique mechanism of action suggest that this compound may be potentially useful in the treatment of leukemia.