RESUMO
Cisplatin is a common chemotherapeutic agent against ovarian cancer; however, drug resistance is a major limiting factor for its use in clinical treatment. The underlying mechanisms of cisplatin resistance in ovarian cancer have not yet been fully elucidated. Thus, this study aimed to elucidate some of the mechanisms responsible for resistance to cisplatin in ovarian cancer. The results demonstrated that the cisplatinresistant human ovarian cancer cell lines, SKOV3/DDP and A2780/DDP, exhibited higher autophagy levels than the control ovarian cancer cell lines, SKOV3 and A2780. Moreover, autophagy inhibition by 3methyladenine or shRNA against autophagyrelated gene (ATG)5 potentiated the cytotoxicity induced by cisplatin, whereas autophagy induction by rapamycin (Rapa) increased cell survival. Exposure to cisplatin induced an upregulation in the expression of thioredoxinrelated protein of 14 kDa (TRP14). Furthermore, TRP14 knockdown or overexpression decreased or increased the autophagy response and cisplatin resistance, and this effect was reversed by treatment with Rapa or ATG5 knockdown. The findings of this study also suggested that TRP14 induced autophagy and chemoresistance via the 5'AMPactivated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/p70S6K signaling pathway. Importantly, the data from a tissue array revealed a positive association between TRP14 and Beclin1 in human ovarian cancer and marginal tissues. These findings have identified, for the first time, to the best of our knowledge, that TRP14 induces autophagy and consequently cisplatin resistance in ovarian cancer cells via the AMPK/mTOR/p70S6K signaling pathway. This in turn renders TRP14 as a potential predictor or target in ovarian cancer therapy.
RESUMO
The pro-inflammatory cytokine interleukin 6 (IL-6), via activating its downstream JAK/STAT3 and Ras/ERK signaling pathways, is involved in cell growth, proliferation and anti-apoptotic activities in various malignancies. To screen inhibitors of IL-6 signaling, we constructed a STAT3 and ERK dual-pathway responsive luciferase reporter vector (Co.RE). Among several candidates, the natural compound 20(S)-25-methoxyl-dammarane-3ß, 12ß, 20-triol (25-OCH3-PPD, GS25) was identified to clearly inhibit the luciferase activity of Co.RE. GS25 was confirmed to indeed inhibit activation of both STAT3 and ERK pathways and expression of downstream target genes of IL-6, and to predominantly decrease the viability of HepG2 cells via induction of cell cycle arrest and apoptosis. Interestingly, GS25 showed preferential inhibition of HepG2 cell viability relative to normal liver L02 cells. Further investigation showed that GS25 could not induce apoptosis and block activation of STAT3 and ERK pathways in L02 cells as efficiently as in HepG2 cells, which may result in differential effects of GS25 on malignant and normal liver cells. In addition, GS25 was found to potently suppress the expression of endogenous STAT3 at a higher concentration and dramatically induce p38 phosphorylation in HepG2 cells, which could mediate its anti-cancer effects. Finally, we demonstrated that GS25 also inhibited tumor growth in HepG2 xenograft mice. Taken together, these findings indicate that GS25 elicits its anti-cancer effects on HepG2 cells through multiple mechanisms and has the potential to be used as an inhibitor of IL-6 signaling. Thus, GS25 may be developed as a treatment for hepatocarcinoma with low toxicity on normal liver tissues as well as other inflammation-associated diseases.
Assuntos
Antineoplásicos Fitogênicos/farmacologia , Regulação Neoplásica da Expressão Gênica , Ginsenosídeos/farmacologia , Hepatoblastoma/tratamento farmacológico , Neoplasias Hepáticas/tratamento farmacológico , Fator de Transcrição STAT3/genética , Animais , Antineoplásicos Fitogênicos/síntese química , Apoptose/efeitos dos fármacos , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/genética , Proliferação de Células/efeitos dos fármacos , Feminino , Genes Reporter , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Ginsenosídeos/química , Células Hep G2 , Hepatoblastoma/genética , Hepatoblastoma/metabolismo , Hepatoblastoma/patologia , Humanos , Interleucina-6/genética , Interleucina-6/metabolismo , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Luciferases/genética , Luciferases/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Camundongos Nus , Fator de Transcrição STAT3/agonistas , Fator de Transcrição STAT3/metabolismo , Carga Tumoral/efeitos dos fármacos , Ensaios Antitumorais Modelo de Xenoenxerto , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
The existing acoustic emission (AE) source location methods assume that acoustic waves propagate along straight lines, and the source location is determined by average wave velocity. Because of the heterogeneity of materials, location results often fail to meet the accuracy requirement. For this reason, an AE source location method considering refraction in different media was proposed in this paper. According to sensor coordinates, the arrival time of acoustic waves, the velocities of acoustic waves in two kinds of media, the space-time relation equations of the AE source point and the measuring point were established by the precise coordinates of the AE source based on Snell's law. The feasibility of the algorithm was verified by experiments, and the factors influencing location accuracy were also analysed. The results show that the algorithm proposed in this paper is applicable for both the same medium and different media, and the accuracy of localization is not affected by the ratio of wave velocities in two media or the distance from the AE source to the refraction surface.
