Autophagy Activation in Hepatocellular Carcinoma Contributes to the Tolerance of Oxaliplatin via Reactive Oxygen Species Modulation

Abstract

Purpose: Understanding the roles of mammalian autophagy in cancer highlights recent advances in the pharmacologic manipulation of autophagic pathways as a therapeutic strategy for cancer. However, autophagy status and corresponding functions in hepatocellular carcinoma (HCC) after therapeutic stress remain to be clarified. This study was to determine whether the autophagic machinery could be activated after chemotherapy and the contribution of autophagy to tolerance of oxaliplatin in HCC.Experimental Design: Autophagy activation and cell death induced by oxaliplatin were examined in two HCC cell lines as well as in vivo using an HCC model in nude mice. HCC tissue samples with or without locoregional chemotherapy before surgery were also examined by immunohistochemical and electron microscopic analysis.Results: Autophagy was functionally activated in HCC cell lines and xenografts after oxaliplatin treatment. Suppression of autophagy using either pharmacologic inhibitors or RNA interference of essential autophagy gene enhanced cell death induced by oxaliplatin in HCC cells. Generation of reactive oxygen species has an important role in the induction of cell death by oxaliplatin in combination with autophagy inhibitors. Critically, the combination of oxaliplatin with autophagy inhibitor chloroquine resulted in a more pronounced tumor suppression in HCC xenografts. Furthermore, autophagy-specific protein LC3 and autophagic autophagosome formation were induced to a significantly higher level in HCC specimens that had been subjected to locoregional chemotherapy.Conclusions: Autophagy activation under therapy stress contributes to HCC tumor cell survival. Targeting the autophagy pathway is a promising therapeutic strategy to enhance the effects of chemotherapy and improve clinical outcomes in HCC patients.

Autophagy Inhibition for Chemosensitization and Radiosensitization in Cancer: Do the Preclinical Data Support This Therapeutic Strategy?

“…as indicated: (a) 25 mg/kg CQ (chloroquine), (b) 50 mg/kg CQ, (c) 100 mg/kg CQ, or (d) phosphate-buffered saline. The CQ doses chosen were based on the available literature, where studies have generally been performed using CQ at 50-60 mg/kg (Fu et al, 2009;Carew et al, 2010;Jiang et al, 2010;Wu et al, 2010;Ding et al, 2011;Lopez et al, 2011;Mirzoeva et al, 2011;Pan et al, 2011;Shi et al, 2011;Xu et al, 2011;Ghadimi et al, 2012;Godbole et al, 2012;Guo et al, 2012;Hu et al, 2012;Liang et al, 2012;Loehberg et al, 2012;Rao et al, 2012;Sasaki et al, 2012). Additional experiments were conducted where the mice were exposed to g-irradiation using a 137 Cs irradiator as indicated: (e) 5 Gy IR (ionizing radiation), (f) 10 Gy IR, (g) 15 Gy IR, (h) 10Gy IR 1 14 days CQ i.p.…”

“…An extensive number of studies in cell culture (for example, among many others, Paglin et al, 2001;Kanzawa et al, 2004;Boya et al, 2005;Zhao et al, 2005;Amaravadi et al, 2007;Apel et al, 2008;Qadir et al, 2008;Livesey et al, 2009;Solomon and Lee, 2009;Ma et al, 2011;Wilson et al, 2011;Bristol et al, 2012), as well as a limited number of studies in animal models (Fu et al, 2009;Carew et al, 2010;Jiang et al, 2010;Wu et al, 2010;Ding et al, 2011;Lopez et al, 2011;Mirzoeva et al, 2011;Pan et al, 2011;Shi et al, 2011;Xu et al, 2011;Ghadimi et al, 2012;Godbole et al, 2012;Guo et al, 2012;Hu et al, 2012;Liang et al, 2012;Loehberg et al, 2012;Rao et al, 2012;Sasaki et al, 2012), have been performed combining chloroquine or hydroxychloroquine with chemotherapeutic drugs or radiation. Furthermore, a number of clinical trials have been initiated to test this premise in patients (Sotelo et al, 2006;Solomon and Lee, 2009).…”

Intratumoral Heterogeneity: From Diversity Comes Resistance

“…Treatment of cancer cell lines with platinum chemotherapies induces autophagy and inhibition of autophagy sensitizes cell lines and xenograft tumors to treatment with these drugs (52,53). Likewise, irradiation also induces autophagy in cancer cell lines and siRNA-mediated inhibition of autophagy sensitizes resistant cells to irradiation (52)(53)(54)(55). Autophagy also contributes to kinase inhibitor resistance.…”

Combination of wogonin and sorafenib effectively kills human hepatocellular carcinoma cells through apoptosis potentiation and autophagy inhibition

“…As regard to response to chemotherapy, autophagy may mediate apoptosis to kill cancer cells or suppress apoptosis to contribute to chemoresistance in different circumstances. Thus, the manipulation of autophagy could be a useful strategy to improve the anticancer activity of therapeutics (11,12). Previous studies revealed that sorafenib is able to activate autophagy, which may confer a survival advantage to cancer cells and lead to sorafenib resistance.…”