Targeting autophagy enhances sorafenib lethality for hepatocellular carcinoma via ER stress-related apoptosis.
TL;DR: Findings indicated that both ER stress and autophagy were involved in the cell death evoked by sorafenib in HCC cells, indicating that the combination of Autophagy modulation and molecular targeted therapy is a promising therapeutic strategy in treatment of HCC.
Abstract: Sorafenib, a potent multikinase inhibitor, has been recognized as the standard systemic treatment for patients with advanced hepatocellular carcinoma (HCC). However, the direct functional mechanism of tumor lethality mediated by sorafenib remains to be fully characterized, and the precise mechanisms of drug resistance are largely unknown. Here, we showed sorafenib induced both apoptosis and autophagy in human HCC cells through a mechanism that involved endoplasmic reticulum (ER) stress and was independent of the MEK1/2-ERK1/2 pathway. Upregulation of IRE1 signals from sorafenib-induced ER stress was critical for the induction of autophagy. Moreover, autophagy activation alleviated the ER stress-induced cell death. Inhibition of autophagy using either pharmacological inhibitors or essential autophagy gene knockdown enhanced cell death in sorafenib treated HCC cell lines. Critically, the combination of sorafenib with the autophagy inhibitor chloroquine produced more pronounced tumor suppression in HCC both ...
Citations
More filters
TL;DR: In this article, the authors define the context-specific role for autophagy in cancer and the mechanisms involved will be important to guide autoophagy-based therapeutic intervention, which can be either tumour suppressive or tumour promoting.
Abstract: Autophagy (also known as macroautophagy) captures intracellular components in autophagosomes and delivers them to lysosomes, where they are degraded and recycled. Autophagy can have two functions in cancer. It can be tumour suppressive through the elimination of oncogenic protein substrates, toxic unfolded proteins and damaged organelles. Alternatively, it can be tumour promoting in established cancers through autophagy-mediated intracellular recycling that provides substrates for metabolism and that maintains the functional pool of mitochondria. Therefore, defining the context-specific role for autophagy in cancer and the mechanisms involved will be important to guide autophagy-based therapeutic intervention.
1,449 citations
TL;DR: Understanding the novel function of autophagy may allow us to develop a promising therapeutic strategy to enhance the effects of chemotherapy and improve clinical outcomes in the treatment of cancer patients.
Abstract: Induction of cell death and inhibition of cell survival are the main principles of cancer therapy. Resistance to chemotherapeutic agents is a major problem in oncology, which limits the effectiveness of anticancer drugs. A variety of factors contribute to drug resistance, including host factors, specific genetic or epigenetic alterations in the cancer cells and so on. Although various mechanisms by which cancer cells become resistant to anticancer drugs in the microenvironment have been well elucidated, how to circumvent this resistance to improve anticancer efficacy remains to be defined. Autophagy, an important homeostatic cellular recycling mechanism, is now emerging as a crucial player in response to metabolic and therapeutic stresses, which attempts to maintain/restore metabolic homeostasis through the catabolic lysis of excessive or unnecessary proteins and injured or aged organelles. Recently, several studies have shown that autophagy constitutes a potential target for cancer therapy and the induction of autophagy in response to therapeutics can be viewed as having a prodeath or a prosurvival role, which contributes to the anticancer efficacy of these drugs as well as drug resistance. Thus, understanding the novel function of autophagy may allow us to develop a promising therapeutic strategy to enhance the effects of chemotherapy and improve clinical outcomes in the treatment of cancer patients.
968 citations
TL;DR: Increasing the understanding of how stromal components interact with cancer cells and the signaling pathways involved could help identify new therapeutic and chemopreventive targets.
589 citations
TL;DR: The tumorigenic and immunoregulatory effects of ER stress in cancer are discussed, and the concept of targeting ER stress responses to enhance the efficacy of standard chemotherapies and evolving cancer immunotherAPies in the clinic is explored.
529 citations
Cites background from "Targeting autophagy enhances sorafe..."
..., 2006), and this pathway facilitates sorafenib resistance in hepatocellular carcinoma cell lines (Shi et al., 2011)....
[...]
...Like PERK, IRE1a-JNK signaling can sustain autophagy (Ogata et al., 2006), and this pathway facilitates sorafenib resistance in hepatocellular carcinoma cell lines (Shi et al., 2011)....
[...]
TL;DR: Recent research related to autophagy and cancer therapy is discussed with a focus on how these processes may be manipulated to improve cancer therapy.
Abstract: Autophagy is the process by which cellular material is delivered to lysosomes for degradation and recycling. There are three different types of autophagy, but macroautophagy, which involves the formation of double membrane vesicles that engulf proteins and organelles that fuse with lysosomes, is by far the most studied and is thought to have important context-dependent roles in cancer development, progression, and treatment. The roles of autophagy in cancer treatment are complicated by two important discoveries over the past few years. First, most (perhaps all) anticancer drugs, as well as ionizing radiation, affect autophagy. In most, but not all cases, these treatments increase autophagy in tumor cells. Second, autophagy affects the ability of tumor cells to die after drug treatment, but the effect of autophagy may be to promote or inhibit cell death, depending on context. Here we discuss recent research related to autophagy and cancer therapy with a focus on how these processes may be manipulated to improve cancer therapy.
390 citations
References
More filters
TL;DR: There are striking variations in the risk of different cancers by geographic area, most of the international variation is due to exposure to known or suspected risk factors related to lifestyle or environment, and provides a clear challenge to prevention.
Abstract: Estimates of the worldwide incidence, mortality and prevalence of 26 cancers in the year 2002 are now available in the GLOBOCAN series of the International Agency for Research on Cancer. The results are presented here in summary form, including the geographic variation between 20 large "areas" of the world. Overall, there were 10.9 million new cases, 6.7 million deaths, and 24.6 million persons alive with cancer (within three years of diagnosis). The most commonly diagnosed cancers are lung (1.35 million), breast (1.15 million), and colorectal (1 million); the most common causes of cancer death are lung cancer (1.18 million deaths), stomach cancer (700,000 deaths), and liver cancer (598,000 deaths). The most prevalent cancer in the world is breast cancer (4.4 million survivors up to 5 years following diagnosis). There are striking variations in the risk of different cancers by geographic area. Most of the international variation is due to exposure to known or suspected risk factors related to lifestyle or environment, and provides a clear challenge to prevention.
17,730 citations
"Targeting autophagy enhances sorafe..." refers background in this paper
...Hepatocellular carcinoma (HCC) is the third cause of cancerrelated death globally, and the majority of patients with HCC die within one year of diagnosis.(1) Recently, sorafenib, a multikinase inhibitor of Raf/MEK/ERK signaling and the receptor tyrosine kinase, was shown to induce apoptosis and inhibit tumor proliferation as well as angiogenesis in a variety of tumors....
[...]
TL;DR: Data demonstrate that BAY 43-9006 is a novel dual action RAF kinase and VEGFR inhibitor that targets tumor cell proliferation and tumor angiogenesis.
Abstract: The RAS/RAF signaling pathway is an important mediator of tumor cell proliferation and angiogenesis. The novel bi-aryl urea BAY 43-9006 is a potent inhibitor of Raf-1, a member of the RAF/MEK/ERK signaling pathway. Additional characterization showed that BAY 43-9006 suppresses both wild-type and V599E mutant BRAF activity in vitro. In addition, BAY 43-9006 demonstrated significant activity against several receptor tyrosine kinases involved in neovascularization and tumor progression, including vascular endothelial growth factor receptor (VEGFR)-2, VEGFR-3, platelet-derived growth factor receptor beta, Flt-3, and c-KIT. In cellular mechanistic assays, BAY 43-9006 demonstrated inhibition of the mitogen-activated protein kinase pathway in colon, pancreatic, and breast tumor cell lines expressing mutant KRAS or wild-type or mutant BRAF, whereas non-small-cell lung cancer cell lines expressing mutant KRAS were insensitive to inhibition of the mitogen-activated protein kinase pathway by BAY 43-9006. Potent inhibition of VEGFR-2, platelet-derived growth factor receptor beta, and VEGFR-3 cellular receptor autophosphorylation was also observed for BAY 43-9006. Once daily oral dosing of BAY 43-9006 demonstrated broad-spectrum antitumor activity in colon, breast, and non-small-cell lung cancer xenograft models. Immunohistochemistry demonstrated a close association between inhibition of tumor growth and inhibition of the extracellular signal-regulated kinases (ERKs) 1/2 phosphorylation in two of three xenograft models examined, consistent with inhibition of the RAF/MEK/ERK pathway in some but not all models. Additional analyses of microvessel density and microvessel area in the same tumor sections using antimurine CD31 antibodies demonstrated significant inhibition of neovascularization in all three of the xenograft models. These data demonstrate that BAY 43-9006 is a novel dual action RAF kinase and VEGFR inhibitor that targets tumor cell proliferation and tumor angiogenesis.
3,749 citations
"Targeting autophagy enhances sorafe..." refers background in this paper
...Recently, sorafenib, a multikinase inhibitor of Raf/MEK/ERK signaling and the receptor tyrosine kinase, was shown to induce apoptosis and inhibit tumor proliferation as well as angiogenesis in a variety of tumors.(2,3) The molecular involvement of the Raf-1 and tyrosine kinase signaling pathways has been well established in the pathogenesis of HCC and provides a rationale for the investigation of sorafenib in HCC treatment....
[...]
TL;DR: The results suggest that the continuous clearance of diffuse cytosolic proteins through basal autophagy is important for preventing the accumulation of abnormal proteins, which can disrupt neural function and ultimately lead to neurodegeneration.
Abstract: Autophagy is an intracellular bulk degradation process through which a portion of the cytoplasm is delivered to lysosomes to be degraded. Although the primary role of autophagy in many organisms is in adaptation to starvation, autophagy is also thought to be important for normal turnover of cytoplasmic contents, particularly in quiescent cells such as neurons. Autophagy may have a protective role against the development of a number of neurodegenerative diseases. Here we report that loss of autophagy causes neurodegeneration even in the absence of any disease-associated mutant proteins. Mice deficient for Atg5 (autophagy-related 5) specifically in neural cells develop progressive deficits in motor function that are accompanied by the accumulation of cytoplasmic inclusion bodies in neurons. In Atg5-/- cells, diffuse, abnormal intracellular proteins accumulate, and then form aggregates and inclusions. These results suggest that the continuous clearance of diffuse cytosolic proteins through basal autophagy is important for preventing the accumulation of abnormal proteins, which can disrupt neural function and ultimately lead to neurodegeneration.
3,684 citations
"Targeting autophagy enhances sorafe..." refers background in this paper
...1168 Autophagy Volume 7 issue 10 pronounced cell toxicity, as exemplified by severe neurodegeneration in Atg5 and Atg7 mice.(33,34) Our data also demonstrated that inhibition of autophagic degradation resulted in ER stress potentiation....
[...]
TL;DR: The core protein machinery that is necessary to drive formation and consumption of intermediates in the macroautophagy pathway includes a ubiquitin-like protein conjugation system and a protein complex that directs membrane docking and fusion at the lysosome or vacuole.
Abstract: Macroautophagy is a dynamic process involving the rearrangement of subcellular membranes to sequester cytoplasm and organelles for delivery to the lysosome or vacuole where the sequestered cargo is degraded and recycled. This process takes place in all eukaryotic cells. It is highly regulated through the action of various kinases, phosphatases, and guanosine triphosphatases (GTPases). The core protein machinery that is necessary to drive formation and consumption of intermediates in the macroautophagy pathway includes a ubiquitin-like protein conjugation system and a protein complex that directs membrane docking and fusion at the lysosome or vacuole. Macroautophagy plays an important role in developmental processes, human disease, and cellular response to nutrient deprivation.
3,398 citations
"Targeting autophagy enhances sorafe..." refers background in this paper
...Unlike proteasomal degradation, the autophagic breakdown of substrates is not limited by steric considerations; therefore, autophagy can sequester and degrade entire organelles.(12) A number of anti-neoplastic therapies have been observed to induce autophagy in cancer cells....
[...]
TL;DR: It is found that mice lacking Atg7 specifically in the central nervous system showed behavioural defects, including abnormal limb-clasping reflexes and a reduction in coordinated movement, and died within 28 weeks of birth, and that impairment of autophagy is implicated in the pathogenesis of neurodegenerative disorders involving ubiquitin-containing inclusion bodies.
Abstract: Protein quality-control, especially the removal of proteins with aberrant structures, has an important role in maintaining the homeostasis of non-dividing neural cells. In addition to the ubiquitin-proteasome system, emerging evidence points to the importance of autophagy--the bulk protein degradation pathway involved in starvation-induced and constitutive protein turnover--in the protein quality-control process. However, little is known about the precise roles of autophagy in neurons. Here we report that loss of Atg7 (autophagy-related 7), a gene essential for autophagy, leads to neurodegeneration. We found that mice lacking Atg7 specifically in the central nervous system showed behavioural defects, including abnormal limb-clasping reflexes and a reduction in coordinated movement, and died within 28 weeks of birth. Atg7 deficiency caused massive neuronal loss in the cerebral and cerebellar cortices. Notably, polyubiquitinated proteins accumulated in autophagy-deficient neurons as inclusion bodies, which increased in size and number with ageing. There was, however, no obvious alteration in proteasome function. Our results indicate that autophagy is essential for the survival of neural cells, and that impairment of autophagy is implicated in the pathogenesis of neurodegenerative disorders involving ubiquitin-containing inclusion bodies.
3,349 citations
"Targeting autophagy enhances sorafe..." refers background in this paper
...1168 Autophagy Volume 7 issue 10 pronounced cell toxicity, as exemplified by severe neurodegeneration in Atg5 and Atg7 mice.(33,34) Our data also demonstrated that inhibition of autophagic degradation resulted in ER stress potentiation....
[...]