Chronic Activation of mTOR Complex 1 Is Sufficient to Cause Hepatocellular Carcinoma in Mice

Menon, Suchithra; Yecies, Jessica L.; Zhang, Hui H.; Howell, Jessica J.; Nicholatos, Justin W.; Harputlugil, Eylul; Bronson, Roderick T.; Kwiatkowski, David J.; Manning, Brendan D.

doi:10.1126/scisignal.2002739

Cited by 167 publications

(162 citation statements)

References 103 publications

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“…Consistent with this notion, activation of AKT has been found in 40%-60% of human HCC samples (12) and is a risk factor for early recurrence and poor prognosis (13). More importantly, recent studies using knockout mice showed that mTOR activation was sufficient to cause HCC in rodent models (14), indicating the pivotal role of mTOR signaling in HCC. The allosteric mTORC1 inhibitor RAD001/everolimus has been tested in a randomized, placebo-controlled phase III clinical trial in patients with advanced HCC who failed sorafenib (EVOLVE-1; ref.…”

Section: Introductionsupporting

confidence: 50%

Loss of Tuberous Sclerosis Complex 2 (TSC2) Is Frequent in Hepatocellular Carcinoma and Predicts Response to mTORC1 Inhibitor Everolimus

Huynh

Hao²,

Chan

et al. 2015

Molecular Cancer Therapeutics

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Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide and hyperactivation of mTOR signaling plays a pivotal role in HCC tumorigenesis. Tuberous sclerosis complex (TSC), a heterodimer of TSC1 and TSC2, functions as a negative regulator of mTOR signaling. In the current study, we discovered that TSC2 loss-of-function is common in HCC. TSC2 loss was found in 4 of 8 HCC cell lines and 8 of 28 (28.6%) patient-derived HCC xenografts. TSC2 mutations and deletions are likely to be the underlying cause of TSC2 loss in HCC cell lines, xenografts, and primary tumors for most cases. We further demonstrated that TSC2-null HCC cell lines and xenografts had elevated mTOR signaling and, more importantly, were significantly more sensitive to RAD001/everolimus, an mTORC1 inhibitor. These preclinical findings led to the analysis of TSC2 status in HCC samples collected in the EVOLVE-1 clinical trial of everolimus using an optimized immunohistochemistry assay and identified 15 of 139 (10.8%) samples with low to undetectable levels of TSC2. Although the sample size is too small for formal statistical analysis, TSC2-null/low tumor patients who received everolimus tended to have longer overall survival than those who received placebo. Finally, we performed an epidemiology survey of more than 239 Asian HCC tumors and found the frequency of TSC2 loss to be approximately 20% in Asian HBV þ HCC. Taken together, our data strongly argue that TSC2 loss is a predictive biomarker for the response to everolimus in HCC patients. Mol Cancer Ther; 14(5); 1224-35. Ó2015 AACR.

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Section: Introductionsupporting

confidence: 50%

Loss of Tuberous Sclerosis Complex 2 (TSC2) Is Frequent in Hepatocellular Carcinoma and Predicts Response to mTORC1 Inhibitor Everolimus

Huynh

Hao²,

Chan

et al. 2015

Molecular Cancer Therapeutics

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“…In another study done by Villanueva et al [38] that aimed at analyzing 314 HCC samples for mutation detection, DNA copy number changes, determination of mRNA levels and protein by immunohistochemistry reported that PTEN the tumor suppressor that inhibits the mTOR pathway, is inactivated in around half of HCC tumors. Furthermore, the importance of mTOR in hepatocarcinogenesis has been shown in a mouse model with a liver-specific knockout of the negative regulator of mTOR, tuberous sclerosis complex 1 (Tsc1) resulted in chronic mTOR activation and led to the sporadic and sequential development of histological features associated with HCC [39]. Taken together, blockade of PI3K/AKT/mTOR signaling appears to be an attractive therapeutic strategy in HCC.…”

Section: Pi3k/akt/mtor Pathwaymentioning

confidence: 99%

Potential Molecular Targets and Drugs for Treatment of Hepatocellular Carcinoma

Mekuria¹,

Abdi²

2017

J Cancer Sci Ther

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Hepatocellular Carcinoma (HCC) is a common type of primary liver cancer. According to the recent world cancer report, the disease ranked as the sixth most common cancer worldwide and the third largest cause of cancer-related death. Deregulation of numerous signaling pathways have been implicate in pathogenesis of HCC, including IGF, EGF/TGF, HGF/cMet, WNT, Hedgehog, notch, hippo, VEGF, PDGF, and FGF. Besides, intracellular mediators such as MAPK and PI3K/AKT/mTOR play a role in HCC development and progression. Currently sorafenib is the only molecularly targeted drug available to treat advanced HCC. It only extends survival by a matter of months. Moreover, there is no alternative agent for patients progressing under treatment with sorafenib. Thus, there remains a critical need for both continued molecular characterization and aggressive drug development. This review provided and updated appraisal of the deregulated signaling and epigenetic pathways, targeted therapeutics that is being investigated and possible challenges in drug development for HCC. Nevertheless, c-Met over-expression was reported to be related to increased metastatic potential and poor prognosis in patients with HCC, providing a rationale for its therapeutic inhibition [26]. Pathways related to neo-angiogenesisHigh vascularization is a hallmark of human HCC [8]. This angiogenesis process relies on autocrine and paracrine interactions between tumor cells, vascular endothelial cells, and pericytes. Tumor cells release pro-angiogenic factors in response to hypoxic conditions and nutrient deprivation and thus activate endothelial cells [27]. Activated endothelial cells break down extracellular matrix and basement membrane which result in a release of angiogenic factors which includes VEGF, FGF, PDGF, and TGF β [16]. These angiogenic factors in turn activate endothelial cells through TKR and their intracellular mediator's MAPK and PI3K/Akt/mTOR pathways, which lead to proliferation and migration of endothelial cells to form a new tubular structure and lumen for new vessels and finally, pericytes are activated and recruited to stabilize the new blood vessels [27,28]. has become a potential investigating area of research to identify target(s) to inhibit proliferation of HCC and metastasis. IGF pathwayThe pathway consists of circulating ligands IGF-I, IGF-II, and the receptor IGF-IR. It has been known for its involvement in the regulation of cell growth and energy metabolism [17]. According to studies, overexpression of IGF-II and IGF-IR has been implicated in cell proliferation and inhibition of apoptosis [18]. In support of this, low expression of IGF I and progressive increase in the level of expression of IGF-IR, IGF-II, and IGF substrates during the hepatocarcinogenesis process was detected at mRNA and protein level, which was associated with cell increased proliferation and reduced apoptosis has been observed in HCC cell lines and rat models as well as in human HCC samples [18]. Other studies also indicated that the major tumorpromoting e...

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“…In experimental models, knockout models of various proteins required for autophagy demonstrated increased cancers, including spontaneous hepatocellular carcinoma. [32][33][34][35] …”

Section: Prevention Of Tumorigenesismentioning

confidence: 99%

Autophagy Modulation As a Potential Therapeutic Target for Liver Diseases

Puri

Chandra

2014

Journal of Clinical and Experimental Hepatology

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Autophagy is a critical intracellular pathway which maintains cellular function by lysosomal degradation of damaged proteins and organelles besides elimination of invading pathogens. Its primary function is to prevent cell death. Autophagy has diverse physiological functions namely; starvation adaptation, prevention of tumorigenesis, energy homeostasis, intracellular quality control and degradation of abnormal intracellular protein aggregates. Understanding the molecular mechanisms of autophagy has given key insights into the pathogenesis of various diseases like Non Alcoholic Steato-Hepatitis, Hepatitis B and C infections, Alpha-1 antitrypsin deficiency and hepatocellular carcinoma. Pharmacological modulation of autophagy may have a therapeutic potential in management of these liver diseases. ( J CLIN EXP HEPATOL 2014;4:51-59) O urobros or Urobros is an ancient symbol depicting a serpent or a dragon eating its own tail, which symbolizes cyclicality in the sense of something recreating itself. In living organisms, cells and intracellular organelles need to be constantly remodeled and renewed. Autophagy is a term derived from Greek terminology for self-eating and signifies the process of cellular selfdigestion in which cytoplasmic components are degraded in lysosomes. Reminiscent of the serpent eating its own tail in the symbol of Ourobros, the cells are able to survive by using autophagy to remove damaged proteins and organelles, eliminate invading microbes and generate nutrients during starvation.After Metchnicoff, a Russian zoologist, first described phagocytosis, the role of lysosomes and autophagy in degrading cytoplasmic components has been elucidated. 1,2 The control of autophagy has been recently delineated by identification of over 30 Autophagy-related (ATG) genes. 3 Autophagy functions to prevent rather than promote cell death. Autophagy has effects of increased cytoprotection, decreased stem cell attrition, decreased oncogenic transformation, decreased dysfunctional mitochondria and decrease in dysfunctional aggregate prone proteins. 4

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Chronic Activation of mTOR Complex 1 Is Sufficient to Cause Hepatocellular Carcinoma in Mice

Cited by 167 publications

References 103 publications

Loss of Tuberous Sclerosis Complex 2 (TSC2) Is Frequent in Hepatocellular Carcinoma and Predicts Response to mTORC1 Inhibitor Everolimus

Loss of Tuberous Sclerosis Complex 2 (TSC2) Is Frequent in Hepatocellular Carcinoma and Predicts Response to mTORC1 Inhibitor Everolimus

Potential Molecular Targets and Drugs for Treatment of Hepatocellular Carcinoma

Autophagy Modulation As a Potential Therapeutic Target for Liver Diseases

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