This is an application for continuation of a project whose long-term goal is the identification of the mechanisms through which obesity and hypernutrition enhance cancer risk. Obesity manifests one of its strongest tumor-promoting effects in hepatocellular carcinoma (HCC), the major primary liver cancer, whose US incidence has increased by 300% during the past 20 years. This increase is due to the obesity epidemic that is still spreading throughout our country. We therefore chose to address the important and general question regarding the mechanisms by which obesity increase cancer risk by studying the relationships between obesity and HCC development. In the previous project period, we developed new models for studying obesity-induced HCC and used them to establish the role of inflammation and ER stress in the progression of non-alcoholic steatohepatitis (NASH) to HCC. During these studies, we had uncovered the key pathogenic function of the autophagy receptor and signaling adaptor p62/SQSTM1, a protein that accumulates in NASH and several other chronic liver diseases, all of which increase HCC risk. We have validated the relevance of p62/SQSTM1 to the pathogenesis of human HCC and shown that its elevated expression in the non-tumor liver provides a strong prediction of HCC recurrence after curative ablation. Since all of this work was done in collaboration with Dr. Jorge Moscat, a pioneer in studying p62 function, we have decided to formalize our joint effort and pursue a more in-depth investigation of p62 involvement in obesity-induced HCC through the multi-investigator R01 mechanism. We propose to further investigate how p62 exerts its HCC-inducing activity by defining the tumorigenic function of various p62 structural motifs that mediate its interactions with other proteins. In particular, we will focus on the role of NRF2, an activator of the anti-oxidant response, and mTORC1, a major metabolism regulating protein kinase complex, as downstream effectors of p62-dependent liver tumorigenesis. We will also conduct unbiased metabolomic analysis to decipher the role of NRF2- and mTORC1-regulated metabolic pathways in obesity-induced HCC development. In addition, we will use state-of-the-art high throughput screens to search for small molecule inhibitors that target p62-driven NRF2 and mTORC1 activation and thereby prevent obesity-induced HCC development or inhibit the growth and progression of such tumors. In addition to greatly improving our understanding of the mechanisms through which obesity induces HCC development, this investigation may lead to new preventive and therapeutic strategies.
In early studies we have identified the critical role of the autophagy receptor and signaling adaptor p62/SQSTM1 in the pathogenesis of obesity- and inflammation-induced hepatocellular carcinoma (HCC) in mice and men. We now propose in-depth studies into the mechanisms through which p62 drives HCC development, focusing on the roles of NRF2 and mTORC1 as p62 effectors. We will also develop small molecules that interfere with p62-driven NRF2 and mTORC1 activation and evaluate their ability to prevent obesity-induced HCC in appropriate mouse models.
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|Umemura, Atsushi; He, Feng; Taniguchi, Koji et al. (2016) p62, Upregulated during Preneoplasia, Induces Hepatocellular Carcinogenesis by Maintaining Survival of Stressed HCC-Initiating Cells. Cancer Cell 29:935-948|