Project description:Esophageal cancer is one of the most common cancers where TP53 is mutated frequently. Esophageal squamous cell carcinoma (ESCC) is the major subtype of esophageal cancer, and is one of the most lethal cancers worldwide. ESCC evolves often to lung metastasis, which is associated with a dismal prognosis. P53R175H (homologous to Trp53R172H in mice) is a common hot spot mutation. How metastasis is regulated by p53R175H in ESCC, or cancers in general, remains to be elucidated. To investigate p53R175H mediated molecular mechanisms, we utilized germline Trp53R172H/- mice, and generated esophageal specific Trp53-/- mice and Trp53+/+ mice treated with the 4-NQO esophageal-specific carcinogen (a common exposure in humans) to model ESCC. In the primary Trp53R172H/- tumor cell lines established from these mouse models, we depleted Trp53R172H (shTrp53) and observed a marked reduction in cell invasion in vitro and lung metastasis burden in a tail-vein injection model in comparing isogenic cells (shCtrl). Furthermore, to understand the molecular basis for mutant p53 driven lung metastasis, we performed bulk RNA-seq to compare gene expression profiles of metastatic and primary shCtrl and shTrp53 cells. We performed Gene Set Enrichment Analysis (GSEA) and identified the YAP-BIRC5 axis as a potential mediator of Trp53R172H mediated metastasis. As a target gene of YAP, BIRC5 encodes an anti-apoptotic protein, namely survivin. We demonstrate that survivin expression increases in the presence of Trp53R172H but not wild-type Trp53. Furthermore, depletion of survivin decreases Trp53R172H driven lung metastasis. Mechanistically, Trp53R172H but not wild-type Trp53, binds with YAP in ESCC cells, suggesting their cooperation to induce survivin expression. Furthermore, survivin high expression level is associated with increased metastasis in several GI cancer, suggesting that survivin may be a key regulator to metastasis. Taken together, this study unravels new insights into how mutant p53 mediates metastasis.

Project description:Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers with high mortality rate. Smoking is one of the established risk factors of ESCC. However, there is limited data on molecular alterations associated with cigarette smoke exposure in esophageal cells. Understanding the effects of cigarette smoke on esophageal squamous epithelial cells at a molecular level would lead to a better understanding of the pathobiology of ESCC which has implications for identification of early biomarkers and therapeutic targets. To investigate the effect of cigarette smoke exposure, we developed a cell line model where Het1A cells (non-neoplastic human esophageal epithelial cells) were chronically treated with cigarette smoke condensate (CSC) for 2 months, 4 months, 6 months and 8 months. We carried out comparative proteomic, phosphoproteomic and whole exome sequencing analyses on CSC treated and untreated cells. Increased cell proliferation and invasion of Het1A cells was observed after chronic exposure to cigarette smoke. Using quantitative proteomic and phosphoproteomic analyses, we identified 56 proteins and 296 phosphoproteins that showed differential expression. Bioinformatics analysis of differentially expressed proteins and phosphoproteins showed enrichment of molecules involved in DNA damage response pathway. Whole exome sequencing (WES) of CSC treated and untreated cells also revealed mutations and copy number alterations in genes associated with DNA damage response. By correlating WES, proteomic and phosphoproteomic results, we observed potential loss of function in HMGN2 and MED1 that were reported as potential tumor suppressors and are known to play important role in DNA damage response. We also observed decreased expression of HMGN2 in tissue section of ESCC. Overexpression of HMGN2 and MED1 lead to decreased proliferative and invasive ability of CSC treated cells. These findings suggest that cigarette smoke affects genes and proteins associated with DNA damage response pathways which might play a vital role in development of ESCC.

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Differential squamous cell fates elicited by NRF2 gain-of-function versus KEAP1 loss-of-function

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