Project description:Genetic lesions drive cancer development and progression, and understanding their origins will reveal the mechanisms of carcinogenesis. We showed that murine FAM72A promotes mutagenic DNA repair during antibody maturation by acting as a substrate adaptor of the CTLHMKLN1 E3 ligase to induce the proteasome degradation of Uracil DNA glycosylase 2 (UNG2), a pivotal enzyme of the base excision repair. In humans, the FAM72 gene has expanded to include four paralogues named FAM72A-D. Bioinformatic studies suggested that the human FAM72 genes are overexpressed in a broad range of cancers. However, the functional roles of FAM72A-D in human biology and cancer are unknown. Here, we show that FAM72 family members are minimally expressed in most healthy tissues except for thymus, and that FAM72A, B and D are overexpressed in primary tumorigenic tissues. Human FAM72 expression inversely correlates with UNG2 protein level in human cell lines and primary tumorigenic tissues suggesting that human FAM72 promotes UNG2 degradation. However, only FAM72A is able to bind to and induce UNG2 degradation in human cells. Our results suggest that the ability of FAM72A to induce UNG2 degradation contributes to neoplasia in a variety of cancer types by promoting mutagenic repair of genomic dUs.
Project description:Prostate cancer is the most common male cancer and androgen receptor (AR) is the major driver of the disease. Here we show that Enoyl-CoA delta isomerase 2 (ECI2) is a novel AR-target that promotes prostate cancer cell survival. Increased ECI2 expression predicts mortality in prostate cancer patients (p=0.0086). ECI2 encodes for an enzyme involved in lipid metabolism, and we use multiple metabolite profiling platforms and RNA-seq to show that inhibition of ECI2 expression leads to decreased glucose utilization, accumulation of fatty acids and down-regulation of cell cycle related genes. In normal cells, decrease in fatty acid degradation is compensated by increased consumption of glucose, and here we demonstrate that prostate cancer cells are not able to respond to decreased fatty acid degradation. Instead, prostate cancer cells activate incomplete autophagy, which is followed by activation of the cell death response. Finally, we identified a clinically approved compound, perhexiline, which inhibits fatty acid degradation, and replicates the major findings for ECI2 knockdown. This work shows that prostate cancer cells require lipid degradation for survival and identifies a small molecule inhibitor with therapeutic potential.
Project description:Liver cancer claims over 800,000 human deaths each year. Liver cancer is notoriously refractory to conventional therapeutics. Further insight into the etiology carries promise for innovative diagnostics and therapeutics. Tumor progression is governed by interplay between tumor promoting genes and suppressor genes. BRD4, an acetyl-lysine binding protein, plays a critical role in development and human diseases. In many cancer types, BRD4 is overexpressed and promotes activation of a pro-tumor gene network. But the underlying mechanism for BRD4 overexpression remains elusive. As BRD4 has risen as a promising therapeutic target, to understand the mechanism regulating BRD4 protein level will shed insight into BRD4-targeting therapeutics. In this study, we find BRD4 protein level in liver cancer is significantly regulated by P53, the most frequently dysregulated tumor suppressor. We identify a strong negative correlation between protein levels of P53 and BRD4 in liver cancer. We then show P53 promotes BRD4 protein degradation. Mechanistically, P53 represses the transcription of USP1, a deubiquitinase, through P21-RB. We show USP1 is a deubiquitinase of BRD4, which increases its stability. We show the pro-tumor role of USP1 is partially mediated by BRD4 and the USP1-BRD4 axis upholds expression of a group of cancer-related genes. In summary, we identify a functional P53-P21-RB-USP1-BRD4 axis in liver cancer.
Project description:<p><b>Reprinted from Roberts et al. "An APOBEC cytidine deaminase mutagenesis pattern is widespread in human cancers", Nature Genetics, 45:970-976, 2013, with permission of Nature Publishing Group:</b></p> <p>Recent studies indicate that a subclass of APOBEC cytidine deaminases, which convert cytosine to uracil during RNA editing and retrovirus or retrotransposon restriction, may induce mutation clusters in human tumors. We show here that throughout cancer genomes APOBEC-mediated mutagenesis is pervasive and correlates with APOBEC mRNA levels. Mutation clusters in whole-genome and exome data sets conformed to the stringent criteria indicative of an APOBEC mutation pattern. Applying these criteria to 954,247 mutations in 2,680 exomes from 14 cancer types, mostly from The Cancer Genome Atlas (TCGA), showed a significant presence of the APOBEC mutation pattern in bladder, cervical, breast, head and neck, and lung cancers, reaching 68% of all mutations in some samples. Within breast cancer, the HER2-enriched subtype was clearly enriched for tumors with the APOBEC mutation pattern, suggesting that this type of mutagenesis is functionally linked with cancer development. The APOBEC mutation pattern also extended to cancer-associated genes, implying that ubiquitous APOBEC-mediated mutagenesis is carcinogenic.</p>