ATDC mediates a TP63-regulated basal cancer invasive program.

Basal subtype cancers are deadly malignancies but the molecular events driving tumor lethality are not completely understood. Ataxia-telangiectasia group D complementing gene (ATDC, also known as TRIM29), is highly expressed and drives tumor formation and invasion in human bladder cancers but the factor(s) regulating its expression in bladder cancer are unknown. Molecular subtyping of bladder cancer has identified an aggressive basal subtype, which shares molecular features of basal/squamous tumors arising in other organs and is defined by activation of a TP63-driven gene program. Here, we demonstrate that ATDC is linked with expression of TP63 and highly expressed in basal bladder cancers. We find that TP63 binds to transcriptional regulatory regions of ATDC and KRT14 directly, increasing their expression, and that ATDC and KRT14 execute a TP63-driven invasive program. In vivo, ATDC is required for TP63-induced bladder tumor invasion and metastasis. These results link TP63 and the basal gene expression program to ATDC and to aggressive tumor behavior. Defining ATDC as a molecular determinant of aggressive, basal cancers may lead to improved biomarkers and therapeutic approaches.

ATDC/TRIM29 Drives Invasive Bladder Cancer Formation through miRNA-Mediated and Epigenetic Mechanisms.

Bladder cancer is a common and deadly malignancy but its treatment has advanced little due to poor understanding of the factors and pathways that promote disease. ATDC/TRIM29 is a highly expressed gene in several lethal tumor types, including bladder tumors, but its role as a pathogenic driver has not been established. Here we show that overexpression of ATDC in vivo is sufficient to drive both noninvasive and invasive bladder carcinoma development in transgenic mice. ATDC-driven bladder tumors were indistinguishable from human bladder cancers, which displayed similar gene expression signatures. Clinically, ATDC was highly expressed in bladder tumors in a manner associated with invasive growth behaviors. Mechanistically, ATDC exerted its oncogenic effects by suppressing miR-29 and subsequent upregulation of DNMT3A, leading to DNA methylation and silencing of the tumor suppressor PTEN. Taken together, our findings established a role for ATDC as a robust pathogenic driver of bladder cancer development, identified downstream effector pathways, and implicated ATDC as a candidate biomarker and therapeutic target.

Oncogenic fusion protein EWS-FLI1 is a network hub that regulates alternative splicing.

The synthesis and processing of mRNA, from transcription to translation initiation, often requires splicing of intragenic material. The final mRNA composition varies based on proteins that modulate splice site selection. EWS-FLI1 is an Ewing sarcoma (ES) oncoprotein with an interactome that we demonstrate to have multiple partners in spliceosomal complexes. We evaluate the effect of EWS-FLI1 on posttranscriptional gene regulation using both exon array and RNA-seq. Genes that potentially regulate oncogenesis, including CLK1, CASP3, PPFIBP1, and TERT, validate as alternatively spliced by EWS-FLI1. In a CLIP-seq experiment, we find that EWS-FLI1 RNA-binding motifs most frequently occur adjacent to intron-exon boundaries. EWS-FLI1 also alters splicing by directly binding to known splicing factors including DDX5, hnRNP K, and PRPF6. Reduction of EWS-FLI1 produces an isoform of γ-TERT that has increased telomerase activity compared with wild-type (WT) TERT. The small molecule YK-4-279 is an inhibitor of EWS-FLI1 oncogenic function that disrupts specific protein interactions, including helicases DDX5 and RNA helicase A (RHA) that alters RNA-splicing ratios. As such, YK-4-279 validates the splicing mechanism of EWS-FLI1, showing alternatively spliced gene patterns that significantly overlap with EWS-FLI1 reduction and WT human mesenchymal stem cells (hMSC). Exon array analysis of 75 ES patient samples shows similar isoform expression patterns to cell line models expressing EWS-FLI1, supporting the clinical relevance of our findings. These experiments establish systemic alternative splicing as an oncogenic process modulated by EWS-FLI1. EWS-FLI1 modulation of mRNA splicing may provide insight into the contribution of splicing toward oncogenesis, and, reciprocally, EWS-FLI1 interactions with splicing proteins may inform the splicing code.

Lack of functional pRb results in attenuated recovery of mRNA synthesis and increased apoptosis following UV radiation in human breast cancer cells.

Lack of functional pRb results in attenuated recovery of mRNA synthesis and increased apoptosis following UV radiation in human breast cancer cells. We have previously demonstrated that a human breast cancer cell line, MDA-MB-468, which lacks the retinoblastoma protein (pRb), is particularly sensitive to low doses of ultraviolet (UV) radiation. These cells are 15-20-fold more sensitive to UV radiation than cells with wild-type pRb. In order to understand the mechanisms of the high apoptotic response of MDA-MB-468 cells to UV radiation, we examined the effects of UV on these cells with regards to both membrane-mediated events and DNA damage. We found that MDA-MB-468 cells were resistant to all ligand-induced death receptor signaling. In addition, although UV activated caspase 8 in MDA-MB-468 cells, a peptide inhibitor of caspase 8 failed to inhibit UV-induced apoptosis. We then tested the possibility that nuclear events mediated the enhanced sensitivity to UV-induced apoptosis in these cells. Unlike UV-resistant cells, MDA-MB-468 cells were unable to recover mRNA synthesis after 5 J/m2 UVC. We also found that the pRb-null DU-145 cells similarly had attenuated recovery of mRNA synthesis after UV radiation. In UV-resistant cells with wild-type pRb, the inactivation of pRb with HPV-16 E7 resulted in significant inhibition in their ability to recover mRNA synthesis and increased levels of apoptosis following UV radiation. Furthermore, pRb-null cells were deficient in repair of UV radiation-induced DNA damage. These data suggest that the sensitivity of MDA-MB-468 cells to UV radiation is due to defects in repair of DNA damage and recovery of mRNA synthesis rather than to membrane death receptor pathways. Inactivation of pRb may contribute to an increased sensitivity to UV radiation by attenuating repair of DNA lesions and recovery of mRNA synthesis following UV radiation.