Project description:The TMPRSS2-ERG gene fusion is the most frequent alteration observed in human prostate cancer but its role in disease progression is still debated. In this study, we uncovered a novel molecular mechanism promoting progression in ERG-fusion positive prostate cancer. We show that ERG is methylated by Enhancer of zest homolog 2 (EZH2) at a specific lysine residue (K362) located within the internal auto-inhibitory domain. Mechanistically, K362 mono- methylation prevents intra-domain interactions, favors DNA binding and promotes ERG transcriptional and oncogenic activity in cellular and mouse models. Consistently with the involvement in ERG oncogenesis, we found that K362 methylation was associated with disease progression in ERG transgenic mouse models and was enhanced by PTEN deficiency and AKT activation, which promoted EZH2 substrate switching from histone H3K27 to ERG. Conversely, EZH2 inhibition blocked ERG methylation along with ERG-induced transcriptional and phenotypic reprogramming in cell cultures and ERG/PTEN mice. We found that ERG and EZH2 co-occupy several genomic regions forming prevalently co-activating complexes. The network of ERG/EZH2 co-regulated target genes was enriched of functionally aggressive features and was associated preferentially with concomitant ERG gain and PTEN loss, castration-resistance and adverse clinical outcome in prostate cancer patients. Collectively, these findings identify ERG methylation as a novel post-translational modification sustaining disease progression in ERG-positive prostate cancers. Our data also provide an attractive rationale for developing molecularly targeted therapeutics to antagonize ERG oncogenic activity.
Project description:Bernasocchi T, El Tekle G, Bolis M, Svinkina T, Zoma M, Rinaldi A, Ceserani V, Janouskova H, Schram P, Carbone G, Alimonti A, Moch H, Carr SA, Udeshi ND, Theurillat JP. 2018.
While the co-operation of cancer driver genes in tumorigenesis has been studied, little is known about the interplay of driver mutations that never co-occur within the same cancer cells. The latter scenario has been identified in prostate cancer where recurrent gene fusions involving the oncogenic ERG transcription factor and point mutations in the ubiquitin ligase adaptor SPOP are strictly mutually exclusive. Nevertheless, the underlying basis of this observation is poorly understood. Here, we show that ERG and mutant SPOP, even though oncogenic on their own, are together synthetic sick. At the molecular level, both driver genes inhibit each other in a reciprocal manner. In ERG-driven tumors, wild type SPOP is required to dampen androgen receptor (AR) signaling and sustain ERG activity in part through its ability to degrade the bromodomain histone reader ZMYND11. Consequently, loss-of-function mutations in SPOP unleash excessive AR signaling and reduce ERG function. Conversely, oncogenic androgen receptor signaling driven by mutant SPOP is repressed by ERG. The incompatibility of mutant SPOP and ERG may help to understand why SPOP mutant tumors frequently harbor gene deletions in the chromatin-modifying enzyme CHD1. We find that mutant SPOP promotes the generation of ERG rearrangements in a CHD1-dependent manner. Thus, CHD1 gene deletions may protect SPOP-mutant tumors from ERG-mediated growth inhibition. Taken together, our findings reveal the existence of divergent and incompatible paths towards prostate cancer that converge on SPOP function.
Project description:The ERG gene belongs to the ETS family of transcription factors and has been found involved in atypical chromosomal rearrangements in several cancers. To gain insight into the oncogenic activity of ERG, we compared the gene expression profile of NIH-3T3 cells stably expressing the coding regions of the three main ERG oncogenic fusions: TMPRSS2/ERG (tERG), EWS/ERG and FUS/ERG,. We found that all the three ERG fusions significantly up-regulate PIM-1 expression in the NIH-3T3 cell line. PIM-1 is a serine/threonine kinase frequently over-expressed in cancers of haematological and epithelial origin. We show here that tERG expression induces PIM-1 in the non-malignant prostate cell line RWPE-1, strengthening the relation between tERG and PIM-1 up-regulation in the initial stages of prostate carcinogenesis. Silencing of tERG reversed PIM-1 induction. A significant association between ERG and PIM-1 expression in clinical prostate carcinoma specimens was found, suggesting that such a mechanism may be relevant in vivo. Chromatin Immunoprecipitation experiments showed that tERG directly binds to PIM-1 promoter in the RWPE-1 prostate cell line, suggesting that tERG could be a direct regulator of PIM-1 expression. The up-regulation of PIM-1 induced by tERG over-expression significantly modified CyclinB1 levels and increased the percentage of aneuploid cells in the RWPE-1 cell line after 24hrs of taxane-based treatment. Here we provide the first evidence for an ERG-mediated PIM-1 up-regulation in prostate cells in vitro and in vivo, suggesting a direct effect of ERG transcriptional activity in the alteration of genetic stability. NIH-3T3 cells stably expressing the coding regions of the three main ERG oncogenic fusions: TMPRSS2/ERG (tERG), EWS/ERG and FUS/ERG together with the empty vector where profiled in triplicate. Quality control using NUSE and RLE plots identified one array as problematic (R540_TMP-ERG_P1) which was removed.