Resistance to androgen receptor signaling is arguably the principal hallmark of lethal prostate cancer. Several mechanisms account for this resistance, including mutations in the AR, restoration of signaling downstream of the pharmacological blocking and activation of alternative oncogenic pathways.
We used the Nkx3.1CreERT2/+; Ptenfloxed/floxed; p53floxed/floxed (NPp53) mice that develop CRPC upon castration and undergo neuroendocrine differentiation with anti-AR treatment to isolate Enzalutamide resistance prostate cancer cells.
Recently, we showed that activation of the chromatin remodeler Nsd2 is required for PCa metastasis and is strongly associated to tumor progression, and that its silencing markedly reduced the metastatic burden and increased survival. Our current data indicates that Nsd2 silencing sensitizes PCa cells to anti-AR treatment. Nsd2 KO using CRISPR/Cas9 resulted in a markedly enhanced efficacy of Enzalutamide and a significant reduction of AR transcriptional activity with either Enzalutamide or Abiraterone using two different reporter assays. Next, To identify Nsd2-dependent AR co-regulators we immunoprecipitated chromatin-bound endogenous AR in NPp53 cells and NPp53-Nsd2KO and performed nano-LC-MS/MS mass spectrometry on the purified peptide mix. In particular, data indicates that AR association with SWI/SNF members is stronger in the absence of Nsd2, suggesting that Nsd2 overexpression might impair AR interaction to the SWI/SNF complex. We next tested whether Nsd2 in fact binds SWI/SNF subunits by co-immunoprecipitation in the NPp53 cells and whether BAF155, BAF170 and BRG1 association to AR increases in the absence of Nsd2. As suspected, there is a remarkable increase in the binding of AR to SWI/SNF subunits BAF155, BAF170 and BRG1 in the absence of Nsd2.
Together, our data suggests that the mechanisms by which Nsd2 overexpression drives aggressive castration resistant and androgen independent PCa may be in part through destabilizing the AR-SWI/SNF interaction and altering the specificity of the AR cistrome. Ongoing work will further elucidate this by analyzing chromatin accessibility data coupled with transcriptomics and ChIPseq data for the AR and the BAF170, BAF155 and Brg1 SWI/SNF subunits.
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All authors have declared no conflicts of interest.