Characterisation of oncogenic pathways driving the pathogenesis of prostate cancer
As the leading cancer diagnosis in men, there is an urgent need to elucidate mechanisms underlying prostate cancer (PCa) progression and metastasis. Legumain (LGMN), an asparaginyl endopeptidase, is highly expressed in PCa and correlates with poor prognosis. LGMN is vital to PCa cell viability and migration, shown through RNAi targeting and selective drug inhibition. HSD17B4 was identified as a novel LGMN interactor through a BioID system, which employs promiscuous biotin labelling and subsequent mass spectrometry, and confirmed via co-immunoprecipitation in various models of PCa. Knockdown of LGMN and HSD17B4 is selectively cytotoxic to PCa cells, indicating that targeting of these two enzymes may provide potential for novel therapeutics. TBX2 is upregulated in a subset of PCa tumours and late-stage models of PCa. Stably overexpressing TBX2 PCa cells had no alteration in proliferation rate but increased migration and invasion. Depletion of TBX2 via siRNA causes inverse effects in PC3 cells, with upregulation of CST6, NDRG1 and p21WAF1, reducing viability and migration. TBX2 shRNA stable lines were also successfully generated with results mirroring siRNA depletion. Ch-IP qPCR assays confirmed TBX2 binds the promoters of CST6, E-cadherin, NDRG1 and p21WAF1 in PC3 cells. Co-immunoprecipitation demonstrated that TBX2 interacts with CoREST complex members LSD1 and ZNF217 and ChIP qPCR confirmed TBX2 shRNA reduced ZNF217 recruitment to E-cadherin and NDRG1 promoters. In accordance, targeting the LSD1/ZNF217 interaction via an allosteric LSD1 inhibitor phenocopied TBX2 knockdown in PCa cells. Effects of LSD1 inhibition, via SP2509, was demethylase independent and initiated a senescence phenotype in both C42B and PC3 cells. Indicating that TBX2 recruits the CoREST complex rather than direct repression to enact a repressive gene network in PCa to bypass senescence and enable EMT. Individual or combination inhibition of CoREST complex members attenuates TBX2 function and has exciting potential for the improved treatment of PCa.
TBX2, coREST complex, signalling, LEGUMAIN, EMT, prostate cancer, metastasis
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