Background: Recent publications have shown patients with defects in the DNA mismatch repair (MMR) pathway driven by either MSH2 or MSH6 loss experience a significant increase in the incidence of prostate cancer. Moreover, this increased incidence of prostate cancer is accompanied by rapid disease progression and poor clinical outcomes. Methods and results: We show that androgen-receptor activation, a key driver of prostate carcinogenesis, can disrupt the MSH2 gene in prostate cancer. We screened tumours from two cohorts (recurrent/non-recurrent) of prostate cancer patients to confirm the loss of MSH2 protein expression and identified decreased MSH2 expression in recurrent cases. Stratifying the independent TCGA prostate cancer cohort for MSH2/6 expression revealed that patients with lower levels of MSH2/6 had significant worse outcomes, in contrast, endometrial and colorectal cancer patients with lower MSH2/6 levels. MMRd endometrial and colorectal tumours showed the expected increase in mutational burden, microsatellite instability and enhanced immune cell mobilisation but this was not evident in prostate tumours. Conclusions: We have shown that loss or reduced levels of MSH2/MSH6 protein in prostate cancer is associated with poor outcome. However, our data indicate that this is not associated with a statistically significant increase in mutational burden, microsatellite instability or immune cell mobilisation in a cohort of primary prostate cancers.
Bibliographical noteFunding Information:
Acknowledgements KC is supported by a Postgraduate Medical Research Scholarship from the Prostate Cancer Research Fund, Foundations for Surgery Research Scholarship from the Royal Australasian College of Surgeons, and the Research Training Program Scholarship from the Australian Commonwealth Government. NMC is supported by a Movember – Distinguished Gentleman’s Ride Clinician Scientist Award through Prostate Cancer Foundation of Australia’s Research Program. MK was supported by the Carlo Vaccari Scholarship and APCR. SM was supported by the David Mayor PhD. Scholarship from the Prostate Cancer Research Foundation, and by the Pamela Galli Single Cell & Computational Genomics Initiative. NK was supported by a PhD scholarship from Australian Prostate Cancer Research. PM was supported by a PhD scholarship from Australian Department of Health and Ageing to the Epworth Cancer Centre, Epworth Hospital. PG is supported by an Australian Government Research Training Program Scholarship. BP is supported by a Victorian Health and Medical Research Fellowship. This work was supported by NHMRC project grants 1104010 (CMH, AJC, NMC) and 1047581 (CMH, AJC, NMC), as well as a federal grant from the Australian Department of Health and Ageing to the Epworth Cancer Centre, Epworth Hospital (AJC, NMC, CMH). In carrying out this research, we received funding and support from Australian Prostate Cancer Research and the University of Melbourne, Australia.
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