Male infertility linked to prostate cancer risk
This Swedish study is interesting as it touches on some of the same territory as recent studies on vasectomy and incident of prostate cancer.
There has been some literature speculating on the action in immmune regulation of the products of the testicles previously which may relate to this somewhat.
This paper from the Journal of the National Cancer Institute covers the elevated risks of prostate cancer through vasectomy.
From what I have managed to gather the products of the sertoli cells seem to have an immune moderating influence that may be protective to the prostate, and that infertile or vasectomised men may not benefit from due to having an incomplete path from the vas defrens.
I have had a vasectomy and then a reversal, but would be interested if that still leaves me at any elevated risks.