NEUROENDOCRINE DIFFERENTIATION IN PROSTATE ADENOCARCINOMA

In this review, we will present some of the information that is known about neuroendocrine (NE) cells and differentiation in the prostate. We will then speculate on the potential role that NE differentiation in prostate carcinoma may play and how this differentiation may be clinically analysed and treated. The androgen-independent growth of prostate cancer can be caused by different mechanisms; one of these is receptor-specific paracrine or autocrine growth modulation of human prostatic cancer cells by neuropeptides secreted by NE cells. Our results affirm that different methods of androgen deprivation can influence the serum chromogranin A (CgA) levels to different extents in prostate cancer. In particular, bicalutamide produces a significantly lower increase in serum CgA compared with castration therapy. In the light of other evidence that supports a significant relationship between serum CgA levels, tissue CgA expression and NE activity, we hypothesise that bicalutamide may reduce the risk of NE cell hyperactivation in prostate cancer. It is important to determine whether increases in CgA levels and NE cell activation are associated with progression towards hormone-independent prostate cancer. We recently proposed as therapy of NE activation in hormone-independent prostate cancer, a combination of oestrogens and somatostatin analogues. The combination of ethinyl estradiol and lanreotide had a favourable toxicity profile, offered objective and symptomatic responses in patients with limited treatment options and refractoriness to conventional hormonal therapy strategies and, in particular, offered a median overall survival that was superior to the 10-month median survival in patients with hormone refractory disease. This combination therapy also sustains the novel concept in cancer treatment in which therapies may target not only cancer cells but also its microenvironment in combination, which can confer protection from apoptosis