Innervation density and types of nerves in prostate cancer

Innervation of cancerous tissue represents an important pathway enabling the nervous system to influence the processes associated with the initiation, progression, and metastasis of a neoplastic process. In the context of prostate cancer, several papers report the presence of innervation and its modulating effect on the cancer prognosis. However, most of the data are experimental, with limited information on human prostate cancer innervation. Morphometric analysis of archival prostate specimen immunohistochemistry with neural markers PGP9.5 and S100 showed a significant decrease of nerve density in the prostate cancer (n=44) compared to the normal prostate tissue (n=18) and benign prostatic hyperplasia (n=28). Sympathetic nerves were detected with TH, parasympathetic with VAChT, and sensory nerves with SP and CGRP protein detection. Dual immunofluorescence revealed numerous sympathetic nerves in normal prostate and benign prostatic hyperplasia, especially in the peripheral parts. Only a few parasympathetic nerves were found between the glands and in the peripheral parts of the prostate and benign hyperplasia. Sporadic positivity for sensory innervation was present only in approximately 1/10 of nerve fibers, especially in the larger nerves. The pattern of innervation in prostate cancer was analogous to that in normal prostate gland and benign prostatic hyperplasia but there was a significantly lower amount of all nerve types, especially in high-grade carcinoma cases. Although not significant, there was a tendency of decreasing innervation density with increasing Gleason score. Regarding the low density of nerves in prostate carcinoma, the significantly lower PCNA counts in nerves of the cancer specimens cannot be ascribed to lower proliferation activity. Our data confirmed the lower nerve density in the prostate cancer compared to the benign prostate tissue. We could not approve an increased nerve proliferation activity in prostate cancer. All nerve types, most the sympathetic, less the parasympathetic, and the sensory nerves, are present in prostate cancer. The highest nerve density at the periphery of the cancer tissue implies this to be the result of an expansive tumor growth. It is evident that the results of experimental prostate cancer models can be applied to human pathology only to a certain extent. The relation between the range of innervation and the biology of prostate cancer is very complex and will require more detailed information to be applied in therapeutic solutions.