Hormone Expression in Melanomas Related to Tumor Angiogenesis

Abstract

Background: Vicarious production of pituitary hormones by malignant tumors is a well known phenomenon. Prolactin [PRL], human growth hormone [HGH], adenocorticotropic hormone [ACTH] and alpha-melanocyte stimulating hormone [α-MSH] expression has been reported in malignant melanoma tumor cell lines. The present study examines the pattern of expression of the hormones ACTH, PRL and HGH in melanoma with regard to tumor growth and differentiation in relation to angiogenesis. Methods: During angiogenesis the tumor cells encircle a central vessel in layers to form a tumor-vascular-complex [TVC] with a central vessel and a mantle of 5 to 6 layers. Hormone expression is assessed by immunopositivity for PRL, HGH, & ACTH in the tumor-vascular complexes, on serial frozen and paraffin sections and subjected to statistical analysis [t-test or Mann-Whitney U- test]. Results: As two layers accrue the tumor cells acquire PRL & HGH positivity and are associated with a wave of mitotic activity in these layers. Further addition of layers shows ACTH positivity in the outer layers in association with pigmentation. Discussion: There is a coordinated growth of melanoma cells around neovascular channels, the cell cycle of malignant melanocytes being orchestrated by the three pituitary hormones, PRL, HGH & ACTH. The expression of PRL & HGH is related to mitotic activity while ACTH & pigment indicate differentiated function.