Background: The mechanisms behind prostate cancer progression are largely unknown, but macrophage inhibitory cytokine 1 (MIC-1) has been suggested to be involved in tumour dissemination in vivo due to its reductive effect on cell adhesion.
Materials and methods: We used two PC-3 prostate cancer epithelial cell line variants as tools to screen for gene expression differences during prostate cancer progression by cDNA microarray analysis. Selected genes were further analysed by Northern blot analysis using mRNA isolated from prostatic cell lines and tissues. MIC-1 expression was studied by in situ hybridization in archival patient specimens containing benign and malignant prostatic tissue.
Results: Gene expression of human collagen type VI, basement membrane heparan sulphate proteoglycan, integrin alpha 1, and fibronectin I were remarkably decreased in suspension-adapted PC-3 (saPC-3) cells, indicating a gene expression profile of reduced cell adhesion. Asparagine synthetase, serine protease 1, stanniocalcin homologue, NAD-dependent methylene tetrahydrate dehydrogenase cyclohydrolase (NMDMC), fortilin, and MIC-1 were overexpressed in saPC-3 cells. In prostate, the MIC-1 gene was mainly expressed in cancer tissue. However, MIC-1 transcripts were detected in benign tissue areas, especially in specimens containing prostate cancer with Gleason sum scores of 5-8. A significant inverse correlation (Spearman's rho correlation coefficient -0.928**) was observed between the ratio of cancerous to benign MIC-1 expression levels and Gleason scores.
Conclusions: Differential expression of the MIC-1 gene occurs during prostate cancer progression. The transcript level of the MIC-1 gene in histologically benign tissue seems to approach that in paired cancer tissue concomitant with an increasing Gleason score.