[en] BACKGROUND. Homeobox (HOX)-containing proteins have been identified as regulators controlling the coordinated expression of genes involved in development and differentiation. Recent data also suggest a possible involvement of HOX genes in malignant transformation and/or progression. We have previously shown that HOXC8 expression was selectively turned on in human cervix cancer cells compared with normal keratinocytes, suggesting that HOXC8 may be involved in the process leading to the transformation of cervix keratinocytes [Alami et al.: Biochem Biophys Res Commun 257:738-745,1999]. METHODS. RT-PCR and in situ hybridization experiments were performed to investigate the expression and cell type localization of HOXC8 transcripts in human prostate cancer cell lines and tissues. In situ hybridization was performed with the use of an HOXC8 anti-sense digoxigenin-labeled probe to investigate HOXC8 mRNA expression in 27 prostate cancer tissue specimens. RESULTS. Out of the three human prostate cancer cell lines tested, DU-145 and PC3 but not LNCaP cells expressed detectable amount of HOXC8 transcripts. Results from in situ hybridization experiments demonstrated that HOXC8 gene was expressed mainly in malignant epithelial cells. Furthermore, the staining intensity in epithelial cells was significantly increased in high Gleason score carcinomas (scores 7-9, n = 12; labeling intensity 2 + to 3 +) compared with the one observed in low and intermediate Gleason score tumors (scores 3-6, n = 15; labeling intensity 0 and 1 +) (ANOVA test, P < 0.0001). CONCLUSIONS. Our data showing that HOXC8 overexpression is associated with the loss of tumor differentiation in human prostate cancer suggests that HOXC8 may play a role in the acquisition of the invasive and metastatic phenotype of this malignancy. (C) 2002 Wiley-Liss, Inc.