Comparison of the malignant phenotype and genotype of the human androgen-independent cell Line DU 145 and a subline derived from metastasis after orthotopic implantation in nude mice

To investigate the potential genetic changes underlying the progression of human hormone-resistant prostate cancer, we related chromosomal alterations of the DU 145 cell line and a subline isolated form a metastasis in an ort hotopic model to tumorigenicity, metastasis and chemoresistance. In 15 mice 1 x 10(5) DU 145 cells were injected into the dorsal prostate. From a resu lting paraaortic lymphnode metastasis, we isolated a subline (DU 145 MN1); which was injected into 15 nude mice. The sulforhodamine B (SRB) assay was used to analyze cell doubling time and the IC50 of cisplatin and 5-fluorour acil for both cell lines. Cytogenetic characterization was performed with c onventional karyotype analysis and fluorescence in situ hybridization (FISH ). After orthotopic implantation of DU 145 cells tumorigenicity was 100% wh ereas only 2 mice revealed lymphnode metastases. In contrast, the take rate after implantation of DU 145 MN1 was 100%, with lymphnode metastases in 7 mice. The SRB assay revealed a 8-fold increased IC50 for cisplatin and a 2. 5-fold increase for 5-FU in DU 145 MN1. as compared to DU 145 cells. There was gain of a chromosome 8 and only two copies of chromosome 17 in the DU 1 45 MN1 cells as compared to the parental cell line. The emergence of an i(9 )(q10) in addition to two normal chromosome 9 homologues in the DU 145 MN1 cell line was confirmed by FISH using a chromosome 9-specific painting prob e. In summary, clonal evolution of the chromosomal changes following repeat ed orthotopic implantation, may assist in locating the genes involved in th e progression and chemoresistance of human hormone-resistant prostate cance r. (C) 2001 Elsevier Science Inc, All rights reserved.