Received for publication June 15, 2005.
Revised August 23, 2005.
Accepted for publication August 23, 2005.

Evaluation of Lipophilins as Determinants of Tumor Cell Response to Estramustine

Abstract

Estramustine administered orally as estramustine phosphate (EMP) remains a major tool in hormone refractory prostate cancer chemotherapy. The presence of estramustine binding protein, prostatin, in prostate tissue may be a determinant of response to treatment. Lipophilins are secretory proteins with homology to prostatin. RT-PCR was performed to estimate expression patterns of lipophilins A, B and C in human biopsies and cell lines resistant to estramustine. Although lipophilin A was not expressed in prostate tissue, both lipophilins B and C were expressed in normal and tumor prostate without significant differences. For lipophilin C, a somatic mutation (T to C transition at positions 409 and 412) was found in human tumor samples and absent in normal prostate tissue. No consistent response to EMP was observed in EGFP-tagged lipophilin C transfected PC3 cells compared to parental controls. Among these EGFP-lipophilin C clones, no direct correlation between response to EMP treatment (IC₅₀ values) and EGFP expression was observed (p = 0.73). Lipophilin C mRNA levels did not vary significantly between wild type and estramustine-resistant cells in prostate (DU145 and PC3) and ovarian (SKOV3) cancer cell lines. Overall, these results suggest that lipophilins are not specific determinants of estramustine efficacy.

Key words: Emcyt, cancer therapy, estramustine, lipophilin, prostate cancer, prostatins