Use of an inhibitor of differentiation-1 (Id1) expression (exp) to discriminate good prognosis (GP) from poor prognosis (PP) prostate cancer (PCa)

Abstract

e16128 Background: In the PSA era a significant proportion of PCa patients (pts) at onset have potential indolent tumors that will not impact their life expectancy or quality of life. Most of them will be radically treated and suffer its consequences. Thus, PCa overtreatment is a great concern among clinicians. Pre-treatment molecular factors may help differentiate indolent from aggressive PCa. Id1, involved in cell differentiation and angiogenesis, has recently showed to mediate lung metastasis (mts) from breast cancer. Its role in PCa endothelial (end) cells is well established but its exp and role in PCa cells is controversial. Using a new monoclonal antibody (MoAb) (195–14) for immunohistochemistry (IHC), Id1 exp is limited to some PP breast and bladder tumors. Whether Id1 exp is relevant in PCa prognosis is unknown. We tested 195–14 in PP and GP PCa samples and matched mts where available. Methods: 52 PCa pts were studied, 20 GP + 32 PP. All formalin-fixed and paraffin-embedded primary biopsies and matched mts of 16 of them were stained for tumor and end cell Id1 exp. 195–14 (1:500), (Biocheck), was used for IHC. Results: GP group: median age 65, all pts T2N0M0, median Gleason score 6 (6–9), median PSA at onset 5,5 ng/ml. After a median follow-up of 38 months (ms) 1 pt showed radiological and PSA progression (P); other PSA P. All but one remain alive. PP group: median age was 70, T3-T4 (70%), Gleason 8–10 (61%), median PSA at onset 58 ng/ml, 2 or more mts locations (79%), 94% showed P to docetaxel, median time-to- progression and overall survival after chemotherapy were 18 weeks and 7 ms. Among PP, 39% of primary PCa and 38% of mts showed Id1 tumor cell exp and 79% of primary tumors and 81% of mts showed end Id1 exp. In the GP group 0% showed Id1 tumor cell exp, and 50% showed end Id1 exp. The unexpected Id1 exp difference in tumor cells in PP compared to GP pts predicted clinical outcome. Consistently with other reports end Id1 exp is high in both groups. PP showed higher levels. Conclusions: Id1 exp discriminated GP from PP in our PCa cohort. These novel results highlight Id1 as a prognostic marker in PCa. Whether Id1 exp in the diagnostic biopsy can impact PCa therapeutic decision-making needs further investigation. No significant financial relationships to disclose.