Association of DAZL expression with risk of recurrence in clinical stage 1 testicular germ cell tumors.

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523 Background: One model for testicular germ cell tumor (TGCT) formation posits that these tumors arise from a failure of germ cell determination characterized by persistent pluripotency and apoptotic escape. Risk assessment for relapse in clinical stage 1 (CS1) TGCT is dictated by clinical factors; molecular biomarkers to improve patient stratification for post-orchiectomy care are lacking. In this study, we examined the relationship between protein expression of pluripotency and apoptosis factors and risk of relapse in clinical stage 1 TGCT. Methods: Orchiectomy specimens from 73 patients treated for clinical stage 1 TGCT at one institution (27 seminoma, 46 non-seminoma) were subjected to immunohistochemistry (IHC) to assess protein expression of DAZL, POU5F1, BAK1, DDX4, NANOG, and PMAIP1. Samples were dichotomized as negative or positive for target protein expression. Patients with CS1 TGCT managed with surveillance were annotated for baseline clinical characteristics and whether they experienced relapse within two years of orchiectomy. Exact logistic regression estimated odds ratios (OR) and 95% confidence intervals were calculated for the association between protein expression and relapse. Results: At two years, 17% of patients in our cohort experienced relapse. DAZL expression (score > 0) was detected in 43% of seminoma samples and 13% of embryonal carcinomas. After adjusting for histology, tumors negative for DAZL expression were more likely to recur within two years (adjusted OR for recurrence 0.08, 95% CI 0 – 0.81, p = 0.03). The direction of this relationship was consistent in seminoma when adjusted for tumor size (adjusted OR 0.14, 95% CI 0-1.83, p = 0.18) and non-seminoma after adjustment for embryonal predominance and lymphovascular invasion (adjusted OR 0.53, 95% CI 0-3.10, p = 0.30). No notable findings were observed for POU5F1, BAK1, DDX4, NANOG, and PMAIP1. Validation studies in two independent cohorts from other institutions are ongoing. Conclusions: The absence of DAZL expression by IHC is associated with a greater risk of relapse in CS1 TGCT. As DAZL promotes germ cell commitment by suppressing the pluripotency program, absence of DAZL expression may promote an oncogenic germ cell phenotype and more aggressive tumor behavior. Validation in larger patient cohorts is required to credential DAZL as a biomarker for clinical stage 1 relapse on surveillance.

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