Prognostic role of PBRM1 marker expression in clear-cell renal-cell carcinoma

Background. Clear-cell renal-cell carcinoma (CCRCC) is the most common histological type of cancer of this localization. Changes in 16 genes were identified as significant in carcinogenesis of CCRCC. After VHL suppressor gene, PBRM1 gene is the second by frequency of genetic abnormalities in CCRCC and it is mutated in 40—50 % cases of CCRCC.

The study objectiveis to analyze the effect of abnormalities in PBRM1 protein expression on survival of patients with CCRCC.

Materials and methods. The study included 137patients with newly diagnosed and histologically confirmed CCRCC. For all study participant, detailed medical history and questionnaire data were acquired. Prior to treatment, blood samples and tumor tissue removed during surgery were obtainedfrom all patients. All patients are annually followed up for current information on their life status, disease dynamics, treatment. Minimalfollow-up time is 22 months, maximal is 128 months, mean is 61.8 months, median is 48 months. Immunohistochemical (IHC) testing of PBRM1 expression was performed using standard technique with polyclonal rabbit antibodies PB1[N1N2] N-term (GeneTex 100781) with 1:50 dilution, DAB staining. Normally, protein product of the wild type PBRM1 gene is functioning and can be detected in the nucleus. Absence of nuclear expression of PBRM1 points to genetic or epigenetic abnormalities.

Results.Renal cancer-specific survival is significantly lower in patients without expression of the PRBM1 protein in tumor cells. The longest 5- (84 %) and 10-year (84 %) survival was observed in patients with diffuse nuclear expression of the PBRM1 protein. Difference in survival of these patients compared to patients without PRBM1 protein expression is statistically significant (p = 0.004). We have performed an analysis of the association between survival of patients with CCRCC andfocal nuclear PBRM1 expression. In these patients, survival is lower than in patients with diffuse expression but higher than in patients without nuclear expression of PBRM1 (p = 0.02). Cytoplasmic expression of PBRM1 doesn’t affect survival.

Conclusion.The obtained results point to prognostic value of PBRM1 gene activity which is abnormal in almost half of all CCRCC cases. IHC testing is an appropriate, reliable and affordable method for determination of PBRM1 protein expression and therefore can be used in practice. Favorable course and prognosis in patients with stage I—II CCRCC and preserved nuclear expression of the PBRM1 protein should be noted: 5-year survival for these patients is 100 %. This observation is crucial for making decisions on treatment of these patients.

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