Clinicopathological Significance of Exosomal Proteins CD9 and CD63 and DNA Mismatch Repair Proteins in Prostate Adenocarcinoma and Benign Hyperplasia

Abstract

Introduction: Recently, it has been shown that exosomal biomarkers and DNA mismatch repair proteins (MMR) could play an important role in cancer risk stratification and prognosis assessment. The gold standard for prostate carcinoma (PCa) diagnosis is biopsy and histopathological examination. Thus, the complex evaluation of exosomal and MMR proteins could be beneficial for prostate cancer risk stratification and diagnostics. The aim of the current study was to evaluate and compare the expression of exosomal proteins CD9 and CD63 and MMR proteins in the tissue of patients with prostate benign hyperplasia (BPH) and PCa.

Methods: The study was retrospective. Altogether, 92 patients with PCa and 20 patients with BPH (control group) were enrolled in the study. Exosomal and MMR protein expression was analyzed by immunohistochemistry (IHC). The follow-up for each PCa patient in our study lasted till disease progression and/or a maximum of 5 years.

Results: Low-grade PCa was observed in 56 patients and high-grade PCa in 36 patients. CD63 expression was significantly higher in patients with high-grade PCa compared to those with low-grade PCa. CD9 expression was significantly downregulated in PCa patients compared to the control group. MMR protein expression deficiency was observed in 10 PCa patients. MMR proteins were maintained in all cases of BPH. The study found a negative correlation between MMR protein loss and PCa ISUP grade groups. Progression-free survival (PFS) in patients with MMR deficiency was significantly shorter than in patients with maintained MMR expression.

Conclusions: CD9 protein expression was downregulated in PCa, compared to BPH, while CD63 protein expression was upregulated in high-grade PCa but downregulated in low-grade PCa. CD63 protein upregulation, CD9 downregulation, and loss of MMR protein characterized the shorter PFS of high-grade PCa patients. CD9, CD63, and MMR could be the routine immunohistochemical biomarkers for the diagnosis and risk stratification of PCa.

Keywords: DNA mismatch repair proteins; benign prostate hyperplasia; exosomal biomarkers; prostate acinar adenocarcinoma.

Figure 1

Association between CD63 expression and grade group via Pearson’s chi-squared test (χ²). Pearson’s χ² = 0.59; p < 0.0001.

Figure 2

Representative photomicrograph of CD63 expression in high-grade prostate cancer. The black arrow indicates CD63 protein expression. Immunohistochemical staining method; magnification ×200; scale bar 100 µm.

Figure 3

Association between CD63 expression and AJCC prognostic stage groups via Pearson’s chi-squared test (χ²). Pearson’s χ² = 0.27; p < 0.0001.

Figure 4

Comparison of CD9 expression in patients with prostate benign hyperplasia and acinar adenocarcinoma; ^ₒ p < 0.0001; Mann–Whitney U test.

Figure 5

Loss of CD9 expression in prostate acinar adenocarcinoma. The black arrow indicates loss of CD9 protein expression in acinar adenocarcinoma, and the white arrow shows preserved CD9 expression in benign prostate glands. Immunohistochemical staining method; magnification ×400; scale bar 100 µm.

Figure 6

MSH-2 expression in prostate acinar adenocarcinoma. The black arrow indicates immunopositive cells. Immunohistochemical staining method; magnification ×200; scale bar 100 µm.

Figure 7

Association between MMR expression and grade group via Pearson’s chi-squared test (χ²). Pearson’s χ² = 0.0088; p = 0.005.

Figure 8

Progression-free survival of prostate cancer patients with MMR deficiency (red line) and maintained MMR expression (blue line). Kaplan–Meier method using the log-rank (Mantel–Cox) test; p = 0.0007.