High SRPX2 protein expression predicts unfavorable clinical outcome in patients with prostate cancer

Background: Sushi repeat-containing protein X-linked 2 (SRPX2) is overexpressed in a variety of different tumor tissues and correlated with poor prognosis in patients. Little research focuses on the role of SRPX2 expression in prostate cancer (PCa), and the clinicopathological significance of the protein expression in this tumor is relatively unknown. However, our previous transcriptome data from those cancer stem-like cells indicated the role of SRPX2 in PCa.

Materials and methods: In this study, RT-PCR and Western blotting were firstly used to examine the SRPX2 expression in three PCa cell lines including LNCaP, DU145, and PC3, and then SRPX2 protein expression was immunohistochemically investigated and statistically analyzed in a series of 106 paraffin-embedded PCa tissue specimens.

Results: Significantly lower levels of SRPX2 expression were verified in the LNCaP cells, compared with the expression in the aggressive DU145 and PC3 cells, in both mRNA and protein levels. Immunohistochemically, there were variable SRPX2 protein expressions in the clinical samples. Moreover, high levels of SRPX2 expression in the PCa tissues were significantly associated with Gleason score (P=0.008), lymph node metastasis (P=0.009), and distant metastasis (P=0.021). Furthermore, higher levels of SRPX2 expression in the PCa tissues were significantly associated with shorter overall survival (OS) (P<0.001).

Conclusion: Our results demonstrate that SRPX2 is highly expressed in aggressive PCa cells in vitro, and its protein expression in PCa is significantly associated with malignant clinical features and shorter OS, strongly indicating its prognostic value in prostate cancers.