Objective To investigate the expression level of piR-35296 in clear cell renal cell carcinoma (ccRCC) and its pathological significance, as well as its effect on ccRCC cell proliferation.

Methods Surgical resection specimens and clinicopathological data from 67 ccRCC patients were collected. Differential expression profiles of piRNAs in ccRCC were detected using piRNA microarray analysis, and validated by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The effect of piR-35296 on the proliferative activity of ccRCC cells was examined by CCK-8 assay. Bioinformatic analysis predicted TAB2 as a potential downstream target gene of piR-35296; qRT-PCR was performed to detect theinfluence of piR-35296 overexpression or knockdown on TAB2 expression levels. Rescue experiments were conducted to verify the regulation of TAB2 by piR-35296 and its impact on ccRCC cell proliferation. The effect of piR-35296 knockdown on the growth of subcutaneous tumors in experimental nude mice was analyzed, and Ki-67 immunohistochemical staining was used to validate the influence of piR-35296 on ccRCC cell proliferation.

Results Both piRNA expression profiling and qRT-PCR revealed an elevated expression level of piR-35296 in ccRCC (P < 0.05). The expression of piR-35296 was closely associated with tumor size and differentiation degree in ccRCC patients (χ²=3.984, 3.974, P < 0.05). CCK-8 proliferation assays demonstrated that piR-35296 overexpression enhanced the proliferative activity of ccRCC cells, whereas its downregulation inhibited cell proliferation (P < 0.05). qRT-PCR experiments showed that TAB2 expression was upregulated after piR-35296 overexpression and downregulated upon piR-35296 knockdown (P < 0.05). Rescue experiments indicated that piR-35296 promoted TAB2 mRNA and its protein expression in ccRCC cells, thereby stimulating cell proliferation; TAB2 downregulation inhibited ccRCC cell proliferation. In experimental nude mice, piR-35296 knockdown reduced the mass andvolume of subcutaneous tumors (P < 0.05). Immunohistochemical staining for Ki-67 revealed a decreased percentage of Ki-67-positive cells after piR-35296 downregulation, suggesting reduced cell proliferation capacity (P < 0.05).

Conclusion The piR-35296 serves as a novel oncogenic growth promoter in ccRCC. By elevating TAB2 expression, piR-35296 promotes the proliferative growth of ccRCC cells.