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Background: The underlying mechanisms of the potential tumor-suppressive effects of ginsenoside Rh2 are complex. N6-methyladenosine (m6A) RNA methylation is usually dysregulated in cancer. This study explored the regulatory effect of ginsenoside Rh2 on m6A RNA methylation in cancer.Methods: m6A RNA quantification and gene-specific m6A RIP-qPCR assays were applied to assess total and gene-specific m6A RNA levels. Co-immunoprecipitation, fractionation western blotting, and immunofluorescence staining were performed to detect protein interactions and distribution. QRT-PCR, dual-luciferase, and ChIP-qPCR assays were conducted to check the transcriptional regulation. Results: Ginsenoside Rh2 reduces m6A RNA methylation and KIF26B expression in a dose-dependent manner in some cancers. KIF26B interacts with ZC3H13 and CBLL1 in the cytoplasm of cancer cells and enhances their nuclear distribution. KIF26B inhibition reduces m6A RNA methylation level in cancer cells. SRF bound to the KIF26B promoter and activated its transcription. SRF mRNA m6A abundance significantly decreased upon KIF26B silencing. SRF knockdown suppressed cancer cell proliferation and growth both in vitro and in vivo, the effect of which was partly rescued by KIF26B overexpression.Conclusion: ginsenoside Rh2 reduces m6A RNA methylation via downregulating KIF26B expression in some cancer cells. KIF26B elevates m6A RNA methylation via enhancing ZC3H13/CBLL1 nuclear localization. KIF26B-SRF forms a positive feedback loop facilitating tumor growth.

Small nucleolar RNA host gene 16 (SNHG16), a long non-coding RNA, was reported to function as an oncogene in multiple cancers. However, its biological function and regulatory mechanism in retinoblastoma (RB) has not yet been revealed. In this study, we attempted to ascertain the biological role and underlying regulatory mechanism of SNHG16 in RB progression. The expression levels of SNHG16 were measured in RB tissues and cell lines. The effects of SNHG16 knockdown on the proliferation, colony formation, cell cycle progression and apoptosis were investigated using corresponding experiments. Bioinformatic analysis, luciferase reporter assay, and RNA immunoprecipitation assay were applied to identify potential microRNAs (miRs) that could bind with SNHG16. A nude model was established to investigate the effect of SNHG16 knockdown on tumor growth in vivo. We found that SNHG16 expression was upregulated in RB tissues and cell lines compared with normal controls. Knockdown of SNHG16 in RB cells significantly inhibited the proliferation and colony formation, and promoted apoptosis in vitro, as well as retarded tumor growth in vivo. Mechanistic investigation illustrated that SNHG16 acted as a sponge for miR-140-5p and regulated its expression in RB cells. Clinical evidence revealed a negative correlation between SNHG16 and miR-140-5p in RB specimens. Rescue experiments showed that inhibition of miR-140-5p partially attenuated the growth-suppressing effects of SNHG16-depletion on RB cells.. Collectively, SNHG16 exerts oncogenic role in RB by sponging miR-140-5p, suggesting that SNHG16 might be a potential therapy target for RB.