Researchers have identified a previously unrecognized tumor-suppressive circuit that controls stem-like behavior in hepatocellular carcinoma (HCC), the most common form of primary liver cancer. The study, published (DOI : 10.20892/j.issn.2095-3941.2025.0247) in Cancer Biology & Medicine, reveals that the protein SPRED2 binds to the tumor suppressor p53, enters the nucleus, and activates transcription of the microRNA miR-506-3p. This microRNA then directly targets KLF4 messenger RNA, reducing KLF4 protein levels and diminishing cancer stem cell (CSC) traits such as sphere formation, colony growth, invasion, and aldehyde dehydrogenase (ALDH) activity.
The implications are significant because liver cancer is the fifth most commonly diagnosed cancer and the second leading cause of cancer death worldwide. HCC accounts for 70–85% of primary liver cancers, and its five-year recurrence rate can reach 70–80%. CSCs, a small but aggressive cell population, drive relapse, metastasis, and chemotherapy resistance. By defining the SPRED2/p53/miR-506-3p/KLF4 axis, the study suggests that restoring this pathway could help suppress HCC progression, recurrence, and treatment resistance.
Led by researchers at Okayama University in Japan, the team used HepG2, HLE, and Hep3B HCC cell lines, SPRED2-deficient and overexpressing cells, a mouse xenograft model, and 40 paired human HCC samples. They combined Western blot, RT-qPCR, co-immunoprecipitation, chromatin immunoprecipitation quantitative PCR, luciferase assays, and immunofluorescence to map the pathway. Clinical samples validated the cell and mouse findings.
KLF4 emerged as the key pluripotency factor. Knocking down KLF4 in HepG2 cells reduced sphere and colony formation, invasion, epithelial–mesenchymal transition (EMT), ALDH activity, and the percentage of CD44+ and CD90+ cells; it also produced smaller tumors in mice. KLF4 knockdown lowered Nanog and c-Myc, whereas Nanog or c-Myc knockdown did not affect KLF4, placing KLF4 upstream. SPRED2 overexpression reduced KLF4, c-Myc, and Nanog, while SPRED2 knockout increased them.
Mechanistically, miR-506-3p directly bound the 3′ untranslated region of KLF4 mRNA. In the 40 human HCC samples, KLF4 and miR-506-3p were negatively correlated, while SPRED2 and miR-506-3p were positively correlated. SPRED2 formed a nuclear complex with p53; p53 supported SPRED2 nuclear localization and bound the miR-506 promoter. SPRED2 increased miR-506-3p in a p53-dependent, dose-dependent manner. ERK and STAT3 inhibition also raised miR-506-3p, linking three pathways to KLF4 suppression.
The authors said the findings reveal a previously unrecognized tumor-suppressive circuit linking SPRED2 to p53 and microRNA regulation. They said SPRED2 does not act only by blocking ERK or STAT3 signaling; it also helps p53 drive miR-506-3p, which then keeps KLF4 in check. They said this axis may explain why loss of SPRED2 promotes CSC-like behavior and could offer a fresh target for therapies aimed at reducing HCC stemness.
Targeting the SPRED2/p53/miR-506-3p/KLF4 axis may provide new therapeutic strategies for HCC. Restoring miR-506-3p or SPRED2 activity could lower KLF4 and inhibit CSC traits, potentially reducing relapse, metastasis, and chemoresistance. Because SPRED2-driven miR-506-3p induction required functional p53, the approach may be most relevant for tumors with intact p53 signaling; HCC cells with mutant or absent p53 may need additional strategies. Future studies should test miR-506-3p mimics, SPRED2-stabilizing agents, or combination therapies in preclinical models and define which patients are most likely to benefit. Such work could help translate this newly defined axis into precision approaches for HCC.
The full text is freely available to clinicians and researchers worldwide through PubMed Central at http://www.ncbi.nlm.nih.gov/pmc/journals/2000/.
