Researchers have identified a novel tumor-suppressive circuit that regulates 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), details how the protein SPRED2 interacts with p53 and microRNA to suppress cancer stem cells (CSCs), which are responsible for tumor recurrence, metastasis, and drug resistance. The findings could lead to new strategies for treating HCC, a disease with limited treatment options and high relapse rates.
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. SPRED2 is known to inhibit Ras/Raf/ERK-MAPK signaling and is downregulated in advanced cancers, including HCC. Previous work linked SPRED2 loss to higher levels of pluripotency factors such as Nanog, c-Myc, and KLF4, but how SPRED2 controls HCC stemness remained unclear.
The study, led by researchers at Okayama University in Japan and published in Cancer Biology & Medicine, used HepG2, HLE, and Hep3B HCC cell lines, SPRED2-deficient and overexpressing cells, a mouse xenograft model, and 40 paired human HCC samples. The team combined Western blot, RT-qPCR, co-immunoprecipitation, ChIP-qPCR, luciferase assays, and immunofluorescence to map the pathway.
KLF4 emerged as the key pluripotency factor. Knocking down KLF4 in HepG2 cells reduced sphere and colony formation, invasion, epithelial–mesenchymal transition (EMT), aldehyde dehydrogenase (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 (3′-UTR) of KLF4 mRNA. In 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 miR-506-3p mimic reduced sphere and colony formation and ALDH activity, whereas its inhibitor increased them. In contrast, SPRED2 expression was not changed by miR-506-3p, placing SPRED2 upstream of the microRNA. These results show SPRED2 coordinates ERK, STAT3, and p53 signaling to reduce HCC stemness.
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. They said the pathway may be especially important because it connects three signaling routes to a single stemness regulator.
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.
For more information, the full study is available in Cancer Biology & Medicine and indexed in http://www.ncbi.nlm.nih.gov/pmc/journals/2000/.
