Breakthrough study reveals how one molecule controls liver cancer stem cells

Hepatocellular carcinoma (HCC) represents 70–85% of primary liver cancers, with a five-year recurrence rate reaching 70–80%. This aggressive malignancy is driven by cancer stem cells (CSCs), a small population responsible for relapse, metastasis, and chemotherapy resistance. While SPRED2 is known to inhibit Ras/Raf/ERK-MAPK signaling and is downregulated in advanced HCC, the precise molecular mechanisms governing its control over stemness remained unclear until recently.

Study methodology and key findings

Researchers at Okayama University in Japan led a comprehensive investigation published in Cancer Biology & Medicine (DOI: 10.20892/j.issn.2095-3941.2025.0247). The team utilized HepG2, HLE, and Hep3B cell lines, alongside SPRED2-deficient and overexpressing variants, a mouse xenograft model, and 40 paired human HCC samples. By combining Western blot, RT-qPCR, Co-IP, ChIP-qPCR, luciferase assays, and immunofluorescence, they mapped the regulatory pathway, validating cell and mouse findings with clinical data.

KLF4 as the central pluripotency factor

The analysis identified KLF4 as the critical pluripotency factor. Knocking down KLF4 in HepG2 cells diminished sphere and colony formation, invasion, epithelial-mesenchymal transition (EMT), aldehyde dehydrogenase (ALDH) activity, and the proportion of CD44+ and CD90+ cells. It also resulted in smaller tumors in mice. Notably, KLF4 knockdown reduced Nanog and c-Myc levels, whereas knocking down Nanog or c-Myc did not affect KLF4, establishing KLF4’s upstream position.

Mechanistic role of miR-506-3p and p53

SPRED2 overexpression decreased KLF4, c-Myc, and Nanog, while SPRED2 knockout increased them. Mechanistically, miR-506-3p directly binds the 3′ untranslated region (3′-UTR) of KLF4 mRNA. In human HCC samples, KLF4 and miR-506-3p showed negative correlation, while SPRED2 and miR-506-3p were positively correlated. SPRED2 forms a nuclear complex with p53, which supports SPRED2’s nuclear localization and binds the miR-506 promoter. Consequently, SPRED2 increases miR-506-3p in a p53-dependent, dose-dependent manner.

Integration of three signaling pathways

Inhibition of ERK and STAT3 also raised miR-506-3p levels, linking three distinct pathways to KLF4 suppression. A miR-506-3p mimic reduced sphere and colony formation and ALDH activity, whereas its inhibitor increased these traits. Conversely, SPRED2 expression was unaffected by miR-506-3p, confirming SPRED2 acts upstream of the microRNA. These results demonstrate that SPRED2 coordinates ERK, STAT3, and p53 signaling to reduce HCC stemness.

Therapeutic implications and future directions

The authors describe a previously unrecognized tumor-suppressive circuit where SPRED2 aids p53 in driving miR-506-3p, which keeps KLF4 in check. This axis may explain why SPRED2 loss promotes CSC-like behavior. Targeting the SPRED2/p53/miR-506-3p/KLF4 pathway could offer new therapeutic strategies. Restoring miR-506-3p or SPRED2 activity might lower KLF4 and inhibit CSC traits, potentially reducing relapse, metastasis, and chemoresistance. However, because SPRED2-driven miR-506-3p induction requires functional p53, this approach may be most relevant for tumors with intact p53 signaling, while those 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 to define patient benefits.