Insulin-like Growth Factor (IGF)/IGF-1 Receptor (IGF-1R) signaling is known to regulate stem cell pluripotency and differentiation to trigger cell proliferation, organ development, and tissue regeneration during embryonic development. Unbalanced IGF/IGF-1R signaling can promote cancer cell proliferation and activate cancer reprogramming in tumor tissues, especially in the liver. Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death, with a high incidence and mortality rate in Asia. Most patients with advanced HCC develop tyrosine kinase inhibitor (TKI)-refractoriness after receiving TKI treatment. Dysregulation of IGF/IGF-1R signaling in HCC may activate expression of cancer stemness that leads to TKI refractoriness and tumor recurrence. In this review, we summarize the evidence for dysregulated IGF/IGF-1R signaling especially in hepatitis B virus (HBV)-associated HCC. The regulation of cancer stemness expression and drug resistance will be highlighted. Current clinical treatments and potential therapies targeting IGF/IGF-1R signaling for the treatment of HCC will be discussed.

The role of a YAP-IGF-1R signaling loop in HCC resistance to sorafenib remains unknown. Method: Sorafenib-resistant cells were generated by treating naïve cells (HepG2215 and Hep3B) with sorafenib. Different cancer cell lines from databases were analyzed through the ONCOMINE web server. BIOSTORM–LIHC patient tissues (46 nonresponders and 21 responders to sorafenib) were used to compare YAP mRNA levels. The HepG2215_R-derived xenograft in SCID mice was used as an in vivo model. HCC tissues from a patient with sorafenib failure were used to examine differences in YAP and IGF-R signaling. Results: Positive associations exist among the levels of YAP, IGF-1R, and EMT markers in HCC tissues and the levels of these proteins increased with sorafenib failure, with a trend of tumor-margin distribution in vivo. Blocking YAP downregulated IGF-1R signaling-related proteins, while IGF-1/2 treatment enhanced the nuclear translocation of YAP in HCC cells through PI3K-mTOR regulation. The combination of YAP-specific inhibitor verteporfin (VP) and sorafenib effectively decreased cell viability in a synergistic manner, evidenced by the combination index (CI). Conclusion: A YAP-IGF-1R signaling loop may play a role in HCC sorafenib resistance and could provide novel potential targets for combination therapy with sorafenib to overcome drug resistance in HCC.

Sorafenib is the first approved systemic targeting agent for advanced HCC; however, when used alone, drug resistance can result in considerably reduced efficacy. Here, we demonstrate that niclosamide, an antihelminthic agent approved by the US Food and Drug Administration, can be repurposed to increase sorafenib sensitivity in sorafenib-resistant HCC cells. We generated sorafenib-resistant HCC cell lines (HepG2215_R and Hep3B_R) with elevated IGF-1R levels and strong properties in terms of stemness and epithelial–mesenchymal transition. Niclosamide was found to increase sorafenib sensitivity effectively in both cell lines and their organoids. The underlying mechanism involves the modulation of cancer stemness, IGF-1R/p-IGF1R/OCT4, and metabolic changes. The combination of sorafenib and niclosamide, but not linsitinib, effectively suppressed the IGF-1R/OCT4 expressions, yielded a synergistic combination index (CI), and attenuated stemness-related properties such as secondary tumor sphere formation and cell migration in sorafenib-resistant HCC cells. Notably, niclosamide significantly suppressed the sorafenib-induced IGF-1R phosphorylation prompted by IGF-1 treatment. Niclosamide effectively downregulated the sorafenib-induced gene expression associated with glycolysis (GLUT1, HK2, LDHA, and PEPCK), stemness (OCT4), and drug resistance (ABCG2) and enhanced the ability of sorafenib to reduce the mitochondrial membrane potential in vitro. The synergistic effect of a combination of niclosamide and sorafenib in vivo was further demonstrated by the decreased tumor size and tumor volume resulting from apoptosis regulation. Our results suggest that niclosamide can enhance sorafenib sensitivity in sorafenib-resistant HCC cells through IGF-1R/stemness regulation and metabolic changes. Our findings highlight a practical clinical strategy for enhancing sorafenib sensitivity in HCC.