Methods  Drug sensitivity, functional genomics, and gene expression data from cell lines were collected to assess the correlation between the expression of c-Myc and drug sensitivity. Differential expression and prognostic relevance of c-Myc in a primary liver cancer cohort were analyzed. Immunohistochemistry (IHC) staining validated c-Myc expression in liver cancer patients and correlated it with the drug sensitivity of organoids obtained from an organoid biobank. Three c-Myc inhibitors were screened on liver cancer cell lines and organoids to test tumor-killing effects in two- and three-dimensional levels. Bioinformatics analysis was conducted to explore the role of c-Myc in targeted drug resistance.

Results  Bioinformatics analyses combined with IHC staining revealed a potential regulatory role of c-Myc in the drug sensitivity of liver cancer. The expression of c-Myc in cancerous tissues was significantly higher than in para-cancerous tissues, and c-Myc expression was higher in patients resistant to targeted drugs than in those sensitive to targeted drugs (P< 0.05). Drug screening experiments showed that c-Myc inhibitors including THZ1, ABBV-744, and JQ1 reduced cell viability in both tumor cells and tumor organoids. The combination of lenvatinib and c-Myc inhibitors exhibited significant synergistic effects (all synergy scores > 1) in the SNU-739 cell line. Analysis of organoids from an organoid biobank indicated a strong association between c-Myc and stemness-mediated targeted drug resistance (R = 0.87).

Conclusions  c-Myc showed increased expression in patients resistant to targeted therapy, suggesting it as a novel target for drugs in liver cancer. Inhibition of c-Myc effectively killed tumors in both two- and three-dimensional ex vivo models.