Organoids as preclinical cancer models of hepatocellular carcinoma to study doxorubicin response

Background & Aims: Transarterial chemoembolization (TACE) is the first-line treatment for intermediate-stage hepatocellular carcinoma (HCC). However, the response rate to TACE varies, and the molecular mechanisms underlying variable responses are poorly understood. Patient-derived HCC organoids (HCCOs) offer a novel platform to investigate variability of doxorubicin responses, the impact of hypoxia on tumor cell proliferation, and the molecular mechanisms underlying doxorubicin resistance.
Methods: We evaluated the effects of hypoxia and doxorubicin on cell viability and cell cycle distribution in twenty patient-derived HCCO models. We also identified HCCO-intrinsic determinants of doxorubicin response by comparing the transcriptomes of sensitive to resistant HCCOs. To validate candidate genes, we used small molecule inhibition and quantified intracellular doxorubicin levels.
Results: Hypoxia reduced the proliferation of HCCOs and increased the number of cells in the G0/G1 phase of the cell cycle, while decreasing the number in the S phase. The IC50s of the doxorubicin response varied widely, from 29nM to >1μM. Doxorubicin and hypoxia did not exhibit synergistic effects but were additive in some HCCOs. Doxorubicin reduced the number of cells in the G0/G1 and S phases and increased the number in the G2 phase under both normoxia and hypoxia. Genes related to drug metabolism and export, most notably ABCB1, were differentially expressed between doxorubicin-resistant and sensitive HCCOs. Small molecule inhibition of ABCB1 increased intracellular doxorubicin levels and decreased drug tolerance in resistant HCCOs.
Conclusions: The inhibitory effects of doxorubicin treatment and hypoxia on HCCO proliferation are variable, suggesting an important role of tumor-cell intrinsic properties in doxorubicin resistance. ABCB1 is a determinant of doxorubicin response in HCCOs.