CDK4/6 inhibitor PD-0332991 suppresses hepatocarcinogenesis by inducing senescence of hepatic tumor-initiating cells.

Introduction: Owing to the limited treatment options for hepatocellular carcinoma (HCC), interventions targeting pre-HCC stages have attracted increasing attention. In the pre-HCC stage, hepatic tumor-initiating cells (hTICs) proliferate abnormally and contribute to hepatocarcinogenesis. Numerous studies have investigated targeted senescence induction as an HCC intervention. However, it remains to be clarified whether senescence induction of hTICs could serve as a pre-HCC intervention.

Objectives: This study was designed to investigate whether senescence induction of hTICs in the precancerous stage inhibit HCC initiation.

Methods and results: HCC models developed from chronic liver injury (CLI) were established by using Fah^-/- mice and N-Ras + AKT mice. PD-0332991, a selective CDK4/6 inhibitor that blocks the G1/S transition in proliferating cells, was used to induce senescence during the pre-HCC stage. Upon administration of PD-0332991, we observed a significant reduction in HCC incidence following selective senescence induction in hTICs, and an alleviation liver injury in the CLI-HCC models. PD-0332991 also induced senescence in vitro in cultured hTICs isolated from CLI-HCC models. Moreover, RNA sequencing (RNA-seq) analysis delineated that the "Cyclin D-CDK4/6-INK4-Rb" pathway was activated in both mouse and human liver samples during the pre-HCC stage, while PD-0332991 exhibited substantial inhibition of this pathway, thereby inducing cellular senescence in hTICs. Regarding the immune microenvironment, we demonstrated that senescent hTICs secrete key senescence-associated secretory phenotypic (SASP) factors, CXCL10 and CCL2, to activate and recruit macrophages, and contribute to immune surveillance.

Conclusion: We found that hTICs can be targeted and induced into a senescent state during the pre-HCC stage. The SASP factors released by senescent hTICs further activate the immune response, facilitating the clearance of hTICs, and consequently suppressing HCC occurrence. We highlight the importance of pre-HCC interventions and propose that senescence-inducing drugs hold promise for preventing HCC initiation under CLI.