Inactivation of TACC2 epigenetically represses CDKN1A and confers sensitivity to CDK inhibitors

Background: The genomic landscape of esophageal squamous cell carcinoma (ESCC) has been characterized extensively, but there remains a significant need for actionable targets and effective therapies.

Methods: Here, we perform integrative analysis of genome-wide loss of heterozygosity and expression to identify potential tumor suppressor genes. The functions and mechanisms of one of the candidates, TACC2, are then explored both in vitro and in vivo, leading to the proposal of a therapeutic strategy based on the concept of synthetic lethality.

Findings: We reveal that the inactivation of TACC2, due to copy number loss and promoter hypermethylation, is associated with poor prognosis in ESCC patients. TACC2 depletion enhances ESCC tumorigenesis and progression, as demonstrated in Tacc2 knockout mouse models and by increased growth abilities of ESCC cells. Mechanistically, TACC2 interacts with components of the NuRD and CoREST co-repressor complexes, including MTA1, MBD3, and HMG20B, in the cytoplasm. TACC2 loss leads to the translocation of these proteins into the nucleus, facilitating the formation of functional NuRD and CoREST complexes and the epigenetic repression of CDKN1A. This repression results in elevated CDK1/2 activation. Furthermore, TACC2-deficient cells and ESCC patient-derived organoids with reduced TACC2 expression show increased sensitivity to CDK inhibitors, particularly dinaciclib, which is currently in a phase III trial. Notably, the combination of TACC2-specific RNAi and dinaciclib in subcutaneous ESCC models significantly impairs tumor growth.

Conclusions: The findings suggest a strategy for cancer treatment based on synthetic lethality.

Funding: Funded by NKRDP, NSFC, GDIIET, GDBABRF, GDECISTP, and SYSUTP.