Base editing of the mutated TERT promoter inhibits liver tumor growth

Background and Aims: Base editing has shown great potential for treating human diseases with mutated genes. However, its potential for treating HCC has not yet been explored. Approach and Results: We employed adenine base editors (ABEs) to correct a telomerase reverse transcriptase ( TERT ) promoter mutation, which frequently occurs in various human cancers, including HCC. The mutated TERT promoter −124 C>T is corrected to −124 C by a single guide (sg) RNA-guided and deactivated Campylobacter jejuni Cas9 (CjCas9)-fused adenine base editor (CjABE). This edit impairs the binding of the E-twenty six/ternary complex factor transcription factor family, including E-twenty six-1 and GABPA, to the TERT promoter, leading to suppressed TERT promoter and telomerase activity, decreased TERT expression and cell proliferation, and increased cell senescence. Importantly, injection of adeno-associated viruses expressing sgRNA-guided CjABE or employment of lipid nanoparticle-mediated delivery of CjABE mRNA and sgRNA inhibits the growth of liver tumors harboring TERT promoter mutations. Conclusions: These findings demonstrate that a sgRNA-guided CjABE efficiently converts the mutated TERT promoter −124 C>T to −124 C in HCC cells and underscore the potential to treat HCC by the base editing-mediated correction of TERT promoter mutations.