Targeting Telomerase Overexpression by Synthetic Dosage Lethality

Abstract

Telomerase reverse transcriptase (hTERT) is upregulated in multiple cancers and accompanied by the evidence suggesting that up-regulation of telomerase expression is linked to tumorigenesis, raised the hypothesis that inhibiting this enzyme is a powerful antitumor strategy. Despite intensive research to seek direct enzyme inhibitors, sufficiently potent and specific small-molecule inhibitor has not been fount yet. This suggests that direct targeting of hTERT might not be an optimal strategy in cancer treatment. Genetic interactions, such as synthetic dosage lethality can overcome these issues and identify targets that is specific only tumor cells that overexpress telomerase. We used a combination of pooled shRNA and CRISPR screening platforms to comprehensively query the entire human genome and identify hTERT-specific Synthetic dosage lethality (SDL) interactions. Our screens identified several potential SDL genes specific to hTERT in the model cell lines. We prioritized 187 candidate SDL genes using different computational approaches and validate them on one-by-one bases in model cell lines. Subsequent validation of these genes in multiple cancer cell lines in arrayed CRISPR/Cas9-based strategy and several xenograft models identified several potential targets that exhibit specify to hTERT overexpressing tumors. Assessment of telomeres structure followed by telomere activity assay results suggest that the knockout of these target affect the canonical and non-canonical functions of hTERT. Our results indicated that validated SDL targets may provide a basis for the development of tumor agnostic therapeutic strategies applicable in a wide range of patients, since hTERT is overexpressed in the majority of human malignancies.