Rajurkar M, Parikh AR, Solovyov A, You E, Kulkarni AS, Chu C, Xu KH, Jaicks C, Taylor MS, Wu C, Alexander KA, Good CR, Szabolcs A, Gerstberger S, Tran AV, Xu N, Ebright RY, Van Seventer EE, Vo KD, Tai EC, Lu C, Joseph-Chazan J, Raabe MJ, Nieman LT, Desai N, Arora KS, Ligorio M, Thapar V, Cohen L, Garden PM, Senussi Y, Zheng H, Allen JN, Blaszkowsky LS, Clark JW, Goyal L, Wo JY, Ryan DP, Corcoran RB, Deshpande V, Rivera MN, Aryee MJ, Hong TS, Berger SL, Walt DR, Burns KH, Park PJ, Greenbaum BD, Ting DT. Reverse Transcriptase Inhibition Disrupts Repeat Element Life Cycle in Colorectal Cancer. Cancer Discov 2022;Abstract
Altered RNA expression of repetitive sequences and retrotransposition are frequently seen in colorectal cancer (CRC) implicating a functional importance of repeat activity in cancer progression. We show the nucleoside reverse transcriptase inhibitor 3TC targets activities of these repeat elements in CRC pre-clinical models with a preferential effect in P53 mutant cell lines linked with direct binding of P53 to repeat elements. We translate these findings to a human Phase 2 trial of single agent 3TC treatment in metastatic CRC with demonstration of clinical benefit in 9 of 32 patients. Analysis of 3TC effects on CRC tumorspheres demonstrates accumulation of immunogenic RNA:DNA hybrids linked with induction of interferon response genes and DNA damage response. Epigenetic and DNA damaging agents induce repeat RNAs and have enhanced cytotoxicity with 3TC. These findings identify a vulnerability in CRC by targeting the viral mimicry of repeat elements.