Amplification of TLK2 Induces Genomic Instability via Impairing the G2-M Checkpoint

Managing aggressive breast cancers with enhanced chromosomal instability (CIN) is a significant challenge in clinics. Previously, we described that a cell cycle-associated kinase called Tousled-like kinase 2 (TLK2) is frequently deregulated by genomic amplifications in aggressive estrogen receptor-positive (ER+) breast cancers. In this study, it was discovered that TLK2 amplification and overexpression mechanistically impair Chk1/2-induced DNA damage checkpoint signaling, leading to a G(2)-Mcheckpoint defect, delayed DNA repair process, and increased CIN. In addition, TLK2 overexpression modestly sensitizes breast cancer cells to DNA-damaging agents, such as irradiation or doxorubicin. To our knowledge, this is the first report linking TLK2 function to CIN, in contrast to the function of its paralog TLK1 as a guardian of genome stability. This finding yields new insight into the deregulated DNA damage pathway and increased genomic instability in aggressive ER+ breast cancers. Implications: Targeting TLK2 presents an attractive therapeutic strategy for the TLK2-amplified breast cancers that possess enhanced genomic instability and aggressiveness. (C) 2016 AACR.