Deficiency in mammalian STN1 promotes colon cancer development via inhibiting DNA repair

Despite the high lethality of colorectal cancers (CRCs), only a limited number of genetic risk factors are identified. The mammalian ssDNA-binding protein complex CTC1-STN1-TEN1 protects genome stability, yet its role in tumorigenesis is unknown. Here, we show that attenuated CTC1/STN1 expression is common in CRCs. We generated an inducible STN1 knockout mouse model and found that STN1 deficiency in young adult mice increased CRC incidence, tumor size, and tumor load. CRC tumors exhibited enhanced proliferation, reduced apoptosis, and elevated DNA damage and replication stress. We found that STN1 deficiency down-regulated multiple DNA glycosylases, resulting in defective base excision repair (BER) and accumulation of oxidative damage. Collectively, this study identifies STN1 deficiency as a risk factor for CRC and implicates the previously unknown STN1-BER axis in protecting colon tissues from oxidative damage, therefore providing insights into the CRC tumor-suppressing mechanism.

Current inhibitors of checkpoint kinase 2

Checkpoint kinase 2 is a serine/threonine protein which functions as an important transducer in apoptosis or DNA repair following activation by DNA damage. Inhibition of checkpoint kinase 2 is thought to sensitize p53-mutated or p53-deficient cancerous cells but protect normal tissue following DNA-damage caused by ionizing radiation or chemotherapeutic agents. The development of checkpoint kinase inhibitors for the treatment of cancer has therefore been a major objective in drug discovery over the past decade. Several inhibitors have been co-crystallized in the active site of checkpoint kinase 2 revealing important features of effective inhibitors. Some of these inhibitors have entered clinical trials in the last decade. This review describes and discusses the most recent inhibitors of checkpoint kinase 2 as reported in the literature, including an evaluation of biological activity.