Abstract
BackgroundDespite an enormous research effort, patients diagnosed with advanced colorectal cancer (CRC) still have low prognosis after surgical resection and chemotherapy. The major obstacle for CRC treatment is chemoresistance to front line anti-cancer drugs, such as 5-fluorouracil (5-FU) and oxaliplatin. However, the mechanism of chemoresistance to these drugs remains unclear.MethodsCell viability to 5-FU and oxaliplatin was measured by the CellTiter-Glo® 2.0 Cell Viability Assay. The endogenous REV7 protein in CRC cells was detected by western blotting. The translesion synthesis (TLS) events were measured by plasmid-based TLS efficiency assay. Cell apoptosis was evaluated by caspase3/7 activity assay. The in vivo tumor progression was analyzed by HT29 xenograft mice model.ResultsIn this study, we found that expression of REV7, which is a key component of translesion synthesis (TLS) polymerase ζ (POL ζ), is significantly increased in both 5-FU and oxaliplatin resistant CRC cells. TLS efficiency analysis revealed that upregulated REV7 protein level results in enhanced TLS in response to 5-FU and oxaliplatin. Importantly, inhibition of REV7 by CRISPR/Cas9 knockout exhibited significant synergy with 5-FU and oxaliplatin in cell culture and murine xenograft model.ConclusionThese results suggest that combination of REV7 deficiency and 5-FU or oxaliplatin has strong inhibitory effects on CRC cells and identified REV7 as a promising target for chemoresistant CRC treatment.
Highlights
Despite an enormous research effort, patients diagnosed with advanced colorectal cancer (CRC) still have low prognosis after surgical resection and chemotherapy
We found that protein expression of REV7 and translesion synthesis (TLS) efficiency were upregulated in both 5-FU and cisplatin-resistant CRC cells
Establishment of chemoresistant CRC cell lines Previous studies show that TLS polymerases, such as REV1 and Polζ (REV3 and REV7), are positively correlated with cisplatin resistance [14]
Summary
Despite an enormous research effort, patients diagnosed with advanced colorectal cancer (CRC) still have low prognosis after surgical resection and chemotherapy. Replicative DNA polymerases are highly efficient and accurate during DNA synthesis. Direct replication of damaged DNA can be achieved by translesion synthesis (TLS), a conserved mechanism throughout species from bacteria to mammals [8]. It relies on specialized DNA polymerases with structural feature to accommodate damaged template at the cost of replication fidelity [9]. Genetic studies of lung cancer show that extension TLS DNA polymerase POL ζ (REV3 and REV7) is related to cisplatin-resistance in lung adenocarcinomas [10, 11]. We found that protein expression of REV7 and TLS efficiency were upregulated in both 5-FU and cisplatin-resistant CRC cells. Genetic inhibition of REV7 significantly improved sensitivity to 5-FU and cisplatin in vivo and in vitro, thereby highlighting the therapeutic potential of inhibiting REV7 in chemoresistant CRC therapy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
