Abstract 3465: FANCD2 depletion suppresses tumor growth in esophageal squamous cell carcinoma

Abstract Introduction: Esophageal squamous cell carcinoma (ESCC) has a remarkably high incidence in Northern China. Our next-generation sequencing analysis on familial ESCC samples suggests that members of the Fanconi Anemia (FA) pathway play important roles in ESCC development. Fanconi anemia complementation group D2 (FANCD2) as a key player of FA pathway has multiple cellular functions. It is well-known for its role in DNA damage repair through the FA pathway. Patients with germline FANCD2 mutations are prone to tumor formation. Identifying roles of FANCD2 in ESCC development may enhance our foundation for future development of specific treatment regimens for this deadly disease. Methods and Results: To study the function of FANCD2 in ESCC, we applied the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) technique to inhibit FANCD2 protein expression by functional knock-out (fKO). As expected, we observed increased DNA damage in FANCD2 fKO cells as shown by Comet assay, consistent with the classic role of FANCD2 in genome integrity. We also observed that the DNA damage by irradiation takes longer to be repaired in FANCD2 fKO cells, indicating that FANCD2 enhances irradiation-induced DNA damage repair but is not necessary. Similarly, cells with FANCD2 fKO are more sensitive to irradiation, as indicated by cell cycle arrest at S/G2 phase. Surprisingly, without inducing any DNA damage, FANCD2 fKO cells also show cell cycle arrest at S/G2 phase. The MTT cell proliferation assay also show that FANCD2 fKO reduces proliferation and colony-forming ability. Consistent with the in vitro data, FANCD2 fKO cells also form smaller tumors in vivo by the nude mouse tumorigenicity assay. Conclusion: These results indicate that FANCD2 plays important roles in ESCC development and suggest a pro-oncogenic feature of wildtype FANCD2 in ESCC. Further investigation is ongoing to examine the functional role and molecular mechanisms of the oncogenic FANCD2, ultimately aiming at improving ESCC disease management. Acknowledgement: We acknowledge the grant support from the Hong Kong Research Grants Council Collaborative Research Fund (C7031.15G) and the Asian Fund for Cancer Research to M.L.L. Citation Format: Chan Lei, Zhuoyou Yu, Lvwen Ning, Mun-Yee Ko, Lidong Wang, Maria Li Lung. FANCD2 depletion suppresses tumor growth in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3465.