Supplementary Material for: Gankyrin Contributes to Tumorigenesis and Chemoresistance in Sporadic Colorectal Cancer

Background: Although Gankyrin is overexpressed in many malignancies, the role of Gankyrin for tumorigenesis and chemoresistance remains to be elucidated in sporadic colorectal cancer (CRC). Aims: We investigate whether Gankyrin affects Adenomatous polyposis coli (Apc) inactivation-induced tumorigenesis and therapeutic response to anti-angiogenic agents. Methods: Epithelial cell-specific APC and/or Gankyrin-deficient mice were used. The patients with metastatic CRC (n = 53) who were enrolled in this study underwent resection of primary cancer followed by systemic chemotherapy containing bevacizumab. We determined whether gene expression in CRC tissues before chemotherapy is associated with radiological responses. Results: Deletion of Gankyrin in epithelial cell reduced the expression of c-Myc, a critical mediator of the APC signaling pathway, and interleukin-6. Gankyrin deficiency decreased the expression of Bmi1, a downstream molecule of c-Myc, and the activity of V-Akt murine thymoma viral oncogene homolog and extracellular signal-regulated protein kinase, leading to reduced Apc inactivation-induced tumorigenesis. Of 53 patients, 38 (72%) had increased Gankyrin expression in tumor cells. The enhanced Gankyrin expression in tumor cells was associated with unfavorable progression-free survival (log-rank test p = 0.026). Conclusion: Gankyrin in epithelial cell contributes to the development of sporadic CRC and the expression could serve as a biomarker to predict therapeutic response in patients with metastatic CRC.