Jumonji domain-containing protein 2A (JMJD2A), belonging to the JMJD2 family of histone lysine demethylases, has been implicated in tumorigenesis. However, its expression profile and role in drug resistance of gastric cancer remains unknown. Previous studies show that docetaxel, cisplatin, and S-1 (DCS) therapy has a high response rate in patients with metastatic gastric cancer, but acquired drug resistance is often observed. In this study, we investigated the role of JMJD2A in drug susceptibility of DCS therapy in patients with gastric cancer, and its clinical relevance in gastric cancer.
siRNA-mediated downregulation of 14 relevant genes from previously identified gene signatures was performed to identify functional factor to modulate drug susceptibility in DCS therapy. In 34 clinical tissues with metastatic gastric cancer, we examined whether JMJD2A expression predicted tumor regression rate in patients. Furthermore, the downstream effects of JMJD2A on drug susceptibility were analyzed by whole-gene expression array and immunoprecipitation.
After specific silencing of 14 candidate genes, inhibition of JMJD2A induced significant drug resistance in three anti-cancer drugs; IC50values for 5-FU, cisplatin, and docetaxel were 15.3-, 2.7-, and 4.0-fold increased, respectively. Overexpressed JMJD2A was universally expressed in 12 gastric cancer cell lines, positively correlated with tumor regression rate in DCS therapy. JMJD2A is physically associated with histone lysine demethylation. By analysis of downstream effect of JMJD2A, cooperation of Coiled-coil domain containing 8 (CCDC8) was identified, using whole-gene expression analysis. Direct interaction of CCDC8 and JMJD2A was verified by immunoprecipitation. Of note, inhibition of CCDC8 also induced significant drug resistance in docetaxel, cisplatin, and S-1.
JMJD2A sensitizes gastric cancer to combination chemotherapy of S-1, cisplatin, and docetaxel by cooperating CCDC8, and JMJD2A/CCDC8 would be a potential biomarker and therapeutic target.
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All authors have declared no conflicts of interest.