Abstract 1216: Overcoming cisplatin resistance through the combination treatment with CK2 inhibitor, CX-4945, in gastric cancer

Abstract

Platinum-based antineoplastic drugs are chemotherapeutic agents to usually treat gastric cancer (GC) include cisplatin. However, the majority of cancer patients will eventually relapse with cisplatin-resistant disease. Especially, increased DNA repair is drug targetable mechanism and useful in the treatment strategy of cisplatin-resistant cancer. Casein kinase 2 (CK2) has critical role of multiple cellular processes with DNA repair. For this reason, research for CK2 expression correlated with DNA repair mechanism is important in gastric cancer. Combination of cisplatin and CK2 inhibitor (CX-4945, also known as Silmitasertib, Senhwa Biosciences, USA) may improve cisplatin-induced DNA damage for GC treatment. In this study, we screened sensitivity of cisplatin and CX-4945 in 49 GC cell lines by MTT assay. For molecular profiling, we analyzed variants and gene expression using whole exome sequencing and RNA sequencing. RNA and protein expression of CK2 subunits (α/α’) using real-time RT-PCR and Western blot. Also, activity of CK2α was measured by ELISA. Combination treatment performed different schedules including concurrent and sequential. Synergistic effect was analyzed by Bliss Independence model. As CK2 profiling, CK2α’ mRNA expression was a tendency to correlated with CX-4945 sensitivity(p=0.0504). Moreover, CK2α’ protein expression was a correlated with CX-4945 sensitivity(p=0.0252). Other molecular profiling did not reveal any clear correlations. Twenty one (Group1: cisplatin extremely resistant and CK2 high, Group2: cisplatin intermediate resistant regardless of CK2 expression) cell lines were performed combination treatment. Both YCC-21 and YCC-28 cell lines show synergistic effect (+20% and +22%, respectively) in concurrent schedule. Only MKN-74 cell line show synergistic effect (+11%) in Pre-addition. The 4 cell lines (YCC-18, YCC-38, SNU-1 and -216) were show synergistic effect (+10%, +37%, +11% and +19%, respectively) in Post-addition. In conclusion, early inhibition of CK2 shows synergistic effect in group 1, because CK2 is high expression. In group 2, late inhibition of CK2 demonstrated synergistic effect. It means CK2-related DNA repair is up-regulating for repair to cisplatin-induced DNA damage. Personalized the treatment schedule for inhibit CK2-induced DNA repair is a new strategy to restore cisplatin resistant in GC. Citation Format: Hyun Myong Kim, Inhye Jeong, Kyu Hyun Park, Tae Soo Kim, Woo Sun Kwon, Hei-Cheul Jeung, Minkyu Jung, Sun Young Rha. Overcoming cisplatin resistance through the combination treatment with CK2 inhibitor, CX-4945, in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1216. doi:10.1158/1538-7445.AM2017-1216