Abstract 1967: Elucidation of signaling pathways that mediate gastrin-induced JNK activation and pGSK3β/Snail induction in gastric cancer cells

Abstract

Abstract The gastrointestinal peptide hormone gastrin is known to regulate various cellular processes including proliferation, migration and metastasis in gastrointestinal cells. Our previous studies indicated that amidated gastrin (G-17) induced gastric cancer cell migration through two separate signaling axes. These revealed that inhibition of Glycogen Synthase Kinase-3β (GSK3β) was necessary to activate G17-induced migratory pathways in gastric cancer cells. Incubation of AGSE gastric cancer cells overexpressing CCK2 receptor (CCK2R) with G17 resulted in a dose and time dependent increase of GSK3βSer9 phosphorylation, indicative of an inhibition of the kinase. Treatment with G-17 was also associated with increased Snail expression, a downstream target of GSK3β and p21-activated protein kinases (PAKs). In a second pathway, G-17 also induced JNK phosphorylation through activation of Mixed Lineage Kinase 3 (MLK3). This axis also promotes gastric cancer cell migration via CCK2R. In the present study our goal was to determine whether PAKs, which are effectors for the Rho GTPases Cdc42 and Rac and are central players in cell proliferation, survival and motility, are involved in the G-17 effects on gastric cancer cells. Our studies showed that in AGSE cells when pretreated with a commercially available PAK4 inhibitor PF 3758309, G-17 was unable to phosphorylate GSK3β and G-17-induced Snail expression was markedly inhibited. G17-induced p-JNK expression was also significantly attenuated with PAK4 inhibitor pretreatment. The inhibitory effect was stronger when PAK4 inhibitor was used in combination with a pan-MLK inhibitor CEP11004. The involvement of PAK4 in G17-induced events were also confirmed by using the PAK4 siRNA. Knockdown of PAK4 inhibited G17-induced p-JNK expression which was more pronounced when both PAK4 and MLK3 were knocked down in AGSE gastric cancer cells. However, knocking down PAK4 alone does-not seem to inhibit G-17-induced p-GSK3β expression completely, which suggest the potential involvement of other PAK family members. Studies are currently underway to determine which PAK(s) is involved in mediating G17-pGSK3β-Snail axis and also to elucidate any crosstalk of PAK4 and MLK3 in this pathway. Elucidation of the signaling pathways that mediate G17-induced cellular events will be very important in designing therapeutic approaches in the future to restrict gastric cancer cell migration and metastasis. Citation Format: Aninda Basu, Goutam Sondarva, Sreevidya Santha, Ajay Rana, Basabi Rana. Elucidation of signaling pathways that mediate gastrin-induced JNK activation and pGSK3β/Snail induction in gastric cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1967. doi:10.1158/1538-7445.AM2015-1967