Abstract 2621: Disruption of mucin synthesis by targeting GCNT3 inhibits pancreatic cancer progression

Abstract Pancreatic cancer (PC) is a lethal disease, and its management is an ongoing challenge. PC is the fourth leading cause of deaths due to cancer in the United States. It is a highly aggressive cancer that is usually diagnosed at an advanced stage, and has the worst prognosis of any malignancy, with a five year survival of <7% due to high chemoresistance. This chemoresistance is due in part to altered expressions of mucins, which form a mesh that makes target sites inaccessible to drugs. Clinical and preclinical studies have shown aberrant expression of mucins during PC development. The mucins may prevent drugs from accessing their sites of action. Although several mucins that lead to chemoresistance have been targeted, to date, no mucin synthesizing genes have been identified as targets. Using human pancreatic cancer patient survival data (90 cases of tumor and matched normal adjacent tissue), next-generation sequencing (NGS) of genetically engineered Kras mouse pancreatic tumors (N = 6/group), human PC cells, we identified novel core mucin synthesizing gene target GCNT3 (core 2 beta 1,6 N-acetylglucosaminyltransferase). NGS revealed that GCNT3 upregulation (103-fold; p<0.0001) was correlated with increased mucins Muc4 (50-fold; p<0.04), Muc5ac (87-fold; p<0.01), Muc6 (67-fold; p<0.008), Muc1 (5-fold; p<0.009), Muc16 (5-fold; p<0.0003) and Muc20 (17-fold; p<0.007)]. Aberrant GCNT3 expression was associated with increased mucin production and aggressive tumorigenesis and reduced patient survival. Patients with low expression of GCNT3 had a longer survival time than patients with high expression of GCNT3 (median survival: 17.5 vs. 10.5 months, p = 0.036). Further, using in-silico approaches of small molecular docking simulations, we identified talniflumate as a novel inhibitor that specifically binds to GCNT3. Our blind docking simulations reveal that talniflumate binds to GNTC3 with a docking affinity of -8.3 kcal/mol and deeper in the pocket of GCNT3. The docking predictions suggest three notable hydrogen bonds between talniflumate and GCNT3: Arg192 (3.0 Angstroms), Try288 (3.5 Angstroms), and Ala287 (2.9 Angstroms). Pancreata from 6-week-old Kras mice treated with talniflumate for 1 week showed a significant decrease in GCNT3 and mucin expression in PanIN lesions. mRNA expression of GCNT3 was also observed to be lower in pancreatic tissues from talniflumate-treated mice. CRISPR knock-out of GCNT3 in PC cells reduced proliferation and spheroid formation. Further, talniflumate alone and in combination with low-dose gefitinib reduced GCNT3 leading to disruption of mucins in vivo and in vitro. Hence, mucin disruption might enhance targeted therapy. These findings suggest a prominent role for Kras activation and aberrant mucin synthesis leading to PC pathogenesis, and warrant consideration of GCNT3 and EGFR inhibitors as a combination treatment for PC. (Grant Support: COMAA, Kerley-Cade Endowed Fund). Citation Format: Altaf Mohammed, Naveena B. Janakiram, Venkateshwar Madka, Gaurav Kumar, Scott Edgar, Gopal Pathuri, Taylor Bryant, Hannah Kutsche, Yuting Zhang, Laura Biddick, Hariprasad Gali, Yan Daniel Zhao, Stan Lightfoot, Chinthalapally V. Rao. Disruption of mucin synthesis by targeting GCNT3 inhibits pancreatic cancer progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2621.