Targeting carcinoembryonic antigen cell adhesion molecule 6 (CEACAM6) reshapes the tumor-stroma in pancreatic ductal adenocarcinoma (PDA)

Background: CEACAM6, a cell adhesion receptor of the Ig-like superfamily, interacts with other CEACAMs (1, 5, 7 & 8) and is over-expressed in human cancers including PDA. Over-expression of CEACAM6 causes resistance to anoikis - regulated apoptosis induced by inadequate or inappropriate cell-matrix interactions, promoting a TGFβ-mediated invasive phenotype. CEACAM6 as a predictive biomarker has not been fully investigated with regard to its potential as a candidate therapeutic target in PDA. We report a detailed analysis of CEACAM6 by expression profiling in several pancreatic tumor types, stromal cells, cell lines and mechanistic studies supporting CEACAM6 as a therapeutic target, when inhibited impacts several hallmarks key to PDA pathogenesis. Methods: RNAseq, expression arrays and clinical data was analyzed from The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC) and GEO using R (v3.4.3). Expression profiles were analyzed across PDA subtypes, stroma types and overall survival. CRISPR/Cas9 knockout (KO) of CEACAM6 in HPAF-II cells was investigated by quantitative proteomics and genomics with corroborative signaling pathway analysis. A therapeutic monoclonal antibody scFv-Fc (IgG) targeting CEACAM6 was tested in an orthotopic mouse PDA model. Results: CEACAM6 is over-expressed in ~90% of primary and metastatic PDA samples, ~10-20 fold higher vs. normal cells. Basal and classical subtypes and activated stroma over-express CEACAM6, compared to low or normal stroma. TCGA dataset shows that PDA patients with high CEACAM6 expression have a poor prognosis vs. low expression. In addition, CEACAM6 over-expression is associated with mutant KRAS and immune suppression elaborated by low cytolytic T-cell activity. Correlation studies show that CEACAM6 is associated with genes involved in cell junctions and membrane integrity. HPAF-II cells with CEACAM6 KO showed changes to cell adhesion-extracellular matrix, transmembrane activity, increase in immune signaling and changes to enzymes of mitochondrial activity with significantly decreased mitochondrial membrane potential and ATP production. In addition, CEACAM6 KO cells have a significantly decreased growth rate with reduced Src, Akt and Fak signaling. The scFv-Fc has anti-PDA activity as a single agent in an orthotopic mouse model. Conclusions: CEACAM6 over-expression is a stroma-associated poor prognostic marker and a novel therapeutic target in PDA. The scFv-Fc targeting CEACAM6 shows promising anti-PDA activity and is being developed to enhance anoikis and restore host anti-tumor immunity. Citation Format: Ritu Pandey, Muhan Zhou, Shariful Islam, Baowei Chen, Paul Langlais, Anup Srivastava, Larry S. Cooke, Eric Weterings, Daruka Mahadevan. Targeting carcinoembryonic antigen cell adhesion molecule 6 (CEACAM6) reshapes the tumor-stroma in pancreatic ductal adenocarcinoma (PDA) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3039.