Abstract 4328: Galectin-3 mediates tumor-stromal interaction by activating pancreatic stellate cell through integrinβ1/ILK/NF-κB signaling
Authors: Zhao Wei , Xu Yan , Sushovan Guha , Hwang Rosa , Ochi Nobuo , Hafley Margarete , Bresalier Robert , Logsdon Craig , Wang Zhenning , Ajani Jaffer , Song Shumei 
Published: July 2017

Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor with poor survival in PDAC patients. Proinflammatory cytokines/chemokines play an essential role in tumor microenvironments associated with its invasive and aggressive phenotype. Galectin-3 (Gal-3), a member of a family of β-galactoside-specific lectins, has been found to be involved in tumor progression and tissue fibrosis. However, the precise molecular mechanisms of Gal-3 mediate tumor-stromal interaction and abundant cytokine production is unknown.

Methods: The effects of Gal-3 on secretion of cytokines/chemokines from stromal cells (HPSC) were assessed by cytokine array. HPSC proliferation and invasion were assessed by the MTS and Matrigel invasion assays. Co-culture and Conditional medium from PDAC tumor cells with genetic alterations of Gal-3 levels were used to study the interaction between tumor cell and stromal cells. IL-8 production in both tumor cells and stromal cells was confirmed by ELISA. Transcriptional activities of NF-κB and IL-8 were determined by transient transfection. An IKB mutant construct (IKBM), Mutation of the IL-8 promoter at the NF-κB site, and inhibitors of NF-κB (Bay11), ILK and neutral antibody of Integrinβ1 were used to determine the signaling pathways evoked by Gal-3.

Results: Gal-3 expression is in both tumor cells and stromal cells of human and genetic mouse model. Secretion of cytokines such as IL-8, GM-CSF, CXCL1, CCL2 and IL6 were significantly increased in HPSC cells treated with rGal-3 which is concomitant with activation of HPSC. Conditioned medium or co-culture from Panc-1 cells in which Gal-3 was down-regulated inhibited the growth and invasion capacity of HPSC cells compared with the vector controls. rGal-3 dramatically induced production and secretion of IL-8 in HPSCs. Mechanistically, Gal-3 stimulates IL-8 secretion at the level of transcription and through Integrinβ1/ILK/NF-kB signaling. rGal-3 strongly stimulated integrin β1 expression and NF-κB transcriptional activity; and inhibitors of ILK inhibitor or NF-κB or neutral antibody of integrin β1 blocked IL-8 transcriptional activity and its secretion. NF-κB mutant construct IKBM or mutation of the NF-κB site in the IL-8 promoter completely block the induction of IL-8 activity by Gal-3. GEO data and our own patients’ cohort analysis of pancreatic tumor samples demonstrated that the level of Gal-3, IL-8 and other cytokines is significantly higher in tumor tissues than those of normal and pancreatitis.

Conclusion: Collectively, these data suggest that Gal-3 secreted from tumor cells activate HPSC cells and induce many inflammatory cytokines including IL-8 production via Integrinβ1/ILK/NF-κB signaling. Thus, Gal-3 may play a critical role in mediating tumor-stromal interaction and remodeling tumor associated microenvironments.

Citation Format: Wei Zhao, Yan Xu, Guha Sushovan, Rosa Hwang, Nobuo Ochi, Margarete Hafley, Robert Bresalier, Craig Logsdon, Zhenning Wang, Jaffer Ajani, Shumei Song. Galectin-3 mediates tumor-stromal interaction by activating pancreatic stellate cell through integrinβ1/ILK/NF-κB signaling [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 4328. doi:10.1158/1538-7445.AM2017-4328