Pancreatic stellate cell secreted IL-6 stimulates STAT3 dependent invasiveness of pancreatic intraepithelial neoplasia and cancer cells

// Nagaraj S. Nagathihalli 1 , Jason A. Castellanos 2 , Michael N. VanSaun 1 , Xizi Dai 1 , Mahogany Ambrose 3 , Qiaozhi Guo 4 , Yanhua Xiong 2 , Nipun B. Merchant 1 1 Division of Surgical Oncology, Department of Surgery, University of Miami Miller School of Medicine, Sylvester Comprehensive Cancer Center, Miami, Florida, USA 2 Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, USA 3 Meharry Medical College, Nashville, Tennessee, USA 4 Yale School of Medicine, New Haven, Connecticut, USA Correspondence to: Nipun B. Merchant, email: nmerchant@med.miami.edu Keywords: pancreatic stellate cells, IL-6, STAT3, PanIN, pancreatic cancer Received: January 06, 2016 Accepted: August 22, 2016 Published: September 01, 2016 ABSTRACT Pancreatic ductal adenocarcinoma (PDAC) is a dynamic tumor supported by several stromal elements such as pancreatic stellate cells (PSC). Significant crosstalk exists between PSCs and tumor cells to stimulate oncogenic signaling and malignant progression of PDAC. However, how PSCs activate intercellular signaling in PDAC cells remains to be elucidated. We have previously shown that activated signal transducer and activator of transcription 3 (STAT3) signaling is a key component in the progression of pancreatic neoplasia. We hypothesize that PSC secreted IL-6 activates STAT3 signaling to promote PanIN progression to PDAC. Human PDAC and mouse PanIN cells were treated with PSC-conditioned media (PSC-CM), and phospho- and total-STAT3 levels by immunoblot analysis were determined. IL-6 was quantified in PSC-CM and cell invasion and colony formation assays were performed in the presence or absence of a neutralizing IL-6 antibody and the JAK/STAT3 inhibitor AZD1480. Serum from Ptf1a Cre/+ ;LSL-Kras G12D/+ ;Tgfbr2 flox/flox’ (PKT) and LSL-Kras G12D/+ ; Trp53 R172H/+ ; Pdx1 Cre/+ (KPC) mice demonstrated increased levels of IL-6 compared to serum from non-PDAC bearing KC and PK mice. PSC secreted IL-6 activated STAT3 signaling in noninvasive, precursor PanIN cells as well as PDAC cells, resulting in enhanced cell invasion and colony formation in both cell types. There was a significant positive linear correlation between IL-6 concentration and the ratio of phosphorylated STAT3/total STAT3. IL-6 neutralization or STAT3 inhibition attenuated PSC-CM induced activation of STAT3 signaling and tumorigenicity. These data provide evidence that PSCs are directly involved in promoting the progression of PanINs towards invasive carcinoma. This study demonstrates a novel role of PSC secreted IL-6 in transitioning noninvasive pancreatic precursor cells into invasive PDAC through the activation of STAT3 signaling.