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

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 Ptf1aCre/+;LSL-KrasG12D/+;Tgfbr2flox/flox' (PKT) and LSL-KrasG12D/+; Trp53R172H/+; Pdx1Cre/+ (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.

Targeting Pancreatic Stellate Cells in Cancer

“…Additionally, aPSCs secrete increased levels of cytokines such as interleukin-1, -6, -8 and -10 (IL-1, -6, -8 and -10) and growth factors, including insulin-like growth factor 1 (IGF1), vascular endothelial growth factor (VEGF), and platelet derived growth factor (PDGF), fibroblast growth factor (FGF), connective tissue growth factor (CTGF) and C-X-C motif chemokine 12 (CXCL12) [6,7]. These cytokines and growth factors promote angiogenesis, and proliferation, migration and invasion of epithelial cancer cells that leads to metastasis [6,8,14].Furthermore, PSCs-secreted soluble factors, especially IL-6, has been shown to be involved in transitioning of non-invasive into invasive PDAC, and to drive immunosuppression in the TME by promoting the accumulation of myeloid-derived suppressor cells (MDSCs), via STAT3-dependent mechanism [16,17]. Moreover, cancer cells also secrete cytokines such as IL-1, IL-6 and TNF-α, and growth factors including TGF-β1, PDGF-BB [2].…”

Metastasis in Pancreatic Ductal Adenocarcinoma: Current Standing and Methodologies

“…For example, PSC-derived hepatocyte growth factor (HGF) [82], insulin growth factor 1 (IGF-1) [82], and interleukin-6 (IL-6) [83] can induce EMT in PDA cells. In addition to facilitating EMT, secreted factors from PSCs such as matrix metalloproteases [84], collagen I [85], IL-6 [86], and galectin-1 [87] can also directly stimulate PDA cell migration. Besides directly activating pro-metastatic properties in the primary tumor, stromal factors also contribute to preparing a pre-metastatic niche in distant organ sites to facilitate the seeding of metastatic cells [88,89].…”

Chemotherapy and tumor microenvironment of pancreatic cancer

“…PSCs secreted-IL-6 stimulates STAT3 to enhance colony formation and progression of PanIN [102]2. PSCs enhance the CSCs phenotype of cancer cells by TGF-β [103]3.…”