Effects of transforming growth factor α1, interleukin-1β, tumor necrosis factor α and platelet-derived growth factor on the collagen synthesis and the proliferation of periacinal fibroblastoid cells isolated and cultured from rat pancreatic acini

The PDAC Extracellular Matrix: A Review of the ECM Protein Composition, Tumor Cell Interaction, and Therapeutic Strategies

Pancreatic ductal adenocarcinoma (PDAC) is notorious for a dense fibrotic stroma that is interlaced with a collagen-based extracellular matrix (ECM) that plays an important role in tumor biology. Traditionally thought to only provide a physical barrier from host responses and systemic chemotherapy, new studies have demonstrated that the ECM maintains biomechanical and biochemical properties of the tumor microenvironment (TME) and restrains tumor growth. Recent studies have shown that the ECM augments tumor stiffness, interstitial fluid pressure, cell-to-cell junctions, and microvascularity using a mix of biomechanical and biochemical signals to influence tumor fate for better or worse. In addition, PDAC tumors have been shown to use ECM-derived peptide fragments as a nutrient source in nutrient-poor conditions. While collagens are the most abundant proteins found in the ECM, several studies have identified growth factors, integrins, glycoproteins, and proteoglycans in the ECM. This review focuses on the dichotomous nature of the PDAC ECM, the types of collagens and other proteins found in the ECM, and therapeutic strategies targeting the PDAC ECM.

The TGF-β/Smad4 Signaling Pathway in Pancreatic Carcinogenesis and Its Clinical Significance

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal human cancers due to its complicated genomic instability. PDAC frequently presents at an advanced stage with extensive metastasis, which portends a poor prognosis. The known risk factors associated with PDAC include advanced age, smoking, long-standing chronic pancreatitis, obesity, and diabetes. Its association with genomic and somatic mutations is the most important factor for its aggressiveness. The most common gene mutations associated with PDAC include KRas2, p16, TP53, and Smad4. Among these, Smad4 mutation is relatively specific and its inactivation is found in more than 50% of invasive pancreatic adenocarcinomas. Smad4 is a member of the Smad family of signal transducers and acts as a central mediator of transforming growth factor beta (TGF-β) signaling pathways. The TGF-β signaling pathway promotes many physiological processes, including cell growth, differentiation, proliferation, fibrosis, and scar formation. It also plays a major role in the development of tumors through induction of angiogenesis and immune suppression. In this review, we will discuss the molecular mechanism of TGF-β/Smad4 signaling in the pathogenesis of pancreatic adenocarcinoma and its clinical implication, particularly potential as a prognostic factor and a therapeutic target.

Pro-inflammatory cytokine-induced matrix metalloproteinase-1 (MMP-1) secretion in human pancreatic periacinar myofibroblasts

Matrix metalloproteinases (MMPs) are the proteases involved in the degradation of the extracellular matrix. MMP-1 is thought to be one of the key enzymes in fibrolysis, a process closely related to tissue remodeling. In the present study, we investigated MMP-1 secretion from human pancreatic periacinar myofibroblasts in response to pro-inflammatory cytokines IL-1beta and TNF-alpha. We also attempted to clarify the intracellular signaling pathways mediating the cytokine-induced MMP-1 secretion. MMP-1 secretion was measured by an enzyme-linked immunosorbent assay. MMP-1 molecules were analyzed by Western blotting. MMP-1 mRNA expression was evaluated by Northern blotting. IL-1l and TNF-alpha stimulated the MMP-1 secretion in a dose- and time-dependent manner. Ninety percent of MMP-1 was secreted as inactive form (pro-MMP-1). The effects of IL-1beta and TNF-alpha were significantly inhibited by PD98059 MEK/ERK inhibitor). In contrast, SB203580 (p38 MAPK inhibitor), GF109203X (PKC inhibitor), and PDTC (NF-kappaB inhibitor) did not alter the MMP-1 secretion induced by IL-1beta and TNF-alpha. These effects were also observed at them RNA level. In conclusion, in human pancreatic periacinar myofibroblasts, MMP-1 secretion was regulated by the pro-inflammatory cytokines via the MEK/ERK cascade. Thus, human pancreatic periacinar myofibroblasts may play an important role in the remodeling of damaged pancreatic tissue in chronic pancreatitis via MMP-1 secretion.

Effects of synthetic serine protease inhibitors on proliferation and collagen synthesis of human pancreatic periacinar fibroblast-like cells

Protease inhibitors are currently used as therapeutic agents for chronic pancreatitis in Japan. We previously reported that human pancreatic periacinar fibroblast-like cells (hPFCs) could be cultured from isolated pancreatic acini, and those are thought to play a crucial role in pancreatic fibrosis correlating with platelet-derived growth factor (PDGF) and transforming growth factor beta1 (TGF-beta1) (Pancreas 1997;14: 373-82). The present study was designed to examine the effects of synthetic serine protease inhibitors (FOY-007 and FOY-305) on proliferation and collagen synthesis of hPFCs under cytokine stimulation. The cell proliferation and collagen synthesis were evaluated using assays of [3H]-thymidine incorporation and procollagen type I c-terminal peptide (PIP), and [14C]-proline incorporation to de novo synthesized collagen, respectively. The cell proliferation stimulated by PDGF was inhibited by the application of FOY-007 dose dependently (1-100 microM) and FOY-305 at 100 microM. FOY-007 attenuated the collagen synthesis and PIP production stimulated by TGF-beta1 dose dependently, but FOY-305 inhibited only PIP production. Both protease inhibitors demonstrated no effect on the proliferation and collagen synthesis of hPFCs when they were not stimulated by PDGF or TGF-beta1. Thus, serine protease inhibitors act on hPFCs to diminish the effects of PDGF on proliferation and the effects of TGF-beta1 on collagen synthesis.