Alterations in integrin expression modulates invasion of pancreatic cancer cells

Background Factors mediating the invasion of pancreatic cancer cells through the extracellular matrix (ECM) are not fully understood. Methods In this study, sub-populations of the human pancreatic cancer cell line, MiaPaCa-2 were established which displayed differences in invasion, adhesion, anoikis, anchorage-independent growth and integrin expression. Results Clone #3 displayed higher invasion with less adhesion, while Clone #8 was less invasive with increased adhesion to ECM proteins compared to MiaPaCa-2. Clone #8 was more sensitive to anoikis than Clone #3 and MiaPaCa-2, and displayed low colony-forming efficiency in an anchorage-independent growth assay. Integrins beta 1, alpha 5 and alpha 6 were over-expressed in Clone #8. Using small interfering RNA (siRNA), integrin β1 knockdown in Clone #8 cells increased invasion through matrigel and fibronectin, increased motility, decreased adhesion and anoikis. Integrin alpha 5 and alpha 6 knockdown also resulted in increased motility, invasion through matrigel and decreased adhesion. Conclusion Our results suggest that altered expression of integrins interacting with different extracellular matrixes may play a significant role in suppressing the aggressive invasive phenotype. Analysis of these clonal populations of MiaPaCa-2 provides a model for investigations into the invasive properties of pancreatic carcinoma

The α2β1 integrin mediates the malignant phenotype on type I collagen in pancreatic cancer cell lines

Pancreatic cancer is characterised by a hallmark desmoplastic response that includes upregulated expression of the extracellular matrix, and type I collagen in particular. Recent studies indicate that pancreatic cancer cells stimulate type I collagen synthesis in adjacent stellate cells, and that this upregulated type I collagen expression promotes the malignant phenotype in tumour cells as defined by increased proliferation, resistance to chemically induced apoptosis, and increased tumorigenesis. The integrin specificity of this interaction between type I collagen and tumour cells was not identified, however. In the present study, we examined eight pancreatic cancer cell lines for adhesion, proliferation, and migration, on types I and IV collagen, fibronectin, laminin, and vitronectin, as well as integrin expression. Our results indicate, for the overwhelming majority of cell lines, that type I collagen promotes the strongest adhesion, proliferation, and migration relative to the other substrates tested. Utilising function-blocking monoclonal antibodies directed against particular integrin subunits in cell adhesion and migration inhibition assays, we demonstrate further that the malignant phenotype on type I collagen is mediated specifically by the α2β1 integrin. These results identify α2β1 integrin-mediated adhesion to type I collagen as a potential therapeutic target in the treatment of pancreatic cancer

T cell adhesion and cytolysis of pancreatic cancer cells: a role for E-cadherin in immunotherapy?

Pancreatic cancer is an aggressive and potent disease, which is largely resistant to conventional forms of treatment. However, the discovery of antigens associated with pancreatic cancer cells has recently suggested the possibility that immunotherapy might become a specific and effective therapeutic option. T cells within many epithelia, including those of the pancreas, are known to express the αEβ7-integrin adhesion molecule, CD103. The only characterised ligand for CD103 is E-cadherin, an epithelial adhesion molecule which exhibits reduced expression in pancreatic cancer. In our study, CD103 was found to be expressed only by activated T cells following exposure to tumour necrosis factor beta 1, a factor produced by many cancer cells. Significantly, the expression of this integrin was restricted mainly to class I major histocompatibility complex-restricted CD8+ T cells. The human pancreatic cancer cell line Panc-1 was transfected with human E-cadherin in order to generate E-cadherin negative (wild type) and positive (transfected) sub-lines. Using a sensitive flow cytometric adhesion assay it was found that the expression of both CD103 (on T cells) and E-cadherin (on cancer cells) was essential for efficient adhesion of activated T cells to pancreatic cancer cells. This adhesion process was inhibited by the addition of antibodies specific for CD103, thereby demonstrating the importance of the CD103→E-cadherin interaction for T-cell adhesion. Using a 51Cr-release cytotoxicity assay it was found that CD103 expressing T cells lysed E-cadherin expressing Panc-1 target cells following T cell receptor stimulation; addition of antibodies specific for CD103 significantly reduced this lysis. Furthermore, absence of either CD103 from the T cells or E-cadherin expression from the cancer cells resulted in a significant reduction in cancer cell lysis. Therefore, potentially antigenic pancreatic cancer cells could evade a local anti-cancer immune response in vivo as a consequence of their loss of E-cadherin expression; this phenotypic change may also favour metastasis by reducing homotypic adhesion between adjacent cancer cells. We conclude that effective immunotherapy is likely to require upregulation of E-cadherin expression by pancreatic cancer cells or the development of cytotoxic immune cells that are less dependent on this adhesion molecule for efficient effecter function

Effector T lymphocyte subsets in human pancreatic cancer: detection of CD8+ CD18+ cells and CD8+ CD103+ cells by multi-epitope imaging

Pancreatic cancer is characterized by an increasing incidence and an extremely poor prognosis. It is resistant to most of the conventional treatment modalities. Histomorphologically, it presents with a strong desmoplastic reaction around cancer cells, and lymphocytes are typically localized as aggregates in the fibrotic interstitial tissue. Using the method of multi-epitope imaging with fluorochrome-tagged specific MoAbs which allows the simultaneous localization and characterization of T cells in tissues, we studied phenotypes and distribution of tumour-infiltrating lymphocytes (TIL) in pancreatic cancer. CD3+ T cells comprised up to 90% of the tumour-infiltrating cells which were either CD4+ or CD8+, most of them being memory cells (CD45RO+). In decreasing order of frequency, T lymphocytes carried the markers for CD45RO, CD18, CD103 and TCR γδ. Very few natural killer cells (CD56+) were observed. Twenty percent of CD8+ were labelled with CD103. These CD8+ CD103+ T cells, analogous to the gut intraepithelial lymphocytes (IEL), were found in the fibrous interstitial tissue. Furthermore, an inverse correlation was found between the expression of CD18, the β2-integrin, which mediates adhesion of activated lymphocytes, and CD45RO in the CD8+ subset of TIL (P = 0.046). In conclusion, phenotyping of T lymphocytes in pancreatic cancer raises the possibility that pancreatic cancer cells develop several strategies to escape the T cell-induced cytolysis by (i) the aggregation of cytotoxic CD8+ CD103+ T cells in the fibrous tissue distant from the tumour cells, and (ii) the presence of CD18-bearing cells which lack the expression of the activation marker CD45RO