Production of autostimulatory growth factors by the human carcinoma line, RPMI 2650

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 beta1 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 novel use of the human nasal epithelial cell line RPMI 2650 as an in vitro model to study the influence of allergens and cytokines on transforming growth factor-beta gene expression and protein release

BACKGROUND

The epithelial accumulation of mast cells is a feature of allergic rhinitis and this has been linked to the expression of the known mast cell chemoattractant transforming growth factor-beta (TGF-beta) at this site. Little is known concerning the regulation of TGF-beta gene expression or protein release by nasal epithelial cells. To address this we have utilized the RPMI 2650 human nasal epithelial cell line, which has some features that closely resemble normal nasal epithelium and has been reported to secrete a TGF-beta-like molecule.

OBJECTIVES

To investigate the regulation of TGF-beta gene expression and protein secretion in RPMI 2650 nasal epithelial cells following exposure to allergens (house dust mite (HDM) and grass pollen) and mast cell associated T-helper type 2 (Th2) cytokines (IL-4, IL-13, and TNF-alpha). Methods Light and scanning electron microscopy was used to evaluate the morphology of RPMI 2650 cells in culture, enzyme-linked immunosorbent assay was used to investigate their TGF-beta secretory capacity and the identification of the TGF-beta isotype(s) involved, flow cytometry was used to demonstrate the presence of TGF-beta receptors on the RPMI 2650 cells, and the quantitative real-time TaqMan PCR was used to measure TGF-beta gene expression.

RESULTS

TGF-beta(2) was identified as the main isotype secreted by the RPMI 2650 cells. HDM allergens and TNF-alpha increased both TGF-beta gene expression and protein release from these cells, whereas grass pollen, IL-4, and IL-13 were without effect.

CONCLUSIONS

The RPMI 2650 nasal epithelial cell line represents a valid in vitro model to evaluate the regulation of TGF-beta biology. In this system HDM allergens have stimulatory activity that is fundamentally different from that of grass pollen allergens, and the Th2 cytokines IL-4 and IL-13 are without effect. The ability of TNF-alpha to up-regulate both TGF-beta gene expression and protein release indicates that mast cell-epithelial interactions concerning TGF-beta are bi-directional and this may be fundamental to epithelial immunoregulation. The availability of a model system, such as the RPMI 2650 cells, will enable the early evaluation of future novel and targeted interventions directed toward the aberrant responses of upper airway structural cells.

Immobilization of Aspergillus fumigatus colonies in a soft agar matrix allows visualization of A549 cell detachment and death

A model to examine the effects of proliferating Aspergillus fumigatus ATCC 26933 colonies embedded in a thin layer of soft agar on a monolayer of A549 cells was developed and enabled an investigation of the response of cultured cells to fungal growth. This model simulates the conditions on the respiratory surface in patients with invasive aspergillosis and also in the mucus secretions of cystic fibrosis patients with allergic bronchopulmonary aspergillosis. Conidia of A. fumigatus adhering to A549 cells were immobilized in a thin layer of soft agar (0.6% (w/v)) and allowed to germinate at 37 degrees C. Fungal colonies greater than 5 mm in diameter caused rounding-up and detachment of A549 cells underneath the colony and towards the hyphal tips. As the fungal colony diameter increased, cell detachment occurred ahead of the hyphal tips. Cells detached for short periods (less than 6 h) showed no annexin-V (AV) or propidium iodide (PI) staining, suggesting no externalization of phosphatidylserine and an intact plasma membrane. Cells that had detached for periods greater than 6 h were positive for AV and PI indicating the rupture of the plasma membrane and cell death by necrosis. Chemical extraction and separation by thin layer chromatography of agar from zones of cell detachment around fungal colonies revealed the presence of three compounds that may play a role in inducing cell death.