Effects of hyaluronan on the invasive properties of human breast cancer cells in vitro

Abstract

Hyaluronan (HA) is a high molecular weight glycosaminoglycan present mostly in the extracellular matrix (ECM). HA binds to specific receptors such as CD44. Its production is increased at the tumour-stroma interface, including those in breast cancer tumours. It has been suggested that it facilitates invasion of tumour cells into the ECM by a hydrodynamic effect, or by altering tumour cell behaviour. Using in vitro tests we studied the effect of immobilized (iHA) and soluble (sHA) HA on the invasive properties of four human breast cancer cell lines with different levels of CD44 expression. Our results show that iHA acts as an adhesive, haptotactic, and motility stimulating factor for the CD44 positive Hs578T cells and induces the expression of membrane CD44. sHA also changes the motility properties of the Hs578T and MDA-231 cells and increases their CD44 expression. sHA or iHA have no measurable effect on the adhesion, motility or CD44 expression of the ZR-75-1 and MCF-7 breast cancer cells. Our results establish that in high CD44 expressing breast cancer cells HA modulates tumour cell adhesion and motility and also increases the expression of its own receptor, CD44.

Figure 1

Adhesion of Hs578T breast cancer cells to different concentrations of immobilized hyaluronan (iHA).The adhesion of cells to BSA and two different concentrations of HA (500 (μg/mL and 5 mg/mL) was evaluated at 1 h. Up to a sevenfold increase in cell adhesion was observed when cells were plated on HA 500 (g/mL and 5 mg/mL, respectively, compared to controls. Bars represent mean values of percentage of adherent cells ± SD.

Figure 2

Immobilized hyaluronan (iHA) as an haptotactic factor. The haptotactic migratory capacity of the Hs578T cell line was evaluated towards two different concentrations of iHA (1 mg/mL or 5 mg/mL) as described in Materials and methods. Hyaluronan acts as an haptotactic factor compared to ‘random motility’ (uncoated membranes). No significant difference was observed between the two iHA concentrations. Bars represent mean values of percentage of cells ± SD.

Figure 3

Effect of immobilized hyaluronan (iHA) on the motility of Hs578T cells. Hs578T cells were plated on HA-coated or HA-uncoated coverslips, wounded, and allowed to migrate in the absence of serum in the culture medium for 24 h as described in Materials and methods. Cells show a 160% increase in motility, error bars refer to SD.

Figure 4

Effect of immobilized hyaluronan (iHA) on CD44 expression by Hs578T cells, at different time points. Cells were grown on uncoated or HA-coated wells for different periods of time. CD44 expression was measured by flow cytometry. Cells grown on iHA show increases of CD44 expression of 60%, 150% and 8% at 1, 3 and 6 days in culture, respectively, as compared to control. Values are expressed in percentage of control, error bars refer to SD.

Figure 6

Effect of soluble and immobilized hyaluronan on CD44 expression by Hs578T cells. (a): Hs578T cells grown with sHA ((c): white profile) for 3 days express more CD44 molecules on their membrane than cells that were cultured in RCM ((b): grey profile). (a): black profile represents background fluorescence, omitting primary antibody. LFL1: fluorescence, COUNT: number of cells. (b): Hs578T cells grown on iHA ((c): white profile) for 3 days express more CD44 molecules on their membrane than cells that were cultured in RCM ((b): grey profile). a: black profile represents background fluorescence, omitting primary antibody.

Figure 5

Effect of soluble hyaluronan (sHA) on adhesion, haptotaxis, CD44 expression and proliferation of Hs578T and MDA-MB-231cells. Cells were grown in regular culture medium (RCM) or in RCM containing soluble hyaluronan (sHA) for 3 days. (a): Hs578T cells that were grown with sHA are more adhesive to HA, less motile towards HA and express more CD44 molecules on their membrane. No differences in proliferation are observed. (b): MDA-MB-231 cells that were grown with sHA express more CD44 molecules on the cell membrane and are less motile towards hyaluronan. Proliferation rate is the same.