Hyaluronan in peritumoral stroma and malignant cells associates with breast cancer spreading and predicts survival

Abstract

Hyaluronan (HA) is an extracellular matrix polysaccharide that promotes cell migration through its cell surface receptors and by effecting changes in the physical environment. HA expression is frequently increased in malignant tumors, whereas its association with the invasive potential and patient outcome in breast cancer has not been reported. The localization and signal intensity of HA was analyzed in 143 paraffin-embedded tumor samples of human breast carcinoma using a biotinylated HA-specific probe. In the immediate peritumoral stroma, HA signal was moderately or strongly increased in 39% and 56% of the cases, respectively. Normal ductal epithelium showed no HA, whereas in 57% of the tumors at least some of the carcinoma cells were HA positive. The intensity of the stromal HA signal and the presence of cell-associated HA were both significantly related to poor differentiation of the tumors, axillary lymph node positivity, and short overall survival of the patients. In Cox's multivariate analysis, both the intensity of stromal HA signal alone and that combined with the HA positivity in tumor cells were independent prognostic factors for overall survival. These results suggest that HA is directly involved in the spreading of breast cancer and may offer a potential target for new therapies.

Figure 1.

The expression patterns of hyaluronan (HA) in breast carcinoma lesions. A: Normal breast tissue. The HA signal in stroma is weak. Epithelial and myoepithelial cells in normal ducts are negative for HA (scale bar, 50 μm). B: Typical HA signal intensity difference between normal⁽⁺⁾ and peritumoral^([star]) stroma (scale bar, 90 μm). Views of breast cancer cases in which the intensity of HA signal in stroma is weak (C; scale bar, 90 μm), moderate (D; scale bar, 50 μm), or strong (E; scale bar, 30 μm). Examples of tumor cell-associated HA from areas with HA signal on plasma membranes (F; scale bar, 10 μm), cytoplasm (G; scale bar, 10 μm), and some of the nuclei (H; scale bar, 10 μm). I: A breast cancer case with cytoplasmic HA signal and its negative control treated with Streptomyces hyaluronidase before the staining (scale bar, 50 μm).

Figure 2.

Survival plots of breast cancer patients scored for HA signal intensity in peritumoral stroma and the presence of HA in malignant cells. a: Overall survival of the 143 patients based on the level of HA signal in peritumoral stroma. b: Overall survival of the 143 patients based on the presence of HA signal on carcinoma cells. c: Disease-free survival of the 137 patients without distant metastases based on the level of HA signal in peritumoral stroma.