Hyaluronan in breast cancer: correlations with nitric oxide synthases and tyrosine nitrosylation

Reactive oxygen species (ROS), including nitric oxide (NO(*)), are associated with all steps of carcinogenesis. Hyaluronan (HA), a high-molecular-mass glycosaminoglycan overexpressed in a variety of human malignancies also has ROS-scavenging properties. We histochemically studied the level of HA in breast carcinoma cells and their stroma and compared it with the expression of NO(*) synthases (NOSs), major antioxidant enzymes, and nitrotyrosine. We also assessed whether the level of HA correlates with traditional prognostic factors of breast cancer and survival. Stromal HA level was moderate or high in all the samples studied (n=185), and 84% of the lesions showed HA-positive carcinoma cells. Intense stromal HA signal was associated with high neuronal NOS expression (p=0.009), whereas tumor-cell associated HA was inversely correlated with nitrotyrosine expression (p=0.027). Of the traditional prognostic factors, tumor cell-associated HA was correlated with poor differentiation (p=0.011), and high stromal HA levels were associated with aggressive features of the carcinomas such as large primary tumor (p=0.002), poor differentiation (p=0.019), and estrogen (p=0.012) and progesterone receptor negativity (p=0.009). High stromal HA level also significantly predicted poorer survival. The strong positive correlation between neuronal NOS and stromal HA could reflect NO(*)-stimulated synthesis of HA, an extracellular matrix alteration that favors breast cancer progression. Furthermore, it is suggested that, while acting as a scavenger of NO(*)-derived radicals, cell-associated HA undergoes partial fragmentation, release from receptors, and further degradation in lysosomes, and thus becomes undetectable in histological sections.