HAS1 and breast carcinoma: Consistently with HA production level, Has2 gene expression and HAS activity were elevated over 4-fold (p < 0.05) in MMTV-PyVT carcinoma cells (Fig. 2e, f), which strengthened the above notion that the coordinated up-regulation of both GFAT and HAS2 expression might confer aggressiveness in human breast cancer.