Hyaluronan accumulation in the tumor microenvironment is associated with poor prognosis in several solid human
cancers. To understand the role of stromal
hyaluronan in
tumor progression, we engineered 3T3HAS3, a
hyaluronan-producing fibroblast cell line, by lentiviral transduction of Balb/c 3T3 cells with the human
hyaluronan synthase 3 (HAS3) gene. 3T3HAS3 cells significantly enhanced
tumor growth when co-grafted with MDA-MB-468 cells in nude mice. Immunohistochemical analysis of the xenograft
tumors showed that MDA-MB-468 cells were surrounded by
hyaluronan-accumulating stroma, closely resembling the morphology observed in human
breast cancer specimens.
Tumor growth of MDA-MB-468 + 3T3HAS3 co-grafts was greatly reduced upon
hyaluronan degradation by lentiviral transduction of a human
hyaluronidase gene in 3T3HAS3 cells, or by systemic administration of
pegvorhyaluronidase alfa (
PEGPH20). In contrast, the growth of the co-graft
tumors was not inhibited when CD44 expression was reduced or ablated by
small hairpin RNA-mediated CD44 knockdown in MDA-MB-468 cells, CD44 CRISPR knockout in 3T3HAS3 cells, or by grafting these cells in CD44 knockout nude mice. Collectively, these data demonstrate that
tumor growth of an engineered xenograft
breast cancer model with
hyaluronan-accumulating stroma can be dependent on
hyaluronan and independent of CD44.