Production of VEGF and expression of the VEGF receptors Flt-1 and KDR in primary cultures of epithelial and stromal cells derived from breast tumours

Production of vascular endothelial growth factor (VEGF) and expression of i ts receptors Flt-1 and KDR was determined in primary cultures of separated epithelial and stromal-enriched cultures derived from ten primary human bre ast carcinomas. By enzyme-linked immunosorbent assay, epithelial cells prod uced a mean VEGF of 33 +/- 7 pg ml(-1) mu g(-1) RNA (range 11-70). Stromal cells produced similar levels, with a mean of 48 +/- 11 pg ml(-1) mu g(-1) RNA (range 7-92). This was significantly greater than the amount produced b y similar cultures derived from normal breast tissue (epithelial mean 19 +/ - 5 pg ml(-1) mu g(-1) RNA, range 9-34, P < 0.05 vs tumour epithelial cultu re; stromal mean 26 +/- 8 pg ml(-1) mu g(-1) RNA, range 3-56). Flt-1 and KD R receptors were analysed by semi-quantitative reverse transcription polyme rase chain reaction. Flt-1 was expressed by four of six epithelial and five of six stromal cultures. When expressed by both cell types, Flt-1 appeared to be significantly more abundant on stromal cells compared with epithelia l cultures. Only a single tumour, a lobular carcinoma, failed to express Fl t-1 on either cell type. With KDR, the reverse was true with constitutive e xpression of this receptor by epithelial cultures and zero or reduced (3/6) expression by stromal cultures. Differences in the expression pattern of V EGF receptors may reflect a differential response to VEGF by specific cell types. Thus, production of VEGF and expression of VEGF receptors Flt-1 and KDR by breast cancer epithelial and stromal cells suggests that VEGF may fu lfil not only an angiogenic role, but also play a fundamental role as an au tocrine/paracrine regulator in breast cancer, thereby facilitating tumour p roliferation and subsequent invasion.