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

Abstract

Production of vascular endothelial growth factor (VEGF) and expression of its receptors Flt-1 and KDR was determined in primary cultures of separated epithelial and stromal-enriched cultures derived from ten primary human breast carcinomas. By enzyme-linked immunosorbent assay, epithelial cells produced a mean VEGF of 33 ± 7 pg ml −1 μg −1 RNA (range 11–70). Stromal cells produced similar levels, with a mean of 48 ± 11 pg ml −1 μg −1 RNA (range 7–92). This was significantly greater than the amount produced by similar cultures derived from normal breast tissue (epithelial mean 19 ± 5 pg ml −1 μg −1 RNA, range 9–34, P < 0.05 vs tumour epithelial culture; stromal mean 26 ± 8 pg ml −1 μg −1 RNA, range 3–56). Flt-1 and KDR receptors were analysed by semi-quantitative reverse transcription polymerase 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 epithelial cultures. Only a single tumour, a lobular carcinoma, failed to express Flt-1 on either cell type. With KDR, the reverse was true with constitutive expression of this receptor by epithelial cultures and zero or reduced (3/6) expression by stromal cultures. Differences in the expression pattern of VEGF 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 fulfil not only an angiogenic role, but also play a fundamental role as an autocrine/paracrine regulator in breast cancer, thereby facilitating tumour proliferation and subsequent invasion. © 1999 Cancer Research Campaign

Inhibition of both paracrine and autocrine VEGF/ VEGFR-2 signaling pathways is essential to induce long-term remission of xenotransplanted human leukemias

“…However, based on evidence shown here, antiangiogenesis therapy targeting the paracrine loop alone may be insufficient to completely eradicate proliferating, VEGFproducing and VEGFR-expressing leukemias. Interestingly, most solid tumors produce VEGF, and subsets of solid tumor cells express at least one of its receptors (17)(18)(19), suggesting that the observations described above may apply to other tumors as well.…”

Phosphorylated KDR expression in endometrial cancer cells relates to HIF1α/VEGF pathway and unfavourable prognosis

“…16 Cancer cell reactivity was thought to represent VEGF content, as KDR was thought to be confined to endothelial cells, despite reports suggesting the presence of KDR in a variety of human tumours, including breast, lung and endometrial carcinomas. [9][10][11][12][13] Constitutive expression of KDR, however, may not necessarily mean an active KDR pathway.…”

“…7,8 Cancer cells and intratumoral endothelium have also been reported to express VEGF receptors. [9][10][11][12][13] The expression of VEGFRs, however, does not necessarily mean active participation in cancer or endothelial cell biology as this can only be analysed by assessing the activated forms of these receptors. Brekken et al 14 produced monoclonal antibodies that preferentially recognize VEGF bound to its receptor KDR, which presumably reflects the activated KDR receptor.…”

Aplidine, a new anticancer agent of marine origin, inhibits vascular endothelial growth factor (VEGF) secretion and blocks VEGF-VEGFR-1 (flt-1) autocrine loop in human leukemia cells MOLT-4

“…[13][14][15][16][17] Increasing evidence suggests, however, that certain cancer cells of different origin, including leukemic cells, also express VEGF receptors on their surface. [18][19][20][21][22][23] On the other hand, VEGF is secreted by virtually all cancer cells as a homodimeric glycoprotein which is able to bind VEGFR-1 and other components of the VEGF receptors family with high affinity. 14,24 The simultaneous presence of a receptor and the ability to secrete the ligand for it, suggests the possible presence of an autocrine loop important for the growth of cancer cells expressing these receptors.…”