The interplay between hypoxia, endothelial and melanoma cells regulates vascularization and cell motility through endothelin-1 and vascular endothelial growth factor.
Reciprocal growth factor exchanges between endothelial and malignant cells within the hypoxic microenvironment determine tumor progression. However, the nature of these exchanges has not yet been fully explored. We studied the mutual regulation between endothelial cells (EC), melanoma cells and hypoxia that dictate tumor aggressiveness and angiogenic activity. Here, we investigated the presence of bidirectional autocrine/paracrine endothelin (ET)-1/ET receptor (ETBR) signaling in melanoma cells, blood and lymphatic EC. In all these cells, hypoxia enhanced ET-1 expression, which in turn induced vascular endothelial growth factor (VEGF)-A and VEGF-C secretion, through the hypoxia-inducible growth factor (HIF)-1α and HIF-2α. Autocrine/paracrine exchanges of ET-1, VEGF-A and VEGF-C promoted tumor aggressiveness and morphological changes in blood and lymphatic EC. Furthermore, conditioned media from EC enhanced melanoma cell migration and vessel-like channel formation. This regulation was inhibited by ETBR blockade, by using the selective ETBR antagonist, or ETBR small interfering RNA (siRNA), and by VEGFR-2/-3 antibodies, indicating that ET-1, VEGF-A/VEGF-C, produced by melanoma cells or EC mediated inter-regulation between these cells. Interestingly, HIF-1α/HIF-2α siRNA, impaired this reciprocal regulation, demonstrating the key role of these transcriptional factors in signaling exchanges. In melanoma xenografts, the ETBR antagonist reduced tumor growth and the number of blood and lymphatic vessels. These results reveal an interplay between melanoma cells and EC mediated by ET-1 and VEGF-A/-C and coordinated by the hypoxic microenvironment through HIF-1α/2α transcriptional programs. Thus, targeting ETBR may improve melanoma treatment for tumor and EC, by inhibiting autocrine/paracrine signaling that sustains melanoma progression.
Experimental Oncology Department, Regina Elena National Cancer Institute, 00144 Rome.
Francesca
F
Spinella
Valentina
V
Caprara
Roberta
R
Cianfrocca
Laura
L
Rosanò
Valeriana
V
Di Castro
Emirena
E
Garrafa
Pier Giorgio
PG
Natali
Anna
A
Bagnato
D000818:Animals; D015687:Cell Hypoxia; D002465:Cell Movement; D019332:Endothelin-1 / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000473:pathology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008545:Melanoma / Q000098:blood supply / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic; D060888:Real-Time Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D019332:Endothelin-1; D042461:Vascular Endothelial Growth Factor A