Activation of the epidermal growth factor receptor promotes lymphangiogenesis in the skin.

BACKGROUND: The lymphatic vascular system regulates tissue fluid homeostasis and plays important roles in immune surveillance, inflammation and cancer metastasis. However, the molecular mechanisms involved in the regulation of lymphangiogenesis remain incompletely characterized.
OBJECTIVE: We aimed to identify new pathways involved in the promotion of skin lymphangiogenesis.
METHODS: We used a mouse embryonic stem cell-derived embryoid body vascular differentiation assay to investigate the effects of a selection of pharmacological agents with the potential to inhibit blood and/or lymphatic vessel formation. We also used a subcutaneous Matrigel assay to study candidate lymphangiogenesis factors as well as skin-specific transgenic mice.
RESULTS: We found that compounds inhibiting the epidermal growth factor (EGF) receptor (EGFR) led to an impaired formation of lymphatic vessel-like structures. In vitro studies with human dermal lymphatic endothelial cells (LECs), that were found to express EGFR, revealed that EGF promotes lymphatic vessel formation. This effect was inhibited by EGFR-blocking antibodies and by low molecular weight inhibitors of the EGFR associated tyrosine kinase. Incorporation of EGF into a mouse matrigel plug assay showed that EGF promotes enlargement of lymphatic vessels in the skin in vivo. Moreover, transgenic mice with skin-specific overexpression of amphiregulin, another agonistic ligand of the EGFR, displayed an enhanced size and density of lymphatic vessels in the skin.
CONCLUSION: These findings reveal that EGFR activation is involved in lymphatic remodeling and suggest that specific EGFR antagonists might be used to inhibit pathological lymphangiogenesis.