CCL2 and melanoma: In agreement with our work, recent reports indicate that β3 integrin-negative pericytes may communicate with lung cancer cells and melanoma cells to support tumor proliferation through the CCL2-MAP kinase kinase 1 (MEK1)-Rho associated coiled-coil containing protein kinase 2 (ROCK2) pathway,21 underscoring the multiple functions of pericytes in promoting tumor progression.