RESUMO
Galectin-1 (Gal-1)-binding to Gal-1 ligands on immune and endothelial cells can influence melanoma development through dampening antitumor immune responses and promoting angiogenesis. However, whether Gal-1 ligands are functionally expressed on melanoma cells to help control intrinsic malignant features remains poorly understood. Here, we analyzed expression, identity, and function of Gal-1 ligands in melanoma progression. Immunofluorescent analysis of benign and malignant human melanocytic neoplasms revealed that Gal-1 ligands were abundant in severely dysplastic nevi, as well as in primary and metastatic melanomas. Biochemical assessments indicated that melanoma cell adhesion molecule (MCAM) was a major Gal-1 ligand on melanoma cells that was largely dependent on its N-glycans. Other melanoma cell Gal-1 ligand activity conferred by O-glycans was negatively regulated by α2,6 sialyltransferase ST6GalNAc2. In Gal-1-deficient mice, MCAM-silenced (MCAM(KD)) or ST6GalNAc2-overexpressing (ST6(O/E)) melanoma cells exhibited slower growth rates, underscoring a key role for melanoma cell Gal-1 ligands and host Gal-1 in melanoma growth. Further analysis of MCAM(KD) or ST6(O/E) melanoma cells in cell migration assays indicated that Gal-1 ligand-dependent melanoma cell migration was severely inhibited. These findings provide a refined perspective on Gal-1/melanoma cell Gal-1 ligand interactions as contributors to melanoma malignancy.
Assuntos
Proliferação de Células/genética , Transformação Celular Neoplásica/genética , Galectina 1/genética , Regulação Neoplásica da Expressão Gênica , Análise de Variância , Animais , Western Blotting , Antígeno CD146/genética , Movimento Celular/genética , Modelos Animais de Doenças , Imunofluorescência , Humanos , Ligantes , Melanoma/genética , Melanoma/patologia , Camundongos , Camundongos Endogâmicos C57BL , Reação em Cadeia da Polimerase em Tempo Real , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Células Tumorais CultivadasRESUMO
Advanced prostate cancer commonly metastasizes to bone, but transit of malignant cells across the bone marrow endothelium (BMEC) remains a poorly understood step in metastasis. Prostate cancer cells roll on E-selectin(+) BMEC through E-selectin ligand-binding interactions under shear flow, and prostate cancer cells exhibit firm adhesion to BMEC via ß1, ß4, and αVß3 integrins in static assays. However, whether these discrete prostate cancer cell-BMEC adhesive contacts culminate in cooperative, step-wise transendothelial migration into bone is not known. Here, we describe how metastatic prostate cancer cells breach BMEC monolayers in a step-wise fashion under physiologic hemodynamic flow. Prostate cancer cells tethered and rolled on BMEC and then firmly adhered to and traversed BMEC via sequential dependence on E-selectin ligands and ß1 and αVß3 integrins. Expression analysis in human metastatic prostate cancer tissue revealed that ß1 was markedly upregulated compared with expression of other ß subunits. Prostate cancer cell breaching was regulated by Rac1 and Rap1 GTPases and, notably, did not require exogenous chemokines as ß1, αVß3, Rac1, and Rap1 were constitutively active. In homing studies, prostate cancer cell trafficking to murine femurs was dependent on E-selectin ligand, ß1 integrin, and Rac1. Moreover, eliminating E-selectin ligand-synthesizing α1,3 fucosyltransferases in transgenic adenoma of mouse prostate mice dramatically reduced prostate cancer incidence. These results unify the requirement for E-selectin ligands, α1,3 fucosyltransferases, ß1 and αVß3 integrins, and Rac/Rap1 GTPases in mediating prostate cancer cell homing and entry into bone and offer new insight into the role of α1,3 fucosylation in prostate cancer development.
