Recent studies have shown that a carbohydrate-binding protein, galectin-3, is a novel pro-angiogenic molecule. The mechanism by which galectin-3 promotes angiogenesis remains unknown. We demonstrate here that galectin-3 is a mediator of vascular endothelial growth factor (VEGF)- and basic fibroblast growth factor (bFGF)-mediated angiogenic response. Angiogenesis assays revealed that galectin-3 inhibitors, β-lactose and dominant-negative galectin-3, reduce VEGF- and bFGF-mediated angiogenesis in vitro and that VEGF- and bFGF-mediated angiogenic response is reduced in galectin-3 knockdown cells and Gal3−/− animals. Integrin αvβ3 was identified as the major galectin-3–binding protein and anti-αv, -β3, and -αvβ3 integrin function-blocking antibodies significantly inhibited the galectin-3–induced angiogenesis. Furthermore, galectin-3 promoted the clustering of integrin αvβ3 and activated focal adhesion kinase. Knockdown of GnTV, an enzyme that synthesizes high-affinity glycan ligands for galectin-3, substantially reduced: (a) complex N-glycans on αvβ3 integrins and (b) VEGF- and bFGF-mediated angiogenesis. Collectively, these data suggest that galectin-3 modulates VEGF- and bFGF-mediated angiogenesis by binding via its carbohydrate recognition domain, to the GnTV synthesized N-glycans of integrin αvβ3, and subsequently activating the signaling pathways that promote the growth of new blood vessels. These findings have broad implications for developing novel, carbohydrate-based therapeutic agents for inhibition of angiogenesis.

Galectin-3 Is an Important Mediator of VEGF- and bFGF-Mediated Angiogenic Response

Approximately 30-40% of the patients with early stage non-small cell lung cancer (NSCLC) will present with recurrent disease within two years of resection. Here, we performed extensive galectin expression profi ling in a retrospective study using frozen and paraffi n embedded tumor tissues from 87 stage I/II NSCLC patients. Our data show that galectin mRNA expression in NSCLC is confi ned to galectin-1,-3,-4,-7,-8, and -9. Next to stage, univariable Cox regression analysis identifi ed galectin-1, galectin-9FL and galectin-9∆5 as possible prognostic markers. KaplanMeier survival estimates revealed that overall survival was signifi cantly shorter in patients that express galectin-1 above median levels, i.e. 23.0 (2.9-43.1) vs. 59.9 (47.7-72.1) months (p=0.020) as well as in patients that express galectin-9∆5 or galectin-9FL below the median, resp. 59.9 (41.9-75.9) vs. 32.8 (8.7-56.9) months (p=0.014) or 23.2 (-0.4-46.8) vs. 58.9 (42.9-74.9) months (p=0.042). All three galectins were also prognostic for disease free survival. Multivariable Cox regression analysis showed that for OS, the most signifi cant prognostic model included stage, age, gal-1 and gal-9∆5 while the model for DFS included stage, age and gal-9∆5. In conclusion, the current study confi rms the prognostic value of galectin-1 and identifi es galectin-9∆5 as a novel potential prognostic marker in early stage NSCLC. These fi ndings could help to identify early stage NSCLC patients that might benefi t most from adjuvant chemotherapy.

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I.A.E. Schulkens

Papers

Galectins as targets for angiostatic cancer therapy