Galectins: emerging regulatory checkpoints linking tumor immunity and angiogenesis

- Galectins engage a number of glycosylated immune checkpoint receptors.
- Galectins alter T-cell and NK-cell activation, signaling and survival.
- Galectins endow myeloid cells with immune regulatory potential.
- Glycosylation-dependent galectin-receptor interactions control angiogenesis.
- Galectin-glycan interactions confer resistance to anti-cancer therapies.

Immune checkpoints, a plethora of inhibitory pathways aimed at maintaining immune cell homeostasis, may be co-opted by cancer cells to evade immune destruction. Therapies targeting immune checkpoints have reached a momentum yielding significant clinical benefits in patients with various malignancies by unleashing anti-tumor immunity. Galectins, a family of glycan-binding proteins, have emerged as novel regulatory checkpoints that promote immune evasive programs by inducing T-cell exhaustion, limiting T-cell survival, favoring expansion of regulatory T cells, de-activating natural killer cells and polarizing myeloid cells toward an immunosuppressive phenotype. Concomitantly, galectins can trigger vascular signaling programs, serving as bifunctional messengers that couple tumor immunity and angiogenesis. Thus, targeting galectin-glycan interactions may halt tumor progression by simultaneously augmenting antitumor immunity and suppressing aberrant angiogenesis.