HLA-G and cancer: Although in colorectal and esophageal cancer, a high variability in the expression levels of HLA-G and its receptors in different areas within the tumor has been demonstrated, it has not been determined which of these isoforms plays a functional role in cancer immunology, nor how the different isoforms relate to ILT-2, ILT-4, and KIR2DL4 receptors in immune cells, or what are the effects of these interactions.