CD44 and cancer: CD44 is a gene expressed on cancer stem cells, which is linked to resistance to apoptosis and uncontrolled growth and promotes cancer progression.75 NIR-PIT targeting CD44 when combined with the immune checkpoint blockade using anti-PD-1 or CTLA4 antibody, or cytokine (IL-15) administration proved to be effective.76 Consistently, the combined CD44 and CD25-targeted therapy proved most effective for colon cancer expressing luciferase (MC38-luc) with high expression of CD44.