An additional NKp44 ligand is the proliferating cell nuclear antigen, a nuclear/cytoplasmic factor that can be expressed on the membrane of cancer cells and upon binding with NKp44 induces NK cell inhibition due to immunoreceptor tyrosine-based inhibitory motifs (ITIMs) located in the NKp44 cytoplasmic tail [111]. This evidence concerns the gene NCR2 and cancer.