Compared to normal tissues, where the expression of ULBP2/5/6 protein is restricted, in non-small-cell lung cancer (NSCLC), head and neck cancer and squamous urothelial carcinoma, the levels of ULBP2/5/6 remain high even following relapse from standard-of-care therapies and is retained in metastatic lesions. Besides, these squamous cell cancers showed a high proportion of CD2+ tumor-infiltrating lymphocytes compared to other co-stimulatory receptors.