Response to anti-CTLA-4 therapy has been associated with a more inflamed tumor microenvironment and potential markers include increased expression of the activation marker, inducible T-cell co-stimulator (ICOS), on peripheral blood CD4+ cells and tumor-infiltrating lymphocytes, and an increase in Teff:Treg cell ratio in tumor tissues [45–50]. Here, ICOS is linked to neoplasm.