CTLA4 and neoplasm: Due to chronic antigen stimulation and the inhospitable hypoxic and nutrient deprived tumor microenvironment several inhibitory immune checkpoint receptors such as PD-1, TIM-3, LAG-3 and CTLA-4 are upregulated on T cells that cooperatively inhibit T cell proliferation, cytokine production and function creating an exhausted T cell phenotype (15, 16).