CTLA4 and malignant colon neoplasm: The US Food and Drug Administration (FDA) approved anti-PD-1 (Pembrolizumab and Nivolumab) as monotherapy or in combination with cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) inhibitor (Ipilimumab) for the treatment of colon cancer with high microsatellite instability (MSI-H) or mismatch repair deficiency (DMMR), unfortunately, only 5-15% of colon cancer patients benefit (5, 6).