A mutation profiling study of Norwegian and British MSI-H/MMR-D CRC patients suggested that a homozygous loss of JAK1 might be associated with resistance to anti-PD-1 therapy.82 However, a retrospective exploratory study in patients with MSI-H/MMR-D CRC treated with nivolumab and ipilimumab identified four patients with a JAK1 loss-of-function mutation that did not appear to impact clinical response.83 Taken together, these findings suggest that a biallelic loss of JAK1/2 might be a better biomarker for predicting response to immunotherapy than JAK1/2 mutations. This evidence concerns the gene JAK1 and colorectal carcinoma.