A study in patients who had initially responded to pembrolizumab and subsequently relapsed used whole-exome sequencing to identify mutations that caused resistance to therapy and found that JAK1 and JAK2 loss of function mutations with deletion of the wildtype allele was associated with resistance due to an inability of JAK1 and JAK2 deficient tumours to respond to IFN-γ stimulation by expressing proteins involved in antigen presentation and suppressing their own growth [55]. The gene discussed is IFNG; the disease is neoplasm.