EXO1 and hyperinsulinemic hypoglycemia, familial, 4: DNA-PK deficiency as a consequence of inactivating PRKDC mutations may also be another way to activate the c-GAS/STING pathway37 responsible for the strong immunogenicity of MMR associated tumors, in addition to the recently reported Exonuclease 1 hyperactivity.37 Therapeutic inhibition of DNA-PK may therefore be an interesting combination with PD1 inhibition in CMMRD-associated tumors without PRKDC mutations.35