To dissect the role of tumor-intrinsic IFN loss we generated the two most common 9p21.3 deletions observed in patients: a 0.4 Mb allele eliminating CDKN2A/B and a 1.3 Mb allele eliminating both CDKN2A/B and the linked cluster of 17 type I IFNs. The gene discussed is IFNA1; the disease is neoplasm.