Fhit loss has been shown to increase replication stress and DNA breaks in the types of cancers displaying APOBEC signature mutations, so we next determined if stratifying the same lung cancers by FHIT mRNA levels, in addition to APOBEC levels, might suggest an explanation for the lack of mutations in some APOBEC high tumors and enrichment of mutations in others. The gene discussed is FHIT; the disease is lung cancer.