In this study, we describe the transcription profiles of cancer patients and healthy individuals who were heterozygous for PV BRCA1Δ9–12 by analyzing the differential expression of both alleles compared with the homozygous BRCA1 control group using RT–qPCR, and we describe the isoforms produced by the BRCA1 wild-type and BRCA1Δ9–12 alleles using nanopore long-sequencing. Here, BRCA1 is linked to cancer.