A total of 7 different BARD1 isoforms were identified in lung and colorectal cancer cells,. Structural analysis shows that the BARD1 isoforms expressed in cancers are derived from either differential splicing or from alternative initiation of transcription. A first description of aberrant expression of BARD1 and differentially spliced isoforms was for breast and ovarian cancer,. Aberrant expression of BARD1 correlated with poor prognosis, and repression of BARD1 led to proliferation arrest–.
More recent research has shown that all tissues from 100 NSCLC cases tested express isoform-specific BARD1 epitopes, whilst in lung tissues from healthy controls BARD1 expression is undetectable both on the mRNA and protein levels. Furthermore, the expression of two BARD1 epitopes was significantly correlated with decreased patient survival.
Colorectal cancer has been studied in 168 cancer samples. The structure and relative expression of BARD1 mRNA isoforms were further determined in 40 tumour and paired normal peri-tumour tissues. BARD1 isoforms were expressed in 98% of cases and did not correlate with BRCA1. BARD1 mRNA isoforms are upregulated in all tumours as compared with paired normal peri-tumour tissues. Importantly, expression of epitopes mapping to the middle of BARD1 correlate with decreased survival