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BARD1: An independent predictor of survival in non‐small cell lung cancer
Author(s) -
Zhang YongQiang,
Bianco Andrea,
Malkinson Alvin M.,
Leoni Vera Piera,
Frau Gianni,
De Rosa Nicolina,
André PierreAlain,
Versace Renato,
Boulvain Michel,
Laurent Geoffrey J.,
Atzori Luigi,
IrmingerFinger Irmgard
Publication year - 2011
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.26346
Subject(s) - gene isoform , immunostaining , lung cancer , epitope , downregulation and upregulation , cancer research , biology , immunohistochemistry , cancer , messenger rna , tumor progression , pathology , microbiology and biotechnology , immunology , antibody , medicine , gene , genetics
Abstract BRCA1 mRNA overexpression is correlated with poor survival in NSCLC. However, BRCA1 functions depend on the interaction with BARD1 for its stability, nuclear localization and ubiquitin ligase activity. Expression of alternatively spliced BARD1 isoforms that lack the BRCA1‐interaction domain was found upregulated and correlated with poor prognosis in breast and ovarian cancer. These BARD1 isoforms are essential for proliferation of cancer cells in vitro . We investigated whether BARD1 isoforms are expressed in NSCLC. While in lung tissues from healthy controls BARD1 expression was undetectable on the mRNA level and protein level, we found two novel isoforms in addition to previously identified mRNAs expressed in all NSCLC samples tested. Furthermore, the pattern of BARD1 isoform expression was similar in tumor and morphologically normal peri‐tumor tissues, and only one novel isoform π was specifically upregulated in tumors. Immunohistochemistry revealed that all 100 NSCLC cases tested expressed isoform‐specific BARD1 epitopes, while BARD1 expression was undetectable in biopsies from healthy controls. Statistical analysis showed that the expression of epitopes PVC and WFS, present on isoform π, or epitope WFS alone, expressed on isoforms π, κ and β, were significantly correlated with decreased patient survival. These findings were corroborated in a mouse model of chemically induced lung cancer. Immunostaining of mouse tumors showed that BARD1 epitopes PVC and WFS were specifically upregulated in invasive, but not in confined lung tumors. Thus, BARD1 isoforms might be involved in tumor initiation and invasive progression and might represent a novel prognostic marker for NSCLC.