The proapoptotic molecule BLID interacts with Bcl-XL and its downregulation in breast cancer correlates with poor disease-free and overall survival.
OBJECTIVE
BLID is a BH3-like motif containing apoptotic member of the Bcl-2 family of proteins. This study was designed to investigate the mechanism of BLID-induced apoptosis and to assess the significance of BLID expression in breast cancer.


METHODS
The interaction between BLID and Bcl-X(L) was examined using in vitro transcription/translation, coimmunoprecipitation, and immunoflourescence assays. The relationship between BLID mRNA expression and pathologic measures in breast cancer specimens (n = 55) was examined using the publicly available ONCOMINE microarray database. Immunohistochemistry was done using formalin-fixed, paraffin-embedded sections of 148 cases of invasive ductal breast carcinomas (IDC) and 58 cases of invasive lobular breast carcinomas, and breast tissue microarrays representing additional 437 cases (>85% IDC) with associated clinicopathologic database and long-term clinical follow-up (median 7 years).


RESULTS
BLID was found to interact with Bcl-X(L), and the binding was enhanced in cancer cells exposed to doxorubicin or cisplatin. Exogenous expression of BLID correlated with activation of Bax and an increase in cytosolic cytochrome c. BLID mRNA expression was significantly reduced in grade 3 relative to grade 1 and 2 breast cancer (P = 0.023). Cytoplasmic BLID immunoreactivity was absent in IDC compared with invasive lobular breast carcinoma (P < 0.001). Lack of BLID expression was associated with younger age (median 40 years), African American ethnicity, tumor size, and triple-negative breast cancer (estrogen receptor negative, progesterone receptor negative, and human epidermal growth factor receptor 2 negative; all P < 0.005). Significant correlations were observed between BLID negativity and declines in overall, cause-specific, and local relapse-free survival (all P < 0.03). Multivariate analysis indicated that BLID is an independent prognostic factor of distant metastasis-free survival (hazard ratio, 0.302; 95% confidence interval, 0.160-0.570, P = 0.0002).


CONCLUSIONS
BLID is a new binding partner of Bcl-X(L) and a significant prognostic factor in breast cancer.
Broustas
Constantinos G
CG
Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia 20057, USA.
Ross
Jeffrey S
JS
Yang
Qifeng
Q
Sheehan
Christine E
CE
Riggins
Rebecca
R
Noone
Anne-Michelle
AM
Haddad
Bassem R
BR
Seillier-Moiseiwitsch
Françoise
F
Kallakury
Bhaskar V S
BV
Haffty
Bruce G
BG
Clarke
Robert
R
Kasid
Usha N
UN
D000328:Adult; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D024682:BRCA2 Protein / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000032:analysis; D001943:Breast Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D045744:Cell Line, Tumor; D018572:Disease-Free Survival; D015536:Down-Regulation; D005260:Female; D006801:Humans; D008875:Middle Aged; D011379:Prognosis; D012333:RNA, Messenger / Q000378:metabolism; D014162:Transfection; D051020:bcl-X Protein / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; C118024:BLID protein, human; D024682:BRCA2 Protein; D014408:Biomarkers, Tumor; D012333:RNA, Messenger; D051020:bcl-X Protein