Numb protein expression correlates with a basal-like phenotype and cancer stem cell markers in primary breast cancer.
Decreased expression of Numb, resulting in activation of the proto-oncogene Notch1 and reduction in the tumor suppressor p53, has been demonstrated in mammary carcinomas. The aim of this study was to investigate the relationship between Numb protein expression and clinicopathological characteristics, tumor biological subtypes and putative cancer stem cell markers in a well-characterized cohort of primary human breast cancers. Immunohistochemistry was performed on tissue microarrays of primary invasive breast tumors using a polyclonal anti-Numb primary antibody. Of the 241 tumors evaluated, 50 (21%) displayed deficient or reduced Numb immunoreactivity. Retained Numb expression was significantly correlated to estrogen (ER) and progesterone receptor (PR) positivity (P < 0.001 and P = 0.004, respectively). Interestingly, we found that a higher percentage of the tumors with deficient or reduced Numb expression belonged to the triple-negative (ER-/PR-/HER2-) subgroup compared to tumors with retained Numb expression (P = 0.004). Transcriptional profiling of a subset of these tumors linked NOTCH1 and BIRC5, both downstream targets of Numb, to the triple-negative subgroup in an inverse manner. Typically, subgroups characterized by the low expression of Numb expressed higher levels of NOTCH1 and BIRC5 (encoding survivin). We also found deficient expression of Numb in a significantly higher proportion of BRCA1 dependent tumors, which are usually triple-negative, compared to sporadic tumors. The expression of Numb in 14 breast cancer cell lines correlated similarly to their respective molecular subtypes. We further established an inverse correlation between the Numb expression levels and the CD44+/CD24- cancer stem cell phenotype (P = 0.05) in primary tumors. Finally, decreased Numb expression was associated with poorer distant disease-free survival (P = 0.01). Taken together, our results indicate that loss of Numb expression is a marker of tumor aggressiveness, potentially linked to BRCA1 status and a cancer stem cell phenotype in primary breast cancer.
Department of Oncology, Clinical Sciences, Lund University, Barngatan 2B, 221 85, Lund, Sweden.
Karin
K
Rennstam
Nicole
N
McMichael
Pontus
P
Berglund
Gabriella
G
Honeth
Cecilia
C
Hegardt
Lisa
L
Rydén
Lena
L
Luts
Pär-Ola
PO
Bendahl
Ingrid
I
Hedenfalk
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019313:BRCA1 Protein / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000401:mortality / Q000556:secondary; D051927:CD24 Antigen / Q000378:metabolism; D045744:Cell Line, Tumor; D018572:Disease-Free Survival; D015536:Down-Regulation; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D007150:Immunohistochemistry; D051034:Inhibitor of Apoptosis Proteins; D053208:Kaplan-Meier Estimate; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011379:Prognosis; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis; D051881:Receptor, Notch1 / Q000378:metabolism; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D000077022:Survivin; D013997:Time Factors; D046888:Tissue Array Analysis
D019313:BRCA1 Protein; D014408:Biomarkers, Tumor; D051927:CD24 Antigen; D018960:Hyaluronan Receptors; D051034:Inhibitor of Apoptosis Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases; D051881:Receptor, Notch1; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D000077022:Survivin; C107489:BIRC5 protein, human; C492913:BRCA1 protein, human; C497889:CD24 protein, human; C497483:CD44 protein, human; C000715470:MAS1 protein, human; C497761:NOTCH1 protein, human; C113026:NUMB protein, human; C508053:ERBB2 protein, human