Abstract P3-12-09: Numb Expression Varies by Hormone Receptor Status among Danish Breast Cancer Patients

Abstract

Background: Numb-mediated regulation of Notch signaling pathway might play a causative role in early breast cancer. Little information is available on whether Numb expression differs according to tumor characteristics including hormone receptor status. We investigated Numb expression status in archival tissue from primary tumor of 197 breast cancer patients identified within the 2004 cohort of the Registry of the Danish Breast Cancer Cooperative Group's (DBCG), where patients were treated according to the guidelines of the DBCG. Materials and Methods: Numb expression was measured by immunohistochemistry method, and Numb(-) was defined as Numb immunoreactivity present in less than 10% of the invasive tumor cells. Chi-square test was used to assess the correlation between Numb(-) and hormone receptor status. Results: The median age was 57 years (range, 26-98), 32% were premenopausal. 82% were ductal, 9% lobular, 9% others. 10% were grade I, 41% grade II, 47% grade III, 2% non-graded. 70% were node positive. 60% were ER+, 41% PR+, and 24% were HER2+ by IHC and FISH. 58% were operated by mastectomy, 42% by lumpectomy. The adjuvant treatment comprised Tamoxifen (36%), cyclophosphamide/methotrexate/fluorouracil (CEF, 19%), CEF+Tamoxifen (11%), and 22% were missing treatment information. 49% relapsed and 3% metastasized during 10 year of follow up. Overall, 10% (19 out of 197) of patients were Numb(-). Numb expression was significantly associated with hormone status, with a Numb(-) frequency of 24% (9/37) among ER+/PR-/HER2-, 9% (6/65) among ER+/PR+/HER2-, 6% (3/47) among HER+ (1/16 among ER+/PR+/HER2+ and 2/31 among ER-/PR-/HER2+), and 2% (1/47) among ER-/PR-/HER2- patients (P<0.01). Similar differences were observed using the H-score matrix where the IHC intensity was summarized with a range of 0-300. Discussion: Our results suggested Numb(-) is correlated with hormone status, with the higher frequency of Numb(-) among ER+/PR-/HER2- patients, and lower frequency among other groups, particularly the triple negative group. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-12-09.