[166] MUC1 Is Expressed at High Frequency in Early-Stage Basal-Like Triple Negative Breast Cancer

Hannah L Gilmore, Fadi W Abdul-Karim, Alan Siroy, John Miedler, Pingfu Fu, Joseph Baar. University Hospitals Case Medical Center, Cleveland, OH; Cleveland Clinic Foundation, Cleveland, OH; University Hospitals Seidman Cancer Center, Cleveland, OH

Background: Triple-negative breast cancer (TNBC) comprises 10-15% of newly-diagnosed breast cancer (BC) and lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and the HER-2/neu receptor. Many of these tumors are basal-like, a molecular intrinsic subtype of BC that has been associated with particularly poor clinical outcomes. Patients with early-stage basal-like TNBC are at a high risk of relapse after adjuvant chemotherapy and may therefore benefit from novel therapies, including immunotherapy. MUC1 is a tumor antigen expressed on adenocarcinomas and represents an ideal target for MUC1-based vaccination.
Design: We evaluated 52 cases of early-stage basal-like TNBC for MUC1 expression by immunohistochemistry (IHC). The intensity of staining was graded according to the intensity (negative (0), positive (1) or strongly-positive (2)) and percent (0 to 100%) of tumor cells staining for MUC1. A specimen was considered positive if immunoreactive cells were found in at least 5% of tumor cells. An overall score of 0 to 2.0 was calculated for each case by multiplying the intensity of staining by the percent of tumor cells staining positively.
Results: Four staining patterns for MUC1 were identified: apical, membranous, cytoplasmic and combinations of the three patterns. Forty nine of the 52 cases of basal-like TNBC (94%) were positive for MUC1 expression. The mean score was 0.90 (range 0 - 1.9). Cases were evenly distributed over this range, where most (67%) exhibited moderate to strong MUC1 expression (score 0.5 to 1.90), 27% demonstrated weak MUC1 expression, and 6% lacked MUC1 expression. There was a significant difference in MUC1 score and percent of MUC1+ cells in favor of the combination pattern.
Conclusions: This study indicates that a large proportion of early-stage basal-like TNBC expresses MUC1 and provides a rationale for MUC1-based immunotherapy in this high-risk patient cohort.
Category: Breast

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 17, Tuesday Morning


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