[227] Difference in Melatonin Receptor (MT1) Expression in Triple Negative Breast Carcinoma (TNBC) between African American (AA) and Caucasian (CS) American Women.

Gabriela M Oprea-Ilies, Erhard Haus, Linda L Sackett-Lundeen, Amy Adams, Cynthia Cohen. Emory University, Atlanta, GA; University of Minnesota, Minneapolis; Regions Hospital, St. Paul, MN

Background: The pineal hormone melatonin exerts a regulatory function on cell proliferation in many tissues and an antiproliferative effect on human tumor cell lines in vitro and on the growth of human breast cancer cell xenografts in vivo. The membrane bound G-protein coupled M1 melatonin receptor (MT1) is present in human breast tumor cell lines and when activated mediates the growth suppressive action of melatonin on breast tumor cells. The MT1 receptor was identified in small studies of largely ER and PR positive primary breast cancers. We studied the presence of the receptor in triple negative breast cancers (TNBC) by immunohistochemical (IHC) methods. Active melatonin receptor may be of interest in TNBC in which no specific adjuvant treatment is available.
Design: Invasive TNBCs diagnosed during a7-year period were reviewed. Only tumor that did not show staining for ER, PR and Her-2 (scored as 0, 1, or 2+, with no amplification by FISH) were included. Tissue microarrays (TMAs), constructed with two 1 mm representative cores from each carcinoma, were stained with the monoclonal antibody MT1. The scoring of the IHC results was semiquantitative, using 0-3 for intensity and percentage for number of tumor cells staining. Tumors that scored 2-3 for intensity with ≥10% tumor cells staining were considered positive. MT1 expression was studied in AA and CS patients.
Results: MT1 was positive in 80 (78%) AA and 53 (98%) CS patients.
The incidence of TNBC expressing melatonin MT1 receptor is significantly lower in AA as compared with CS ( 78 vs 98 % ; Chi square 4.019, p = 0.045). Table 1 details MT1 IHC staining in the AA and CS population.

MT1 IHC by age and race
GroupNumberMeanSt DevSE
AA younger than 50 yo3569.0672.5412.26
AA older than 50 yo4575.2082.6412.32
CS younger than 50 yo10138.5089.0128.15
CS older then 50 yo43170.60106.7116.27
df: 3; F-test: 11.665, p Value: 0.0001

Conclusions: 1. The incidence of TNBC expressing melatonin MT1 receptor is significantly lower in AA as compared with CS.
2. The degree of immunohistochemical staining of MT1 receptor in TNBC expressing the receptor as measured by a score of staining intensity and percentage of cells staining is significantly (p=0.001) lower in the AA.
3. This may indicate a biologic difference of TNBC in AA and CS, which will have to be further explored.
Category: Breast

Monday, February 28, 2011 1:00 PM

Poster Session II # 73, Monday Afternoon


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