[228] Melatonin MT1 Receptor in Triple Negative Breast Carcinoma (TNBC) and Estrogen Receptor Positive Invasive Ductal Carcinoma (ER+DC).

Gabriela M Oprea-Ilies, Erhard Haus, Linda L Sackett-Lundeen, Harold Sullivan, Robert Bush, 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 is present in human breast tumor cell lines and when activated mediates the growth suppressive action of melatonin on breast tumor cells. The M1 receptor was identified in small studies of largely ER and PR positive primary breast cancers. Breast carcinomas with TNBC and ER+DC phenotypes show differences in biologic behavior, drug sensitivity, course of disease and survival. In view of the experimental work showing varying melatonin effects on different human breast cancer cell lines and xenografts it appeared of interest to explore the presence of melatonin receptors in TNBC and ER+DC.
Design: Invasive TNBCs and ER positive IDC diagnosed in our institution were reviewed. Tissue microarrays (TMAs), constructed with two 1 mm representative cores from each carcinoma, were stained with monoclonal antibody to MT1. The scoring of the immunohistochemistry results was semiquantitative, using 0-3 for intensity and % for number of tumor cells staining. Tumors that scored 2-3 for intensity with ≥10% tumor cells staining were considered positive. MT1 expression was compared in TNBC vs. ER+ IDCs. Statistical analysis was performed using Anova and chi square.
Results: 115 TNTB and 111 ER+ cases were evaluated.
MT1 was positive in 86% TNTB and in 90% ER+ IDC. The frequency and intensity of MT1 staining are presented in table 1.

MT1 IHC by age and race
df = 3F-test: 11.665p Value: 0.0001NumberMeanSt DevSE
AA younger then 50 year of age3569.0672.5412.26
AA older then 50 year of age4575.2082.6412.32
CS younger then50 year of age10138.5089.0128.15
CS older then 50 year of age43170.60106.7116.27

Conclusions: 1. The MT1 melatonin receptor is expressed in a high percentage in both TNBC and ER+BC with no difference in incidence between the two phenotypes.
2. However, the immunohistochemical expression of MT1 is significantly stronger in the ER+BC tumors than in the TNBC
3.This difference may contribute to the different behavior of the two phenotypes and may represent a possible pathway for novel therapeutic approach.
Category: Breast

Monday, February 28, 2011 1:00 PM

Poster Session II # 72, Monday Afternoon


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