[1186] Laminin β1 and β2 Immunostaining in Ovarian Carcinoma

Anna R Laury, Ann E Walts. Cedars-Sinai Medical Center, Los Angeles, CA

Background: Laminins are a family of trimeric extracellular matrix glycoproteins that contain α, β, and γ chains and form the major component of basement membranes (BM). Each chain type has several isoforms. Two of the β chain variants are β1 and β2. Alterations in BM composition and/or assembly play a role in diverse processes that include cell integrity, adhesion, migration, and metastasis. Recent studies have shown that disruption of angiogenesis via laminin-targeted therapy may be possible. Laminin has been less studied in epithelial tumor cells.
Design: Formalin fixed paraffin embedded sections of 20 primary ovarian carcinomas (7 high grade serous, 5 mixed serous/undifferentiated, 2 clear cell, 2 mixed mullerian, 2 endometrioid, 1 clear cell/serous, 1 undifferentiated) were stained with Laminin β1 antibody (clone 3G133, abcam) and Laminin β2 antibody (clone C4, Santa Cruz Biotechnology). Intensity (0 negative, 1+ weak, 2+ moderate, 3+ strong) and extent (percentage) of staining were assessed in tumor-associated blood vessels (TA-BV) and tumor basement membrane (TBM). The presence of cytoplasmic staining in tumor cells was also recorded.
Results: TA-BV in 18 (90%) of the 20 cases stained for both β1 and β2; TA-BV in 1 serous and in 1 mixed serous/undifferentiated carcinoma were negative for β1 and β2, respectively. Extent of TA-BV staining ranged from <10% to 90% and intensity ranged from 1+ to 3+. TBM in 18 (90%) cases stained for β2; 1 endometrioid and 1 mixed mullerian carcinoma were negative. In 16 (80%) cases, TBM staining (extent & intensity) for β2>β1; in 3 cases β1 and β2 staining were equal. In only 1 case (endometrioid) was TBM β1>β2 staining. β1 staining was absent in TBM of 11 cases, including all 7 high grade serous and 4 of 5 mixed serous/undifferentiated carcinomas. Three cases showed cytoplasmic staining for β1 (2 clear cell, 1 undifferentiated). None of the carcinomas showed cytoplasmic staining for β2.
Conclusions: Our preliminary findings suggest that:
-Laminin β1 and β2 are both expressed in TA-BV of diverse histologic types of ovarian carcinoma, representing potentials for laminin-targeted therapy;
-Laminin β1 is not expressed in TBM of high grade serous but is expressed in other ovarian carcinomas, possibly reflecting differences in tumorogenesis and/or tumor spread;
-Laminin β2 is expressed in TBM of most ovarian carcinomas irrespective of histologic type whereas β1 expression seems to be histologic type dependent. In epithelial tumor cells, Laminin β2 expression appears confined to TBM whereas β1 expression is detected in both TBM and cytoplasm of clear cell carcinoma.
Category: Gynecologic & Obstetrics

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 175, Wednesday Morning

 

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