[164] Detection of Short Forms of HER2 in FFPE Specimens in Breast Cancer: Biological Significance and Impact on Patient Care

Jian Huang. Medical College of Wisconsin, Milwaukee, WI

Background: Studies from others have demonstrated that short forms of HER2 are strongly associated with poor outcome and trastuzimab resistance in breast cancer. However, the detection of such short forms of HER2 in formalin-fixed, paraffin-embedded (FFPE) specimens has not yet been established in routine clinical practice. In this study we evaluated the expression levels of HER2 in breast cancer and then explored whether the short forms of HER2 could be detected by IHC. Finally, we explored whether the short forms of HER2 could potentially activate Akt and MAPK signaling pathways and promote tumor cell proliferation in breast cancer.
Design: A TMA made up of 284 FFPE specimens with invasive breast carcinomas was utilized in this study. HER2 was examined by IHC with antibodies to A0485, SP3, CB11 and 4B5. HER2 gene amplification was analyzed with chromogenic in situ hybridization (CISH) in all cases. The expressions of short forms of HER2 were confirmed by western blot (WB). The expression of P-Akt, P-MAPK and Ki67 were also examined by IHC.
Results: Of 284 cases examined by IHC, 49 (17%), 54 (19%), 89 (31%) and 114 (40%) were HER2-positive with SP3, 4B5, CB11 and A0485, respectively. 68 of 284 cases (24%) evaluated by CISH showed HER2 gene amplification. The concordance between CISH and IHC was 47 (96%), 52(96%), 58(65%) and 65(57%) with antibodies for SP3, 4B5, CB11 and A0485, respectively. Short forms of HER2 ranging from 95 to 110 KD were detected by WB with A0485 in 58 of 65 cases (89%), which were both HER2-positive with A0485 and HER2-negative with SP3 by IHC. P-Akt and P-MAPK were strongly increased in the cases with short forms of HER2 compared with the ones without short forms of HER2 (P<0.001). The proliferation index (Ki67) was higher in the cases with short forms of HER2 than those without the short forms of HER2 (P<0.01).
Conclusions: The data indicates that the expression of HER2 examined by IHC with different anti-HER2 antibodies is variable in breast cancer. The short forms of HER2 were detected by IHC with A0485 and confirmed by WB. These short forms might activate intercellular signaling pathways, such as Akt and MAPK which might promote tumor cell proliferation in breast cancer. The data suggests that a combination of anti-HER2 antibodies that includes A0485 should be utilized in routine clinical practice for assessment of the short forms.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 67, Monday Afternoon

 

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