gms | German Medical Science

Background: The humanized monoclonal antibodies Trastuzumab and, recently, Pertuzumab have been established for the treatment of Her-2-overexpressing metastatic breast cancers. Resistance to Her2-targeted therapy still remains a common phenomenon. Recent evidence shows that receptor activation status may be a predictor for Her-2 directed therapy response. In the herein presented study, biochemical features of the Her-2 molecule have been analysed by immunohistochemistry (IHC) and Western blot analysis.

Methods: Her-2 protein expression status in FFPE tissue was determined using DAKO HercepTest and scoring system. Her-2 phosphorylation was analysed by IHC in cases scored 2+ or 3+ by DAKO scoring. Whole tissue lysates of corresponding fresh frozen tissue samples were prepared and analysed for the same parameters by Western blot.

Results: Tissue specimens from 34 patients and the Herceptin-sensitive SkBr3-cell line were analysed. By means of IHC, Her-2 Tyr1248 phosphorylation was detected in 16 (50%) of Her-2 positive cases. Western blot analysis revealed Her-2p95 expression in almost equal amounts in every patient, whereas expression levels of Her-2 full length protein varied greatly. Phosphorylation of the full-length Her-2p185 molecule was detected in only 10 (31%) cases, including the SkBr3 cell line.

Conclusion: These preliminary results suggest that presence of phosphorylated Her-2p185 protein may be a predictor of Her-2 targeted therapy response. The diagnostic relevance of these findings will be evaluated in a subsequent study where samples from patients with known clinical follow-up data will be analysed.