Immunohistochemical analysis of the monoclonal antibody 4B5 in breast tissue expressing human epidermal growth factor receptor 4 (HER4).

AIMS: A recent study examining the specificity of human epidermal growth factor receptor (HER) 2 pharmacodiagnostic antibodies demonstrated that CB11 and 4B5 stain both HER2-transfected and HER4-transfected cell lines. However, there has been no evidence showing that 4B5 has affinity for HER4 in clinically obtained tissues, and, if so, whether this has any impact on the assessment of HER2. We therefore sought to determine the expression of membrane-bound HER4 in clinical breast carcinomas, and evaluate its impact on the clinical utility of 4B5 in determining HER2 status. METHODS AND RESULTS: Breast carcinomas were assessed by immunohistochemistry (IHC) for membrane-bound HER4 using anti-HER4 clone E200. HER2 expression in these cases was then assessed using anti-HER2 clone 4B5, and a reference clone, SP3. In all 117 membrane HER4-positive cases (out of 241), 4B5 scored equal to or less than the reference anti-HER2 clone SP3. Eighteen cases were positive for membrane-bound HER4 by E200 and negative by 4B5, including a membrane HER4 level 3+ case. CONCLUSIONS: No cross-reactivity of 4B5 with membrane-bound HER4 was identified in the clinical IHC analysis of formalin-fixed paraffin-embedded breast carcinoma cases as evidenced by the HER4 antibody clone E200.

Low GILT Expression is Associated with Poor Patient Survival in Diffuse Large B-Cell Lymphoma.

The major histocompatibility complex (MHC) class II-restricted antigen processing pathway presents antigenic peptides acquired in the endocytic route for the activation of CD4(+) T cells. Multiple cancers express MHC class II, which may influence the anti-tumor immune response and patient outcome. Low MHC class II expression is associated with poor survival in diffuse large B-cell lymphoma (DLBCL), the most common form of aggressive non-Hodgkin lymphoma. Therefore, we investigated whether gamma-interferon-inducible lysosomal thiol reductase (GILT), an upstream component of the MHC class II-restricted antigen processing pathway that is not regulated by the transcription factor class II transactivator, may be important in DLBCL biology. GILT reduces protein disulfide bonds in the endocytic compartment, exposing additional epitopes for binding to MHC class II and facilitating antigen presentation. In each of four independent gene expression profiling cohorts with a total of 585 DLBCL patients, low GILT expression was significantly associated with poor overall survival. In contrast, low expression of a classical MHC class II gene, HLA-DRA, was associated with poor survival in one of four cohorts. The association of low GILT expression with poor survival was independent of established clinical and molecular prognostic factors, the International Prognostic Index and the cell of origin classification, respectively. Immunohistochemical analysis of GILT expression in 96 DLBCL cases demonstrated variation in GILT protein expression within tumor cells which correlated strongly with GILT mRNA expression. These studies identify a novel association between GILT expression and clinical outcome in lymphoma. Our findings underscore the role of antigen processing in DLBCL and suggest that molecules targeting this pathway warrant investigation as potential therapeutics.