Overexpression of Her-2/neu Is Observed in One Third of Adult B-ALL Patients and Is Associated with Chemoresistance in These Patients.

The availability of Herceptin® ,an humanized equivalent of the murine 4D5 monoclonal antibody targeted against the Her-2/neu cell-surface receptor, as a therapeutic agent, incited us to re-evaluate the incidence of Her-2/neu expression in some malignant hematological diseases.Her2/neu expression has been evaluated retrospectively in 186 patients with different hematological disorders (AML: n= 31; B-ALL: n= 87; T-ALL: n=13; CLL: n=23; Multiple Myeloma: n=18; Macroglobulinemia: n=2; Lymphoma: n=12) including 173 at diagnosis and 13 at relapse, and 132 adults and 54 children (<18 years). Cells were analyzed on a FACSCALIBUR flow cytometer (Becton Dickinson) with the Her-2/neu Neu 24.7 antibody (BD). The mean fluorescence intensity (MFI) ratio was obtained by dividing the MFI of Her-2/neu antigen by the MFI of its isotypic control. The threshold of positivity for Her-2/neu expression was defined by a ratio > or = 2. All the patients with Her-2/neu expression detected by FACS analysis were analyzed by FISH using the Her-2/neu DNA probe kit (Vysis, Downers Grove, IL). Two breast tumor cell lines were used as positive controls: MCF-7 and BT-474, obtained from the DSMZ (Braunschweig, Germany). The two control specimens demonstrated Her-2/neu surface expression for 96% (BT-474) and 93% (MCF7) of the cell line population with a ratio intensity of 46 and 26 respectively. Only BT-474 showed an amplification of the Her-2/neu oncogene by FISH. Only 15 B-ALL patients were found positive for Her2/neu surface expression, including 2 children and 13 adults, 11 male and 4 female. Median percentage of Her-2/neu positive blasts population was 94% (range: 11–99%). Median ratio intensity was 7,7 (range: 3,5–54,5). Considering only B-ALL patients (n=87), incidence in children was only of 4% (2 patients/48) compared to 33% in adults (13 patients/39) (p=0,001). None of the positive B-ALL patients showed gene amplification by FISH analysis, suggesting that an other mechanism is involved, such as transcriptional activation or post-translational modifications. Considering only adult B-ALL patients (n=38) and without significant differences for main prognostic parameters and treatment (70% of patients were treated according to or in the GOELAL2 trial) between Her2/neu positive and negative patients, we observed that Her2/neu positive patients (n=12, 1 patient was not informed) are significantly associated with chemoresistance (50% versus 11%, p=0,03). Trends for correlation with refractory disease (41% versus 11%, p=0,08) and disease relapse (55% versus 36%, p=0,08) were also observed, suggesting that Her-2/neu surface expression could be a prognostic marker of poor clinical outcome in B-ALL. OS and DFS were similar between Her2/neu positive and negative patients (median 9 months versus 18 months, p=0,17; median 11 months versus 39 months, p=0,27, respectively), maybe due to a small number of patients in the series, but also because, in the same proportion of Her-2/neu negative patients, some patients received autologous or allogeneic stem cell transplants because of the poor results of the first chemotherapy. In conclusion, our results highlight Her2/neu surface expression only on blasts of one third of adult B-ALL patients. Therapy using anti her2neu monoclonal antibody may be a possibility in this selected group of poor-prognostic adult B-ALL patients.