Cell Surface Targets for Monoclonal Antibody Therapy in Lymphoid Neoplasms of Children and Adolescents.

Recently, monoclonal antibodies have become available for treatment of lymphoid neoplasms in adults, but have not been studied in children and adolescents. These monoclonal antibodies are directed against cell surface antigens CD20 (Rituximab, Ibritumomab-Tiuxetan, Tositumomab), CD22 (Epratuzumab), CD52 (CAMPATH-1H), HLA-DR Beta-chain (Hu1D10), CD23 (IDEC-152), and CD33 (Gemtuzumab Ozogamicin). The objective of this study is to identify cell surface targets eligible for monoclonal antibody therapy in lymphoid neoplasms of children and adolescents. This is a retrospective analysis of lymphoid neoplasms evaluated by flow cytometry immunophenotyping at a single institution from January 2002 to July 2004. All patients were less than 21 years old at primary diagnosis. Flow cytometry immunophenotyping employed a 3-color method. Fluorochrome-conjugated monoclonal antibodies were utilized to detect cell surface antigens: CD20, CD22, CD23 (Becton-Dickinson), and CD52 (CALTAG) conjugated with PE; HLA-DR and CD33 (Becton-Dickinson) conjugated with FITC. For this study, a cell surface antigen was interpreted as positive when neoplastic cells exhibited moderate or bright intensity staining, or interpreted as negative when staining was dim or absent. A total of 95 patients are included in this study. Demographic data: Age <1 to 20 years (median 7); Male=52, Female=43. Diagnoses included: Precursor-B Acute Lymphoblastic Leukemia (Pre-B ALL) = 80, Precursor-T Acute Lymphoblastic Leukemia or Precursor-T Lymphoblastic Lymphoma (Pre-T ALL/LBL) = 11, Burkitt Lymphoma = 4. Total specimens = 105 (primary diagnosis = 82, relapse = 23). Immunophenotyping results for the number of specimens tested are in the Table.

Table 1

CD22 was positive (usually bright intensity) in all Pre-B ALL and Burkitt Lymphoma specimens. CD20 was positive in all Burkitt Lymphoma (bright intensity) and in a subset of Pre-B ALL (usually moderate intensity) specimens. CD22 and CD20 were negative in Pre-T ALL/LBL specimens. In a subset, CD52 was positive (moderate to bright intensity) in nearly all specimens. HLA-DR was positive (moderate to bright intensity) in all Pre-B ALL and Burkitt Lymphoma specimens. In a subset, CD23 was negative in all specimens. Also, CD33 was negative in nearly all specimens. In conclusion, lymphoid neoplasms in children and adolescents have cell surface antigens that are eligible targets for currently available monoclonal antibody therapy. Patients with Pre-B ALL are candidates for therapy directed to CD22, CD52, HLA-DR, and a subset to CD20, but not to CD23 or CD33. Patients with Burkitt Lymphoma are eligible for therapy to CD20, CD22, CD52, and HLA-DR, but not CD23 or CD33. Patients with Pre-T ALL/LBL are eligible for therapy to CD52, but not CD20, CD22, HLA-DR, CD23 or CD33. These results indicate that future clinical therapeutic trials can be designed for children and adolescents with lymphoid neoplasms to evaluate monoclonal antibody therapy directed to CD20, CD22, CD52, or HLA-DR, employing single or multiple antibodies as a new modality, in addition to chemotherapy.