Quantitation of GD2 synthase mRNA by real-time reverse transcription-polymerase chain reaction: utility in bone marrow purging of neuroblastoma by anti-GD2 antibody 3F8.
BACKGROUND
Antigen ganglioside GD2 is expressed abundantly on neuroblastoma (NB) cells. Anti-GD2 monoclonal antibody (MoAb) 3F8 kills NB cells by complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity. Its utility in bone marrow (BM) purging is evaluated by a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay to quantify the mRNA of GD2 synthase, the key enzyme in GD2 synthesis.


METHODS
From 1990 to 1993, 10 patients with relapsed/refractory Stage 4 NB participated in a pilot study. In these patients, MoAb 3F8 was used to purge tumor cells from harvested BM that had 5% or less tumor content by immunofluorescence (IF). Subsequently, 31 Stage 4 NB patients who underwent treatment on the N7 protocol (1994-1999) had their BM, which was in remission, purged by 3F8 before (131)I-3F8 myeloablative radioimmunotherapy. GD2-positive tumor cells before and after purging were quantified by real-time quantitative RT-PCR of GD2 synthase.


RESULTS
GD2 positivity by IF was found before purging in six of eight patients in the pilot study. Five of six patients became negative postpurging. Of 31 patients on the N7 protocol, the more sensitive real-time quantitative RT-PCR detected GD2 synthase mRNA in the BM samples of 7 patients even though the prepurge BM samples were negative by histology and IF. Six of the seven BM samples became negative after 3F8 purging. Marker positivity before purging was statistically significant in predicting overall survival (P = 0.04), but not progression-free survival (P = 0.1). In vitro hematopoietic stem cell recovery and the median time to engraftment were acceptable.


CONCLUSIONS
Tumor cell depletion quantified by real-time RT-PCR demonstrated efficacy of MoAb 3F8 in BM purging.
Cheung
Irene Y
IY
Department of Pediatrics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. cheungi@mskcc.org
Lo Piccolo
M Serena
MS
Collins
Nancy
N
Kushner
Brian H
BH
Cheung
Nai-Kong V
NK
D000911:Antibodies, Monoclonal; D001854:Bone Marrow Cells / Q000201:enzymology* / Q000473:pathology; D019046:Bone Marrow Neoplasms / Q000175:diagnosis*; D016465:Bone Marrow Purging; D018450:Disease Progression; D005455:Fluorescent Antibody Technique; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics* / Q000276:immunology; D009447:Neuroblastoma / Q000097:blood / Q000532:radiotherapy*; D010865:Pilot Projects; D012333:RNA, Messenger / Q000378:metabolism*; D016499:Radioimmunotherapy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity
D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D012333:RNA, Messenger; D017350:N-Acetylgalactosaminyltransferases; C023220:(N-acetylneuraminyl)-galactosylglucosylceramide N-acetylgalactosaminyltransferase