Detection of microscopic disease: Comparing histology, immunocytology, and RT-PCR of tyrosine hydroxylase,GAGE, andMAGE

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Abstract
We first explored the use of multiple molecular markers to overcome tumor heterogeneity. Sixty-seven neuroblastoma (NB) tumors were tested for the expression of GAGE, MAGE-2, MAGE-2, MAGE-3, and MAGE-4 by RT-PCR and then chemiluminescence; 82% of tumors had detectable GAGE, and 88% expressed at least one of the four MAGE genes. By combining GAGE and MAGE, 64 of 67 (95%) of tumors became detectable; 17 of 67 coexpressed all five molecular markers. Neither GAGE nor MAGE expression correlated with stage. GAGE was found to have the broadest (18 of 18) expression among stage 4 tumors. Two hundred fifty-nine bone marrows from 99 patients were then studied for NB positivity by four detection methods: histology, immunocytology, and molecular detection by GAGE and tyrosine hydroxylase (TH) mRNA. Two hundred seven samples were NB-positive by one detection method. All four techniques were comparable in detecting tumor cells at diagnosis and at relapse. GAGE and immunocytology were far more sensitive than histology and TH mRNA when marrows were sampled during chemotherapy and at the time of clinical remission. By combining multiple molecular markers and independent screening techniques, we may be able to overcome tumor heterogeneity and expedite the detection of microscopic disease in the clinical management of neuroblastoma.