Optimization of molecular detection of GD2 synthase mRNA in retinoblastoma

Abstract

Extraocular dissemination is the main cause of death in patients with retinoblastoma in developing countries and there are few molecular markers that could be used for evaluation of minimal disseminated disease. The expression of the ganglioside GD2 is present in retinoblastoma cells metastatic to the bone marrow and the enzyme GD2 synthase activity is detected in neuroblastoma, which shares many phenotypic features with retinoblastoma. Our purpose was to optimize the detection of GD2 synthase expression by reverse transcription-polymerase chain reaction (RT-PCR) followed by nested-PCR in human retinoblastoma cell lines and patient samples. The optimization strategy was carried out by using the retinoblastoma cell lines Y79 and WERI-Rb1 and specific primers designed for the human sequence of the GD2 synthase mRNA. We detected GD2 synthase expression with at least 200 pg and 40 pg of total RNA extracted from cultured retinoblastoma cells, using a first round of RT-PCR amplification and a second round of nested-PCR, respectively. We have also confirmed the detection of GD2 synthase by RT-PCR and immunohistochemical expression of the ganglioside in human retinoblastoma tumors xenotransplanted in nude mice. In a study from tumor bank specimens from 8 retinoblastoma patients, we were able to demonstrate the presence of GD2 synthase mRNA in blood and cerebrospinal fluid samples in cases of extraocular dissemination of the tumor. The sequence was not detected in samples from children with low-risk disease or healthy adult volunteers. The detection of GD2 synthase mRNA through an optimized nested RT-PCR assay may be a promising tool for the assessment of minimal disseminated disease in enucleated patients.