Determination of the prognostic value of loss of heterozygosity at the retinoblastoma gene in osteosarcoma

Abstract

The retinoblastoma (RB) tumour suppressor gene is implicated in the development of several malignancies including osteosarcoma. Recent studies postulated its loss of heterozygosity (LOH) to be a poor prognostic factor at diagnosis of osteosarcoma (OS). It remains unclear whether LOH of the RB gene is suitable as a prognostic factor at diagnosis in patients with osteosarcoma. In this study we aimed to determine the early prognostic value of RB-LOH as well as the ability of denaturating high performance liquid chromatography (DHPLC) to detect LOH at this gene locus in comparison to classical PAGE. We therefore analysed 41 samples of OS on restriction fragment length polymorphisms in introns 1, 17 and 25, and variable numbers of tandem repeats (VNTRs) in intron 20. PCR fragments were separated on 1.5% agarose gel electrophoresis. VNTRs with length differentiation of only a few base pairs were analysed by 8% PAA/Spreadex gels and additionally by DHPLC. One-hundred percent concordance was observed between the results obtained by classical PAGE and DHPLC. The latter improved intron 20 analysis as a sensitive and high throughput method for detecting LOH. Overall we found 16 RB-LOH in 41 OS (39%). Three tumours exhibited additional microsatellite instability. There was no significant correlation of the event-free-and overall-survival rate or response to chemotherapy with RB-LOH found in our study. LOH positivity was associated with a significantly younger age at diagnosis. In conclusion RB-LOH could not be verified as a poor prognostic factor for osteosarcoma in the present study.

Aberrant Retinoblastoma (RB)-E2F Transcriptional Regulation Defines Molecular Phenotypes of Osteosarcoma

“…The observation that ectopic expression of constitutively active RB resulted in transcriptional repression of E2F targets and other genes associated with cell cycle control and DNA replication is consistent with previously defined mechanisms (15). However, assessments of individual components of the RB pathway have not always correlated with event free or overall survival (37,38). Loss of heterozygosity of RB has been proposed as an indicator of poor prognosis in human osteosarcoma patients (39), but our work is the first .…”

Genomic Alterations and Allelic Imbalances Are Strong Prognostic Predictors in Osteosarcoma

“…The RB1-LOH rate of 43% in our study was comparable with the rate of 37.2% to 39% published in the literature (19,20). Allelic imbalances of the RB1 locus have previously been reported in osteosarcoma, but their predictive impact remains controversial.…”

“…Earlier studies revealed high LOH rates for osteosarcoma at the 13q14 locus, and the authors found them to be associated with a poor prognosis (20,21). More recently, Heinsohn et al were not able to confirm this prognostic impact, which is in accordance with our findings (19). Remarkably, the LOH region on chromosome 10q21.1, harboring PCDH15 and ZWINT1, was more important in respect of prognostic discrimination (Fig.…”

Correlation of Oncologic Long-Term Results and Genetic Instability in Soft Tissue Sarcomas

“…MSI is considered as a dysfunction of the mismatch repair (MMR) genes [5, 10 -12, 14], whereas LOH seems to correspond to genetic defects of tumour suppressor genes [7,16,21,22,24,26,27].…”