Glutathione S-transferase polymorphisms in osteosarcoma patients.

BACKGROUND: Osteosarcoma is the most common malignant bone tumor in children and adolescents. Multidrug resistance and poor clinical outcome are the problems that still affect osteosarcoma patients. The glutathione S-transferase supergene family includes several genes that encode enzymes involved in the detoxification of many xenobiotic agents, including carcinogens and anticancer drugs. The polymorphisms in these genes have already been associated both with cancer susceptibility and anticancer drugs resistance. OBJECTIVES: This study aims to investigate the genotype frequencies of GSTM1, GSTT1 and GSTM3 genes in 80 osteosarcoma patients and 160 normal control participants, and also the influence of these polymorphisms in the clinical outcome of osteosarcoma patients. METHODS: GSTM1 and GSTT1 deletion polymorphisms were examined through a multiplex-PCR and the GSTM3 polymorphism of three base pair-deletion at intron 6 using PCR-restriction fragments length polymorphism method. RESULTS: We found that GSTM1 null genotype is correlated to poor clinical outcome characterized by the increased lung relapse occurrence [odds ratio (OR)=2.71, P=0.036], while the presence of at least one GSTM1 allele is associated with a good response to treatment and better survival (OR=4.28, P=0.020 and hazards ratio=4.09, P=0.0078, respectively). The GSTT1 null genotype was correlated with a better overall survival (hazards ratio=7.15, P=0.0247), whereas GSTM3*B allele was associated with metastasis at diagnosis (OR=2.83, P=0.028). CONCLUSION: The findings of this study suggest that GST polymorphisms may have a role in treatment response and osteosarcoma progression.

Effects of THBS3, SPARC and SPP1 expression on biological behavior and survival in patients with osteosarcoma.

BACKGROUND: Osteosarcoma is a very aggressive tumor with a propensity to metastasize and invade surrounding tissue. Identification of the molecular determinants of invasion and metastatic potential may guide the development of a rational strategy for devising specific therapies that target the pathways leading to osteosarcoma. METHODS: In this study, we used pathway-focused low density expression cDNA arrays to screen for candidate genes related to tumor progression. Expression patterns of the selected genes were validated by real time PCR on osteosarcoma patient tumor samples and correlated with clinical and pathological data. RESULTS: THBS3, SPARC and SPP1 were identified as genes differentially expressed in osteosarcoma. In particular, THBS3 was expressed at significantly high levels (p = 0.0001) in biopsies from patients with metastasis at diagnosis, which is a predictor of worse overall survival, event-free survival and relapse free survival at diagnosis. After chemotherapy, patients with tumors over-expressing THBS3 have worse relapse free survival. High SPARC expression was found in 51/55 (96.3%) osteosarcoma samples derived from 43 patients, and correlated with the worst event-free survival (p = 0.03) and relapse free survival (p = 0.07). Overexpression of SPP1 was found in 47 of 53 (89%) osteosarcomas correlating with better overall survival, event-free survival and relapse free survival at diagnosis. CONCLUSION: In this study three genes were identified with pattern of differential gene expression associated with a phenotypic role in metastasis and invasion. Interestingly all encode for proteins involved in extracellular remodeling suggesting potential roles in osteosarcoma progression. This is the first report on the THBS3 gene working as a stimulator of tumor progression. Higher levels of THBS3 maintain the capacity of angiogenesis. High levels of SPARC are not required for tumor progression but are necessary for tumor growth and maintenance. SPP1 is not necessary for tumor progression in osteosarcoma and may be associated with inflammatory response and bone remodeling, functioning as a good biomarker.

Metaphase and array comparative genomic hybridization: unique copy number changes and gene amplification of medulloblastomas in South America.

Tumors of the central nervous system are the second most frequent malignancy of childhood, accounting for the majority of cancer-related deaths in this age group. Among these tumors, medulloblastomas (MB) remain in need of further genomic characterization toward understanding of pathogenesis and outcome predictors. Eight pediatric embryonal brain tumors were analyzed: five MB (one being desmoplastic), one PNET, one medulloepithelioma, and one ependymoblastoma. Analyses identified genomic imbalances, including the gain of 16p and the nonsyntenic coamplification of MYCN and TERT loci. More detailed FISH analysis showed that coamplification of MYCN and TERT in one of the MBs manifested as dispersed nuclear speckling, consistent with the presence of double minute chromosomes. There was considerable cell-to-cell copy number heterogeneity present, but it was clear that both genes were amplified concordantly. The amplification of oncogenes seems to play an important role in the pathogenesis of MB, and the association between MYCN and TERT amplifications and poor prognosis has not been well recognized. The uncharacteristic pattern of genomic imbalances detected in MB tumors may be a reflection of the characteristics of these tumors occurring in South America.