Allelic Losses from Chromosome 17 in Human Osteosarcomas

Fluorescent In Situ Hybridization for TP53 in the Diagnosis of Pediatric Osteogenic Sarcoma

Osteogenic sarcoma (OS) is the most common malignant bone tumor in children and adolescents. Despite advances in molecular genetic characterization of pediatric and adult tumors, the diagnosis of OS still depends almost entirely on light microscopy. The lack of consistent genetic changes in OS has greatly hindered the development of any diagnostic molecular test. Recently, whole-genome sequencing has shown that ~50% of cases of OS have a translocation involving the TP53 gene with breakpoints confined to the first intron. We developed a 2 color break-apart fluorescent in situ hybridization (FISH) probe for intron 1 of TP53 and applied it to an archived series to assess its diagnostic utility. The study group included 37 cases of OS (including osteoblastic, chondroblastic, and fibroblastic), as well as 53 cases of non-OS pediatric sarcomas (including Ewing sarcoma, rhabdomyosarcoma, undifferentiated small cell sarcoma, CCNB3-BCOR sarcoma, CIC-DUX sarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumor) and 27 cases of benign bone lesions (including osteoblastoma, chondromyxoid fibroma, fibrous dysplasia, and fibro-osseous dysplasia). A rearranged signal was found in 20/37 cases (54%) of OS and in none of the other sarcomas or benign bone lesions, giving the FISH test 100% specificity for a diagnosis of OS. p53 immunostaining was generally not predictive of the results obtained by FISH and could not substitute for this test. This FISH probe offers a simple and specific genetic test to aid in the diagnosis of OS, despite the genetic complexity of this tumor.

Downregulation of RSK2 influences the biological activities of human osteosarcoma cells through inactivating AKT/mTOR signaling pathways

RSK2 (90 kDa ribosomal S6 kinase) is a downstream effector of the Ras/ERK (extracellular signal-regulated kinase) signaling pathway that has major functions in cell biological activities, including regulating nuclear signaling, cell cycle progression, cell proliferation, cell growth, protein synthesis, cell migration and cell survival, and is expressed in most types of human malignant tumors, including lung cancer, prostate and breast tumors, skin cancer and osteosarcomas (OS). RSK2 was found to be essential for osteosarcoma formation. To investigate whether RSK2 is expressed at high levels in human osteosarcome tissues and whether its expression is correlated with the aggressive biological behavior of osteosarcoma cell line (OCLs), we assessed the association between RSK2 expression and OS cell progression, as well as the effects of RSK2 inhibition on the biological activities of osteosarcoma cells. We performed immunohistochemistry to analyze the expression of RSK2 in specimens from 30 humans with osteosarcoma, and 15 normal tissues. RSK2 gene expression levels in 30 specimens with osteosarcoma were significantly higher than those of normal tissues. We performed RNA interference on three OCLs to evaluate cell apoptosis, cell growth, cell proliferation, cell motility, chemosensitivity and oncogenicity. After transfection with RSK2 shRNA, increased cell apoptosis, cell growth inhibition, cell cycle progression, weaker cell proliferation, cell migration and weaker tumor formation were observed in all OCLs. These results suggested that RSK2 expression may mediate the biological activities of OS cells and RSK2 may be an effective therapeutic target for the treatment of osteosarcomas. The AKT/mTOR, MAPK/ERK/c-Fos and Bcl2/Bax pathways were analysed to clarify the mechanisms involved.

Network analysis of microRNAs and genes in human osteosarcoma

To date, numerous studies have suggested that microRNAs (miRNAs) and genes play key roles in osteosarcoma (OS); however, the majority of these studies have been conducted with a specific focus on either the genes or the miRNAs, which has made the regulatory mechanisms of OS difficult to decipher. The aim of the present study was to systematically investigate the elements [genes, miRNAs and transcription factors (TFs)] associated with the morbidity of OS and to explore the associations among these elements, instead of focusing on one or several elements. The scattered data were collected from existing studies of OS, and three regulatory networks (abnormally expressed, related and global) were constructed to explore OS at a macroscopic level. The abnormally expressed network showed the numerous incorrect data linkages that are present when OS emerges, making it useful as a map of the faults in OS. In theory, the correction of these errors could lead to the prevention and even cure of the disease. Unlike studies in which cancer networks have been formed based purely on gene data, the present study focused on genes and miRNAs, as well as the associations among them, to form the regulatory networks of OS. The constructed regulatory networks were shown to contain numerous self-adaptation associations, which may aid in the analysis of the pathogenesis of OS. By comparing and analyzing the similarities and differences, a number of important pathways were highlighted. A notable finding was the predicted TFs obtained by the P-Match method, which could be used to further study the pathogenesis of OS. In the present study, the mechanism of OS has been systematically analyzed and a theoretical foundation for the mechanism has been provided, which may assist the development of gene therapy targeting OS.

Genetically engineered mouse models and human osteosarcoma

Osteosarcoma is the most common form of bone cancer. Pivotal insight into the genes involved in human osteosarcoma has been provided by the study of rare familial cancer predisposition syndromes. Three kindreds stand out as predisposing to the development of osteosarcoma: Li-Fraumeni syndrome, familial retinoblastoma and RecQ helicase disorders, which include Rothmund-Thomson Syndrome in particular. These disorders have highlighted the important roles of P53 and RB respectively, in the development of osteosarcoma. The association of OS with RECQL4 mutations is apparent but the relevance of this to OS is uncertain as mutations in RECQL4 are not found in sporadic OS. Application of the knowledge or mutations of P53 and RB in familial and sporadic OS has enabled the development of tractable, highly penetrant murine models of OS. These models share many of the cardinal features associated with human osteosarcoma including, importantly, a high incidence of spontaneous metastasis. The recent development of these models has been a significant advance for efforts to improve our understanding of the genetics of human OS and, more critically, to provide a high-throughput genetically modifiable platform for preclinical evaluation of new therapeutics.

The genetics of osteosarcoma

Osteosarcoma is a primary bone malignancy with a particularly high incidence rate in children and adolescents relative to other age groups. The etiology of this often aggressive cancer is currently unknown, because complicated structural and numeric genomic rearrangements in cancer cells preclude understanding of tumour development. In addition, few consistent genetic changes that may indicate effective molecular therapeutic targets have been reported. However, high-resolution techniques continue to improve knowledge of distinct areas of the genome that are more commonly associated with osteosarcomas. Copy number gains at chromosomes 1p, 1q, 6p, 8q, and 17p as well as copy number losses at chromosomes 3q, 6q, 9, 10, 13, 17p, and 18q have been detected by numerous groups, but definitive oncogenes or tumour suppressor genes remain elusive with respect to many loci. In this paper, we examine studies of the genetics of osteosarcoma to comprehensively describe the heterogeneity and complexity of this cancer.

Deletion of the WWOX gene and frequent loss of its protein expression in human osteosarcoma

To evaluate the role of WWOX gene in human osteosarcoma, array comparative genomic hybridization on 10 frozen osteosarcoma specimens and immunohistochemical staining of 55 formalin-fixed and paraffin-embedded tissues for WWOX was performed. Deletion of the WWOX gene was observed in 3 of 10 samples and the WWOX protein was undetectable in 34 of 55 osteosarcomas. This is the first investigation of the role of WWOX gene in human osteosarcoma. The WWOX gene deletion, loss of its protein expression, and lack of correlation of WWOX expression with patient survival suggest loss of WWOX expression is an early event in the pathogenesis of osteosarcoma and the phenotypic results of its deletion do not imminently result in patient death.

An integrative multi-platform analysis for discovering biomarkers of osteosarcoma

BACKGROUND

SELDI-TOF-MS (Surface Enhanced Laser Desorption/Ionization-Time of Flight-Mass Spectrometry) has become an attractive approach for cancer biomarker discovery due to its ability to resolve low mass proteins and high-throughput capability. However, the analytes from mass spectrometry are described only by their mass-to-charge ratio (m/z) values without further identification and annotation. To discover potential biomarkers for early diagnosis of osteosarcoma, we designed an integrative workflow combining data sets from both SELDI-TOF-MS and gene microarray analysis.

METHODS

After extracting the information for potential biomarkers from SELDI data and microarray analysis, their associations were further inferred by link-test to identify biomarkers that could likely be used for diagnosis. Immuno-blot analysis was then performed to examine whether the expression of the putative biomarkers were indeed altered in serum from patients with osteosarcoma.

RESULTS

Six differentially expressed protein peaks with strong statistical significances were detected by SELDI-TOF-MS. Four of the proteins were up-regulated and two of them were down-regulated. Microarray analysis showed that, compared with an osteoblastic cell line, the expression of 653 genes was changed more than 2 folds in three osteosarcoma cell lines. While expression of 310 genes was increased, expression of the other 343 genes was decreased. The two sets of biomarkers candidates were combined by the link-test statistics, indicating that 13 genes were potential biomarkers for early diagnosis of osteosarcoma. Among these genes, cytochrome c1 (CYC-1) was selected for further experimental validation.

CONCLUSION

Link-test on datasets from both SELDI-TOF-MS and microarray high-throughput analysis can accelerate the identification of tumor biomarkers. The result confirmed that CYC-1 may be a promising biomarker for early diagnosis of osteosarcoma.

Her-2/neu, p-53, and their coexpression in osteosarcoma

BACKGROUND

There is controversy regarding the patterns and prognostic significance of Her-2/neu and p-53 expression in osteosarcoma. Further, their combined expression has not been studied.

PROCEDURE

Prechemotherapy biopsy specimens of 63 osteosarcoma patients from June 2004 to August 2006 were analyzed for Her-2/neu and p-53 using immunohistochemistry and compared with grade, stage, and morphologic subtype of tumor.

RESULTS

There were 59 high-grade tumors; 32 of 63 had metastases. Histopathologic types included 36 of 63 osteoblastic and 18 of 63 chondroblastic subtypes. Male sex (P=0.045) and chondroblastic type (P=0.004) were associated with metastatic disease. Her-2/neu cytoplasmic staining was seen in 30 of 63 (47.1%) cases, 4 of 30 had additional membranous staining, 17 of 30 were metastatic, and 29 of 30 were high-grade tumors. Staining grade was 3+ in 10 of 30 samples whereas staining intensity 3+ was observed in 26 of 30 samples. Her-2/neu 3+ staining grade was significantly associated with chondroblastic subtype (6/18, P=0.026). P-53 staining was seen in 20 of 63 (31.74%) cases (all high grade), of which 11 were metastatic. Staining grades 3+ and 4+ were seen in 16 of 20 samples whereas staining intensity 3+ in 13 of 20 samples. P-53 expression was higher in chondroblastic (7/18, P value was not significant) and fibroblastic (3/3, P<0.05) subtypes. Coexpression of Her-2/neu and p-53 was seen in 10 cases (15.87%); 3 of 10 cases showed Her-2/neu membranous staining (P=0.01).

CONCLUSIONS

Her-2/neu (47.1%), p-53 (31.74%), and their combined expression (15.87%) were not related to grade or stage of tumor. Chondroblastic subtype was associated with staining grade 3+ of Her-2/neu staining whereas coexpression of Her-2/neu and p-53 was significantly associated with membranous Her-2/neu staining.

Osteosarcoma development and stem cell differentiation

Osteosarcoma is the most common nonhematologic malignancy of bone in children and adults. The peak incidence occurs in the second decade of life, with a smaller peak after age 50. Osteosarcoma typically arises around the growth plate of long bones. Most osteosarcoma tumors are of high grade and tend to develop pulmonary metastases. Despite clinical improvements, patients with metastatic or recurrent diseases have a poor prognosis. Here, we reviewed the current understanding of human osteosarcoma, with an emphasis on potential links between defective osteogenic differentiation and bone tumorigenesis. Existing data indicate osteosarcoma tumors display a broad range of genetic and molecular alterations, including the gains, losses, or arrangements of chromosomal regions, inactivation of tumor suppressor genes, and the deregulation of major signaling pathways. However, except for p53 and/or RB mutations, most alterations are not constantly detected in the majority of osteosarcoma tumors. With a rapid expansion of our knowledge about stem cell biology, emerging evidence suggests osteosarcoma should be regarded as a differentiation disease caused by genetic and epigenetic changes that interrupt osteoblast differentiation from mesenchymal stem cells. Understanding the molecular pathogenesis of human osteosarcoma could ultimately lead to the development of diagnostic and prognostic markers, as well as targeted therapeutics for osteosarcoma patients.

Monoallelic deletion of the p53 gene through chromosomal translocation in a small cell osteosarcoma

Small cell osteosarcoma is a rare bone tumor of high-grade malignancy that most often arises in the metaphysis of long bones in the second decade of life. Cytogenetic and molecular genetic findings in small cell osteosarcoma are poorly defined. Conventional cytogenetic analysis of a small cell osteosarcoma arising in the proximal tibia of a 9-year-old male revealed a diploid chromosomal complement with complex structural rearrangements involving chromosomes 6, 16, and 17. Immunohistochemical assessment of p53 protein expression revealed nuclear p53 immunoreactivity in approximately 15% of the neoplastic cells. Subsequent fluorescence in situ hybridization (FISH) analyses confirmed loss of the p53 gene locus on the derivative chromosome 17 homolog and were negative for amplification of the MDM2, CDK4, c-MYC, HER-2/neu, CCND1, and COPS3 gene loci. To the best of our knowledge, this represents the first demonstration of monoallelic deletion of p53 in small cell osteosarcoma, suggesting that p53 alterations may play an important role in the development of small cell osteosarcoma as well as conventional osteosarcoma.

Allelic imbalances in endometrial stromal neoplasms: frequent genetic alterations in the nontumorous normal-appearing endometrial and myometrial tissues

OBJECTIVES

Endometrial stromal sarcoma (ESS) is among the rarest primary malignant tumors of the uterus. The aim of this study was to examine the possibility of loss of heterozygosity (LOH) and microsatellite instability (MIS) in different tissue components of ESS.

METHODS AND MATERIALS

Using PCR, we examined DNA extracts from microdissected tissues of 27 uterus samples containing malignant stromal cells of ESS (20 low grade and 3 high grade sarcomas), benign tumor cells of endometrial stromal nodules (ESN, 4 cases) as well as tumor-free myometrial and endometrial tissues close to and distant from the tumors. Normal cervical tissues (epithelial cells, stroma cells) were also microdissected and analyzed. Fifteen polymorphic DNA markers (chromosomes 2p, 3p, 5q, 10q, 11q, 13q, and 17p) were tested to identify possible genetic alterations. Samples from 10 women with prolapsed uteri without any histopathologic abnormalities were also selected as controls.

RESULTS

While no genetic alterations could be identified in 12 (44.5%) ESS cases, 15 (55.5%) revealed LOH with at least one polymorphic DNA marker. LOH were found in 3 (100%) high-grade sarcomas, 10 (50%) low-grade ESS, and 2 (50%) benign ESN. Although LOH was found more often in the neoplastic stromal cells, several cases showed concurrent and independent LOH in the tumor-free myometrial or endometrial tissues either close to or distant from the tumors. The most common genetic abnormality (LOH) was observed at PTEN, a tumor suppressor gene located on chromosome 10q. No tumor was associated with microsatellite instability (MSI). The control group without any histologic abnormalities did not show LOH or MSI.

CONCLUSIONS

The frequent occurrence of LOH and the lack of MSI suggest that loss of function(s) of tumor suppressor genes and not mismatch repair deficiency plays a key role in the pathogenesis of endometrial stromal neoplasms. The concurrent and independent occurrence of LOH in the stromal tumor cells and the tumor-free and normal-appearing myometrial and endometrial tissues strongly support the concept of genetic alterations in microenvironmental tissues and the interaction(s) between different tissue components in the development and progression of endometrial stromal neoplasms.

Mutational screening of breast cancer susceptibility gene 1 from early onset, bi-lateral, and familial breast cancer patients in Taiwan

The BRCA1 gene has been shown to be strongly associated with the occurrence of familial breast cancer. The spectrum of BRCA1 gene mutations in breast cancer patients in various populations has been investigated. In this study, patients in Central Taiwan with breast cancer were screened for BRCA1 mutations by sequencing PCR products spanning the coding region and partial intronic regions of the BRCA1 gene. Twelve polymorphisms in four exons and three introns were found. One mutation was found in one patient with familial breast cancer. Two patients showed LOH at the locus of BRCA1. Also found in the Taiwanese population were two common haplotypes and one rare haplotype of BRCA1. These results suggest that the mutation of BRCA1 contributes little to the occurrence of breast cancer in the Taiwanese population.

Population-based genetic alterations in Ewing's tumors from Japanese and European Caucasian patients

BACKGROUND

The incidence of Ewing's tumors (ETs) is lower in Asians or African-Americans than in Caucasians.

PATIENTS AND METHODS

Japanese ETs were available for analysis of chromosomal aberrations by comparative genomic hybridization (n = 16) and for expression of chimeric EWS transcripts by reverse-transcriptase polymerase chain reaction (n = 11). These results in Japanese patients were compared with those of 62 ETs in European Caucasian patients registered in the European Intergroup Cooperative Ewing's Sarcoma Study.

RESULTS

Japanese patients with ET had lower overall survival (P = 0.0446) and relapse-free survival (P = 0.0371) compared with European Caucasian patients. Ten of 11 Japanese ETs and 31 of 62 European Caucasian ETs had type I (EWS exon 7 to FLI1 exon 6) fusion transcripts. In Japanese ETs, the median numbers of chromosomal aberrations were 2.0 and 6.0 in 11 primary tumors and five relapsed tumors, respectively. In European Caucasian ETs, the median number of changes were 2.5 and 5.0 in 52 primary and 10 relapsed tumors, respectively. Frequent gains were 8q (38%), 8p (31%) and 12q (25%) in Japanese ETs and 8q (52%), 8p (48%) and 12q (19%) in European Caucasian ETs. Frequent losses were 19q (44%), 19p (38%) and 17p (25%) in Japanese ETs and 16q (21%), 19q (18%) and 17p (15%) in European Caucasian ETs. The incidence of losses of 19p (P = 0.0215) and 19q (P = 0.0277) were significantly higher in Japanese ETs than in European Caucasian ETs. An amplification (1p33-p34) was observed in only one Japanese ET.

CONCLUSIONS

Japanese patients with ET in this study had a worse prognosis than European Caucasian patients. In molecular genetic analyses, Japanese ETs had a higher frequency of loss of chromosome 19 than European Caucasian ETs. Different genetic aberrations may explain the different incidences and prognoses of ET between Caucasian and Japanese patients.