Amalia Conti

miRNA expression profile in human osteosarcoma: role of miR-1 and miR-133b in proliferation and cell cycle control.

miRNA profile deregulation affecting downstream signaling pathways activates endpoints that represent potential biomarkers for prognosis and treatment of tumor patients. In the past 20 years conventional therapy for osteosarcoma (OS) reached a survival plateau, highlighting the need for new therapeutic approaches. In this study, microarray unsupervised and supervised analysis identified, respectively, 100 and 40 differentially expressed miRNAs in OS samples with different grades of malignancy compared to normal bone. When analyzing low-grade and high-grade OS by unsupervised analysis, 12 miRNAs were found to be differentially expressed. Real‑time PCR performed on a larger series of OS confirmed a significant lower expression of miR-1, miR‑133b and miR-378* in tumors with respect to control, also showing lower mRNA levels in 31 high-grade OS than in 25 low-grade and in metastatic versus non‑metastatic patients. We demonstrated that miR-1 and miR133b were downregulated in OS cell lines compared to normal osteoblasts. Secondly, by transfection with miRNA precursor molecules, we demonstrated that the ectopic expression of miR-1 and miR-133b in U2-OS cell lines significantly reduced cell proliferation and MET protein expression and negatively regulated cell invasiveness and motility in a short-term assay. Cell cycle distribution revealed block in G(1) and delay of cell cycle progression associated with increased apoptosis in miR-1- and miR‑133b‑transfected cells, respectively. Our data assessed specific miRNA profiling deregulation in OS clinical samples and suggest that the expression of miR-1 and miR-133b may control cell proliferation and cell cycle through MET protein expression modulation.

Identification of Potential Biomarkers for Giant Cell Tumor of Bone Using Comparative Proteomics Analysis

Giant cell tumor of bone can be locally aggressive and occasionally can metastasize in the lungs. To identify new markers predictive of aggressive behavior, we analyzed five patients who developed lung metastasis and five who remained disease free for a minimum of 5 years. Using two-dimensional electrophoresis, we detected 28 differentially expressed spots. Fourteen spots were identified using mass spectrometry, including seven up-regulated and seven down-regulated in metastatic samples and classified according to functional categories. We then selected five proteins involved in cell cycle or apoptosis. Thioredoxin peroxidase, allograft inflammatory factor 1, and ubiquitin E2N had more than threefold up-regulation; glutathione peroxidase 1 had 1.9-fold up-regulation; and heat shock protein 27 showed down-regulation in metastatic samples with a very low P value. After validation and analysis of protein levels, evaluation of clinical impact was assessed in a much wider cohort of primary archival specimens. Immunodetection showed a higher frequency of thioredoxin peroxidase, allograft inflammatory factor 1, ubiquitin E2N, and glutathione peroxidase 1 overexpression in primary tumors that developed into lung metastases or that locally relapsed than in the disease-free group, with variable stain intensity and distribution. Kaplan-Meier analysis showed that high expression of glutathione peroxidase 1 was strongly related to local recurrence and metastasis, suggesting that its up-regulation may identify a subset of high-risk patients with giant cell tumor prone to receive diverse clinical management.

MicroRNA cloning and sequencing in osteosarcoma cell lines: differential role of miR-93

BackgroundStudies show that abnormalities in non-coding genes can contribute to carcinogenesis; microRNA levels may modulate cancer growth and metastatic diffusion.MethodMicroRNA libraries were built and sequenced from two osteosarcoma cell lines (MG-63 and 143B), which differ in proliferation and transmigration. By cloning and transfection, miR-93, expressed in both cell lines, was then investigated for its involvement in osteosarcoma progression.ResultsSix of the 19 miRNA identified were expressed in both cell lines with higher expression levels of miR-93 in 143B and in primary osteosarcoma cultures compared to normal osteoblasts. Interestingly, levels of miR-93 were significantly higher in metastases from osteosarcoma than in paired primary tumours. When 143B and MG-63 were transfected with miR-93, clones appeared to respond differently to microRNA overexpression. Ectopic expression of miR-93 more significantly increased cell proliferation and invasivity in 143B than in MG-63 clones. Furthermore, increased mRNA and protein levels of E2F1, one of the potential miR-93 targets, were seen in osteosarcoma cellular clones and its involvement in 143B cell proliferation was confirmed by E2F1 silencing.ConclusionAlthough further studies are needed to evaluate miRNA involvement in osteosarcoma progression, miR-93 overexpression seems to play an important role in osteosarcoma cell growth and invasion.

NG2 expression predicts the metastasis formation in soft-tissue sarcoma patients

Enhanced expression levels of NG2 proteoglycan in presurgical original lesions of soft‐tissue sarcoma (STS) patients defines with 55% probability the immediate (i.e., within 12 months postsurgery) risk in these individuals to develop postsurgical secondary lesions, independently of any other clinical trait. It, therefore, provides a molecular factor that alone prospects a particularly unfavorable clinical outcome in such patients. Evaluation of the timing of metastasis formation in patients with high and low levels of NG2 in their primitive lesions further stratified the patients in subsets with diverse lag phases in the occurrence of metastatic disease. In our cohort of high‐grade STS cases, transcription of NG2 also showed a 81‐fold amplification in metastatic lesions, when compared to primitive ones, and this gene overexpression was accompanied by an abundant but nonuniform in situ expression of its product. In a similar manner as seen in primitive lesions, patients with higher levels of metastatic NG2 encountered a significantly more dismal clinical course. Multivariate analysis asserted that in these individuals upregulation of NG2 represented an absolute independent prognostic parameter. Therefore, minimally invasive assessment of the transcription levels of the NG2 gene represents a parameter capable of predicting the arising of metastatic disease within a definite postsurgery time interval, and affords in adjunct in the definition of life expectance in STS patients.

p53-dependent activation of microRNA-34a in response to etoposide-induced DNA damage in osteosarcoma cell lines not impaired by dominant negative p53 expression.

Osteosarcoma (OS) is the most common primary malignant bone tumor and prevalently occurs in the second decade of life. Etoposide, a chemotherapeutic agent used in combined treatments of recurrent human OS, belongs to the topoisomerase inhibitor family and causes DNA breakage. In this study we evaluated the cascade of events determined by etoposide-induced DNA damage in OS cell lines with different p53 status focusing on methylation status and expression of miR-34a that modulate tumor cell growth and cell cycle progression. Wild-type p53 U2-OS cells and U2-OS cells expressing dominant-negative form of p53 (U2- OS175) were more sensitive to etoposide than p53-deficient MG63 and Saos-2 cells, showing increased levels of unmethylated miR-34a, reduced expression of CDK4 and cell cycle arrest in G1 phase. In contrast, MG63 and Saos-2 cell lines presented aberrant methylation of miR-34a promoter gene with no miR-34a induction after etoposide treatment, underlining the close connection between p53 expression and miR-34a methylation status. Consistently, in p53siRNA transfected U2-OS cells we observed loss of miR-34a induction after etoposide exposure associated with a partial gain of gene methylation and cell cycle progress towards G2/M phase. Our results suggest that the open and unmethylated conformation of the miR-34a gene may be regulated by p53 able to bind the gene promoter. In conclusion, cell response to etoposide-induced DNA damage was not compromised in cells with dominant-negative p53 expression.

Mapping protein signal pathway interaction in sarcoma bone metastasis: linkage between rank, metalloproteinases turnover and growth factor signaling pathways.

We applied reverse phase protein microarrays technology to map signal pathway interactions in a discovery set of 34 soft tissue sarcoma (STS) bone metastases compared to healthy bone. Proteins associated with matrix remodeling (MMP), adhesion (FAK Y576/577, Syndecan-1), and growth/survival (IGF1R Y1135/1136, PI3K, EGFR) were elevated in metastasis compared to normal bone. Linkage between Syndecan-1, FAK Y576/577, Shc Y317, and EGFR, IGF Y1135/1136, PI3K/AKT was a prominent feature of STS bone metastasis. Elevated linkage between RANKL and 4EBP1 T37/46, EGFR, IGF1R Y1135/1136, Src Y41, Shc Y317, PI3Kp110γ was associated with short survival. Finally, we tested the hypothesis that signal pathway proteins augmented in the STS bone metastasis may provide clues to understand the subset of primary STS that metastasize. The most representative molecules identified in the discovery set were validated on an independent series of 82 primary STS by immunohistochemistry applied to a tissue microarray. The goal was to correlate the molecular profile in the primary tumors with a higher likelihood of metastasis. Elevation of activated kinase substrate endpoints IRS1 S612, 4EBP1 T37/46, FAK Y576/577 and loss of Fibronectin, were associated with a higher likelihood of metastases. These data indicate that the linkage between matrix remodeling, adhesion, and growth signaling may drive STS metastasis and can be the basis for prognostic and therapeutic strategies.

Metformin inhibits growth and sensitizes osteosarcoma cell lines to cisplatin through cell cycle modulation

Osteosarcoma (OS) is the most common cancer that affects the bone and appears to be resistant to several chemotherapeutic drugs. The aim of the present study was to verify whether the combination of metformin and cisplatin has an effect on OS cell lines. OS cell lines U2OS, 143B and MG63 were treated with metformin, cisplatin or a combination of both drugs. Viability, apoptosis and cell cycle were evaluated to characterize the effects of the treatments. Western blot analyses were used to evaluate protein expression. All OS cell lines were found to be sensitive to metformin with different values of IC50, showing a slowdown of cell cycle associated or not with apoptosis. In particular, metformin was able to sensitize cells to cisplatin, to which all OS cell lines were resistant, demonstrating a synergistic effect in the combined treatment of the two drugs. The data obtained may have clinical relevance for novel therapeutic strategies for the treatment of OS; metformin inhibits tumor cell growth and amplifies the effect of cisplatin.

Prognostic role of nuclear factor/IB and bone remodeling proteins in metastatic giant cell tumor of bone: A retrospective study

Giant cell tumor of bone (GCTb) represents 5% of bone tumors, and although considered benign, 5% metastasize to the lung. The expression of proteins directly or indirectly associated with osteolysis and tumor growth was studied on 163 samples of GCTb. Of these, 33 patients developed lung metastasis during follow‐up. The impact of tumor–host interaction on clinical aspects was evaluated with the aim of finding specific markers for new biological therapies, thus improving clinical management of GCTb. Protein expression was evaluated by immunohistochemical analysis on Tissue Microarray. The majority of GCTb samples from patients with metastatic disease were strongly positive to RANKL and its receptor RANK as well as to CAII and MMP‐2 and to pro‐survival proteins NFIB and c‐Fos. Kaplan–Meier analysis indicated a significant difference in metastasis free survival curves based on protein staining. Interestingly, the statistical correlation established a strong association between all variables studied with a higher τ coefficient for RANK/RANKL, RANK/NFIB, and RANKL/NFIB pairs. At multivariate analysis co‐overexpression of NFIB, RANK and RANKL significantly increased the risk of metastasis with an odds ratio of 13.59 (95%CI 4.12–44.82; p < 0.0005). In conclusion, the interconnection between matrix remodeling and tumor cell activity may identify tumor–host endpoints for new biological treatments.

Epidermal growth factor receptor signalling contributes to osteoblastic stromal cell proliferation, osteoclastogenesis and disease progression in giant cell tumour of bone.

Balla P, Moskovszky L, Sapi Z, Forsyth R, Knowles H, Athanasou N A, Szendroi M, Kopper L, Rajnai H, Pinter F, Petak I, Benassi M S, Picci P, Conti A & Krenacs T
(2011) Histopathology59, 376–389

miR-196a expression in human and canine osteosarcomas: A comparative study

Osteosarcoma (OS) is the most common primary malignant bone tumour in dogs and humans. MicroRNAs are short non-coding RNA molecules involved in post-transcriptional gene expression. Here, we compared the effects of miR-196a deregulation in human and canine OS cells after having observed a more uniform distribution and stronger down-expression in the human specimens. Cell response to miR-196a transfection was different in human and canine OS. A decreased proliferation rate was seen in human MG63 and 143B OS cells, while no appreciable changes occurred in canine DAN cells. Transient decrease of motility was highly remarkable and longer in MG63, concomitant with decreased levels of annexin1, a target of miR-196a promoting cell migration and invasion. In conclusion, the effects of miR-196a over-expression on tumour cell response may be strictly related to species and cell type. Further studies are needed to define the impact of miRNA deregulation on OS development.