Potential for treatment of liposarcomas with the MDM2 antagonist Nutlin-3A

Nutlin-3a efficacy in sarcoma predicted by transcriptomic and epigenetic profiling

Nutlin-3a is a small-molecule antagonist of p53/MDM2 that is being explored as a treatment for sarcoma. In this study, we examined the molecular mechanisms underlying the sensitivity of sarcomas to Nutlin-3a. In an ex vivo tissue explant system, we found that TP53 pathway alterations (TP53 status, MDM2/MDM4 genomic amplification/mRNA overexpression, MDM2 SNP309, and TP53 SNP72) did not confer apoptotic or cytostatic responses in sarcoma tissue biopsies (n = 24). Unexpectedly, MDM2 status did not predict Nutlin-3a sensitivity. RNA sequencing revealed that the global transcriptomic profiles of these sarcomas provided a more robust prediction of apoptotic responses to Nutlin-3a. Expression profiling revealed a subset of TP53 target genes that were transactivated specifically in sarcomas that were highly sensitive to Nutlin-3a. Of these target genes, the GADD45A promoter region was shown to be hypermethylated in 82% of wild-type TP53 sarcomas that did not respond to Nutlin-3a, thereby providing mechanistic insight into the innate ability of sarcomas to resist apoptotic death following Nutlin-3a treatment. Collectively, our findings argue that the existing benchmark biomarker for MDM2 antagonist efficacy (MDM2 amplification) should not be used to predict outcome but rather global gene expression profiles and epigenetic status of sarcomas dictate their sensitivity to p53/MDM2 antagonists.

Liposarcomas: diagnostic pitfalls and new insights

Liposarcomas represent the most common histotype among soft tissue sarcomas. However, liposarcomas in fact constitute a heterogeneous group of distinctive lesions that pose several diagnostic difficulties. The current World Health Organization classification of soft tissue and bone tumours recognizes four major liposarcoma subtypes: (i) atypical lipomatous tumour/well-differentiated liposarcoma; (ii) de-differentiated liposarcoma; (iii) myxoid liposarcoma; and (iv) pleomorphic liposarcoma. These four main subgroups are characterized by distinctive morphologies, unique genetic findings as well as distinct clinical behaviour. Accurate classification requires the integration of morphological, immunohistochemical and (in selected situations) genetic findings, and is essential for providing patients with the best available treatments. This review will focus upon the main diagnostic pitfalls encountered in the routine diagnosis of liposarcoma, underlining the diagnostic value of combining morphology with cytogenetics and molecular genetics.

A current perspective on the role for molecular studies in soft tissue tumor pathology

Soft tissue sarcomas represent an heterogenous group of malignancies. They represent a diagnostic challenge, and their accurate classification impact over treatment options. Sarcomas, similarly to hematologic neoplasm, often harbor relatively specific genetic aberrations, the recognition of which can be used to improved diagnostic accuracy. This review will focus on the clinical relevance of molecular analysis in soft tissue sarcomas, trying to elucidate its role as a diagnostic tool as well as a potential prognostic/predictive marker.

In vitro and in silico studies of MDM2/MDMX isoforms predict Nutlin-3A sensitivity in well/de-differentiated liposarcomas

The molecular marker of well-differentiated/de-differentiated liposarcomas is MDM2 gene amplification coupled with protein overexpression and wild-type TP53. MDMX is a recently identified MDM2 homolog and its presence in this tumor is unexplored. Our aim was to investigate the role of full-length MDM2 and MDMX proteins and their isoforms in surgical specimens of well-differentiated/de-differentiated liposarcomas in view of Nutlin-3A (a MDM2 inhibitor) treatment. Frozen and matched formalin-fixed, paraffin-embedded material from surgical specimens was examined by means of: (1) fluorescence in situ hybridization to determine MDM2 and MDMX gene copy numbers; (2) RT-PCR and densitometry to analyze alternative splicing forms of mdm2 and mdmx; (3) immunoblotting and immunohistochemistry to assess the corresponding translated proteins; and (4) in vitro and in silico assays to determine their affinity for Nutlin-3A. All these cases showed MDM2 gene amplification with an MDMX disomic pattern. In all cases, the full-length mdm2 transcript was associated with the mdm2-b transcript, with ratios ranging from 0.07 to 5.6, and both were translated into protein; mdmx and mdmx-s were co-transcripted, with ratios ranging from 0.1 to 5.6. MDMX-S was frequently more upregulated than MDMX at both transcriptional and protein level. Each case showed different amounts of mdm2, mdm2-b, mdmx, and mdmx-s transcripts and the corresponding proteins. In vitro assays showed that Nutlin-3A was ineffective against MDM2-B and was unable to disrupt the MDMX/TP53 and MSMX-S/TP53 complexes. Molecular simulations confirmed these in vitro findings by showing that MDM2 has high Nutlin-3A affinity, followed by MDMX-S, MDMX, and MDM2-B. Nutlin-3A is predicted to be a good therapeutic option for well-differentiated/de-differentiated liposarcomas. However, our findings predict heterogeneous responses depending on the relative expression of mdm2, mdm2-b, mdmx, and mdmx-s transcripts and proteins.

Overexpression of miR-26a-2 in human liposarcoma is correlated with poor patient survival

Approximately 90% of well-differentiated/de-differentiated liposarcomas (WDLPS/DDLPS), the most common LPS subtype, have chromosomal amplification at 12q13-q22. Many protein-coding genes in the region, such as MDM2 and , have been studied as potential therapeutic targets for LPS treatment, with minimal success. In the amplified region near the MDM2 gene, our single nucleotide polymorphism (SNP) array analysis of 75 LPS samples identified frequent amplification of miR-26a-2. Besides being in the amplicon, miR-26a-2 was overexpressed significantly in WDLPS/DDLPS (P<0.001), as well as in myxoid/round cell LPS (MRC) (P<0.05). Furthermore, Kaplan–Meier survival analysis showed that overexpression of miR-26a-2 significantly correlated with poor patient survival in both types of LPS (P<0.05 for WDLPS/DDLPS; P<0.001 for MRC). Based on these findings, we hypothesized that miR-26a-2 has an important role in LPS tumorigenesis, regardless of LPS subtypes. Overexpression of miR-26a-2 in three LPS cell lines (SW872, LPS141 and LP6) enhanced the growth and survival of these cells, including faster cell proliferation and migration, enhanced clonogenicity, suppressed adipocyte differentiation and/or resistance to apoptosis. Inhibition of miR-26a-2 in LPS cells using anti-miR-26a-2 resulted in the opposite responses. To explain further the effect of miR-26a-2 overexpression in LPS cells, we performed in silico analysis and identified 93 candidate targets of miR-26a-2. Among these genes, RCBTB1 (regulator of chromosome condensation and BTB domain-containing protein 1) is located at 13q12.3-q14.3, a region of recurrent loss of heterozygosity (LOH) in LPS. Indeed, either overexpression or inhibition of RCBTB1 made LPS cells more susceptible or resistant to apoptosis, respectively. In conclusion, our study for the first time reveals the contribution of miR-26a-2 to LPS tumorigenesis, partly through inhibiting RCBTB1, suggesting that miR-26a-2 is a novel therapeutic target for human LPS.

Novel systemic therapies in advanced liposarcoma: a review of recent clinical trial results

Liposarcoma is one of the most common adult soft tissue sarcomas an consists of three histologic subtypes (well and dedifferentiated, myxoid/round cell, and pleomorphic). Surgery is the mainstay of treatment for localized disease; however for unresectable or metastatic disease, effective treatment options are currently limited. In the past decade, a better understanding of the distinct genetic and molecular aberrations for each of the three histologic subtypes has led to the development of several novel systemic therapies. Data from phase I and early phase II clinical trials have been reported. Despite challenges with conducting clinical trials in liposarcoma, preliminary results for several of these novel, biology-driven therapies are encouraging.

Correlation of TP53 and MDM2 genotypes with response to therapy in sarcoma

BACKGROUND

Relatively few sarcomas harbor TP53 (tumor protein p53) mutations, but in many cases, amplification of MDM2 (murine double minute 2) effectively inactivate p53. The p53 pathway activity can also be affected by normal genetic variation.

METHODS

The mutation status of TP53 and expression of MDM2, TP53, and their genetic variants SNP309 and R72P (Arg72Pro) were investigated in 125 sarcoma patient samples and 18 sarcoma cell lines. Association of the different genotypes and gene aberrations with chemotherapy response and survival, as well as response to MDM2 antagonists in vitro was evaluated.

RESULTS

Twenty-two percent of the tumors had mutant TP53 and 20% MDM2 gene amplification. Patients with wild-type TP53 (TP53(Wt) ) tumors had improved survival (P < .001) and TP53(Wt) was an independent prognostic factor (hazard ratio = 0.41; 95% confidence interval = 0.23-0.74; P = .03). Interestingly, there was a trend toward longer time to progression after chemotherapy for tumors with the apoptosis-prone p53 variant R72 (P = .07), which was strongest with doxorubicin/ifosfamide-based regimens (P = .01). Liposarcomas had low R72 frequency (33% versus 56%), but increased levels of MDM2 and MDM4 (51% and 11%, P < .001). MDM2 overexpression on a TP53(Wt) background predicted better response to MDM2 antagonist Nutlin-3a, irrespective of R72P or SNP309 status.

CONCLUSIONS

Improved survival after chemotherapy was found in patients with TP53(Wt) tumors harboring the R72 variant. MDM2 overexpression in TP53(Wt) tumors predicted good response to MDM2 antagonists, irrespective of R72P or SNP309 status. Thus, detailed TP53 and MDM2 genotype analyses prior to systemic therapy are recommended.

MDM2 inhibitor Nutlin-3a suppresses proliferation and promotes apoptosis in osteosarcoma cells

Restoring p53 activity by inhibiting the interaction between p53 and the mouse double minutes clone 2 (MDM2) offers an attractive approach to cancer therapy. Nutlin-3a is a small-molecule inhibitor that inhibits MDM2 binding to p53 and subsequent p53-dependent DNA damage signaling. In this study, we determined the efficacy of Nutlin-3a in inducing p53-mediated cell death in osteosarcoma (OS) cell lines both in vivo and in vitro. Targeted disruption of the p53-MDM2 interaction by Nutlin-3a stabilizes p53 and selectively activates the p53 pathway only in OS cells with wild-type p53, resulting in a pronounced anti-proliferative and cytotoxic effect due to G1 cell cycle arrest and apoptosis both in vitro and in vivo. p53 dependence of these alternative outcomes of Nutlin-3a treatment was shown by the abrogation of these effects when p53 was knocked-down by small interfering RNA. These data suggest that the disruption of p53-MDM2 interaction by Nutlin-3a might be beneficial for OS patients with MDM2 amplification and wt p53 status.

Characterization of liposarcoma cell lines for preclinical and biological studies

Liposarcoma cell lines represent in vitro models for studying disease mechanisms at the cellular level and for preclinical evaluation of novel drugs. To date there are a limited number of well-characterized models available. In this study, nine immortal liposarcoma cell lines were evaluated for tumor-forming ability, stem cell- and differentiation potential, and metastatic potential, with the aim to generate a well-characterized liposarcoma cell line panel. Detailed stem cell and differentiation marker analyses were also performed. Five of the liposarcoma cell lines were tumorigenic, forming tumors in mice. Interestingly, tumor-forming ability correlated with high proliferative capacity in vitro. All the cell lines underwent adipocytic differentiation, but the degree varied. Surprisingly, the expression of stem cell and differentiation markers did not correlate well with function. Overall, the panel contains cell lines suited for in vivo analyses (LPS141, SA-4, T778, SW872, and LISA-2), for testing novel drugs targeting cancer stem cells (LPS141) and for studying tumor progression and metastasis (T449 and T778).

Attenuation of soft-tissue sarcomas resistance to the cytotoxic action of TNF-α by restoring p53 function

Background

Isolated limb perfusion with TNF-α and melphalan is used with remarkable efficiency to treat unresectable limb sarcomas. Here we tested the ability of TNF-α to directly induce apoptosis of sarcoma cells. In addition, we investigated the impact of p53 in the regulation of such effect.

Methodology/Principal Findings

We first analysed the ability of TNF-α to induce apoptosis in freshly isolated tumour cells. For this purpose, sarcoma tumours (n = 8) treated ex vivo with TNF-α were processed for TUNEL staining. It revealed substantial endothelial cell apoptosis and levels of tumour cell apoptosis that varied from low to high. In order to investigate the role of p53 in TNF-α-induced cell death, human sarcoma cell lines (n = 9) with different TP53 and MDM2 status were studied for their sensitivity to TNF-α. TP53^Wt cell lines were sensitive to TNF-α unless MDM2 was over-expressed. However, TP53^Mut and TP53^Null cell lines were resistant. TP53 suppression in TP53^Wt cell lines abrogated TNF-α sensitivity and TP53 overexpression in TP53^Null cell lines restored it. The use of small molecules that restore p53 activity, such as CP-31398 or Nutlin-3a, in association with TNF-α, potentiated the cell death of respectively TP53^Mut and TP53^Wt/MDM2^Ampl. In particular, CP-31398 was able to induce p53 as well as some of its apoptotic target genes in TP53^Mut cells. In TP53^Wt/MDM2^Ampl cells, Nutlin-3a effects were associated with a decrease of TNF-α-induced NF-κB-DNA binding and correlated with a differential regulation of pro- and anti-apoptotic genes such as TP53BP2, GADD45, TGF-β1 and FAIM.

Conclusion/Significance

More effective therapeutic approaches are critically needed for the treatment of unresectable limb sarcomas. Our results show that restoring p53 activity in sarcoma cells correlated with increased sensitivity to TNF-α, suggesting that this strategy may be an important determinant of TNF-α-based sarcomas treatment.

Targeted therapies in sarcomas: challenging the challenge

Sarcomas are a heterogeneous group of mesenchymal malignancies that very often lead to death. Nowadays, chemotherapy is the only available treatment for most sarcomas but there are few active drugs and clinical results still remain very poor. Thus, there is an imperious need to find new therapeutic alternatives in order to improve sarcoma patient's outcome. During the last years, there have been described a number of new molecular pathways that have allowed us to know more about cancer biology and tumorigenesis. Sarcomas are one of the tumors in which more advances have been made. Identification of specific chromosomal translocations, some important pathways characterization such as mTOR pathway or the insulin-like growth factor pathway, the stunning development in angiogenesis knowledge, and brand new agents like viruses have lead to the development of new therapeutic options with promising results. This paper makes an exhaustive review of preclinical and clinical evidence of the most recent targeted therapies in sarcomas and provides a future view of treatments that may lead to improve prognosis of patients affected with this disease.

Comparison of the antitumor effects of an MDM2 inhibitor, nutlin-3, in feline lymphoma cell lines with or without p53 mutation

The P53 tumor suppressor protein is a multifunctional transcription factor that prevents the malignant transformation of normal cells. In human malignancies, p53 is the most frequently altered gene and is mutated in approximately 50% of all malignancies. In contrast, p53 gene mutation has been rarely detected in feline malignancies, and most feline malignancies conceivably retain the wild-type p53 (wt-p53) gene. MDM2 negatively regulates the P53 protein by inhibiting its transcriptional activity and nuclear transport and by inducing its degradation. Inhibition of P53-MDM2 interaction stabilizes P53 protein and activates P53 pathway. Nutlin-3, a small molecule that inhibits P53-MDM2 interaction, was shown to have an antitumor effect in several human cancer cells retaining the wt-p53 gene. In the present study, we evaluated and compared the antitumor effect of nutlin-3 in 5 different feline lymphoma cell lines, of which 3 harbored wt-p53, and 2, mutated p53 (mt-p53). Treatment with nutlin-3 resulted in increased amounts of P53 protein in conjunction with augmented expression of P53-target genes in 3 feline lymphoma cell lines with the wt-p53 gene, but not in 2 feline lymphoma cell lines with the mt-p53 gene. Nutlin-3 treatment also induced G1-S and/or G2-M cell cycle arrest and apoptosis in lymphoma cell lines with wt-p53. Nutlin-3 treatment induced cell cycle arrest but not apoptosis in the cell lines with mt-p53. From these results, we concluded that nutlin-3 has an antitumor effect on feline lymphoma cell lines harboring the wt-p53 gene through accumulation and activation of P53 leading to cell cycle arrest and apoptosis. The present study suggests that inhibition of P53-MDM2 interaction using nutlin-3 may be a new therapeutic strategy for treating feline lymphoma retaining the wt-p53 gene.

Diagnostic utility of p16, CDK4, and MDM2 as an immunohistochemical panel in distinguishing well-differentiated and dedifferentiated liposarcomas from other adipocytic tumors

Adipocytic tumors are the most common type of soft tissue neoplasms. Distinguishing atypical lipomatous tumor-well-differentiated liposarcoma (WDL) from benign adipocytic neoplasms and dedifferentiated liposarcoma (DDL) from pleomorphic or myxoid liposarcoma (LPS) can be difficult. WDL and DDL characteristically harbor amplifications of the MDM2 and CDK4 cell cycle oncogenes with protein overexpression and can also overexpress the cell cycle regulator p16. We assessed the utility of immunohistochemistry for CDK4, MDM2, and p16 in the routine histopathologic diagnosis of WDL/DDL from other adipocytic tumors. Immunohistochemistry for the trio of markers was performed on 216 adipocytic neoplasms (31 WDLs, 57 DDLs, 11 myxoid LPS, 2 pleomorphic LPS, 91 lipomas (including intramuscular, fibro, angio, and ossifying subtypes), 18 spindle/pleomorphic lipomas, and 6 hibernomas. Sixty-eight percent of WDLs and 72% of DDLs expressed all 3 antigens, whereas 100% of WDLs and 93% of DDLs expressed at least 2 antigens. The sensitivity and specificity of the trio for detecting WDLs/DDLs were 71% and 98%, respectively. The sensitivity and specificity of CDK4 for detecting WDLs/DDLs were 86% and 89%, those of MDM2 were 86% and 74%, and those of p16 were 93% and 92%, respectively. The immunohistochemical trio of CDK4, MDM2, and p16 is a useful ancillary diagnostic tool that provides strong support in distinguishing WDLs and DDLs from other adipocytic neoplasms and is potentially more sensitive than previously assessed combinations of CDK4 and MDM2. p16 was the most sensitive and specific marker for detecting WDL/DDL, and the combination of CDK4 and p16 is of more discriminatory value than the combination of either with MDM2, the least sensitive and specific of the 3 markers.

The Cancer Cell Line Encyclopedia enables predictive modelling of anticancer drug sensitivity

The systematic translation of cancer genomic data into knowledge of tumour biology and therapeutic possibilities remains challenging. Such efforts should be greatly aided by robust preclinical model systems that reflect the genomic diversity of human cancers and for which detailed genetic and pharmacological annotation is available. Here we describe the Cancer Cell Line Encyclopedia (CCLE): a compilation of gene expression, chromosomal copy number and massively parallel sequencing data from 947 human cancer cell lines. When coupled with pharmacological profiles for 24 anticancer drugs across 479 of the cell lines, this collection allowed identification of genetic, lineage, and gene-expression-based predictors of drug sensitivity. In addition to known predictors, we found that plasma cell lineage correlated with sensitivity to IGF1 receptor inhibitors; AHR expression was associated with MEK inhibitor efficacy in NRAS-mutant lines; and SLFN11 expression predicted sensitivity to topoisomerase inhibitors. Together, our results indicate that large, annotated cell-line collections may help to enable preclinical stratification schemata for anticancer agents. The generation of genetic predictions of drug response in the preclinical setting and their incorporation into cancer clinical trial design could speed the emergence of 'personalized' therapeutic regimens.

The Cancer Cell Line Encyclopedia enables predictive modelling of anticancer drug sensitivity

The systematic translation of cancer genomic data into knowledge of tumour biology and therapeutic possibilities remains challenging. Such efforts should be greatly aided by robust preclinical model systems that reflect the genomic diversity of human cancers and for which detailed genetic and pharmacological annotation is available. Here we describe the Cancer Cell Line Encyclopedia (CCLE): a compilation of gene expression, chromosomal copy number and massively parallel sequencing data from 947 human cancer cell lines. When coupled with pharmacological profiles for 24 anticancer drugs across 479 of the cell lines, this collection allowed identification of genetic, lineage, and gene-expression-based predictors of drug sensitivity. In addition to known predictors, we found that plasma cell lineage correlated with sensitivity to IGF1 receptor inhibitors; AHR expression was associated with MEK inhibitor efficacy in NRAS-mutant lines; and SLFN11 expression predicted sensitivity to topoisomerase inhibitors. Together, our results indicate that large, annotated cell-line collections may help to enable preclinical stratification schemata for anticancer agents. The generation of genetic predictions of drug response in the preclinical setting and their incorporation into cancer clinical trial design could speed the emergence of 'personalized' therapeutic regimens.

Liposarcoma in children and young adults: a multi-institutional experience

BACKGROUND

There are limited data regarding the differences in clinical presentation and outcome of liposarcomas between adult and pediatric patients. The role of adjuvant radiotherapy in the treatment of childhood liposarcoma is unclear.

PROCEDURE

A multi-institutional retrospective analysis of medical records was performed for patients ≤ 21 years of age presenting with a verified histologic diagnosis of liposarcoma.

RESULTS

Thirty-three patients were evaluable for this study, 23 of whom were male. Median age was 17.2 years. Twenty-four cases were myxoid subtype and 7 were pleomorphic subtype. In myxoid cases, 17 (71%) presented with extremity tumors; none had metastases. Eleven of these patients with myxoid subtype were treated with surgery only, seven with surgery + radiation, three with surgery + radiation + chemotherapy. Median radiation therapy dose for patients with myxoid tumors was 60 Gy. At median follow-up of 4.2 years (range 0.1-32.2 years), two patients relapsed with one death from progressive disease. In seven pleomorphic cases, four patients had primary tumors at central axial sites. Six patients (86%) received multimodal therapy, but six patients experienced relapse of disease. Four patients died from progressive disease.

CONCLUSIONS

Pediatric liposarcoma has a different spectrum of presentation compared to adult cases. Myxoid liposarcoma is the more common subtype, usually occurs in extremities, and has an excellent prognosis. Pleomorphic liposarcoma occurs in axial sites, and despite multimodal therapy, outcome is poor. Further study is needed to identify the optimal therapy for pediatric liposarcoma.

Advanced well-differentiated/dedifferentiated liposarcomas: role of chemotherapy and survival

BACKGROUND

Data regarding the role of systemic therapy in patients with advanced well-differentiated/dedifferentiated liposarcomas (WDLPS/DDLPS) are limited.

METHODS

From 2000 to 2010, 208 patients with advanced WDLPS/DDLPS received chemotherapy in 11 participating institutions. Clinical and pathological data were collected by reviewing medical records.

RESULTS

Median age was 63 years (range 32-84). Combination chemotherapy was delivered in 85 cases (41%) and single agent in 123 cases (59%), respectively. One hundred and seventy-one patients (82%) received an anthracycline-containing regimen. Using RECIST, objective response was observed in 21 patients (12%), all treated with anthracyclines. Median progression-free survival (PFS) was 4.6 months [95% confidence interval (CI) 3.3-5.9]. On multivariate analysis, age and performance status (PS) were the sole factors significantly associated with poor PFS. Median overall survival (OS) was 15.2 months (95% CI 11.8 -18.7). On multivariate analysis, grade and PS were the sole factors significantly associated with OS.

CONCLUSIONS

Chemotherapy was associated with clinical benefit in 46% of patients with advanced WDLPS/DDLPS. OS remains poor, even though visceral metastatic disease is less frequent than in other sarcomas.

Clinical application of molecular pathology in sarcomas

PURPOSE OF REVIEW

This review is intended to highlight the clinical application of molecular pathology as a tool for diagnostic accuracy and prognostic and predictive use and finally to discover novel molecular therapeutic targets.

RECENT FINDINGS

We are living an exciting era in sarcomas' therapy. This is the result of overcoming two crucial obstacles: lack of effective and specific drugs; lack of specific therapeutic regimen for distinct clinical entities. As new specific drugs have become available, it has become clear that an accurate diagnosis is the prerequisite for a specific therapy. This approach has been successfully applied to gastrointestinal stromal tumor and is now also being used in other sarcomas. The more recent findings are hereby reviewed.

SUMMARY

The inclusion of the molecular pathology in the diagnostic surgical pathology is instrumental for the application of molecularly tailored therapy. However, the degree of complexity of this approach requires additional caution in the data interpretation and in the reproducibility of the results. As molecular knowledge is improving and more sophisticated and powerful techniques are going to be routinely used, the success rate in treating sarcomas is expected to significantly increase.

Liposarcomas

Liposarcoma is a common soft tissue sarcoma and represents a group of neoplasms, each with distinct clinical behavior and pathologic findings. Proper classification is critical for clinical management and prognostication. Until recently, immunohistochemistry played a limited role in diagnosis of these tumors. Increased understanding of the underlying genetic basis of disease has paved the way for development of improved tools for diagnosis and new forms of targeted therapy. This article summarizes the clinical, pathologic, and molecular findings of the main liposarcoma subtypes. Special attention to the differential diagnosis and difficulties the pathologist may face when interpreting these lesions is discussed.

Advances in sarcoma genomics and new therapeutic targets

Increasingly, human mesenchymal malignancies are being classified by the abnormalities that drive their pathogenesis. Although many of these aberrations are highly prevalent within particular sarcoma subtypes, few are currently targeted therapeutically. Indeed, most subtypes of sarcoma are still treated with traditional therapeutic modalities, and in many cases sarcomas are resistant to adjuvant therapies. In this Review, we discuss the core molecular determinants of sarcomagenesis and emphasize the emerging genomic and functional genetic approaches that, coupled with novel therapeutic strategies, have the potential to transform the care of patients with sarcoma.

MYCN sensitizes neuroblastoma to the MDM2-p53 antagonists Nutlin-3 and MI-63

MYCN amplification is a major biomarker of poor prognosis, occurring in 25-30% of neuroblastomas. MYCN plays contradictory roles in promoting cell growth and sensitizing cells to apoptosis. We have recently shown that p53 is a direct transcriptional target of MYCN in neuroblastoma and that p53-mediated apoptosis may be an important mechanism of MYCN-induced apoptosis. Although p53 mutations are rare in neuroblastoma at diagnosis, the p53/MDM2/p14^ARF pathway is often inactivated through MDM2 amplification or p14^ARF inactivation. We hypothesised that reactivation of p53 by inhibition of its negative regulator MDM2, using the MDM2-p53 antagonists Nutlin-3 and MI-63, will result in p53-mediated growth arrest and apoptosis especially in MYCN amplified cells. Using the SHEP Tet21N MYCN regulatable system, MYCN(−) cells were more resistant to both Nutlin-3 and MI-63 mediated growth inhibition and apoptosis compared to MYCN(+) cells and siRNA mediated knockdown of MYCN in 4 MYCN amplified cell lines resulted in decreased p53 expression and activation, as well as decreased levels of apoptosis following treatment with MDM2-p53 antagonists. In a panel of 18 neuroblastoma cell lines treated with Nutlin-3 and MI-63, the sub-set amplified for MYCN had a significantly lower mean GI₅₀ value and increased caspase 3/7 activity compared to the non MYCN amplified group of cell lines, but p53 mutant cell lines were resistant to the antagonists regardless of MYCN status. We conclude that amplification or overexpression of MYCN sensitizes neuroblastoma cell lines with wildtype p53 to MDM2-p53 antagonists and that these compounds may therefore be particularly effective in treating high risk MYCN amplified disease.

MDM2 antagonist Nutlin-3a potentiates antitumour activity of cytotoxic drugs in sarcoma cell lines

Background

Frequent failure and severe side effects of current sarcoma therapy warrants new therapeutic approaches. The small-molecule MDM2 antagonist Nutlin-3a activates the p53 pathway and efficiently induces apoptosis in tumours with amplified MDM2 gene and overexpression of MDM2 protein. However, the majority of human sarcomas have normal level of MDM2 and the therapeutic potential of MDM2 antagonists in this group is still unclear. We have investigated if Nutlin-3a could be employed to augment the response to traditional therapy and/or reduce the genotoxic burden of chemotherapy.

Methods

A panel of sarcoma cell lines with different TP53 and MDM2 status were treated with Nutlin-3a combined with Doxorubicin, Methotrexate or Cisplatin, and their combination index determined.

Results

Clear synergism was observed when Doxorubicin and Nutlin-3a were combined in cell lines with wild-type TP53 and amplified MDM2, or with Methotrexate in both MDM2 normal and amplified sarcoma cell lines, allowing for up to tenfold reduction of cytotoxic drug dose. Interestingly, Nutlin-3a seemed to potentiate the effect of classical drugs as Doxorubicin and Cisplatin in cell lines with mutated TP53, but inhibited the effect of Methotrexate.

Conclusion

The use of Nutlin in combination with classical sarcoma chemotherapy shows promising preclinical potential, but since clear biomarkers are still lacking, clinical trials should be followed up with detailed tumour profiling.

Constant p53 pathway inactivation in a large series of soft tissue sarcomas with complex genetics

Alterations of the p53 pathway are among the most frequent aberrations observed in human cancers. We have performed an exhaustive analysis of TP53, p14, p15, and p16 status in a large series of 143 soft tissue sarcomas, rare tumors accounting for around 1% of all adult cancers, with complex genetics. For this purpose, we performed genomic studies, combining sequencing, copy number assessment, and expression analyses. TP53 mutations and deletions are more frequent in leiomyosarcomas than in undifferentiated pleomorphic sarcomas. Moreover, 50% of leiomyosarcomas present TP53 biallelic inactivation, whereas most undifferentiated pleomorphic sarcomas retain one wild-type TP53 allele (87.2%). The spectrum of mutations between these two groups of sarcomas is different, particularly with a higher rate of complex mutations in undifferentiated pleomorphic sarcomas. Most tumors without TP53 alteration exhibit a deletion of p14 and/or lack of mRNA expression, suggesting that p14 loss could be an alternative genotype for direct TP53 inactivation. Nevertheless, the fact that even in tumors altered for TP53, we could not detect p14 protein suggests that other p14 functions, independent of p53, could be implicated in sarcoma oncogenesis. In addition, both p15 and p16 are frequently codeleted or transcriptionally co-inhibited with p14, essentially in tumors with two wild-type TP53 alleles. Conversely, in TP53-altered tumors, p15 and p16 are well expressed, a feature not incompatible with an oncogenic process.

An experimental model for the study of well-differentiated and dedifferentiated liposarcoma; deregulation of targetable tyrosine kinase receptors

Therapeutic progress in well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS) is hampered by lack of relevant experimental models, thereby limiting comprehensive molecularly based investigations. Our goal is to bridge this experimental gap by establishing and characterizing an in vitro/in vivo model useful for examining WDLPS/DDLPS molecular pathogenesis and also therapeutic screening and testing. WDLPS/DDLPS cells were isolated from freshly resected human surgical specimens and were phenotypically and molecularly characterized. MDM2 amplification was determined via FISH analysis. Adipogenic differentiation was evaluated using Oil Red O staining and western blotting (WB). Tyrosine kinase receptors' (TKRs) expression in pre-adipocytes, adipocytes, WDLPS, and DDLPS cells was determined via western blot analysis. SCID mouse xenograft growth was assessed after subcutaneous and/or intraperitoneal tumor cell injection. There was enhanced proliferation, migration, invasion, survival, and pro-angiogenic capacity in DDLPS cells vs WDLPS cells. DDLPS cells formed tumors in SCID mice whereas WDLPS did not. WDLPS/DDLPS cells, especially those that exhibited baseline PPARγ expression, partially retained terminal adipogenic differentiation capacity. MDM2 amplification was found in all WDLPS/DDLPS cell strains, CDK4 overexpression was observed in LPS cells as compared with normal adipocytes, and enhanced JUN expression and phosphorylation was seen in DDLPS cells as compared with WDLPS cells. The TKRs: MET, AXL, KIT, and IGF-1R were overexpressed in LPS cells vs normal adipocytes and pre-adipocytes. In conclusion, these newly established cellular and xenograft models can facilitate investigation of liposarcomagenesis, dedifferentiation, and tumor progression. Further studies of the molecular deregulations so identified may lead to improved therapeutic strategies for patients afflicted by these unfavorable malignancies.

Liposarcoma: molecular genetics and therapeutics

Sarcomas are a group of heterogeneous tumours with varying genetic basis. Cytogenetic abnormalities range from distinct genomic rearrangements such as pathognomonic translocation events and common chromosomal amplification or loss, to more complex rearrangements involving multiple chromosomes. The different subtypes of liposarcoma are spread across this spectrum and constitute an interesting tumour type for molecular review. This paper will outline molecular pathogenesis of the three main subtypes of liposarcoma: well-differentiated/dedifferentiated, myxoid/round cell, and pleomorphic liposarcoma. Both the molecular basis and future avenues for therapeutic intervention will be discussed.

New frontiers in the treatment of liposarcoma, a therapeutically resistant malignant cohort

The adipogenic origin-derived liposarcoma (LPS) family is the most common soft tissue sarcoma histological subtype. This group is composed of three categories as per the 2002 WHO guidelines: (1) well-differentiated and dedifferentiated liposarcoma (WDLPS/DDLPS); (2) myxoid and round cell liposarcoma (MLS and RCL); and (3) pleomorphic liposarcoma (PLS). While clustered together, these histological subtypes are widely diverse in their clinical, pathological, and molecular characteristics. In general, surgery still remains the mainstay of LPS therapy and the only approach offering the potential of cure. Effective therapeutic strategies for locally advanced and metastatic disease are currently lacking and are crucially needed. With the current gradually increasing knowledge of LPS genetic- and epigenetic-associated deregulations, the ultimate goal is to develop drugs that can specifically eliminate LPS cells while sparing normal tissues. This tumor-tailored target-orientated approach will hopefully result in a significant improvement in the outcome of patients suffering from these poor prognosis malignancies.

Targeting the p53 Pathway in Ewing Sarcoma

The p53 tumour suppressor plays a pivotal role in the prevention of oncogenic transformation. Cancers frequently evade the potent antitumour surveillance mechanisms of p53 through mutation of the TP53 gene, with approximately 50% of all human malignancies expressing dysfunctional, mutated p53 proteins. Interestingly, genetic lesions in the TP53 gene are only observed in 10% of Ewing Sarcomas, with the majority of these sarcomas expressing a functional wild-type p53. In addition, the p53 downstream signaling pathways and DNA-damage cell cycle checkpoints remain functionally intact in these sarcomas. This paper summarizes recent insights into the functional capabilities and regulation of p53 in Ewing Sarcoma, with a particular focus on the cross-talk between p53 and the EWS-FLI1 gene rearrangement frequently associated with this disease. The development of several activators of p53 is discussed, with recent evidence demonstrating the potential of small molecule p53 activators as a promising systemic therapeutic approach for the treatment of Ewing Sarcomas with wild-type p53.

Emerging drugs for high-grade osteosarcoma

IMPORTANCE OF THE FIELD

Osteosarcoma (OS) is the most common primary malignant bone tumour in children and adolescents. This review focuses on the most promising therapeutic markers and drugs which may potentially be considered for innovative high-grade OS treatments.

AREAS COVERED IN THIS REVIEW

The list of drugs and compounds reviewed has been generated by taking into account those which target markers of potential clinical interest for high-grade OS and have been included in Phase I, II or III clinical trials. The literature search covers the last 40 years, starting from the first OS chemotherapy reports of the early 1970s. Particular relevance was given to reports and reviews on new targeted therapies of possible clinical usefulness for high-grade OS.

WHAT THE READER WILL GAIN

This review gives an updated overview of novel therapeutic approaches which have been or are going to be evaluated in Phase I/II/III clinical studies for high-grade OS.

TAKE HOME MESSAGE

On the basis of the information that has emerged so far, it can be predicted that in the next 5 - 10 years, new agents to be included in innovative treatment strategies for selected subgroups of high-grade OS patients may become available.

Subtype-specific genomic alterations define new targets for soft-tissue sarcoma therapy

Soft-tissue sarcomas, which result in approximately 10,700 diagnoses and 3,800 deaths per year in the United States, show remarkable histologic diversity, with more than 50 recognized subtypes. However, knowledge of their genomic alterations is limited. We describe an integrative analysis of DNA sequence, copy number and mRNA expression in 207 samples encompassing seven major subtypes. Frequently mutated genes included TP53 (17% of pleomorphic liposarcomas), NF1 (10.5% of myxofibrosarcomas and 8% of pleomorphic liposarcomas) and PIK3CA (18% of myxoid/round-cell liposarcomas, or MRCs). PIK3CA mutations in MRCs were associated with Akt activation and poor clinical outcomes. In myxofibrosarcomas and pleomorphic liposarcomas, we found both point mutations and genomic deletions affecting the tumor suppressor NF1. Finally, we found that short hairpin RNA (shRNA)-based knockdown of several genes amplified in dedifferentiated liposarcoma, including CDK4 and YEATS4, decreased cell proliferation. Our study yields a detailed map of molecular alterations across diverse sarcoma subtypes and suggests potential subtype-specific targets for therapy.

Betulinic acid induces apoptosis and inhibits hedgehog signalling in rhabdomyosarcoma

Background:

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in childhood with the ability to resist apoptosis by the activation of survival promoting and anti-apoptotic proteins.

Methods:

Efficacy of the apoptosis-inducing agent betulinic acid (BA) was determined in RMS cell cultures and in vivo by measuring cell viability, survival, apoptosis, hedgehog signalling activity, and neovascularisation.

Results:

Betulinic acid had a strong cytotoxic effect on RMS cells in a dose-dependent manner. The BA treatment caused a massive induction of apoptosis mediated by the intrinsic mitochondrial pathway, which could be inhibited by the broad-range caspase inhibitor zVAD.fmk. Exposure of hedgehog-activated RMS-13 cells to BA resulted in a strong decrease in GLI1, GLI2, PTCH1, and IGF2 expression as well as hedgehog-responsive luciferase activity. Intraperitoneal injection of 20 mg BA per kg per day significantly retarded growth of RMS-13 xenografts in association with markedly higher counts of apoptotic cells and down-regulation of GLI1 expression compared with control tumours, while leaving microvascular density, cell proliferation, and myogenic differentiation unaffected.

Conclusion:

Our data show that induction of apoptosis and inhibition of hedgehog signalling are important features of the anti-tumourigenic effect of BA in RMS and advices this compound for the use in a multimodal therapy of this highly aggressive paediatric tumour.

The clinical relevance of molecular genetics in soft tissue sarcomas

Bone and soft tissue sarcomas are an infrequent and heterogeneous group of mesenchymal tumors including more than a hundred different entities attending to histologic patterns. Research into the molecular aspects of sarcomas has increased greatly in the last few years. This enormous amount of knowledge has allowed, for instance, to refine the classification of sarcomas, improve the diagnosis, and increase the number of therapeutical targets available, most of them under preclinical evaluation. However, other important key issues, such as sarcomagenesis and the cell of origin of sarcomas, remain unresolved. From a molecular point of view, these neoplasias are grouped into 2 main types: (a) sarcomas showing relatively simple karyotypes and translocations, which originate gene fusions (eg, EWS-FLI1 in Ewing sarcoma) or point mutations (eg, c-kit in the gastrointestinal tumors) and (b) sarcomas showing unspecific gene alterations, very complex karyotypes, and no translocations. The discovery of the early mechanisms involved in the genesis of sarcomas, the more relevant signaling pathways, and the development of genetically engineered mouse models could also provide a new individualized therapeutic strategy against these tumors. This review describes the clinical application of some of the molecular alterations found in sarcomas, some advances in the field of sarcomagenesis, and the development of animal models.

Benefits of molecular pathology in the diagnosis of musculoskeletal disease : Part II of a two-part review: bone tumors and metabolic disorders

The second part of this review, on the benefits of molecular pathology in the diagnosis disease, focuses on the genetics of bone tumors and metabolic disease. Unlike soft tissue tumors, the number of currently exploitable molecular abnormalities for diagnosing bone neoplasms is small, although the same gene rearrangements are found in primitive neuroectodermal tumor/Ewing sarcoma in both skeletal and extraskeletal sites. Compared with soft tissue tumors, genetic abnormalities, which are valuable to diagnosticians in skeletal disease, are often germline and post-zygotic aberrations rather than somatic translocations. In addition, the review highlights the range of disease entities classified as "osteoclast-rich lesions," some of which harbor germline mutations. It also addresses the importance of phosphate metabolism in skeletal disorders including phosphaturic mesenchymal tumor, vitamin D-resistant rickets, and tumoral calcinosis.

Well-differentiated and dedifferentiated liposarcomas

Atypical lipomatous tumor or well-differentiated liposarcoma (ALT-WDLPS) and dedifferentiated liposarcoma (DDLPS) share the same basic genetic abnormality characterized by a simple genomic profile with a 12q14-15 amplification involving MDM2 gene. These tumors are the most frequent LPS. This paper reviews the molecular pathology, general clinical and imaging features, histopathology, new diagnostic tools, and prognosis of ALT-WDLPS and DDLPS.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

BACKGROUND

In eukaryotes, endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are coordinately regulated to maintain steady-state levels and activities of various cellular proteins to ensure cell survival.

OBJECTIVE

This review (Part I of II) focuses on specific ERS and UPR signalling regulators, their expression in the cancer phenotype and apoptosis, and proposes how their implication in these processes can be rationalised into proteasome inhibition, apoptosis induction and the development of more efficacious targeted molecular cancer therapies.

METHOD

In this review, we contextualise many ERS and UPR client proteins that are deregulated or mutated in cancers and show links between ERS and the UPR, their implication in oncogenic transformation, tumour progression and escape from immune surveillance, apoptosis inhibition, angiogenesis, metastasis, acquired drug resistance and poor cancer prognosis.

CONCLUSION

Evasion of programmed cell death or apoptosis is a hallmark of cancer that enables tumour cells to proliferate uncontrollably. Successful eradication of cancer cells through targeting ERS- and UPR-associated proteins to induce apoptosis is currently being pursued as a central tenet of anticancer drug discovery.

Normalization method for transcriptional studies of heterogeneous samples--simultaneous array normalization and identification of equivalent expression

Normalization is an important step in the analysis of microarray data of transcription profiles as systematic non-biological variations often arise from the multiple steps involved in any transcription profiling experiment. Existing methods for data normalization often assume that there are few or symmetric differential expression, but this assumption does not always hold. Alternatively, non-differentially expressed genes may be used for array normalization. However, it is unknown at the outset which genes are non-differentially expressed. In this paper we propose a hierarchical mixture model framework to simultaneously identify non-differentially expressed genes and normalize arrays using these genes. The Fisher's information matrix corresponding to array effects is derived, which provides useful intuition for guiding the choice of array normalization method. The operating characteristics of the proposed method are evaluated using simulated data. The simulations conducted under a wide range of parametric configurations suggest that the proposed method provides a useful alternative for array normalization. For example, the proposed method has better sensitivity than median normalization under modest prevalence of differentially expressed genes and when the magnitudes of over-expression and under-expression are not the same. Further, the proposed method has properties similar to median normalization when the prevalence of differentially expressed genes is very small. Empirical illustration of the proposed method is provided using a liposarcoma study from MSKCC to identify genes differentially expressed between normal fat tissue versus liposarcoma tissue samples.

HMGA2 is the partner of MDM2 in well-differentiated and dedifferentiated liposarcomas whereas CDK4 belongs to a distinct inconsistent amplicon

Data concerning the fine structure of the 12q13-15 amplicon which contains MDM2 and CDK4 in well-differentiated and dedifferentiated liposarcomas (WDLPS/DDLPS) are scarce. We investigated a series of 38 WDLPS/DDLPS using fluorescence in situ hybridization analysis with 17 probes encompassing the 12q13-15 region. In addition, using quantitative RT-PCR we studied the expression of MDM2, CDK4, DDIT3 (CHOP/GADD153), DYRK2, HMGA2, TSPAN31 and YEATS4 (GAS41) in 11 cases. We showed that CDK4 (12q14.1) belonged to a distinct amplicon than MDM2 (12q15). There was no continuity in the amplified sequences between MDM2 and CDK4. Moreover, while MDM2 was amplified and overexpressed in all cases, CDK4 was not amplified or overexpressed in 13% of cases. The centromeric border of the CDK4 amplicon was located immediately downstream the 5' end of DDIT3, a gene known for being involved in myxoid liposarcoma translocations. DDIT3 was amplified in 3 cases and overexpressed in 9 cases. The overexpression of DDIT3 was correlated to the CDK4 amplification and not to its own amplification status. This suggested that the CDK4 amplicon, as well as the overexpression of DDIT3, might be generated by the disruption of a fragile region in 5' DDIT3. HMGA2 was always amplified and rearranged indicating that it plays a central role in WDLPS/DDLPS. HMGA2 rearrangement frequently resulted in a loss of the 3' end region that is a binding site for let-7. We also found a frequent amplification and overexpression of YEATS4, an oncogene that inactivates P53, suggesting that YEATS4 might play an important role together with MDM2 in WDLPS/DDLPS oncogenesis.