恶性胸膜间皮瘤的影像学诊断

恶性胸膜间皮瘤（MPM）是起源于胸膜间皮细胞一种罕见肿瘤，该病无典型表现，恶性程度较高，预后较差。影像学检查在MPM的诊断、分期及病情评估中起重要作用。现就恶性胸膜间皮瘤的影像学表现，以及各种影像学检查方法对恶性胸膜间皮瘤诊断、分期、预后判断的价值作一综述。     

恶性间皮瘤p53基因点突变和蛋白表达

p53基因是在人类多数肿瘤中发生高频突变的肿瘤相关性最强的抑癌基因，其突变特征为80%的点突变均集中在进化的高保区内，即对应的第5-8外显子部位. 恶性间皮瘤是一种与接触石棉有明确关系的间叶源性肿瘤. 为深入阐明p53基因在人恶性间皮瘤发生发展中的作用，应用聚合酶链反应-单链构象多态性(PCR-SSCP)和免疫组化技术研究了34例恶性间皮瘤p53 基因的点突变情况. 结果表明： 56%(19/34)的病例存在p53基因的点突变，突变率在不同的组织学类型之间有一定的差异；在所发现的22次突变中有16次均发生在第7外显子，表明第7外显子是本组恶性间皮瘤的突变热点所在；免疫组化染色：23%（8/34）的病例P53蛋白免疫组化染色为阳性，阳性率低于基因突变率. 以上资料提示p53基因突变可能在恶性间皮瘤的癌变机制中起着重要作用.     

Animal models of malignant mesothelioma

Animal models of diffuse malignant mesothelioma have historically been used to assess carcinogenicity of various fiber types and to study the pathogenesis of this unusual neoplasm. Pleural and peritoneal mesotheliomas have been induced in rodents following exposure to erionite or asbestos fibers, radionuclides, particulate nickel compounds, and chemicals such as 3-methylcholanthrene. The role of SV40 virus as a cofactor with asbestos fibers in the development of diffuse malignant mesotheliomas in humans has been explored in animal models. SV40 virus alone induces mesotheliomas in hamsters. Generation of new transgenic mouse strains with targeted expression of SV40 large T and small t antigens in the mesothelium would be very useful for mechanistic studies. Human malignant mesotheliomas frequently show hypermethylation or deletions at the Cdkn2a/Arf and Cdkn2b gene loci and deletions or mutations at the NF2 gene locus. Heterozygous Nf2 (+/-) mice exposed to crocidolite asbestos fibers exhibited accelerated development of malignant mesotheliomas compared to wild-type littermates. Loss of the wild-type Nf2 allele, leading to biallelic inactivation, was observed in nine mesothelioma cell lines derived from Nf2 (+/-) mice. Similar to human malignant mesotheliomas, tumors from Nf2 (+/-) mice showed frequent homozygous deletions of the Cdkn2a/Arf locus and adjacent Cdkn2b tumor suppressor gene. As in the human disease, murine mesotheliomas also showed constitutive activation of Akt. This murine model of asbestos carcinogenesis recapitulates the molecular and histopathological features of the human disease and has significant implications for preclinical testing of novel preventive or therapeutic modalities.     

The Role of SV40 in Malignant Mesothelioma and Other Human Malignancies

SV40 is a DNA tumor virus thrust upon human populations primarily as a contaminant in various vaccine preparations. Some estimates suggest that millions of people are currently infected with the virus. The virus causes primary brain tumors, bone tumors, lymphomas, and mesotheliomas when injected into some rodent models. It has also been detected in a similar spectrum of human tumors. However, epidemiological studies have failed to conclusively demonstrate a higher incidence of disease in affected populations. To date, over 60 reports from 49 different laboratories have shown SV40 sequences in tissues from human cancer patients. Six studies, however, have failed to detect evidence of virus in similar tissues. Some have suggested that SV40 may act as a cocarcinogen with asbestos to cause mesothelioma formation, or that it may be responsible for the 10–20% of mesotheliomas with no reported history of asbestos exposure. This report briefly covers the historical evidence for SV40 carcinogenesis and then covers experiments now underway to better understand the role of SV40 in human mesotheliomas.     

Chemotherapy of malignant pleural mesothelioma

Background: Owing to worldwide use of asbestos during the past century, the global incidence of mesothelioma is still increasing. Although the outcome for patients remains poor, there has been definite progress in the systemic treatment of this disease within the past 5 years. Objective: By examining the clinical trials performed and the role of novel emerging agents, this review aims to provide an ‘expert opinion’ on evidences that validate chemotherapy as current ‘standard of care’ for inoperable mesothelioma. Methods: Relevant literature about clinical trials was reviewed using a PubMed search and other relevant data about novel therapeutic approaches both established and in development. Conclusion: The response rates achieved using chemotherapeutic treatments are higher than previous ones, and in the future may be improved by the use of combined and personalized therapies.     

Comparative proteomic analysis of human osteosarcoma and SV40-immortalized normal osteoblastic cell lines

Aim： Comparative proteomics provide a powerful approach in screening for alterations in protein levels and post-translational modifications that are associated with tumors. In the present study, we aimed to identify candidate biomarkers to distinguish osteosarcoma （OS） cells from normal osteoblastic cells. Methods： We employed 3OS cell lines （U2OS, IOR/OS9, and SaOS-2）, and used the SV40-immortalized normal osteoblastic cell line （hFOB 1.19） as the control. The differential protein levels in OS and osteoblastic cells were identified using 2-D gel electrophoresis followed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry analyses. Two proteins of interest, the levels of which were significantly increased in OS cells, were further characterized by Western blot analyses. Results： Twenty-six proteins were identified, the expression level of which was either significantly increased or decreased in the OS cells as compared to the control cells. The expression level of the activator of 90 kDa shock protein ATPase homolog 1 （AHA1）, was enhanced 12.4-, 24.1-, and 23.8-fold in SaOS-2, IOR/OS9, and U2OS cells, respectively, and the level of the stomatin-like protein 2 （SLP-2） was increased by 10.4- and 7.8-fold in IOR/OS9 and U2OS cells, respectively, as compared to normal osteoblastic cells. Those observations were confirmed by Western blot analyses. Conclusion： A differential proteomic analysis was suc- cessfully used to identify AHA1 and SLP-2 that were significantly overproduced in OS cells as compared to normal osteoblastic cells, suggesting that those proteins among others may be effective biomarker candidates for the identification of OS cells.     

Can pemetrexed help in malignant mesothelioma?

Mesothelioma is a cancer that originates in the pleura or, more rarely, the peritoneum, and is almost always due to exposure to asbestos fibres. It is typically fatal, with a median survival of about 8-14 months after diagnosis. Conventional treatment options have not improved this poor outlook. Also, the number of deaths attributable to malignant mesothelioma has been rising rapidly in the UK since the late 1960s, and is set to peak at about 1,950-2,450 per year between 2011 and 2015. It is against this background that pemetrexed (pronounced pe-me-treks-ed) (Alimta - Lilly) has recently become available for use with cisplatin for the treatment of patients with unresectable malignant pleural mesothelioma who have not previously been treated with chemotherapy. Currently, this is the only chemotherapy regimen licensed for patients with malignant pleural mesothelioma in the UK. Here we review the care of patients with malignant pleural mesothelioma, focusing on what, if anything, pemetrexed might offer such individuals.     

Five years update on relationships between malignant pleural mesothelioma and exposure to asbestos and other elongated mineral particles

ABSTRACT

Despite the reduction of global asbestos consumption and production due to the ban or restriction of asbestos uses in more than 50 countries since the 1970s, malignant mesothelioma remains a disease of concern. Asbestos is still used, imported, and exported in several countries, and the number of mesothelioma deaths may be expected to increase in the next decades in these countries. Asbestos exposure is the main risk factor for malignant pleural mesothelioma, but other types of exposures are linked to the occurrence of this type of cancer. Although recent treatments improve the quality of life of patients with mesothelioma, malignant pleural mesothelioma remains an aggressive disease. Recent treatments have not resulted in appreciable improvement in survival, and thus development of more efficient therapies is urgently needed. The development of novel therapeutic strategies is dependent on our level of knowledge of the physiopathological and molecular changes that mesothelial cells acquired during the neoplastic process. During the past 5 years, new findings have been published on the etiology, epidemiology, molecular changes, and innovative treatments of malignant pleural mesothelioma. This review aims to update the findings of recent investigations on etiology, epidemiology, and molecular changes with a focus on (1) attributable risk of asbestos exposure in men and women and (2) coexposure to other minerals and other elongated mineral particles or high aspect ratio nanoparticles. Recent data obtained on genomic and gene alterations, pathways deregulations, and predisposing factors are summarized.     

Combined chemotherapy with cytotoxic and targeted compounds for the management of human malignant pleural mesothelioma

Human malignant pleural mesothelioma (hMPM) is an aggressive asbestos-associated cancer, the incidence of which is increasing and which, despite progress in diagnosis and therapy, continues to have a poor prognosis. Asbestos fibers induce aberrant cell signaling, leading to proto-oncogene activation and chemoresistance. In this review, we discuss the evolution of pharmacological management of hMPM up to the most recent advances. Monotherapy with single cytotoxic drugs achieves modest objective response rates, seldom reaching 30%. However, combination regimens using novel drugs and standard molecules are showing gradually improving responses and clinical benefits. Phase II/III studies have identified pemetrexed, a multitarget folate pathway inhibitor in combination with platinum derivatives, and the cisplatin/gemcitabine association as front-line chemotherapy for hMPM. Detailed knowledge of molecular mechanisms of signal transduction and neoangiogenesis in hMPM should aid in the design and screening of other promising compounds such as more efficacious receptor tyrosine kinase inhibitors.     

弥漫性胸膜间皮瘤的CT诊断

目的总结弥漫性胸膜间皮瘤的CT表现及诊断方法,提高对此病的认识及诊断的正确率。方法回顾性分析我院自1997-2008年收治的13例经组织学证实的弥漫性胸膜间皮瘤的临床及CT影像资料。结果右侧胸腔7例,左侧胸腔6例。所有的病例CT均表现为不同程度的弥漫性胸膜增厚（〉1 cm）：呈广泛性、结节样、瘤样、不规则状、盔甲样增厚、大量胸水等征象。结论CT在弥漫性胸膜间皮瘤的诊断中具有重要地位。能发现和显示病变、确定病变的范围,为选择治疗方法及判断预后提供重要参考。     

The Fluorinated and Chlorinated Nuclear Localization Sequence of the SV 40 T Antigen

Nuclear uptake of the simian virus (SV) 40 T antigen is triggered by a specific nuclear localization sequence. However, such a nuclear localization sequence is only poorly taken up by the cytoplasm of cells when administered to the culture medium. Our aim was to improve the cytoplasmic uptake of the SV 40 T antigen nuclear localization sequence. Consequently, we synthesized novel fluorescein isothiocyanate‐labelled conjugates containing the nuclear localization sequences of the SV 40 T antigen and either trichlorobenzoic or trifluorobenzoic acid. Applied at 260 μm such halogenated NLS conjugates were nuclearly taken up by 75–85% of U373 and LN18 glioma cells and resulted in cell death. Nuclear staining and cell death were also found at lower concentrations (130 and 65 μm ) of halogenated nuclear localization sequence conjugates. By contrast only a low cellular staining rate and no cell death could be observed after co‐incubation with a trichlorobenzoic acid or trifluorobenzoic acid‐lacking nuclear localization sequence conjugate and free, unbound trichlorobenzoic acid or trifluorobenzoic acid at the high concentration (260 μm ). Such small non‐radioactive fluorinated and chlorinated nuclear localization sequences may be used as important components for future antiglioma drug development.     

Current chemotherapeutic treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive malignancy which is almost always fatal; median survival is usually < 1 year. Most patients present with symptoms including pain, dyspnoea, pleural effusions and chest wall masses. Until recently, there has been no effective treatment which can improve symptoms and prolong survival. This article reviews recent developments in the treatment of mesothelioma, particularly advances in drug therapy and the use of the current most active drug combination: pemetrexed and cisplatin. Pemetrexed is a novel antifolate drug with multiple enzyme targets. The combination of pemetrexed and cisplatin demonstrated a survival advantage over cisplatin alone in patients with pleural mesothelioma, and can give symptomatic benefits. This combination has become the standard of care in mesothelioma treatment.     

Current chemotherapeutic treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive malignancy which is almost always fatal; median survival is usually < 1 year. Most patients present with symptoms including pain, dyspnoea, pleural effusions and chest wall masses. Until recently, there has been no effective treatment which can improve symptoms and prolong survival. This article reviews recent developments in the treatment of mesothelioma, particularly advances in drug therapy and the use of the current most active drug combination: pemetrexed and cisplatin. Pemetrexed is a novel antifolate drug with multiple enzyme targets. The combination of pemetrexed and cisplatin demonstrated a survival advantage over cisplatin alone in patients with pleural mesothelioma, and can give symptomatic benefits. This combination has become the standard of care in mesothelioma treatment.     

Protein kinase C beta in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a disease with few therapeutic options. Protein kinase C beta (PKCbeta) is involved in important cellular functions. Enzastaurin (LY317615.HCl) is a novel inhibitor of PKC in clinical development. MPM cell lines (7) and patient tumor tissues (24) were evaluated for expression of PKCbeta by immunoblotting and immunohistochemistry, respectively. In-vitro cell growth assays were performed with enzastaurin with or without cisplatin. Cell migration was evaluated with the wound healing assay. Downstream signaling (survival and focal adhesion pathways) was studied by immunoblotting for related molecules in the presence of phorbol ester with or without enzastaurin. Expression for PKCbeta1 was seen in all cases, with a mean integrated optical density of 152.5 (standard deviation=95.47, n=24), whereas PKCbeta2 expression was less intense, with a mean integrated optical density of 11.45 (standard deviation=16.27, n=21). There was a trend toward lower overall survival among patients expressing above-median PKCbeta1 (P=0.064), but not PKCbeta2. Robust expression of PKCbeta1 and low expression of PKCbeta2 were observed in MPM cell lines. Treatment of MPM cell lines with enzastaurin revealed an IC50 of 5 mumol/l, and strong synergism was observed when combined with cisplatin. Wound healing assay revealed that treatment of H2461 cells with enzastaurin reduced migration by 59.2%. Enzastaurin treatment led to disruption of F-actin architecture. Downstream signaling showed reduced phosphorylation of AKT, FAK (focal adhesion kinase), p130Cas, S6 ribosomal protein, and paxillin. PKCbeta1 was expressed in the majority of MPM samples. Enzastaurin has preclinical activity against MPM, and exhibited synergism with cisplatin. PKCbeta inhibition in MPM might be able to reduce the invasiveness of MPM by affecting cytoskeletal function.     

Calcium induced differentiation of SV40 immortalized human epidermal keratinocytes cultured in a defined medium.

Human epidermal keratinocytes, immortalized by the introduction of SV40-adenovirus recombinants (9), were maintained in a low calcium (0.15 mM) defined medium. When differentiation was induced by a higher extracellular calcium concentration (1.5 mM), these cells altered in shape and developed stratification with formation of desmosomes, while they demonstrated limited terminal keratinization. The expression of involucrin, one of the precursor proteins of the cornified envelope, became elevated as the cell density increased, but was not affected by calcium. These results indicate that the SV40 immortalized human keratinocytes, maintained in a low calcium defined medium, partially respond to changes in extracellular calcium concentration.     

Molecular targets and targeted therapies for malignant mesothelioma

Malignant mesothelioma is a highly invasive tumor originating from the mesothelial linings of the pleura, peritoneum and pericardium. It is seldom amenable to surgical intervention and poorly responsive to radiotherapy, leaving chemotherapy as the main therapeutic option for most patients. The development of effective drug regimens against mesothelioma has proven extremely difficult and a standard first-line treatment for patients with unresectable tumors has not been established until recently. Despite the benefits obtained with this newly validated standard of care, which is based on the combination of pemetrexed and cisplatin, the prognosis for mesothelioma patients remains poor, median survival is still less than two years and more active treatments are urgently needed. This article will focus on the molecular basis providing the rationale for targeted interventions against mesothelioma and will review targeted agents under evaluation as new potential therapeutic options for mesothelioma patients. Such agents include inhibitors of growth factor receptors, ligands and intracellular effectors. The agents targeting vascular endothelial growth factor signaling are of particular interest, due to the involvement of this pathway both in tumor angiogenesis and autocrine stimulation of mesothelioma cell growth. Alternative approaches are based on inhibitors of the ubiquitin-proteasome pathway and of histone deacetylases which, notwithstanding the functional divergence of the corresponding targets, share the ability to determine a wide modulation of the cancer cell phenotype that can lead to cell cycle arrest, apoptosis and sensitization to different antineoplastic treatments. A recombinant immunotoxin targeted to the membrane antigen mesothelin is an additional agent whose activity is being evaluated in mesothelioma patients.     

Preclinical studies identify novel targeted pharmacological strategies for treatment of human malignant pleural mesothelioma

The incidence of human malignant pleural mesothelioma (hMPM) is still increasing worldwide. hMPM prognosis is poor even if the median survival time has been slightly improved after the introduction of the up-to-date chemotherapy. Nevertheless, large phase II/III trials support the combination of platinum derivatives and pemetrexed or raltitrexed, as preferred first-line schedule. Better understanding of the molecular machinery of hMPM will lead to the design and synthesis of novel compounds targeted against pathways identified as crucial for hMPM cell proliferation and spreading. Among them, several receptors tyrosine kinase show altered activity in subsets of hMPM. This observation suggests that these kinases might represent novel therapeutic targets in this chemotherapy-resistant disease. Over these foundations, several promising studies are ongoing at preclinical level and novel molecules are currently under evaluation as well. Yet, established tumour cell lines, used for decades to investigate the efficacy of anticancer agents, although still the main source of drug efficacy studies, after long-term cultures tend to biologically diverge from the original tumour, limiting the predictive potential of in vivo efficacy. Cancer stem cells (CSCs), a subpopulation of malignant cells capable of self-renewal and multilineage differentiation, are believed to play an essential role in cancer initiation, growth, metastasization and relapse, being responsible of chemo- and radiotherapy refractoriness. According to the current carcinogenesis theory, CSCs represent the tumour-initiating cell (TIC) fraction, the only clonogenic subpopulation able to originate a tumour mass. Consequently, the recently described isolation of TICs from hMPM, the proposed main pharmacological target for novel antitumoural drugs, may contribute to better dissect the biology and multidrug resistance pathways controlling hMPM growth.