Expression of p21 in SV40 large T antigen positive human pleural mesothelioma: relationship with survival

Critical review about MDM2 in cancer: Possible role in malignant mesothelioma and implications for treatment

The tumor suppressor p53 regulates genes involved in DNA repair, metabolism, cell cycle arrest, apoptosis and senescence. p53 is mutated in about 50% of the human cancers, while in tumors with wild-type p53 gene, the protein function may be lost because of overexpression of Murine Double Minute 2 (MDM2). MDM2 targets p53 for ubiquitylation and proteasomal degradation. p53 reactivation through MDM2 inhibitors seems to be a promising strategy to sensitize p53 wild-type cancer cells to apoptosis. Moreover, additional p53-independent molecular functions of MDM2, such as neoangiogenesis promotion, have been suggested. Thus, MDM2 might be a target for anticancer treatment because of its antiapoptotic and proangiogenetic role. Malignant pleural mesothelioma (MPM) is an aggressive asbestos-related tumor where wild-type p53 might be present. The present review gives a complete landscape about the role of MDM2 in cancer pathogenesis, prognosis and treatment, with particular focus on Malignant Pleural Mesothelioma.

Cyclooxygenase-2, epidermal growth factor receptor, and aromatase signaling in inflammation and mesothelioma

Malignant mesothelioma or mesothelioma is a rare form of cancer that develops from transformed cells originating in the mesothelium, the protective lining that covers many of the internal organs of the body. It is directly linked to asbestos exposure, which acts as a carcinogen by initiating the carcinogenic process. Because of their shape, asbestos fibers can cross the membrane barriers inside the body and cause inflammatory and fibrotic reactions. Such reactions are believed to be the mechanism by which asbestos fibers may trigger malignant mesothelioma in the pleural membrane around the lungs. Carcinogens are known to modulate the transcription factors, antiapoptotic proteins, proapoptotic proteins, protein kinases, cell-cycle proteins, cell adhesion molecules, COX-2, and growth factor signaling pathways. This article reviews recent studies regarding some malignant mesothelioma molecular targets not only for cancer prevention but also for cancer therapy.

Clinical and biologic prognostic factors in malignant pleural mesothelioma

Malignant pleural mesothelioma is an extremely aggressive neoplasm of the pleura mainly attributable to asbestos exposure. Conventional medical, physical, and surgical treatments and their combinations are basically ineffective and just a few subjects experience some benefit. No definite guidelines can be provided in patient selection and therapeutic strategies. Currently, malignant pleural mesothelioma therapy is guided by clinical stage and patient characteristics, which are quite unreliable, rather than by the histological or molecular features of the tumor. In the present review the impact on prognosis of classic (i.e. etiology, age, gender, histology, staging), as well as relatively new clinical factors such as quality of life, positron emission tomography assessment, and occult residual disease, are firstly evaluated. In the second section of the review several biological variables and genetic markers, which have been recently recognized as the bases of the disease onset and development, are listed and discussed. There are serum and tissue markers. The latter are mainly related to cell cycle regulation, apoptosis, and growth factor pathways. These novel factors may play an important role in defining the prognosis of the disease and, subsequently, may have a place in addressing therapy.

Targeted inhibition of multiple receptor tyrosine kinases in mesothelioma

The receptor tyrosine kinases (RTKs) epidermal growth factor receptor (EGFR) and MET are activated in subsets of mesothelioma, suggesting that these kinases might represent novel therapeutic targets in this notoriously chemotherapy-resistant cancer. However, clinical trials have shown little activity for EGFR inhibitors in mesothelioma. Despite the evidence for RTK activation in mesothelioma pathogenesis, it is unclear whether transforming activity is dependent on an individual kinase oncoprotein or the coordinated activity of multiple kinases. Using phospho-RTK and immunoblot assays, we herein demonstrate activation of multiple RTKs (EGFR, MET, AXL, and ERBB3) in individual mesothelioma cell lines but not in normal mesothelioma cells. Inhibition of mesothelioma multi-RTK signaling was accomplished using combinations of RTK direct inhibitors or by inhibition of the RTK chaperone, heat shock protein 90 (HSP90). Multi-RTK inhibition by the HSP90 inhibitor 17-allyloamino-17-demethoxygeldanamycin (17-AAG) had a substantially greater effect on mesothelioma proliferation and survival compared with inhibition of individual activated RTKs. HSP90 inhibition also suppressed phosphorylation of downstream signaling intermediates (AKT, mitogen-activated protein kinase, and S6); upregulated the p53, p21, and p27 cell cycle checkpoints; induced G(2) phase arrest; induced caspase 3/7 activity; and led to an increase in the sub-G(1) apoptotic population. These compelling proapoptotic and antiproliferative responses indicate that HSP90 inhibition warrants clinical evaluation as a novel therapeutic strategy in mesothelioma.

Synergistic effect of gefitinib and rofecoxib in mesothelioma cells

BACKGROUND

Malignant mesothelioma (MM) is an aggressive tumor that is resistant to conventional modes of treatment with chemotherapy, surgery or radiation. Research into the molecular pathways involved in the development of MM should yield information that will guide therapeutic decisions. Epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) are involved in the carcinogenesis of MM. Combination of COX-2 and EGFR inhibitors, therefore, could be an effective strategy for reducing cell growth in those lines expressing the two molecular markers.

RESULTS

In order to verify the effect of COX-2 and EGFR inhibitors, five MM cell lines NCI-2452, MPP89, Ist-Mes-1, Ist-Mes-2 and MSTO-211 were characterized for COX-2 and EGFR and then treated with respective inhibitors (rofecoxib and gefitinib) alone and in combination. Only MPP89, Ist-Mes-1 and Ist-Mes-2 were sensitive to rofecoxib and showed growth-inhibition upon gefitinib treatment. The combination of two drugs demonstrated synergistic effects on cell killing only in Ist-Mes-2, the cell line that was more sensitive to gefitinib and rofecoxib alone. Down-regulation of COX-2, EGFR, p-EGFR and up-regulation of p21 and p27 were found in Ist-Mes-2, after treatment with single agents and in combination. In contrast, association of two drugs resulted in antagonistic effect in Ist-Mes-1 and MPP89. In these cell lines after rofecoxib exposition, only an evident reduction of p-AKT was observed. No change in p-AKT in Ist-Mes-1 and MPP89 was observed after treatment with gefitinib alone and in combination with rofecoxib.

CONCLUSIONS

Gefitinib and rofecoxib exert cell type-specific effects that vary between different MM cells. Total EGFR expression and downstream signalling does not correlate with gefitinib sensitivity. These data suggest that the effect of gefitinib can be potentiated by rofecoxib in MM cell lines where AKT is not activated.

Expression of the embryonic lethal abnormal vision-like protein HuR in human mesothelioma: association with cyclooxygenase-2 and prognosis

BACKGROUND

The human embryonic lethal abnormal vision (ELAV)-like protein HuR is a messenger RNA (mRNA)-binding protein that controls the stability of certain transcripts, including cyclooxygenase2 (COX-2).

METHODS

To investigate a possible contribution of dysregulation of mRNA stability to the progression of cancer and to COX-2 over expression in mesothelioma, the authors studied expression of COX-2 and HuR in 5 mesothelioma cell lines (MSTO, NCI, Ist-Mes1, Ist-Mes2, and MPP89) and in a group of 29 human mesothelioma specimens that were characterized previously for COX-2 expression.

RESULTS

All 5 cell lines expressed HuR, whereas COX-2 was not detectable in MSTO or NCI cells. Treatment with cytokines induced a shift in systolic HuR protein levels in MPP89 and Ist-Mes2 cells that was accompanied by an increase in the expression of COX-2 mRNA and protein. In Ist-Mes1 cells, cytokine stimulation did not cause the passage of HuR from nucleus to cytoplasm, and the synthesis of COX-2 did not increase. In tumor tissues, immunohistochemistry revealed a positive, statistically significant correlation between high COX-2 expression and cytoplasmic localization of HuR (P = .016). Moreover, on univariate analysis, overall survival was found to be influenced strongly by cytoplasmic HuR localization (P = .004).

CONCLUSIONS

The current results suggested that HuR plays a role in tumor progression in mesothelioma and that COX-2 may be a target of its activity in neoplastic cells. Together, these observations indicate that strategies aiming toward the modulation of HuR may have a potential clinical benefit in mesothelioma.

Molecular analysis of the effects of Piroxicam and Cisplatin on mesothelioma cells growth and viability

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed for prevention and treatment of a variety of human cancers. Piroxicam, in particular, has been recently shown to exert significant anti-tumoral activity in combination with cisplatin (CDDP) on mesothelioma cells. However, the mechanisms through which NSAIDs regulate the cell cycle as well as the signal pathways involved in the growth inhibition, remain unclear. In the present study, using two mesothelioma cell lines, MSTO-211H and NCI-H2452, we have investigated the influence of piroxicam alone and in association with CDDP on proliferation, cell cycle regulation and apoptosis. In both cell lines a significant effect on cell growth inhibition, respect to the control, was observed with all the drugs tested. Moreover, treatment with piroxicam or CDDP alone altered the cell cycle phase distribution as well as the expression of some cell cycle regulatory proteins in both cell lines. These effects were increased, even if in a not completely overlapping manner, after treatment with the association of piroxicam and CDDP. In particular, the two drugs in NCI cell line had a synergistic effect on apoptosis, probably through activation of caspase 8 and caspase 9, while the most evident targets among the cell cycle regulators were cyclin D1 and p21waf1. These results suggest that the association of piroxicam and CDDP specifically triggers cell cycle regulation and apoptosis in different mesothelioma cell lines and may hold promise in the treatment of mesothelioma.

Expression of cancer-associated molecules in malignant mesothelioma

Malignant mesothelioma (MM) is a malignant tumor derived from mesothelial cells, native cells of the body cavities. Exposure to asbestos is the most strongly established etiologic factor, predominantly for the most common disease form, pleural mesothelioma. The pathogenesis of MM involves the accumulation of extensive cytogenetic changes, as well as cancer-related phenotypic alterations that facilitate tumor cell survival, invasion and metastasis. This review presents current knowledge regarding the biological characteristics of this disease that are linked to the so-called hallmarks of cancer. In addition, data suggesting that the anatomic site (solid tumor vs. effusion) affects the expression of metastasis-associated and regulatory molecules in MM are presented. Finally, recent work in which high-throughput methodology has been applied to MM research is reviewed. The data obtained in the reviewed research may aid in defining new prognostic markers and therapeutic targets for this aggressive disease in the future.

Expression of Cancer-Associated Molecules in Malignant Mesothelioma

Malignant mesothelioma (MM) is a malignant tumor derived from mesothelial cells, native cells of the body cavities. Exposure to asbestos is the most strongly established etiologic factor, predominantly for the most common disease form, pleural mesothelioma. The pathogenesis of MM involves the accumulation of extensive cytogenetic changes, as well as cancer-related phenotypic alterations that facilitate tumor cell survival, invasion and metastasis. This review presents current knowledge regarding the biological characteristics of this disease that are linked to the so-called hallmarks of cancer. In addition, data suggesting that the anatomic site (solid tumor vs. effusion) affects the expression of metastasis-associated and regulatory molecules in MM are presented. Finally, recent work in which high-throughput methodology has been applied to MM research is reviewed. The data obtained in the reviewed research may aid in defining new prognostic markers and therapeutic targets for this aggressive disease in the future.

Piroxicam and cisplatin in a mouse model of peritoneal mesothelioma

PURPOSE

The aim of the present study was to evaluate the effects of piroxicam, a widely used nonsteroidal anti-inflammatory drug, alone and in combination with cisplatin (CDDP), on cell growth of mesothelioma cells.

EXPERIMENTAL DESIGN

Cell proliferation, cell cycle analysis, and microarray technology were done on MSTO-211H and NCI-H2452 cells treated with piroxicam. Moreover, the effects of piroxicam and CDDP on tumor growth and survival of mouse xenograft models of mesothelioma were determined.

RESULTS

Piroxicam treatment of MSTO-211H and NCI-H2452 cells resulted in a significant inhibition of proliferation. Cell cycle analysis revealed that there was an increase in the rate of apoptosis in MSTO-211H cells and an increase in the cells accumulating in G2-M in NCI-H2452. Moreover, a marked tumor growth inhibition and an extended survival of mice treated with a combination of piroxicam and CDDP in MSTO-211H cell-induced peritoneal mesotheliomas was observed. Last, GeneChip array analysis of MSTO-211H mesothelioma cell line revealed that piroxicam treatment caused up-regulation of metabolic pathway-associated genes and down-regulation of genes related to RNA processing apparatus. Of note, epidermal growth factor receptor, one of the new biological targets of chemotherapy for mesothelioma, was down-regulated and HtrA1, a serine protease recently shown to be an endogenous mediator of CDDP cytotoxicity, was up-regulated following piroxicam treatment both in vitro and in vivo.

CONCLUSION

These data suggest that piroxicam sensitizes mesothelioma cells to CDDP-induced cytotoxicity by modulating the expression of several target genes. Therefore, piroxicam in combination with CDDP might potentially be useful in the treatment of patients with mesothelioma.

Human malignant mesothelioma: molecular mechanisms of pathogenesis and progression

The continuing identification and elucidation of the molecular defects involved in mesothelioma pathogenesis and progression should lead to better disease control and greater therapeutic options in the near future. Goal of this review article is to summarize the most recent advances in molecular pathogenesis of mesothelioma and discuss possible therapeutic implications of these findings.

Molecular pathways in malignant pleural mesothelioma

Malignant pleural mesothelioma, although uncommon, is highly lethal. There is a high correlation between associated environmental exposure factors, carcinogens, and its development. Carcinogenesis is also mediated by genetic defects that result in loss of tumor suppressors or over expression of proto-oncogenes. Factors such as the loss of CDK inhibition function, IGF stimulatory pathways, p14(ARF), p15(INK4b), p16(INK4a), p21, and p53 loss or mutation, VEGF and COX over expression are discussed. Correlations to potential therapeutic modalities are made.

Biologic, cytogenetic, and molecular factors in mesothelial proliferations

Although mesothelioma cases may have peaked in the 1990s in developed countries, it is expected that there will be over 70,000 cases diagnosed in the United States over the next 5 decades. With the industrial expansion in Southeast Asia and China and the continued use of asbestos, an epidemic of mesothelioma cases is anticipated over the next several decades. A considerable amount has been learned about the cytogenetic and molecular genetics of mesotheliomas. However, in-depth studies are needed to further define specific factors that may provide for early diagnosis, surgical treatment, oncologic management, and gene therapy. Serologic markers for surveillance of those with asbestos exposure and at risk for mesothelioma are needed. Targeted therapy using molecular markers and gene therapy may provide a means to reverse mesothelial proliferations or stabilize tumor growth and allow for surgical resection. The future holds great promise in identifying mesothelioma gene expression profiles (genomics, gene microarrays) and proteins (proteomics) that may produce the key to dealing with this dismal and devastating neoplasm.

Role of asbestos in etiology of malignant pleural mesothelioma

The evidence presented in this article demonstrates that asbestos fibers may be genotoxic to mesothelial cells through their distinctive structure and chemistry and through their interactions with complex cellular response mechanisms. Reactive oxygen and nitrogen species play a key role. Understanding the balance between these complex mechanisms that permit neoplastic transformation and facilitate the proliferation of tumor cells is the focus of current investigation in the development of mesothelial malignancy. In human disease, the persistence of asbestos fibers in the lung and pleural tumor is a critical feature that links the exposure to asbestos with the development of disease.

Prognostic significance of cyclooxygenase-2 (COX-2) and expression of cell cycle inhibitors p21 and p27 in human pleural malignant mesothelioma

BACKGROUND

A study was undertaken to analyse the potential prognostic value of the immunohistochemical expression of cyclooxygenase-2 (COX-2) and p27 in 29 malignant mesotheliomas already screened for the expression of p21 and p53.

METHODS

Immunohistochemistry was used to determine the expression of COX-2 and p27. The correlation with survival of these factors and of p21 and p53 expression was assessed by univariate and multivariate analyses.

RESULTS

A positive statistically significant correlation was found between p27 and p21 expression (p<0.0001), but there was a negative correlation between COX-2 expression and both p27 (p = 0.001) and p21 (p<0.0001). No statistically significant correlation was recorded between p53 and all the other immunohistochemical parameters. Univariate analysis showed that overall survival was strongly influenced by p21, p27, and COX-2 expression, but multivariate Cox regression analysis showed that the only immunohistochemical parameter to influence overall survival of patients with mesothelioma was COX-2.

CONCLUSIONS

These findings suggest that COX-2 expression may be a useful prognostic parameter for mesothelioma.

Asbestos-induced pulmonary toxicity: role of DNA damage and apoptosis

Asbestos causes asbestosis and various malignancies by mechanisms that are not clearly defined. Here, we review the accumulating evidence showing that asbestos is directly genotoxic by inducing DNA strand breaks (DNA-SB) and apoptosis in relevant lung target cells. Although the exact mechanisms by which asbestos causes DNA damage and apoptosis are not firmly established, some of the implicated mechanisms include the generation of iron-derived reactive oxygen species (ROS) as well as reactive nitrogen species (RNS), alteration in the mitochondrial function, and activation of the death receptor pathway. We focus on the accumulating evidence implicating ROS. DNA repair mechanisms have a key role in limiting the extent of DNA damage. Recent studies show that asbestos activates DNA repair enzymes such as apurinic/apyrimidinic endonuclease (APE) and poly (ADP-ribose) polymerase (PARP). Asbestos-induced neoplastic transformation may result in the setting where DNA damage overwhelms DNA repair in the face of a persistent proliferative signal. Strategies aimed at limiting asbestos-induced oxidative stress may reduce DNA damage and, as such, prevent malignant transformation.