Cell cycle checkpoint status in human malignant mesothelioma cell lines: response to gamma radiation

BMP and activin membrane-bound inhibitor regulate connective tissue growth factor controlling mesothelioma cell proliferation

Background

Malignant mesothelioma (MM) is an aggressive mesothelial cell cancer type linked mainly to asbestos inhalation. MM characterizes by rapid progression and resistance to standard therapeutic modalities such as surgery, chemotherapy, and radiotherapy. Our previous studies have suggested that tumor cell-derived connective tissue growth factor (CTGF) regulates the proliferation of MM cells as well as the tumor growth in mouse xenograft models.

Methods

In this study, we knock downed the bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) and CTGF in MM cells and investigated the relationship between both and their impact on the cell cycle and cell proliferation.

Results

The knockdown of CTGF or BAMBI reduced MM cell proliferation. In contrast to CTGF knockdown which decreased BAMBI, knockdown of BAMBI increased CTGF levels. Knockdown of either BAMBI or CTGF reduced expression of the cell cycle regulators; cyclin D3, cyclin-dependent kinase (CDK)2, and CDK4. Further, in silico analysis revealed that higher BAMBI expression was associated with shorter overall survival rates among MM patients.

Conclusions

Our findings suggest that BAMBI is regulated by CTGF promoting mesothelioma growth by driving cell cycle progression. Therefore, the crosstalk between BAMBI and CTGF may be an effective therapeutic target for MM treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10080-x.

Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, potentiate the anti-angiogenic effects of bevacizumab by suppressing angiopoietin2, BiP, and Hsp90α in human colorectal cancer

Background:

Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are commonly prescribed because of their therapeutic and preventive effects on cardiovascular diseases. Even though they have been occasionally reported to have antitumour activity, it is unknown whether statins have anti-angiogenic effect in human colorectal cancer (CRC).

Methods:

A total of 11 human CRC cell lines were used to test the effects of bevacizumab, statins, and bevacizumab plus statins on human umbilical vein endothelial cell (HUVEC) viability and invasion in vitro. To determine the molecular mechanism of statins as anti-angiogenic agents, we performed an angiogenesis antibody array and proteomics analysis and confirmed the results using immunoblot assay, HUVEC invasion rescue assay, and siRNA assay. The antitumoural effects of bevacizumab and statins were evaluated in xenograft models.

Results:

A conventional dose of statins (simvastatin 0.2 μM, lovastatin 0.4 μM, atorvastatin 0.1 μM, and pravastatin 0.4 μM) in combination with bevacizumab directly reduced the cell viability, migration, invasion, and tube formation of HUVECs. The culture media of the CRC cells treated with bevacizumab or statins were also found to inhibit HUVEC invasion by suppressing angiogenic mediators, such as angiopoietin2, binding immunoglobulin protein (BiP), and Hsp90α. The combined treatment with bevacizumab and simvastatin significantly reduced the growth and metastases of xenograft tumours compared with treatment with bevacizumab alone.

Conclusions:

The addition of simvastatin at a dose used in patients with cardiovascular diseases (40–80 mg once daily) may potentiate the anti-angiogenic effects of bevacizumab on CRC by suppressing angiopoietin2, BiP, and Hsp90α in cancer cells. A clinical trial of simvastatin in combination with bevacizumab in patients with CRC is needed.

The function, mechanisms, and role of the genes PTEN and TP53 and the effects of asbestos in the development of malignant mesothelioma: a review focused on the genes' molecular mechanisms

The malignant mesothelioma is an aggressive form of cancer with a mean survival rate of less than a year. Moreover, environmental exposure to minerals is an important factor in the development of malignant mesothelioma (MM), especially the mineral asbestos, which has a well-documented role in MM, and more recently, the mineral erionite has been proven to be a strong carcinogenic inducer of MM. In addition, the virus simian virus 40 has been implicated as a co-carcinogenic player in MM. However, the molecular mechanisms involved in the pathogenesis of this cancer are still not fully understood. Indeed, it is known that several genes are altered or mutated in MM, among those are p16(INK4A), p14(ARF), and neurofibromatosis type II. Furthermore, TP53 has been reported to be mutated in the majority of the cancers; however, in MM, it is very uncommon mutations in this gene. Also, the PTEN gene has been shown to play an important role in endometrial cancer and glioblastoma, although the role of PTEN in MM has yet to be established. Taken altogether, this review focuses on the historical aspects, molecular mechanisms, interaction with other genes and proteins, and the role of these genes in MM. Lastly, this review questions the cancer theory of the two hits because the functions of both PTEN and TP53 are not fully explained by this theory.

Sphingosine kinase 1 is required for mesothelioma cell proliferation: role of histone acetylation

Background

Malignant pleural mesothelioma (MPM) is a devastating disease with an overall poor prognosis. Despite the recent advances in targeted molecular therapies, there is a clear and urgent need for the identification of novel mesothelioma targets for the development of highly efficacious therapeutics.

Methodology/Principal Findings

In this study, we report that the expression of Sphingosine Kinase 1 (SphK1) protein was preferentially elevated in MPM tumor tissues (49 epithelioid and 13 sarcomatoid) compared to normal tissue (n = 13). In addition, we also observed significantly elevated levels of SphK1 and SphK2 mRNA and SphK1 protein expression in MPM cell lines such as H2691, H513 and H2461 compared to the non-malignant mesothelial Met5 cells. The underlying mechanism appears to be mediated by SphK1 induced upregulation of select gene transcription programs such as that of CBP/p300 and PCAF, two histone acetyl transferases (HAT), and the down regulation of cell cycle dependent kinase inhibitor genes such as p27Kip1 and p21Cip1. In addition, using immunoprecipitates of anti-acetylated histone antibody from SphK inhibitor, SphK-I2 treated Met5A and H2691 cell lysates, we also showed activation of other cell proliferation related genes, such as Top2A (DNA replication), AKB (chromosome remodeling and mitotic spindle formation), and suppression of p21 CIP1 and p27KIP1. The CDK2, HAT1 and MYST2 were, however, unaffected in the above study. Using SphK inhibitor and specific siRNA targeting either SphK1 or SphK2, we also unequivocally established that SphK1, but not SphK2, promotes H2691 mesothelioma cell proliferation. Using a multi-walled carbon nanotubes induced peritoneal mesothelioma mouse model, we showed that the SphK1−/− null mice exhibited significantly less inflammation and granulamatous nodules compared to their wild type counterparts.

Conclusions/Significance

The lipid kinase SphK1 plays a positive and essential role in the growth and development of malignant mesothelioma and is therefore a likely therapeutic target.

Molecular changes in mesothelioma with an impact on prognosis and treatment

CONTEXT

In recent decades, research on malignant pleural mesothelioma (MPM) has been developed to improve patients' outcomes by increasing the level of confidence in MPM diagnosis and prognosis.

OBJECTIVE

To summarize data on genetic and epigenetic abnormalities in MPM that may be of interest for a better management of patients with MPM.

DATA SOURCES

Data were obtained from scientific publications on genetic and epigenetic abnormalities in MPM by studying gene mutations, DNA methylation, and gene and microRNA expression profiling.

CONCLUSIONS

Molecular changes in MPM consist in altered expression and in activation or inactivation of critical genes in oncogenesis, especially tumor suppressor genes at the INK4 and NF2 loci. Activation of membrane receptor tyrosine kinases and deregulation of signaling pathways related to differentiation, survival, proliferation, apoptosis, cell cycle control, metabolism, migration, and invasion have been demonstrated. Alterations that could be targeted at a global level (methylation) have been recently reported. Experimental research has succeeded especially in abolishing proliferation and triggering apoptosis in MPM cells. So far, targeted clinical approaches focusing on receptor tyrosine kinases have had limited success. Molecular analyses of series of MPM cases have shown that defined alterations are present in MPM subsets, consistent with interindividual variations of molecular alterations, and suggesting that identification of patient subgroups will be essential to develop more specific therapies.

von Hippel-Lindau protein promotes Skp2 destabilization on DNA damage

Germline mutations in the von Hippel-Lindau (VHL) tumor suppressor gene cause VHL disease, a rare and autosomal-dominant genetic syndrome. Because VHL protein (pVHL) is the master regulator of hypoxia-inducible factor alpha (HIFα), the most prominent feature of VHL disease is the deregulation of HIFα proteins. However, the precise mechanism by which the loss of pVHL function contributes to tumorigenesis is not fully understood. Here, we show that pVHL destabilizes the F-box protein Skp2, a chief component of Skp, Cullin, F-box-containing complex that promotes DNA synthesis in the S phase. The β-domain of pVHL interacts with Skp2, stimulating proteasome-dependent Skp2 degradation, but the destabilization of Skp2 does not depend on the E3 ubiquitin ligase activity of pVHL. Notably, the generation of DNA damage induces Skp2 degradation, which is attenuated by the suppression of endogenous pVHL expression. One possible mechanism of pVHL-dependent Skp2 degradation entails the antagonizing of Akt-mediated Skp2 phosphorylation, which maintains Skp2 stability. Reintroduction of VHL into VHL-null renal cell carcinoma (RCC) cells decreased Skp2 levels and restored DNA damage-dependent Skp2 degradation. These results identify the tumor suppressor function of pVHL in delaying the S-phase progression to inhibit cell proliferation on DNA damage. Clinically, this report explains as to why Skp2 accumulates abnormally in RCC tissues.

Pathogenesis of malignant pleural mesothelioma and the role of environmental and genetic factors

BACKGROUND

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor for which no effective therapy exists despite the discovery of many possible molecular and genetic targets. The late stage of MPM diagnosis and the long latency that exist between some exposures and diagnosis have made it difficult to comprehensively evaluate the role of risk factors and their downstream molecular effects.

METHODS

This manuscript is a review of current literature about the pathogenesis of malignant mesothelioma. In this overview, current published studies concerning pathogenesis of malignant mesothelioma are reviewed, with insights into its etiology and pathogenesis. We searched pubmed using the following subjects: mesothelioma, radiation, genetics, pediatric malignant mesothelioma, SV40 virus, and growth factors. We selected 350 valuable articles of which 152 sources were used to complete this review.

CONCLUSION

Many risk factors for MPM development have been recognized including environmental exposures, genetic susceptibility, viral contamination, and radiation. In this review, we discuss the current molecular and genetic contributors to MPM pathogenesis and the risk factors associated with these carcinogenic processes.

Pathogenesis of malignant pleural mesothelioma and the role of environmental and genetic factors

Malignant pleural mesothelioma (MPM) is a rare, aggressive tumor for which no effective therapy exists despite the discovery of many possible molecular and genetic targets. Many risk factors for MPM development have been recognized including environmental exposures, genetic susceptibility, viral contamination, and radiation. However, the late stage of MPM diagnosis and the long latency that exists between some exposures and diagnosis have made it difficult to comprehensively evaluate the role of risk factors and their downstream molecular effects. In this review, we discuss the current molecular and genetic contributors in MPM pathogenesis and the risk factors associated with these carcinogenic processes.

SV40 oncoproteins enhance asbestos-induced DNA double-strand breaks and abrogate senescence in murine mesothelial cells

SV40 virus has emerged as a potential cofactor with asbestos in the development of diffuse malignant mesothelioma, but its precise role in the pathogenesis of this tumor is unclear. SV40 large T antigen is known to inactivate cellular proteins involved in DNA damage and senescence, including p53 and pRb. We hypothesize that SV40 oncoproteins will sensitize mesothelial cells to DNA damage induced by asbestos or chemotherapeutic agents. SV40 oncoprotein expression in murine mesothelial cell lines enhanced spontaneous and asbestos-induced double-strand breaks, indicated by gamma-H2AX foci, and potentiated micronucleus formation. Mesothelial cells exposed to asbestos or bleomycin for 96 h acquired senescent-like morphology and displayed elevated senescence-associated beta-galactosidase activity, reduced bromodeoxyuridine (BrdUrd) incorporation, and reduced colony formation. SV40 oncoprotein expression abrogated the senescent phenotype, and transfected cell lines showed an increase in both BrdUrd incorporation and colony formation after prolonged DNA damage. Murine mesothelial cell lines lacking wild-type p53 due to a point mutation or gene rearrangement also failed to senesce in response to asbestos or chemotherapeutic agents. In addition, stress-induced senescence in human mesothelial cell lines was impaired by SV40 oncoprotein expression (MeT-5A), p53 small interfering RNA, or spontaneous p53 mutation (REN). These studies suggest that exposure to DNA-damaging agents can induce senescence in both murine and human mesothelioma cell lines and suggest a major, although not exclusive, role for p53 in this response. SV40 virus may contribute to mesothelioma progression by impairing stress-induced senescence, in part through p53 inactivation, thereby favoring survival and proliferation of mesothelial cells that have sustained DNA damage.

Upregulation of p27 and its inhibition of CDK2/cyclin E activity following DNA damage by a novel platinum agent are dependent on the expression of p21

The cisplatin analogue 1R,2R-diaminocyclohexane(trans-diacetato)(dichloro)platinum^IV (DAP) is a DNA-damaging agent that will be entering clinical trials for its potent cytotoxic effects against cisplatin-resistant tumour cells. This cytotoxicity may reside in its ability to selectively activate G1-phase checkpoint response by inhibiting CDKs via the p53/p21 pathway. We have now evaluated the role of another CDK inhibitor p27 as a contributor to DAP-mediated inhibition of G1-phase CDK2 activity. Our studies in ovarian A2780 tumour cells demonstrate that p27 levels induced by DAP are comparable to or greater than those seen for p21. The induction of p27 is not through a transcriptional mechanism, but rather is due to a four-fold increase in protein stabilisation through a mechanism dependent on p21. Moreover, DAP-induced p21 promoted the selective increase of p27 in the CDK2 complex, but not in CDK4 complex, and this selective increase contributed to inhibition of the CDK2 kinase activity. The inhibited complex contained either p27 or p21, but not both, with the relative levels of cyclin E associated with p27 and p21 indicating that about 25% of the inhibition of CDK2 activity was due to p27 and 75% due to p21. This study provides the first evidence that p27 upregulation is directly attributable to activation of the p53/p21 pathway by a DNA-damaging agent, and promulgates p53/p21/p27 axis as a significant component of checkpoint response.

Tumor suppressor gene alterations in patients with malignant mesothelioma due to environmental asbestos exposure in Turkey

BACKGROUND

Environmental asbestos exposure can cause the grave lung and pleura malignancies with a high mortality rate, and it is also associated with increased rate of other organ malignancies. Asbestos exposure can develop genotoxic effects and damage in the pleura and lungs.

OBJECTIVE

In this study, we aimed to determine tumor suppressor gene (TSG) loss in genomic DNA which was isolated from pleural fluid and blood samples of patients with Malignant Pleural Mesothelioma (MPM) due to environmental asbestos exposure.

DESIGN AND PATIENTS

Prospective study of period from 2001 to 2003 in 17 patients with MPM.

METHODS

A total of 12 chromosomal regions were researched by comparing genomic DNA samples isolated from blood and pleural effusion (using PCR, and polyacrylamide gel electrophoresis denaturizing), on 2 different chromosomes which have 9 different polymorphic determinants at 6q and 3 different polymorphic determinants at 9p using molecular genetic methods on 13 patients clinico-pathologically diagnosed MPM.

RESULTS

Loss of Heterozygosity (LOH) was determined at D6S275 in one patient, at D6S301 in another, at D6S474 in 2, at ARG1 in 2, at D6S1038 in 2 and at D6S1008 in 3 patients. In 7 (54%) of the 13 patients, we found LOH in at least one site. No LOH was determined at any informative loci in 6 patients. Of the 13 patients, no investigated markers were determined at 9p.

CONCLUSION

In this study, genomic DNA samples obtained from MPM patients with asbestos exposure revealed that they contained important genotoxic damage. We found no other study on this subject at molecular level in pleural effusion either in Turkey or in the Med-line literature. We believe that this study will provide important support for other research into molecular-genetic variations, both on this subject and other malignancies, and may also constitute a base for early diagnosis and gene therapy research in the future.

Mesothelioma pathogenesis, facts and expectations

It is the merit of Dr J.C. Wagner and his co-workers to have triggered the research on mesothelioma, going back to 1960 when they published data demonstrating a relationship between mesothelioma occurrence and exposure to asbestos fibres in the Cape Province, in South Africa. From that time, epidemiological and toxicological investigations were performed in order to better define the occupational and environmental background of this pathology, to identify the fibre parameters accounting for the toxic effects, and to understand their mechanisms of action. Improvements in our knowledge in these areas benefited to health issues, by preventing risks associated with exposure to mineral fibres and by recognising the disease. Due to the actual progresses in the fields of biology and biotechnologies, the research on mesothelioma presently focuses on study of the mechanisms of mesothelial cell transformation, and on development of strategies to kill tumour cells. While mesothelioma benefited to fibre toxicology and allowed to improve the management health related issue, it would be a just return if the present advances in different scientific areas will permit a rapid eradication of the disease.

Pathogenesis of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) results from neoplastic transformation of mesothelial cells. Past asbestos exposure represents the major risk factor for MPM, as the link between asbestos fibres and MPM has been largely proved by epidemiological and experimental studies. Asbestos fibres induce DNA and chromosome damage linked to oxidative stress following phagocytosis. Recently, simian virus 40 (SV40) has been implicated in the aetiology of MPM. The origin of human infection has been associated with SV40-contaminated polio vaccines, although to date, no epidemiological data supports this hypothesis. SV40 may act as a coactivator of asbestos in mesothelial oncogenesis. The transforming potency of SV40 results from the activity of two viral proteins, large T and small t antigens. SV40 infection stimulates production of growth factors elsewhere implicated in autocrine growth of mesothelioma cells and inactivates RASSF1, a gene silenced in MPM. Roles for ionising radiation, chemicals or genetic factors have also been suggested from the observation of sporadic MPM cases or animal studies. Genetic alterations in the tumour suppressor genes, P16/CDKN2A and neurofibromatosis 2 (NF2), are found both in human MPM and in asbestos-exposed Nf2-deficient mice. MPM is still of great international concern. Despite a ban on asbestos use in Western countries, the incidence of MPM is increasing, due to the long delay between asbestos exposure and diagnosis. Moreover, asbestos is still used in developing countries. The implication of other risk factors, especially SV40, supports a need for further research into MPM.

5-lipoxygenase antagonizes genotoxic stress-induced apoptosis by altering p53 nuclear trafficking

5-lipoxygenase (5-LO) promotes cancer cell proliferation and survival by unclear mechanisms. Here, we show that 5-LO expression and activity were induced by genotoxic agents in a p53-independent manner and antagonized p53- or genotoxic drug-induced apoptosis in a variety of cancer cells. 5-LO inhibited p53-governed transactivation of the pro-apoptotic genes bax and pig3 but not of p21(WAF1/CIP1) or mdm2. This may be explained by 5-LO capability to inhibit the binding of p53 to promyelocytic leukemia protein (PML) and p53 subnuclear relocalization into PML-nuclear bodies in response to genotoxic stress. Interestingly, 5-LO activity appears to be involved in nuclear retention and inactivation of wild-type p53 in malignant mesothelioma cells. In these cells, genetic or pharmacological inhibition of 5-LO enabled suppression of in vitro tumorigenicity by low doses of chemotherapeutic drugs. Together, these results uncover novel functions of 5-LO and contribute to the understanding of 5-LO involvement in tumor progression. Moreover, they provide a rationale to the therapeutic use of 5-LO inhibitors to enhance cancer chemosensitivity in selected tumors.