Chemosensitivity and cytokine sensitivity of malignant mesothelioma

Extracellular signal regulated kinase 5 and inflammasome in progression of mesothelioma

Malignant mesothelioma is an aggressive cancer in desperate need of treatment. We have previously shown that extracellular signaling regulated kinase 5 (ERK5) plays an important role in mesothelioma pathogenesis using ERK5 silenced human mesothelioma cells exhibiting significantly reduced tumor growth in immunocompromised mice. Here, we used a specific ERK 5 inhibitor, XMD8-92 in various in vitro and in vivo models to demonstrate that inhibition of ERK5 can slow down mesothelioma tumorigenesis. First, we show a dose dependent toxicity of XMD8-92 to 2 human mesothelioma cell lines growing as a monolayer. We also demonstrate the inhibition of ERK5 phosphorylation in various human mesothelioma cell lines by XMD8-92. We further confirmed the toxicity of XMD8-92 towards mesothelioma cell lines grown as spheroids in a 3-D model as well as in intraperitoneal (immune-competent) and intrapleural (immune-deficient) mouse models with and without chemotherapeutic drugs. To ascertain the mechanism, we explored the role of the nod-like receptor family member containing a pyrin domain 3 (NLRP3) inflammasome in the process. We found XMD8-92 attenuated naïve and chemotherapeutic-induced inflammasome priming and activation in mesothelioma cells. It can thus be concluded that ERK5 inhibition attenuates mesothelioma tumor growth and this phenomenon in part is regulated by the inflammasome.

Extracellular signal-regulated kinase 5 and cyclic AMP response element binding protein are novel pathways inhibited by vandetanib (ZD6474) and doxorubicin in mesotheliomas

Malignant mesothelioma (MM), lung cancers, and asbestosis are hyperproliferative diseases associated with exposures to asbestos. All have a poor prognosis; thus, the need to develop novel and effective therapies is urgent. Vandetanib (Van) (ZD6474, ZACTIMA) is a tyrosine kinase inhibitor that has shown equivocal results in clinical trials for advanced non-small cell lung cancer. However, tyrosine kinase inhibitors alone have shown no significant clinical activity in phase II trials of patients with unresectable MM. Using epithelioid (HMESO) and sarcomatoid (H2373) human MM lines, the efficacy of tumor cell killing and signaling pathways modulated by Van with and without doxorubicin (Dox) was examined. Van alone reduced total cell numbers in HMESO MM and synergistically increased the toxicity of Dox in HMESO and H2373 cells. Most importantly, we identified two novel cell survival/resistance pathways, ERK5 and cyclic AMP response element binding protein (CREB), that were inhibited by Van and Dox. After silencing of either ERK5 or CREB, significant decreases in cell numbers in the Dox-resistant sarcomatoid H2373 line were observed. Results suggest that a plethora of cell signaling pathways associated with cell survival are induced by Dox but inhibited by the addition of Van in MM. Data from our study support the combined efficacy of Van and Dox as a novel approach in the treatment of MM that is further enhanced by blocking ERK5 or CREB signaling cascades.

Blocking of ERK1 and ERK2 sensitizes human mesothelioma cells to doxorubicin

BACKGROUND

Malignant mesotheliomas (MM) have a poor prognosis, largely because of their chemoresistance to anti-cancer drugs such as doxorubicin (Dox). Here we show using human MM lines that Dox activates extracellular signal-regulated kinases (ERK1 and 2), causally linked to increased expression of ABC transporter genes, decreased accumulation of Dox, and enhanced MM growth. Using the MEK1/2 inhibitor, U0126 and stably transfected shERK1 and shERK2 MM cell lines, we show that inhibition of both ERK1 and 2 sensitizes MM cells to Dox.

RESULTS

U0126 significantly modulated endogenous expression of several important drug resistance (BCL2, ABCB1, ABCC3), prosurvival (BCL2), DNA repair (BRCA1, BRCA2), hormone receptor (AR, ESR2, PPARγ) and drug metabolism (CYP3A4) genes newly identified in MM cells. In comparison to shControl lines, MM cell lines stably transfected with shERK1 or shERK2 exhibited significant increases in intracellular accumulation of Dox and decreases in cell viability. Affymetrix microarray analysis on stable shERK1 and shERK2 MM lines showed more than 2-fold inhibition (p ≤ 0.05) of expression of ATP binding cassette genes (ABCG1, ABCA5, ABCA2, MDR/TAP, ABCA1, ABCA8, ABCC2) in comparison to shControl lines. Moreover, injection of human MM lines into SCID mice showed that stable shERK1 or shERK2 lines had significantly slower tumor growth rates in comparison to shControl lines after Dox treatment.

CONCLUSIONS

These studies suggest that blocking ERK1 and 2, which play critical roles in multi-drug resistance and survival, may be beneficial in combination with chemotherapeutic drugs in the treatment of MMs and other tumors.

Ifosfamide, mesna, and interferon-alpha2A combination chemoimmunotherapy in malignant mesothelioma: results of a single center in central anatolia

Our aim was to determine the efficacy of ifosfamide, mesna, and interferon alpha combination therapy in malignant mesothelioma (MM) patients. Fourty-two patients (39 evaluable) with histologically proven MM were enrolled into this study from January 1999 to October 2002. The drug schedule consisted of a combination of ifosfamide, 3000 mg/m2 1-3 d intravenous infusion (iv), the uroprotective agent mesna, 3000 mg/m2 1-3 d iv every 3 wk, and interferon alpha2a, 4.5 MU subcutaneously (sc) 3 d/wk for 6 mo as first-line chemotherapy. Overall, 140 cycles were administered to the 39 patients (median, 3.5 cycles; range, 1 to 6 cycles). Among the 39 patients, 8 partial remissions (PR) (21%) were observed. Thirteen patients (33%) had stable disease for at least 8 wk and 18 (46%) had progressive disease. Overall survival (OAS) and progression free survival (PFS) for all patients were 10.0 +/- 2.9 mo (95%CI 4.3-15.7) and 5.0 +/- 1.9 mo (95%CI 1.38-8.62), respectively. One and two year survival rates were calculated as 39% and 5%, respectively. All of the PR patients had the epithelial type of MM. Their survival time was 21.0 +/- 5.7 mo (95% CI 9.9-32.1) and significantly longer than that of nonresponders (p=0.0061). The toxicity of the drug combination was mild and well tolerated. There were no treatment-related deaths. Grade 3-4 neutropenia and febrile neutropenia were seen in 10 patients (26%) and 3 patients (8%), respectively. Chemotherapy was stopped in three patients because of renal function deficiency. One of these patients who had peritoneal MM required hemodialysis. In conclusion, this combination therapy showed encouraging antitumor activity with modest toxicity.

Quantitative evaluation of the apoptosis regulating genes Survivin, Bcl-2 and Bax in inflammatory and malignant pleural lesions

AIM

We aimed to identify defects in the programmed cell death pathway that can be related to pleural malignant mesothelioma (MM) unresponsiveness to chemotherapy.

MATERIALS AND METHODS

We quantified mRNA levels of the apoptosis regulating genes Survivin, member of the IAP family, Bcl-2 and Bax, members of the Bcl-2 family. We studied 22 non-neoplastic pleural samples, comprising normal and inflammatory tissue specimens, and 42 pleural MMs using real-time RT-PCR.

RESULTS

Very low mRNA levels of each apoptotic gene were detected in all normal pleural samples. All three genes displayed increased mRNA levels in inflammatory and tumor specimens. Survivin levels in pleuritis and MMs were significantly increased (333% and 908%, respectively) compared to normal counterparts (p=0.0147 and 0.00349, respectively). Bcl-2 and Bax levels were increased in inflammatory pleural samples (394%, p=0.001 and 188%, p=ns, respectively) and in MMs (94%, p=ns and 88%, p=0.0163, respectively). The Bcl-2/Bax ratio was higher in pleuritis than in MMs, compared to normal pleurae (441%, p=ns and 22%, p=ns, respectively); the difference between Bcl-2/Bax ratio in inflammatory and neoplastic pleural samples was significant (p=0.00375).

CONCLUSIONS

These results suggest that apoptotic defects in pleural MMs are linked to increased levels of Survivin, whereas variations in Bcl-2 and Bax expression appear less significant, although further studies are needed to highlight Bcl-2 family members interactions in apoptosis control. Survivin progressive accumulation from normal pleura to MM suggests this gene may be important in mesothelial cancerogenesis. Survivin overexpression may also be involved in pleural MM resistance to oncological therapies. Therefore, Survivin may represent a promising novel target for selective therapies.

Enhanced effectiveness of last generation antiblastic compounds vs. cisplatin on malignant pleural mesothelioma cell lines

The purpose of this study was to examine the antiproliferative potentialities of a pool of new generation compounds (Paclitaxel, Docetaxel, Gemcitabine, Topotecan, SN-38) together with fenretinide, a synthetic derivative of retinoic acid, in comparison with the current first choice treatment cisplatin molecule, on a pool of human malignant pleural mesothelioma cell lines derived from either bioptic and pleural effusions samples. To evaluate the chemosensitivity features of malignant mesothelioma cells in vitro, we resorted to a rapid and reproducible colorimetric assay, a useful widely recognized tool for preclinical drug screening. In addition, by DNA content analysis and cellular morphologic assessment, we focused on the apoptosis as a potential mechanism of drug activity. The main results clearly indicate that, in all the models of malignant mesothelioma we handled in vitro, each tested antineoplastic agent is more powerful than cisplatin in inhibiting cell proliferation. Moreover, on experimental evidences basis, we can assume that the cytotoxic activity of tested compounds could be related, at least partially, to the drug-induced programmed cell death. This experimental study gives substance to the expected pharmacologic worth of the second generation antineoplastic drugs even if, in order to afford the most satisfactory biopharmacological approach, allowing to bypass the refractoriness to chemotherapy of this highly lethal tumour, further investigations at preclinical level are required.

Potential of interferon-alpha in solid tumours: part 2

The second part of this review examines the use of recombinant interferon-alpha (rIFNalpha) in the following solid tumours: superficial bladder cancer, Kaposi's sarcoma, head and neck cancer, gastrointestinal cancers, lung cancer, mesothelioma and ovarian, breast and cervical malignancies. In superficial bladder cancer, intravesical rIFNalpha has a promising role as second-line therapy in patients resistant or intolerant to intravesical bacille Calmette-Guérin (BCG). In HIV-associated Kaposi's sarcoma, rIFNalpha is active as monotherapy and in combination with antiretroviral agents, especially in patients with CD4 counts >200/mm(3), no prior opportunistic infections and nonvisceral disease. rIFNalpha has shown encouraging results when used in combination with retinoids in the chemoprevention of head and neck squamous cell cancers. It is effective in the chemoprevention of hepatocellular cancer in hepatitis C-seropositive patients. In neuroendocrine tumours, including carcinoid tumour, low-dosage (</=3 MU) or intermediate-dosage (5 to 10 MU) rIFNalpha is indicated as second-line treatment, either with octreotide or alone in patients resistant to somatostatin analogues. Intracavitary IFNalpha may be useful in malignant pleural effusions from mesothelioma. Similarly, intraperitoneal IFNalpha may have a role in the treatment of minimal residual disease in ovarian cancer. In breast cancer, the only possible role for IFNalpha appears to be intralesional administration for resistant disease. IFNalpha may have a role as a radiosensitising agent for the treatment of cervical cancer; however, this requires confirmation in randomised trials. On the basis of current evidence, the routine use of rIFNalpha is not recommended in the therapy of head and neck squamous cell cancers, upper gastrointestinal tract, colorectal and lung cancers, or mesothelioma. Pegylated IFNalpha (peginterferon-alpha) is an exciting development that offers theoretical advantages of increased efficacy, reduced toxicity and improved compliance. Further data from randomised studies in solid tumours are needed where rIFNalpha has activity, such as neuroendocrine tumours, minimal residual disease in ovarian cancer, and cervical cancer. A better understanding of the biological mechanisms that determine response to rIFNalpha is needed. Studies of IFNalpha-stimulated gene expression, which are now feasible, should help to identify molecular predictors of response and allow us to target therapy more selectively to patients with solid tumours responsive to IFNalpha.

Intrapleural infusion of activated macrophages and gamma-interferon in malignant pleural mesothelioma: a phase II study

STUDY OBJECTIVES

Intrapleural immunotherapy has shown some activity in patients with malignant mesothelioma. We conducted a multicentric pilot phase II study to evaluate the tolerance and the activity of intrapleurally infused autologous human activated macrophages (AM Phi) in patients with stage IA, IB, and IIA malignant pleural mesothelioma (MPM).

DESIGN

AM Phi derived from in vitro monocyte culture were infused into the pleura of patients every week for 8 consecutive weeks. Each infusion was followed 3 days later by an intrapleural injection of 9 millions units of gamma-interferon (gamma-IFN) in an attempt to prolong the in vivo activation of infused AM Phi. Response was assessed by CT scan and thoracoscopy when possible. If the patient's disease progressed after AM Phi treatment, an additional treatment was left to the choice of the investigator.

PATIENTS

Nineteen patients with histologically proven stage IA, IB, or IIA MPM were enrolled. Two patients were excluded before any AM Phi infusion because of complications impeding infusion. Seventeen patients were actually treated. After completion of the AM Phi cellular therapy, 10 patients were treated with chemotherapy as their diseases progressed.

RESULTS

The overall response rate of patients actually treated was 14%. When including the two patients enrolled but not treated, the overall response "in intention to treat" was 11%; two patients had a partial response, with a duration of response of 30 months and 3 months, respectively. One patient, who could not be evaluated by thoracoscopy because of pleural symphysis, is still alive without any clinical or radiologic sign of disease 69 months after treatment. No major adverse effects were observed during the infusion of either AM Phi or gamma-IFN, and there was no interruption of treatment because of toxicity. However, symphysis was observed in 7 of 14 patients who received the complete treatment. The median survival of patients actually treated, including those who received chemotherapy after AM Phi, was 29.2 months.

CONCLUSION

Combined infusion of AM Phi and gamma-IFN was well tolerated in patients with MPM; however, it had limited antitumor activity.

New approaches for mesothelioma: biologics, vaccines, gene therapy, and other novel agents

Although malignant mesothelioma is not a classically immunogenic cancer, there is abundant evidence for immune recognition. The relative ease of obtaining tumor tissue makes mesothelioma ideal for studying surrogate biomarkers such as lymphocytic infiltration or expression of transduced genes. There is evidence that malignant mesothelioma patients as well as asbestos-exposed persons without mesothelioma have impaired immune responsiveness. Substantial progress has been made in animal models using several biological and immunological techniques, but clinical application has been problematic. Systems studied have included lysis by interleukin-2 (IL-2)-activated lymphokine-activated killer (LAK) cells, tumor necrosis factor-alpha (TNF-alpha), a p16-expressing adenovirus vector, suicide gene therapy using the herpes simplex virus-tyrosine kinase (HSV-tk) followed by ganciclovir, and immunomodulatory gene therapy with IL-2, IL-4, interferon-gamma (IFN-gamma), IFN-alpha, TNF-alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, and IL-1beta transfected into tumors. Vaccinia virus has been studied as a vector for cytokine gene transfer. Suicide gene therapy has been combined with a tumor vaccine. The University of Western Australia is initiating a pilot study of autologous vaccination in malignant mesothelioma. Novel agents under study include the angiogenesis inhibitors SU5416, bevacizumab, and thalidomide. ZD1839, an orally administered, highly selective inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase, is being tested in a phase II trial. Since platelet-derived growth factor (PDGF) is thought to be an autocrine growth factor for mesothelioma STI-571 (Gleevec; Novartis, Basel, Switzerland), a highly selective inhibitor of the PDGF receptor tyrosine kinase, is being tested in a phase II trial. The development of more active cytotoxic combinations in this disease should facilitate further studies of chemoimmunotherapy. It seems likely that no single treatment modality will be effective by itself.

Combined regimen of cisplatin, doxorubicin, and alpha-2b interferon in the treatment of advanced malignant pleural mesothelioma: a Phase II multicenter trial of the Italian Group on Rare Tumors (GITR) and the Italian Lung Cancer Task Force (FONICAP)

BACKGROUND

The cisplatin-doxorubicin combination has shown moderate activity in malignant pleural mesothelioma (MPM; objective response, 25%), and preclinical studies suggest that interferons (IFNs) may have an antiproliferative effect on mesothelioma cell lines with a marked increase in cisplatin cytotoxicity. Therefore, the combined chemoimmunotherapy regimen is an worthwhile approach to evaluate in a Phase II trial.

METHODS

From December 1995 to June 1999, 37 previously untreated patients with MPM were treated with cisplatin 60 mg/m(2) intravenously on Day 1 plus doxorubicin 60 mg/m(2), recycled every 3-4 weeks and IFN-alpha-2b, 3 x 10((6)) international units subcutaneously 3 times a week for a total of 6 courses or until progression. Inclusion criteria were histologic diagnosis of MPM and measurable disease defined by computed tomography scan or magnetic resonance imaging.

RESULTS

Thirty-four patients were assessable for toxicity and 35 for efficacy according to World Health Organization criteria. One hundred thirty-five courses were administered with a median of 4 cycles per patients. Seventy-six percent of patient presented at least 1 episode of severe myelosuppression (Grade 3 and 4). Severe anemia and thrombocytopenia occurred in 30% and 24% of patients, respectively. Sixty percent of patients presented constitutional symptoms. In the 35 patients assessable for response, the overall response rate was 29% (95% confidence interval, 15-47%). The median duration of response was 8.4 months. With a median follow-up of 19.6 months, the median survival was 9.3 months. One- and 2-year survival was 45% and 34%, respectively.

CONCLUSIONS

This combined regimen has definite activity in MPM. However, toxicity, particularly myelosuppression and fatigue, is not negligible and may limit its application.

Control of cell cycle progression in human mesothelioma cells treated with gamma interferon

Recombinant human interferon gamma (r-hu-IFNgamma) exerts both antitumoral activity in the early stages of human malignant mesothelioma and a cytostatic effect in human mesothelioma (HM) cell lines in vitro. The antiproliferative effect of interferons (IFNs) reported in a variety of cells has been attributed to several mechanisms. In order to progress in the understanding of HM cell growth modulation by r-hu-IFNgamma, modifications of cell cycle progression and expression of key cell cycle regulator proteins in response to r-hu-IFNgamma were examined. Nine HM cell lines were studied, including one resistant to the antiproliferative effect of r-hu-IFNgamma. Except in the resistant cell line r-hu-IFNgamma produced an arrest in the G1 and G2-M phases of the cell cycle, associated with a reduction in both cyclin A and cyclin dependent kinase inhibitors (CDKIs) expression. Moreover cyclin B1/cdc2 activity was decreased. The present study provides the first evidence of a G2-arrest in r-hu-IFNgamma-treated HM cell lines and indicates that HM cell lines, despite their tumorigenic origin still support cell cycle control. The cell cycle arrest induced by r-hu-IFNgamma seems to depend on cyclin regulation through p21(WAF1/CIP1)- and p27(Kip1)-independent mechanisms and is not directly related to the induced DNA damage.

Strategies to circumvent SV40 oncoprotein expression in malignant pleural mesotheliomas

Although nearly 60% of mesotheliomas contain SV40 early region DNA sequences, the role of T/t antigens in initiating and maintaining the transformed state of mesothelioma cells remains unclear. The majority of mesothelioma cells which contain SV40 early region sequences exhibit extremely low basal expression of SV40 oncoproteins; however, T/t antigen expression can be induced under conditions of cellular stress. Abrogation of SV40 T/t expression by antisense techniques induces apoptosis in part via restoration of p53 function, and enhances chemosensitivity in SV40 (+) MPM cells by mechanisms which have not been fully elucidated. This review briefly summarizes our ongoing efforts to define the role of SV40 oncoproteins in modulating the malignant phenotype of mesothelioma cells, and highlights strategies which may prove efficacious in vivo for circumventing SV40 T/t antigen expression in mesotheliomas.

Pericardial mesothelioma

Primary pericardial mesothelioma is a rare but lethal disease. Altogether there are about 150 cases reported in the literature. In most cases the diagnosis is made at autopsy or postoperatively. Clinical signs and symptoms are typically nonspecific and are similar to compromised cardiac function. Surgical resection remains the main treatment modality. When the disease is localized and completely resected, long-term survival can result. Most often the tumor invades the myocardium or the great vessels and therefore is at best palliative in relieving pericardial tamponade or constriction. Addition of chemotherapy or radiation has been disappointing. Newer therapeutic approaches for malignant pleural mesothelioma are likely to influence the treatment of pericardial mesothelioma in the future.

Cisplatin, mitomycin, and interferon-alpha2a combination chemoimmunotherapy in the treatment of diffuse malignant pleural mesothelioma

STUDY OBJECTIVE

To investigate the therapeutic activity and toxicity of combination chemoimmunotherapy with cisplatin, mitomycin, and interferon (IFN)-alpha2a, by comparing the responses in a group of patients with diffuse malignant pleural mesothelioma (DMPM) to the responses in a control group of DMPM patients given supportive care alone.

DESIGN

Patients with histopathologically confirmed DMPM were evaluated for treatment with chemoimmunotherapy.

SETTING

After the initial evaluation, all patients received either chemoimmunotherapy or supportive care from the Osmangazi University Medical Faculty, Department of Chest Diseases.

PATIENTS

Forty-three patients with DMPM received chemoimmunotherapy until the end of the survey; 19 patients were given supportive therapy alone after refusing chemoimmunotherapy.

INTERVENTIONS

Drugs were administered according to the following schedule: IV cisplatin, 30 mg/m2 qd on days 1 and 2; IV mitomycin, 8 mg/m2 on day 1; and subcutaneous IFN-alpha2a, 4.5 million IU twice weekly. The courses were repeated every 4 weeks.

RESULTS

Overall, 232 chemoimmunotherapy cycles were administered. A total of 10 objective responses (ORs) in 43 patients (23%) were assessed, including 2 complete responses (5%), 4 partial responses, and 4 regressions. Seventeen patients had stable disease, and 16 patients had progression. The median survival time was 11.5 months for the 43 patients who received chemoimmunotherapy and 7.0 months for the 19 patients who received supportive therapy alone. The difference in survival times between the chemoimmunotherapy and supportive therapy groups was not significant. However, the median survival time for the patients who had OR was 21.3 months, which is significantly longer than that of the patients who received supportive care alone and that of patients with progressive disease (6 months). The toxicities associated with the treatment schedule of this study were, for the most part, tolerable.

CONCLUSIONS

The drug combination used in this study is moderately effective and well tolerated in patients with DMPM, especially in those who responded to the treatment.

Asbestos induction of extended lifespan in normal human mesothelial cells: interindividual susceptibility and SV40 T antigen

Normal human mesothelial cells from individual donors were studied for susceptibility to asbestos-induction of apoptosis and generation of an extended lifespan population. Such populations were generated after death of the majority of cells and arose from a subset of mesothelial cultures (4/16) whereas fibroblastic cells (5/5) did not develop extended lifespan populations after asbestos exposure. All mesothelial cultures were examined for the presence of SV40 T antigen to obtain information on (i) the presence of SV40 T antigen expression in normal human mesothelial cells and (ii) the relationship between generation of an extended lifespan population and expression of SV40 T antigen. Immunostaining for SV40 T antigen was positive in 2/38 normal human mesothelial cultures. These cultures also had elevated p53 expression. However, the two isolates expressing SV40 T antigen did not exhibit enhanced proliferative potential or develop an extended lifespan population. Asbestos-generated extended lifespan populations were specifically resistant to asbestos-mediated but not to alpha-Fas-induced apoptosis. Deletion of p16Ink4a was shown in 70% of tumor samples. All mesothelioma cell lines examined showed homozygous deletion of this locus which extended to exon 1beta. Extended lifespan cultures were examined for expression of p16Ink4a to establish whether deletion was an early response to asbestos exposure. During their rapid growth phase, extended lifespan cultures showed decreased expression of p16Ink4a relative to untreated cultures, but methylation was not observed, and p16Ink4a expression became elevated when cells entered culture crisis. These data extend the earlier observation that asbestos can generate extended lifespan populations, providing data on frequency and cell type specificity. In addition, this report shows that generation of such populations does not require expression of SV40 T antigen. Extended lifespan cells could represent a population expressing early changes critical for mesothelioma development. Further study of these populations could identify such changes.

Weekly systemic combination of cisplatin and interferon alpha 2a in diffuse malignant pleural mesothelioma

The treatment of diffuse malignant pleural mesothelioma (DMPM) remains grim. Neither surgery, radiotherapy nor chemotherapy can be considered as a standard therapy. Immunotherapy with interferon (IFN) in combination with chemotherapy may be an interesting new approach. In 13 consecutive patients with DMPM, we used a weekly combination of cisplatin (CDDP) (60 mg/m2; day 2) and IFN alpha 2a (6 MU/day; days 1-4) in a protocol of two cycles of 4 weeks on/4 weeks off followed by 3 weeks on/3 weeks off. Total treatment duration was thus 25 weeks. In responders, IFN as maintenance monotherapy was continued for a further 6 months. There were nine males and four females with an average age of 65.3 years (range 51-72 years). Eleven had epithelial, one had mixed and one had a sarcomatoid form of DMPM. Five patients were classified as stage II, six as stage III and two as stage IV, as per the International Mesothelioma Interest Group. Thirty-five cycles were administered with a median of three cycles/patient (range 0.75-4). The median total cumulative dose of CDDP was 596 mg/m2 (range 114-861) and that of IFN alpha 2a was 264 MU (range 72-336). Four patients received IFN maintenance therapy, one for 3 months and three for 6 months. One patient had a complete response, four had a partial response, six had a stable disease and the disease progressed in one. One patient was non evaluable for response. All patients were assessable for toxicity. Hematological toxicity was the most frequently observed but was manageable (grade 3 anemia in five patients, grade 3 thrombocytopenia in three patients, grade 3 neutropenia in five patients). Grade 1 renal toxicity was observed in six patients, grade 2-3 asthenia in six patients and an average 5-kg weight loss was noted in nine patients. In conclusion, systemic combination of CDDP and IFN alpha 2a in large doses is effective at the expense of non-negligible toxicity.

Successful immunochemotherapy for patients with malignant mesothelioma: report of two cases

Malignant mesothelioma is a clinically aggressive tumor and has a poor prognosis; therefore, the selection of therapeutic strategies is important to improve the prognosis. Two patients with intraperitoneal malignant mesothelioma received combination therapy as follows: (1) case-oriented chemotherapy according to the results of a chemosensitivity test, and (2) adoptive immunotherapy using cytotoxic T lymphocytes (CTL). The chemosensitivity test was assessed by an MTT colorimetric assay. CTL was generated by a mixed culture with autologous tumor cells, and activated by immobilized anti-CD3 monoclonal antibody and interleukin-2. The MTT assay indicated that cisplatin and adriamycin were sensitive drugs in both patients, and they thus received the case-oriented chemotherapy according to the MTT assay. The activated CTL exhibited a high cytotoxicity against autologous malignant mesothelioma cells, and were transferred intraperitoneally. The patients were controllable for ascites, and the tumor masses gradually vanished (partial response). Chemoimmunotherapy is thus considered to be an effective treatment for intraperitoneal malignant mesothelioma, especially to improve the quality of life.

Resistance of pleural mesothelioma cell lines to apoptosis: relation to expression of Bcl-2 and Bax

A failure of normal apoptosis, often due to mutant p53, may contribute to the formation of a cancer and to its resistance to therapy. Mesothelioma, an asbestos-induced tumor, is highly resistant to therapy but generally expresses wild-type p53. We asked whether mesothelioma was resistant to apoptosis and whether resistance was associated with altered expression of the antiapoptotic protein Bcl-2 or proapoptotic protein Bax. We found that three mesothelioma cell lines (1 with wild-type p53) were highly resistant to apoptosis induced by oxidant stimuli (asbestos, H2O2) or nonoxidant stimuli (calcium ionophore) compared with primary cultured mesothelial cells. By immunostaining, one of these three lines expressed Bcl-2 but only during mitosis. By immunoblotting, 3 of 14 additional mesothelioma lines (9 of 14 with wild type p53) expressed Bcl-2 but all 14 of 14 expressed the proapoptotic Bax, giving a low ratio of Bcl-2 to Bax. We conclude that mesothelioma cell lines are resistant to apoptosis and that the failure in apoptosis is not explained by Bcl-2 but by other mechanisms that counteract the proapoptotic effect of Bax.

Co-ordinated over-expression of the MRP and gamma-glutamylcysteine synthetase genes, but not MDR1, correlates with doxorubicin resistance in human malignant mesothelioma cell lines

While human malignant mesothelioma is extremely resistant to chemotherapy, its intrinsic resistance mechanisms remain largely unknown. In this study, we used normal human mesothelial cells and 5 human mesothelioma cell lines not previously exposed to chemotherapeutic agents to demonstrate that the mRNA for the multidrug resistance-associated protein (MRP) and gamma-glutamylcysteine synthetase (gamma-GCSh) heavy subunit genes, but not the P-glycoprotein (MDR1) gene, are co-ordinately over-expressed in mesothelioma cell lines. Expression of MRP as detected with an anti-MRP antibody correlated with decreased doxorubicin accumulation and resistance of mesothelioma cells to this drug. Our results strongly suggest roles for MRP and gamma-GCSh in chemoresistance in mesotheliomas.

Doxorubicin retention and chemoresistance in human mesothelioma cell lines

Eight cell lines were established from the pleural effusion of 4 patients with malignant mesothelioma. The most sensitive (FCCMES-4) and the most resistant (FCCMES-2) mesothelioma cell lines had IC50 of 0.66 and 1.85 microM for doxorubicin in clonogenic assays, respectively. In comparison with murine leukemic P388 cells, mesothelioma cell lines were 7.5- to 21-fold more resistant to doxorubicin. Co-incubation with verapamil significantly increased doxorubicin retention in one of the cell lines (FCCMES-2) expressing P-glycoprotein in 16.8% of the cells. These results indicate that doxorubicin resistance may be intrinsic in refractory mesothelioma patients and P-glycoprotein-mediated drug efflux may be involved in resistance of some of the mesotheliomas.

Immunocytochemical characterization of cell lines from human malignant mesothelioma: characterization of human mesothelioma cell lines by immunocytochemistry with a panel of monoclonal antibodies

A panel of nine monoclonal antibodies was used to characterize human mesothelioma cell lines that we established from human malignant mesothelioma. The antigens detected were cytokeratin, vimentin, epithelial membrane antigen, carcinoembryonic antigen, Leu-M1 (CD15), desmin, factor VIII-related antigen (von Willebrand factor antigen), OV632, and ME1, a specific monoclonal antibody directed against human malignant mesothelioma. The technique used was the alkaline phosphatase anti-alkaline phosphatase method. All 30 cell lines, either epithelial, sarcomatous, or mixed, showed strong reactivity with cytokeratin and vimentin antibodies. None of the cell lines demonstrated any reactivity with carcinoembryonic antigen, Leu-M1, or factor VIII antibodies; moreover, all of 22 cell lines studied were positive for ME1 antibody and 10 of 12 cell lines studied were positive for OV632. Some interesting features were noted: only two of the 30 cell lines presented a weak positive staining with epithelial membrane antigen, and nine of 19 cell lines tested demonstrated a cytoplasmic staining pattern with desmin antibody. These results show that established human mesothelioma cell lines still possess the immunocytochemical characteristics that are basically consistent with the immunohistochemical features described in tumor tissues of malignant mesothelioma. These characteristics can be used to identify the mesothelioma cells grown from human malignant mesothelioma. Hence, the mesothelioma cell lines will provide a useful tool for the investigation of the cell biology of the tumor and the mechanisms of mesothelial cell transformation, as well as the in vitro evaluation of the effects of some drugs in order to develop new therapies for malignant mesothelioma.

In vitro effects of recombinant human interferon gamma on human mesothelioma cell lines

Malignant mesothelioma is a tumor arising from serous surfaces and often related to asbestos exposure. Malignant mesothelioma is resistant to various forms of therapy. Radiotherapy, surgery or chemotherapy only slightly improve prognosis. IFN-gamma produces complete or partial responses in stage-I patients with malignant mesothelioma. The in vitro biological effect of IFN-gamma on malignant mesothelioma cells remains poorly elucidated. In the present study, 32 well-characterized human mesothelioma cell lines (HMCL) were treated with r-hu IFN-gamma at 4 doses and cell growth was determined by a colorimetric method (MTT assay). Among the 32 HMCLs tested, II exhibited significant cell-growth inhibition; 16 were insensitive to r-hu IFN-gamma, and 5 were slightly inhibited. The sensitive cell lines were strongly inhibited by r-hu IFN-gamma. Our results show that HMCL exhibit a large range of responses to r-hu IFN-gamma, some of which can be compared with those obtained in vivo in humans.

Effects of natural interferon alpha, natural tumor necrosis factor alpha and their combination on human mesothelioma xenografts in nude mice

Effects of human natural interferon alpha (nIFN) alone, human natural tumor necrosis factor alpha (nTNF) alone and their combination (OH-1) were tested on three human mesothelioma lines implanted in nude mice. Tumors were transplanted subcutaneously by trocar on treatment day -12. nIFN was given intraperitoneally (i.p.) at a dose of 2 x 10(7) or 2 x 10(8) IU kg-1 day-1, 5 days a week for 3 weeks. nTNF was given i.p. at a dose of 2 x 10(7) or 2 x 10(8) U kg-1 day-1 in the same schedule as that of nIFN. Tumor diameters were serially measured and tumor volumes were calculated. Antitumor effects were assessed by two methods: comparison of final tumor volumes in treated and control groups (T/C), and changes in median average total tumor volume. The treatment produced no clinically discernible toxicities. nIFN had strong inhibitory activity against all three human mesothelioma lines. nTNF alone had modest activity only at the high dose used. The combination of the two produced activity essentially similar to that produced by nIFN alone. High-dose nIFN may have a role as an active agent in the treatment of patients with mesothelioma.