Evaluation of tumour angiogenesis as a prognostic marker in malignant mesothelioma

Biological basis for novel mesothelioma therapies

Mesothelioma is an aggressive cancer that is associated with exposure to asbestos. Although asbestos is banned in several countries, including the UK, an epidemic of mesothelioma is predicted to affect middle-income countries during this century owing to their heavy consumption of asbestos. The prognosis for patients with mesothelioma is poor, reflecting a failure of conventional chemotherapy that has ultimately resulted from an inadequate understanding of its biology. However, recent work has revolutionised the study of mesothelioma, identifying genetic and pathophysiological vulnerabilities, including the loss of tumour suppressors, epigenetic dysregulation and susceptibility to nutrient stress. We discuss how this knowledge, combined with advances in immunotherapy, is enabling the development of novel targeted therapies.

Syndecan-1 Overexpressing Mesothelioma Cells Inhibit Proliferation, Wound Healing, and Tube Formation of Endothelial Cells

Simple Summary

The transmembrane proteoglycan syndecan-1 (SDC-1) is an important mediator of cell-matrix interactions. The heparan sulfate side-chains of SDC-1 can bind to a multitude of growth factors, cytokines, and chemokines, thereby regulating a plethora of physiological and pathological processes, including angiogenesis. The extracellular region of SDC-1 can be released from the cell surface by the action of sheddases including matrix metalloproteinase-7 and 9, resulting in a soluble protein that is still active and can act as a competitive activator or inhibitor of the cell surface receptor. Accelerated shedding and loss of cell surface SDC-1 is associated with epithelial to mesenchymal transition (EMT) and achievement of a more invasive phenotype in malignant mesothelioma (MM). Transfection with SDC-1 reverts the morphology in epithelioid direction and inhibits the proliferation and migration of MM cells. This study aimed to investigate the role of SDC-1 in angiogenesis. We demonstrate that overexpression and silencing of SDC-1 alters the secretion of angiogenic proteins in MM cells. Upon SDC-1 overexpression, several factors collectively inhibit the proliferation, wound closure, and tube formation of endothelial cells, whereas SDC-1 silencing only affects wound healing.

Abstract

Malignant mesothelioma (MM) is an aggressive tumor of the serosal cavities. Angiogenesis is important for mesothelioma progression, but so far, anti-angiogenic agents have not improved patient survival. Our hypothesis is that better understanding of the regulation of angiogenesis in this tumor would largely improve the success of such a therapy. Syndecan-1 (SDC-1) is a transmembrane heparan sulfate proteoglycan that acts as a co-receptor in various cellular processes including angiogenesis. In MM, the expression of SDC-1 is generally low but when present, SDC-1 associates to epithelioid differentiation, inhibition of tumor cell migration and favorable prognosis, meanwhile SDC-1 decrease deteriorates the prognosis. In the present study, we studied the effect of SDC-1 overexpression and silencing on MM cells ability to secrete angiogenic factors and monitored the downstream effect of SDC-1 modulation on endothelial cells proliferation, wound healing, and tube formation. This was done by adding conditioned medium from SDC-1 transfected and SDC-1 silenced mesothelioma cells to endothelial cells. Moreover, we investigated the interplay and molecular functional changes in angiogenesis in a co-culture system and characterized the soluble angiogenesis-related factors secreted to the conditioned media. We demonstrated that SDC-1 over-expression inhibited the proliferation, wound healing, and tube formation of endothelial cells. This effect was mediated by a multitude of angiogenic factors comprising angiopoietin-1 (Fold change ± SD: 0.65 ± 0.07), FGF-4 (1.45 ± 0.04), HGF (1.33 ± 0.07), NRG1-β1 (1.35 ± 0.08), TSP-1 (0.8 ± 0.02), TIMP-1 (0.89 ± 0.01) and TGF-β1 (1.35 ± 0.01). SDC-1 silencing increased IL8 (1.33 ± 0.06), promoted wound closure, but did not influence the tube formation of endothelial cells. Pleural effusions from mesothelioma patients showed that Vascular Endothelial Growth Factor (VEGF) levels correlate to soluble SDC-1 levels and have prognostic value. In conclusion, SDC-1 over-expression affects the angiogenic factor secretion of mesothelioma cells and thereby inhibits endothelial cells proliferation, tube formation, and wound healing. VEGF could be used in prognostic evaluation of mesothelioma patients together with SDC-1.

Analysis of angiogenic and stromal biomarkers in a large malignant mesothelioma cohort

BACKGROUND

Malignant mesothelioma (MM) is an aggressive malignancy of the pleura and other mesothelial membranes. Agents targeting vascular endothelial growth factor (VEGF) such as bevacizumab; and multi-kinase inhibitors such as nintedanib [angiokinase inhibitor of VEGF, platelet-derived growth factor (PDGF) receptor and fibroblast growth factor receptor (FGFR)] have recently demonstrated efficacy in MM.

METHODS

Tissue microarrays (TMAs) were created from formalin-fixed, paraffin-embedded tissue samples obtained from 326 patients with MM who were treated surgically. PDGF-CC, FGFR-1, VEGF and CD31 expression were analysed by immunohistochemical (IHC) staining. The H-score method assigned a score of 0-300 to each sample, based on the percentage of cells stained at different intensities. CD31 was evaluated via Chalkley's method to evaluate microvessel density. We evaluated the association between expression of the biomarkers, clinicopathological factors and outcomes, in patients with MM.

RESULTS

CD31 high (≥5) was seen in only 31/302 (10.3%) irrespective of histology. PDGF-CC high (≥150) was seen in 203 /310 (65%) of all samples. VEGF high (≥80) was seen in 219/322 (68%) of all MM with 143/209 (68%) of epithelioid histology. FGFR-1 high (≥40) was seen in 127/310 (41%) of all MM. There was no association of VEGF and FGFR-1 IHC with survival nor differences between histological subtypes. There was a non-significant trend towards poorer survival in epithelioid tumours with increased PDGF-CC expression (OS 18.5 vs 13.2 months; HR 0.7928; 95% CI 0.5958 to 1.055, P = 0.1110). High CD31 score was associated with significantly poorer survival (OS 12 vs 8.6 months; HR 0.48; 95% CI 0.2873 to 0.7941, P = 0.0044). Of the 31 patients with high CD31 scores; 23/31 (74%) were also high for PDGF-CC and 20/31 (64%) with high VEGF scores. CD31 was found to be an independent prognostic factor in multivariate analysis (HR 1.540; 95% CI 1.018 to 2.330; p = 0.041).

CONCLUSIONS

High CD31 was an independent poor prognostic factor and high PDGF-CC expression was associated with poor survival in MM. Abrogating these pathways may have prognostic implications.

Aminopeptidase N/CD13 as a potential therapeutic target in malignant pleural mesothelioma

Angiogenesis is a crucial factor in the progression of malignant pleural mesothelioma (MPM) and antiangiogenic strategies might be effective against MPM. Aminopeptidase N (APN)/CD13 promotes tumour angiogenesis and is associated with poor prognosis; however, its clinical significance in MPM remains unclear.In 37 consecutive patients with surgically resected MPM, we evaluated the association between immunohistochemical APN/CD13 expression in resected tumours and survival. Additionally, the antitumour and antiangiogenic effects of MT95-4, a fully humanised anti-APN/CD13 monoclonal antibody, were evaluated in mice orthotopically implanted with EHMES-10 (abundantly expressing APN/CD13) and MSTO-211H (scarcely expressing APN/CD13) MPM cells.High tumour APN/CD13 expression was associated with poor prognosis in MPM patients (p=0.04), and MT95-4 treatment reduced tumour growth and angiogenesis in mice harbouring EHMES-10 but not MSTO-211H cells. Furthermore, in mice harbouring EHMES-10 cells, MT95-4 combined with cisplatin more effectively suppressed tumour progression than cisplatin alone.Taken together, these results suggest that APN/CD13 is implicated in the aggressiveness of MPM. Here, MT95-4 treatment reduced tumour progression likely by inhibiting angiogenesis, suggesting APN/CD13 as a potential molecular target for MPM treatment. Additionally, combination treatment with MT95-4 and cisplatin could represent a promising approach to treating MPM exhibiting high APN/CD13 expression.

Nintedanib Is Active in Malignant Pleural Mesothelioma Cell Models and Inhibits Angiogenesis and Tumor Growth In Vivo

Purpose: Malignant pleural mesothelioma (MPM) is an aggressive thoracic tumor type with limited treatment options and poor prognosis. The angiokinase inhibitor nintedanib has shown promising activity in the LUME-Meso phase II MPM trial and thus is currently being evaluated in the confirmatory LUME-Meso phase III trial. However, the anti-MPM potential of nintedanib has not been studied in the preclinical setting.Experimental Design: We have examined the antineoplastic activity of nintedanib in various in vitro and in vivo models of human MPM.Results: Nintedanib's target receptors were (co)expressed in all the 20 investigated human MPM cell lines. Nintedanib inhibited MPM cell growth in both short- and long-term viability assays. Reduced MPM cell proliferation and migration and the inhibition of Erk1/2 phosphorylation were also observed upon nintedanib treatment in vitro Additive effects on cell viability were detected when nintedanib was combined with cisplatin, a drug routinely used for systemic MPM therapy. In an orthotopic mouse model of human MPM, survival of animals receiving nintedanib per os showed a favorable trend, but no significant benefit. Nintedanib significantly reduced tumor burden and vascularization and prolonged the survival of mice when it was administered intraperitoneally. Importantly, unlike bevacizumab, nintedanib demonstrated significant in vivo antivascular and antitumor potential independently of baseline VEGF-A levels.Conclusions: Nintedanib exerts significant antitumor activity in MPM both in vitro and in vivo These data provide preclinical support for the concept of LUME-Meso trials evaluating nintedanib in patients with unresectable MPM. Clin Cancer Res; 24(15); 3729-40. ©2018 AACR.

Early Contrast Enhancement: A novel magnetic resonance imaging biomarker of pleural malignancy

INTRODUCTION

Pleural Malignancy (PM) is often occult on subjective radiological assessment. We sought to define a novel, semi-objective Magnetic Resonance Imaging (MRI) biomarker of PM, targeted to increased tumour microvessel density (MVD) and applicable to minimal pleural thickening.

MATERIALS AND METHODS

60 consecutive patients with suspected PM underwent contrast-enhanced 3-T MRI then pleural biopsy. In 58/60, parietal pleura signal intensity (SI) was measured in multiple regions of interest (ROI) at multiple time-points, generating ROI SI/time curves and Mean SI gradient (MSIG: SI increment/time). The diagnostic performance of Early Contrast Enhancement (ECE; which was defined as a SI peak in at least one ROI at or before 4.5 min) was compared with subjective MRI and Computed Tomography (CT) morphology results. MSIG was correlated against tumour MVD (based on Factor VIII immunostain) in 31 patients with Mesothelioma.

RESULTS

71% (41/58) patients had PM. Pleural thickening was <10 mm in 49/58 (84%). ECE sensitivity was 83% (95% CI 61-94%), specificity 83% (95% CI 68-91%), positive predictive value 68% (95% CI 47-84%), negative predictive value 92% (78-97%). ECE performance was similar or superior to subjective CT and MRI. MSIG correlated with MVD (r = 0.4258, p = .02).

DISCUSSION

ECE is a semi-objective, perfusion-based biomarker of PM, measurable in minimal pleural thickening. Further studies are warranted.

Circulating Angiogenesis Regulators in Cancer Patients

Background/Aims

To date, numerous studies have demonstrated that several angiogenesis regulators circulate in the blood and may function as endocrine factors in cancer patients. This review aims to give a comprehensive insight into the possible clinical value of circulating angiogenesis regulators, mainly basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF), angiogenin, pleiotrophin, thrombospondin (TSP) and endostatin (ES) in cancer patients.

Methods

A computerized (MEDLINE) and a manual search based on the reference lists of the publications were performed to identify articles published on this topic.

Results

In a detailed literature search, approximately 100 publications were found up to the end of 1999. Circulating angiogenic factors such as bFGF, VEGF, HGF and angiogenin have been evaluated not only as diagnostic and/or prognostic factors but also as predictive factors in cancer patients. On the other hand, little is known about the clinical significance of negative regulators. Neither the source nor the mechanism of protein externalization has been clarified in detail.

Conclusions

Although there are no known factors with established clinical utility, circulating angiogenesis regulators may be useful in several situations. They could be used to determine the risk of developing cancer, to screen for early detection, to distinguish benign from malignant disease, and to distinguish between different types of malignancies. In patients with established malignancies such factors might be used to determine prognosis, to predict the response to therapy, and to monitor the clinical course. Further investigations are warranted to assess the specific utility of each factor.

The Effect of Aquaporin 1-Inhibition on Vasculogenic Mimicry in Malignant Mesothelioma

Malignant mesothelioma (MM) is an aggressive malignancy of the serosal membranes, with poor overall survival and quality of life. Limited targeted treatment strategies exist due to restricted knowledge of pathogenic pathways. Vasculogenic mimicry (VM) is a newly described phenomenon associated with increased aggressiveness in other malignancies, and has been characterized in MM. Normal mesothelium expresses aquaporin 1 (AQP1) and retained expression has been associated with improved survival in MM. AQP1 is expressed by normal vascular endothelium and is involved in mediating MM cell motility and proliferation. We investigated the role of AQP1 in VM, and its interaction with the pro-angiogenic factor vascular endothelial growth factor A (VEGFA), which is variably expressed in MM. Matrigel VM assays were performed using NCI-H226 and NCI-H28 MM cell lines and primary cells in hypoxia and normoxia. The synthetic blocker AqB050 and siRNA were used to inhibit AQP1, and bevacizumab was used to inhibit VEGF. Inhibition of AQP1 resulted in increased VEGFA secretion by MM cells and reduced VM in MM cell lines in hypoxia but not normoxia. No change in VM was seen in MM primary cells. Combined inhibition of AQP1 and VEGF had no effect on VM in normoxia. In a heterotopic xenograft mouse model, AqB050 treatment did not alter vessel formation. AQP1 may interact with VEGFA and play a role in VM, especially under hypoxic conditions, but the heterogeneity of MM cells may result in different dominant pathways between patients.

A phase II trial of dovitinib in previously-treated advanced pleural mesothelioma: The Ontario Clinical Oncology Group

OBJECTIVES

Following failure of a platinum-antifolate combination regimen, there is no standard therapy for advanced malignant pleural mesothelioma (MPM). The fibroblast growth factor receptor (FGFR) signaling pathways may be a relevant target in MPM. Dovitinib inhibits multiple tyrosine receptor kinases, predominantly the vascular endothelial growth factor receptors (VEGFR), but also FGFRs, and could be active in MPM.

METHODS

This open-label multicentre phase II trial [NCT01769547] enrolled fit, consenting adult patients with advanced MPM who had previously received platinum-antifolate combination chemotherapy and up to one additional line of systemic therapy. Dovitinib was administered orally at 500mg/day for 5days on, 2days off, in 28-day cycles. Response was assessed every 2 cycles using RECIST 1.1 criteria modified for MPM. Correlative studies included FGFR-1 amplification on archival tumour and serum samples for circulating angiogenesis factors. The primary end-point was the proportion of patients progression-free at 3 months (PF3) using a two-stage design.

RESULTS

12 patients (10 males, median age 67) were enrolled. The median number of cycles administered was 2.5 (range 1-8). One unconfirmed partial response was observed. PF3 was 50% (95% confidence interval 28.4% to 88.0%); although the criterion for proceeding to stage II accrual was met, the trial was halted due to a combination of minimal activity with several early progression events and poor tolerability in this patient population. One of 12 tumour specimens had low amplification of FGFR-1.

CONCLUSIONS

Dovitinib has minimal activity in previously-treated MPM. The role of the FGFR pathway in MPM remains unclear.

Vasculogenic mimicry in malignant mesothelioma: an experimental and immunohistochemical analysis

Vasculogenic mimicry, the process in which cancer cells form angiomatoid structures independent of or in addition to host angiogenesis has been recorded in several otherwise non-endothelial malignant neoplasms. This study describes evidence of routine vascular mimicry by human mesothelioma cell lines in vitro, when the cell lines are cultured alone or co-cultured with human umbilical vascular endothelial cells, with the formation of angiomatoid tubular networks. Vasculogenic mimicry is also supported by immunohistochemical demonstration of human-specific anti-mitochondria antibody labelling of tumour-associated vasculature of human mesothelioma cells xenotransplanted into nude mice, and by evidence of vascular mimicry in some biopsy samples of human malignant mesotheliomas. These studies show mosaic interlacing of cells that co-label or label individually for immunohistochemical markers of endothelial and mesothelial differentiation. If vascular mimicry in mesothelioma can be characterised more fully, this may facilitate identification of more specific and targeted therapeutic approaches such as anti-angiogenesis in combination with chemotherapy and immunotherapy or other therapeutic approaches.

Functional Analysis of the Adrenomedullin Pathway in Malignant Pleural Mesothelioma

INTRODUCTION

Malignant pleural mesothelioma (MPM) grows aggressively within the thoracic cavity and has a very low cure rate, thus highlighting the need for identification of new therapeutic targets. Adrenomedullin (AM) is a multifunctional peptide that is highly expressed in several tumors and plays an important role in angiogenesis and tumor growth after binding to its receptors, calcitonin receptor-like receptor/receptor activity-modifying protein 2 (CLR/RAMP2) and calcitonin receptor-like receptor/receptor activity-modifying protein 3 (CLR/RAMP3).

METHODS

Real time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was used to assess the steady-state levels of AM, CLR, RAMP2 and RAMP3 messenger RNA (mRNA) transcripts in normal pleural tissue (n=5) and MPM (n=24). The expression of these candidates at protein level was revealed by immunohistochemistry. We also characterized the expression and regulation by hypoxia of AM system in MPM cell lines and MeT-5A cells. In vitro and in vivo studies were performed to determine the functional role of AM system in MPM.

RESULTS

In this study, real-time quantitative reverse transcriptase polymerase chain reaction showed twofold to 10-fold higher levels of AM messenger RNA in MPM tissue than in normal pleural tissue. The MPM cell lines H2452, H2052, and human mesothelioma cell line MSTO-211H showed a significant increase in expression of AM messenger RNA under hypoxic conditions. Our results also show that AM stimulates cell proliferation in vitro through the Raf1 proto-oncogene, serine/threonine kinase (CRAF)/ Mitogen-activated protein kinase kinase 1 (MEK)/Extracellular regulated MAPKinase (ERK) pathway. Furthermore, the proliferation, migration, and invasion of MPM cells were decreased after treatment with anti-AM (αAM) and anti-AM receptor antibodies, thus indicating that MPM cells are regulated by AM. The action of AM was specific and mediated by CLR/RAMP2 and CLR/RAMP3 receptors. In vivo, αAM and AM22-52 antagonist therapies blocked angiogenesis and induced apoptosis in MSTO-211H xenografts, thereby resulting in tumor regression. Histologic examination of tumors treated with AM22-52 and αAM antibody showed evidence of disruption of tumor vasculature with depletion of vascular endothelial cells and a significant decrease in lymphatic endothelial cells.

CONCLUSIONS

Our findings highlight the importance of the AM pathway in growth of MPM and in neovascularization by supplying and amplifying signals that are essential for pathologic neoangiogenesis and lymphangiogenesis.

Progranulin and granulin-like protein as novel VEGF-independent angiogenic factors derived from human mesothelioma cells

Malignant mesothelioma is an aggressive tumor arising from the mesothelial cells of serous membranes and is associated with tumor angiogenesis, which is a prerequisite for tumor progression. Vascular endothelial growth factors (VEGFs) including VEGF-A have a crucial role in tumor angiogenesis. However, bevacizumab, a monoclonal antibody to VEGF-A, has recently been reported not to improve the progression-free survival of patients with malignant mesothelioma. Cell culture supernatant contains extracellular components such as serum, which can mask the existence of unknown cell-derived factors in the supernatant and make it difficult to detect the factors by subsequent protein analysis. We tried using serum-free culture for human mesothelioma cell lines, NCI-H28, NCI-H2452 and NCI-H2052, and only NCI-H2052 cells adapted to serum-free culture. We found that serum-free culture supernatant derived from NCI-H2052 cells induces the formation of capillary-like tube structures (tube formation) in three-dimensional culture, in which endothelial cells sandwiched between two layers of collagen or embedded in collagen are incubated with various angiogenic inducers. However, neither neutralization of VEGF-A nor RNA interference of VEGF receptor 2 (VEGFR2) suppressed the supernatant-induced tube formation. Using mass spectrometry, we identified a total of 399 proteins in the supernatant, among which interleukin-8 (IL-8), growth-regulated α-protein, midkine, IL-18, IL-6, hepatoma-derived growth factor, clusterin and granulin (GRN), also known as progranulin (PGRN), were included as a candidate protein inducing angiogenesis. Neutralizing assays and RNA interference showed that PGRN, but not the above seven candidate proteins, caused the supernatant-induced tube formation. We also found that NCI-H28 and NCI-H2452 cells express PGRN. Furthermore, we demonstrate that not only PGRN but also GRN-like protein have an important role in the supernatant-induced tube formation. Thus, mesothelioma-derived GRNs induce VEGF-independent angiogenesis.

Oral cyclophosphamide and etoposide in treatment of malignant pleural mesothelioma

BACKGROUND

Malignant mesothelioma (MM) is almost always fatal and few treatment options are available. The aim of this study was to evaluate the efficacy of oral cyclophosphamide and etoposide for patients who underwent standard treatment for advanced MM.

MATERIALS AND METHODS

This study included 22 malignant pleural mesothelioma patients who were treated with oral cyclophosphamide and etoposide (EE).

RESULTS

The average follow-up period of the patients was 39.1 months. Under the treatment of oral EE, median progression- free survival was 7.7 months [95%CI HR (4.3-11.1)] and median overall survival was 28.1 months [95%CI HR (5.8-50.3)]. The treatment response rates were as follows: 4 patients (27.3%) had a partial response (PR), 12 (54.5%) had stable disease (SD), and progressive disease (PD) was observed in 6 (35.9%).

CONCLUSIONS

Oral EE can be administered effectively to patients with inoperable malignant mesothelioma who had previously received standard treatments.

SU6668, a multiple tyrosine kinase inhibitor, inhibits progression of human malignant pleural mesothelioma in an orthotopic model

BACKGROUND AND OBJECTIVE

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm of the mesothelium with high chemotherapeutic resistance. In this study, the preclinical therapeutic activity of the multiple tyrosine kinase inhibitor, SU6668, against MPM was examined.

METHODS

Two human MPM cell lines with different pro-angiogenic cytokine expression, Y-MESO-14 cells that express high levels of vascular endothelial growth factor (VEGF) and MSTO-211H cells that express high levels of basic fibroblast growth factor (bFGF), were orthotopically inoculated into the thoracic cavities of mice with severe combined immunodeficiency. The mice with MPM were treated or not treated with SU6668 (200 mg/kg/day).

RESULTS

SU6668 abrogated the proliferation of endothelial cells stimulated by VEGF or bFGF, but did not directly affect the growth of human MPM cells in vitro. In this orthotopic implantation model, treatment with SU6668 effectively reduced tumour weight and pleural effusion volumes, in association with inhibition of the growth of tumour vasculature. More importantly, treatment with SU6668 significantly prolonged survival time in mice with MPM.

CONCLUSIONS

These findings suggest that SU6668 has a promising therapeutic effect on the progression of MPM in vivo through its anti-angiogenic effects.

A multicenter phase II study of cisplatin, pemetrexed, and bevacizumab in patients with advanced malignant mesothelioma

INTRODUCTION

Malignant mesothelioma (MM) cells express the vascular endothelial growth factor (VEGF) receptor, and VEGF protein expression is detected in a majority of human mesothelioma biopsy specimens. Bevacizumab is a recombinant humanized monoclonal antibody that blocks the binding of VEGF to its receptor. We evaluated the addition of bevacizumab to cisplatin and pemetrexed as first-line treatment in patients with advanced, unresectable MM.

METHODS

Previously untreated MM patients with advanced, unresectable disease received cisplatin (75 mg/m(2)), pemetrexed (500 mg/m(2)), and bevacizumab (15 mg/kg) intravenously every 21 days for a maximum of 6 cycles. Patients with responsive or stable disease received bevacizumab (15 mg/kg) intravenously every 21 days until progression or intolerance. The primary endpoint was progression-free survival rate at 6 months.

RESULTS

53 patients were enrolled at 4 centers; 52 were evaluable for this analysis. The progression-free survival rate at 6 months was 56% and the median progression-free survival was 6.9 months (95% confidence interval [CI], 5.3-7.8 months). The partial response rate was 40% and 35% of patients had stable disease. Median overall survival was 14.8 months (95% CI; 10.0-17.0 months). Grade 3/4 toxicities included neutropenia in 11%, hypertension in 6%, and venous thromboembolism in 13% of patients.

CONCLUSION

This trial evaluating the addition of bevacizumab to cisplatin and pemetrexed in patients with previously untreated, advanced MM failed to meet the primary endpoint of a 33% improvement in the progression-free survival rate at 6 months compared with historical controls treated with cisplatin and pemetrexed alone.

Translational therapies for malignant pleural mesothelioma

Malignant pleural mesothelioma is a highly invasive tumor arising from the mesothelial cells of serosal surfaces. Several chemotherapeutic agents have been tested for the treatment of this disease and doublet cisplatin with antifolates has been demonstrated to have significant efficacy in Phase III studies. However, the benefit of these treatments remains poor and the median survival time of patients is low, ranging between 9 and 17 months. Targeted therapies are being developed in oncology and emerging evidence suggests that they offer disease control in several tumors. This article reviews the knowledge on the malignant pleural mesothelioma molecular pathway and focuses on results of clinical trials conducted on this devastating disease.

Pharmacokinetic analysis of malignant pleural mesothelioma-initial results of tumor microcirculation and its correlation to microvessel density (CD-34)

RATIONALE AND OBJECTIVES

Malignant mesothelioma (MM) of the pleura is an aggressive and often fatal neoplasm. Because MM frequently demonstrates marked angiogenesis, it may be responsive to antiangiogenic therapy, but effective methods for selecting and monitoring of patients are further needed. We employed dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and quantitative immunohistochemistry (IHC) to characterize the microvascularity of MM using both a physiologic and ultrastructural method.

MATERIALS AND METHODS

Nineteen patients diagnosed with MM were enrolled and DCE-MRI was performed before antiangiogenic treatment. For each patient, tumor regions were characterized by their DCE-MRI-derived pharmacokinetic parameters (Amp, k(ep), k(el)), which were also compared to those of normal tissue (aorta, liver, spleen, and muscle). In addition, quantitative IHC of representative samples was performed with CD-34 staining to compare the calculated microvessel density (MVD) results with DCE-MRI results.

RESULTS

MM demonstrated markedly abnormal pharmacokinetic properties compared with normal tissues. Among the parameters tested, Amp was significantly different in MM (P < or = .001) compared to normal organs. Despite the observation that the MVD of mesotheliomas in this series was high compared to other tumors, DCE-MRI pharmacokinetic parameters had a moderately positive correlation with MVD (r = 0.5).

CONCLUSIONS

DCE-MRI and IHC can be used in patients with MM to visualize tumor microvascularity and to characterize tumor heterogeneity. DCE-MRI and IHC results positively correlated, though moderately, but these two methods present as essential tumor biomarkers. This multimodal characterization may be useful in selecting possible tumor subtypes that would benefit from antiangiogenic therapy.

Inhibition of c-Src expression and activation in malignant pleural mesothelioma tissues leads to apoptosis, cell cycle arrest, and decreased migration and invasion

Malignant pleural mesothelioma (MPM) is a deadly disease with few systemic treatment options. One potential therapeutic target, the non-receptor tyrosine kinase c-Src, causes changes in proliferation, motility, invasion, survival, and angiogenesis in cancer cells and may be a valid therapeutic target in MPM. To test this hypothesis, we determined the effects of c-Src inhibition in MPM cell lines and examined c-Src expression and activation in tissue samples. We analyzed four MPM cell lines and found that all expressed total and activated c-Src. Three of the four cell lines were sensitive by in vitro cytotoxicity assays to the c-Src inhibitor dasatinib, which led to cell cycle arrest and increased apoptosis. Dasatinib also inhibited migration and invasion independent of the cytotoxic effects, and led to the rapid and durable inhibition of c-Src and its downstream pathways. We used immunohistochemical analysis to determine the levels of c-Src expression and activation in 46 archived MPM tumor specimens. The Src protein was highly expressed in tumor cells, but expression did not correlate with survival. However, expression of activated Src (p-Src Y419) on the tumor cell membrane was higher in patients with advanced-stage disease; the presence of metastasis correlated with higher membrane (P = 0.03) and cytoplasmic (P = 0.04) expression of p-Src Y419. Lower levels of membrane expression of inactive c-Src (p-Src Y530) correlated with advanced N stage (P = 0.02). Activated c-Src may play a role in survival, metastasis, and invasion of MPM, and targeting c-Src may be an important therapeutic strategy.

Emerging drugs for mesothelioma

Malignant mesothelioma is an aggressive, but relatively rare, malignancy, affecting the pleura and peritoneum. The prognosis for malignant pleural mesothelioma (MPM) is poor, with median survival in the range of 8-14 months, depending on stage and presentation of disease. Long-term results of available treatments are disappointing not only in terms of prognosis, but also of local control of the disease. Therefore, relief of symptoms and improvement of quality of life parameters are the short-term goals of therapy. In advanced disease not amenable to any local approach, such as surgery, combination chemotherapy represents the current standard of care. At present, the regimen of cisplatin/pemetrexed is the medical treatment of choice. This review summarizes standard chemotherapy options and focuses on the molecular basis of the newest biologically targeted therapies to be implemented in the near future, in the management of MPM.

Dynamic Contrast-Enhanced MRI of Malignant Pleural Mesothelioma

STUDY OBJECTIVE

Dynamic contrast-enhanced MRI (DCE-MRI) followed by pharmacokinetic analysis has been successfully used in a variety of solid tumors. The aims of this study were to evaluate the feasibility of DCE-MRI in malignant pleural mesothelioma (MPM), to differentiate benign from pathologic tissue and compare pharmacokinetic with clinical parameters and survival in order to map out its microcirculation; and to compare pharmacokinetic with clinical parameter and survival in order to improve our understanding of the in vivo biology of this malignancy.

METHODS

Nineteen patients with a diagnosis of MPM who were scheduled to receive chemotherapy with gemcitabine were enrolled in the study. DCE-MRI was performed before treatment (n = 19) and after the third cycle (n = 12) and sixth cycle (n = 7) of chemotherapy. An established pharmacokinetic two-compartment model was used to analyze DCE-MRI. Tumor regions were characterized by the pharmacokinetic parameters amplitude (Amp), redistribution rate constant (kep), and elimination rate constant (kel). Kinetic parameters of tumor tissue and normal tissue were compared using the Student t test. Patients were classified as clinical responders or nonresponders according to clinical outcome, and these groups were compared with the pharmacokinetic parameters derived from DCE-MRI.

RESULTS

Normal and tumor tissue could be distinguished by the pharmacokinetic parameters Amp and kel (p </= 0.001). Clinical responders had a median kep value within the tumor of 2.6 min, while nonresponders showed a higher value (3.6 min), which coincided with longer survival (780 days vs 460 days).

CONCLUSIONS

DCE-MRI can be used in patients with MPM to assess tumor microvascular properties and to demonstrate tumor heterogeneity for therapy monitoring. High pretherapeutic values of kep within the tumor correlated with a poor overall response to therapy.

Antiangiogenic therapies for mesothelioma

A large body of preclinical evidence suggests that angiogenesis plays a key role in the pathogenesis of malignant mesothelioma. Several mediators of angiogenesis seem to be autocrine growth factors in mesothelioma, and in preclinical models, agents that target angiogenesis produce tumor regression. Several clinical trials are currently evaluating the efficacy of inhibitors of angiogenesis in mesothelioma. This article details the preliminary results of these trials and future directions.

Dense-core plaques in Tg2576 and PSAPP mouse models of Alzheimer's disease are centered on vessel walls

Occurrence of amyloid beta (Abeta) dense-core plaques in the brain is one of the chief hallmarks of Alzheimer's disease (AD). It is not yet clear what factors are responsible for the aggregation of Abeta in the formation of these plaques. Using Tg2576 and PSAPP mouse models that exhibit age-related development of amyloid plaques similar to that observed in AD, we showed that approximately 95% of dense plaques in Tg2576 and approximately 85% in PSAPP mice are centered on vessel walls or in the immediate perivascular regions. Stereoscopy and simulation studies focusing on smaller plaques suggested that vascular associations for both Tg2576 and PSAPP mice were dramatically higher than those encountered by chance alone. We further identified ultrastructural microvascular abnormalities occurring in association with dense plaques. Although occurrence of gross cerebral hemorrhage was infrequent, we identified considerable infiltration of the serum proteins immunoglobulin and albumin in association with dense plaques. Together with earlier evidence of vascular clearance of Abeta, our data suggest that perturbed vascular transport and/or perivascular enrichment of Abeta leads to the formation of vasocentric dense plaques in Tg2576 and PSAPP mouse models of AD.

Molecular prognostic markers in malignant mesothelioma

Malignant mesothelioma remains a highly lethal cancer. Recent advances in both surgical and medical therapy have improved survival, but the treatments remain toxic and selection of appropriate patients for these therapies is difficult. Research into the molecular pathways involved in the development of mesothelioma should yield information that will guide therapeutic decisions in the near future. In particular, expression of EGFR and VEGF receptor hold promise to alter standards of patient care in the next few years. Alterations in cell cycle control proteins such as p16, p21, and p27 also offer information on prognosis and represent potential targets for therapy.

Metastasis in pleural mesothelioma. Immunohistochemical markers for disseminated disease

AIMS

To examine 13 cases of mesothelioma with metastases and compare these with 29 biopsy samples of patients without metastases. Metastatic disease was defined as tumour in which tumour appeared in a different cavity/tissue of the body and which showed no direct spread. Consequently, mediastinal nodal and parenchymal lung spread was excluded.

METHODS AND RESULTS

Standard sections were prepared and stained according to the manufacturers' protocols. The antibodies used were MIB-1, nm23, Bcl-2, MMP-9, EMMPRIN (CD147) and alpha-catenin. Scoring employed a grading system (0/1/2/3), and was performed by two pathologists independently. The tissues revealed no significant staining differences for MIB-1, Bcl-2, MMP-9 or EMMPRIN, and therefore no linkage to metastatic potential was determined. Alpha-Catenin showed a diminished level of expression in cases of metastatic mesothelioma (P = 0.024), possibly reflecting dimished catenin-cadherin binding and paralleling data from other tumours. nm23 showed greater staining in metastatic tumours when compared with the controls (P = 0.001). Intriguingly, the nm23 staining pattern was the reverse of that expected. This reversed pattern has been noted before in other tumours and therefore a biological prognostic event may exist for this antibody test and mesothelioma metastasis.

CONCLUSION

There may be a place for nm23 and possibly alpha-catenin in immunohistochemical assessment of mesothelioma metastatic potential. However, MIB-1, Bcl-2, MMP-9 and EMMPRIN (CD147) do not show significant staining results.

Microvascular density does not correlate with histopathology and outcome in neuroendocrine tumors of the pancreas

Microvascular density (MVD), a marker for tumor angiogenesis, has been demonstrated to have prognostic significance in various malignancies. Previous studies have demonstrated that MVD is an independent prognostic factor in pancreatic adenocarcinoma and that longer survival is associated with hypovascular tumors. The prognostic importance of MVD in pancreatic neuroendocrine tumor (NET) has not been documented. We evaluated MVD in pancreatic NET and correlated it with clinicopathologic features and patient outcome to determine whether MVD is a useful prognostic indicator for these patients. Twenty-five pancreatic NETs from our archival files resected between 1981 and 2000 were identified. The mean MVD was determined for each tumor from the 3 most vascularized 200 x fields. Clinical follow-up ranged from 1 to 19 years, with a mean of 4.9 years. At last follow-up, 6 patients were dead of disease, 10 patients were alive without disease, 4 patients were alive with disease, and 5 patients were alive with disease status unknown. Mean MVD ranged from 43 to 527 microvessels per 200 x field. MVD did not correlate with tumor size, the examined histologic parameters, or patient outcome. MVD in pancreatic NET does not correlate with the clinicohistologic features evaluated in this study or with the patient outcome and is not a useful prognostic indicator in these patients. These results suggest that factors other than the simple number of microvessels are important in determining pancreatic NET behavior. However, most tumors were highly vascular, and additional studies may be helpful to clarify further the role of vascularity and assess the utility of antiangiogenic agents in the treatment of pancreatic NET.

Determination of tumour prognosis based on angiogenesis-related vascular patterns measured by fractal and syntactic structure analysis

AIMS

Intratumoural micro-vessel density (IMD) has recently been shown to be a valuable prognostic tool in many tumours. Yet, IMD does not take into account the spatial arrangement of the vessels, therefore only partly reflecting the angiogenic situation. In order to describe contextual vascular relationships more accurately, we have used fractal and syntactic structure analysis (SSA) based on computerised image processing to quantify micro-vascular hot spots.

MATERIALS AND METHODS

The parametric performance in prediction of patients' outcome was evaluated by univariate analysis and compared with manually obtained IMDs, whereas an automated K-nearest-neighbour (KNN) classifier searched most discriminative parametric combinations. The method is based on analysis of vascular 'hot-spots' of paraffin-embedded tissue sections of invasive cervical carcinoma, colorectal carcinoma and malignant mesothelioma.

RESULTS

For all three cancers, prediction of prognosis based on SSA yielded in general much higher recognition scores compared with IMD or fractal dimension. Survival of cervical carcinoma was mostly correlated with clinical data, with the vascular permeation being the only parameter with independent value. Prognosis of colorectal carcinoma is best described by SSA, completed with IMD, indicating an inverse correlation of survival time with a more irregular pattern and a slight increase in vessel number. For mesothelioma, we found a strong correlation with SSA and patients' outcome, with two SSA-parameters having independent prognostic value.

CONCLUSIONS

The more accurate angiogenic description obtained with SSA may be useful for further exploitation as a prognosticator in a general diagnostic pathology service.

Effect of inhibition of multiple steps of angiogenesis in syngeneic murine pleural mesothelioma

BACKGROUND

Angiogenesis is a multistep process in which the endothelial cell plays a pivotal role. We hypothesized that the combination of two antiangiogenic agents with distinct mechanisms of action would more effectively inhibit tumor growth than either agent alone in a murine mesothelioma model.

METHODS

A syngeneic murine mesothelioma flank tumor model (AB-12) was established in BALB/c mice. Separate adenovirus vectors expressing the cDNAs for human pigment epithelium-derived factor (AdPEDF) and a soluble form of the human vascular endothelial growth factor receptor-1 (Adsflt-1) were administered intratumorally. End points measured included tumor size, animal survival, and microvessel density using CD31 immunohistochemistry. An orthotopic model of mesothelioma was established by implanting AB-12 cells into the murine pleural cavity. Simultaneously, AdPEDF and Adsflt-1 were instilled intrapleurally and tumor burden and survival were recorded. The development of pulmonary emphysema was also assessed by calculating the mean linear intercept (a measure of interalveolar septal distance) in histologic lung sections from tumor-free mice after vector administration.

RESULTS

In the flank tumor model, the combination of AdPEDF and Adsflt-1 inhibited tumor growth, prolonged survival, and decreased microvessel density more profoundly compared with either AdPEDF or Adsflt-1 alone. In the orthotopic model, the combination was also more effective in prolonging survival. Intrapleural AdPEDF or Adsflt-1 did not increase the mean linear intercept compared with controls in tumor-free mice.

CONCLUSIONS

In this murine model, inhibiting multiple mechanisms of angiogenesis using two agents is a more effective antineoplastic strategy than using either agent alone. In addition, instillation of antiangiogenic gene transfer vectors into the pleural space does not result in histologic evidence of pulmonary emphysema.

Experimental therapy of malignant mesothelioma: new perspectives from anti-angiogenic treatments

We reviewed the published literature of clinical studies in malignant mesothelioma (MM), including phase II as well as older single-agent and combination chemotherapy trials with more than 15 patients. While response rates exceeding 30% have been achieved with established cytotoxic drugs in MM therapy, novel chemotherapeutic agents and their combinations appear more promising. This applies especially to the anti-metabolites (i.e. pemetrexed) that produced response rates of up to 45% in combination with platinum compounds. Moreover, agents targeting novel proliferative and survival pathways in MM are developed to improve treatment outcomes. Here, we focused on the role of several angiogenic growth factors in MM biology and the data of MM-oriented studies on angiostatic agents tested in a phase I-II trial. It seems likely that no single treatment modality will be effective by itself. Studies that use combinations of the newer agents, including angiostatic drugs, with chemotherapy, should be conducted.

Automated tracing and change analysis of angiogenic vasculature from in vivo multiphoton confocal image time series

Automated methods are described for tracing and analysis of changes in angiogenic vasculature imaged by a multiphoton laser-scanning confocal microscope. Utilizing chronic animal window models, time series of in vivo 3-D images were acquired on approximately the same target volume of the same specimen while undergoing angiogenic change (typically every 24 h for 7 days). Objective, precise, 3-D, rapid, and fully automated vessel morphometry was performed using an adaptive tracing algorithm that is based on a generalized irregular cylinder model of the vasculature. This algorithm was found to be not only adaptive enough for tracing angiogenic vasculature, but also very efficient in its use of computer memory, and fast, taking less than 1 min to trace a 768 x 512 x 32, 8-bit/pixel 3-D image stack on a Dell Pentium III 1-GHz computer. The automatically traced centerlines were manually validated on six image stacks and the average spatial error was measured to be 2 pixels, with an average concordance of 81% between manual and automated traces on a voxel basis. The tracing output includes geometrical statistics of traced vasculature and serves as the basis of statistical change analysis. The computer methods described here are designed to be scalable to much larger hypothesis testing studies involving quantitative measurements of tumor angiogenesis, gene expression relative to known vascular structures, and impact of drug delivery.

Matrix metalloproteinases 2 and 9 (gelatinases A and B) expression in malignant mesothelioma and benign pleura

Matrix metalloproteinases (MMPs), in particular the gelatinases (MMP-2 and -9), play a significant role in tumour invasion and angiogenesis. The expression and activities of MMPs have not been characterised in malignant mesothelioma (MM) tumour samples. In a prospective study, gelatinase activity was evaluated in homogenised supernatants of snap frozen MM (n=35), inflamed pleura (IP, n=12) and uninflammed pleura (UP, n=14) tissue specimens by semiquantitative gelatin zymography. Matrix metalloproteinases were correlated with clinicopathological factors and with survival using Kaplan-Meier and Cox proportional hazard models. In MM, pro- and active MMP-2 levels were significantly greater than for MMP-9 (P=0.006, P<0.001). Active MMP-2 was significantly greater in MM than in UP (P=0.04). MMP-2 activity was equivalent between IP and MM, but both pro- and active MMP-9 activities were greater in IP (P=0.02, P=0.009). While there were trends towards poor survival with increasing total and pro-MMP-2 activity (P=0.08) in univariate analysis, they were both independent poor prognostic factors in multivariate analysis in conjunction with weight loss (pro-MMP-2 P=0.03, total MMP-2 P=0.04). Total and pro-MMP-2 also contributed to the Cancer and Leukemia Group B prognostic groups. MMP-9 activities were not prognostic. Matrix metalloproteinases, and in particular MMP-2, the most abundant gelatinase, may play an important role in MM tumour growth and metastasis. Agents that reduce MMP synthesis and/or activity may have a role to play in the management of MM.

Biomarkers in drug discovery and development: from target identification through drug marketing

Biomarkers of disease play an important role in medicine and have begun to assume a greater role in drug discovery and development. The challenge for biomarkers is to allow earlier, more robust drug safety and efficacy measurements. Their role in drug development will continue to grow for the foreseeable future. For biomarkers to assume their rightful role, greater understanding of the mechanism of disease progression and therapeutic intervention is needed. In addition, greater understanding of the requirements for biomarker selection and validation, biomarker assay method validation and application, and clinical endpoint validation and application is needed. Biomarkers need to be taken into account while the therapeutic target is still being identified and the concept is being formulated. Biomarkers need to be incorporated into a continuous cycle that takes what is learned from the discovery and development of one series of biomarkers and translates it into the next series of biomarkers. Optimum biomarker development and application will require a team approach because of the multifaceted nature of biomarker selection, validation, and application, using such techniques as pharmacoepidemiology, pharmacogenetics, pharmacogenomics, and functional proteomics; bioanalytical method development and validation; disease process and therapeutic intervention assessments; and pharmacokinetic/pharmacodynamic modeling and simulation to improve and refine drug development. The potential for biomarkers in medicine and drug development will be limited by the least effective component of the processes. The team approach will minimize the potential for the least effective component to be fatal to the rest of the process. As scientific/regulatory foundations for biomarkers in medicine and drug development begin to be established, successes and applications will need to be effectively communicated with all of the stakeholders, including not only internal and external drug developers and regulators but also the medical community, to ensure that biomarkers are totally integrated into drug discovery and development as well as the practice of medicine.

Predictive and prognostic factors in malignant pleural mesothelioma

Predictive and prognostic factors are of great importance in patients with malignant pleural mesothelioma. In the following article, the recent knowledge about these factors is presented in order to determine the patients who may benefit most from current experimental therapies.

Increased angiogenesis in bone marrow of children with acute lymphoblastic leukaemia has no prognostic significance

The importance of angiogenesis for the growth and viability of solid tumours has been established. Similarly, prognostic information may be gained from the extent of angiogenesis in these tumours. Haematopoietic malignancies should have equal requirements for angiogenesis and important prognostic information may be derived from quantification of bone marrow angiogenic activity. We retrospectively investigated 82 bone marrow trephine biopsies from 41 children with acute lymphoblastic leukaemia (ALL) at diagnosis and following treatment. Nine normal bone marrow trephines from age-matched children were also analysed as controls. The microvessels were stained immunohistochemically with anti-Factor VIII-related antigen (antivWF) and antithrombomodulin (anti-THR). Angiogenesis was quantified manually by two independent observers and was highly reproducible (Pearson's r = 0.91). Staining with anti-vWF and anti-THR was highly specific for microvessels and thetwo stains closely correlated (r = 0.68). Microvessel densities (MVD) at presentation were significantly increased in the majority of patients in comparison with controls (P < 0.0001) and MVD dropped towards normal in remission (P < 0.0001). Of interest, the difference in total vessel counts between leukaemic and normal/remission marrows was contributed solely by small microvessels. There was no significant difference in MVD at presentation or remission from children in poor prognostic groups or those who subsequently relapsed. Similarly, we could not find an association with age, sex, cytogenetic abnormality or disease phenotype.

Dense-core senile plaques in the Flemish variant of Alzheimer's disease are vasocentric

Alzheimer's disease (AD) is characterized by deposition of beta-amyloid (Abeta) in diffuse and senile plaques, and variably in vessels. Mutations in the Abeta-encoding region of the amyloid precursor protein (APP) gene are frequently associated with very severe forms of vascular Abeta deposition, sometimes also accompanied by AD pathology. We earlier described a Flemish APP (A692G) mutation causing a form of early-onset AD with a prominent cerebral amyloid angiopathy and unusually large senile plaque cores. The pathogenic basis of Flemish AD is unknown. By image and mass spectrometric Abeta analyses, we demonstrated that in contrast to other familial AD cases with predominant brain Abeta42, Flemish AD patients predominantly deposit Abeta40. On serial histological section analysis we further showed that the neuritic senile plaques in APP692 brains were centered on vessels. Of a total of 2400 senile plaque cores studied from various brain regions from three patients, 68% enclosed a vessel, whereas the remainder were associated with vascular walls. These observations were confirmed by electron microscopy coupled with examination of serial semi-thin plastic sections, as well as three-dimensional observations by confocal microscopy. Diffuse plaques did not associate with vessels, or with neuritic or inflammatory pathology. Together with earlier in vitro data on APP692, our analyses suggest that the altered biological properties of the Flemish APP and Abeta facilitate progressive Abeta deposition in vascular walls that in addition to causing strokes, initiates formation of dense-core senile plaques in the Flemish variant of AD.

The presence of simian-virus 40 sequences in mesothelioma and mesothelial cells is associated with high levels of vascular endothelial growth factor

The aim of this study was to evaluate whether the presence of simian virus-40 (SV40) is associated with increased release of vascular endothelial growth factor (VEGF) in human malignant mesothelioma (MM) cells. We studied nine cell lines derived from pleural effusion (PE) of patients with MM, and three different cultures of normal human mesothelial cells (NHMC) derived from pleural fluid of patients with congestive heart failure. NHMC were transfected with full length SV40 (NHMC-FL) or large T antigen (NHMC Tag) DNAs. High levels of VEGF were detected in conditioned media of each of two MM cells that tested positive for SV40 by PCR amplification and Southern blot hybridization and for Tag transcript by reverse transcription- polymerase chain reaction (RT-PCR) and immunoprecipitation. We also found that NHMC-FL released high amounts of VEGF. Conditioned media from SV40-positive MM cells and from FL-NHMC increased proliferation of human umbilical vein cells (HUVEC) and this effect was partially abrogated by adding specific blocking antibodies against VEGF. These results offer the first evidence that SV40 can cause VEGF release in SV40-positive MM cells and that entire viral genome is required for this effect.

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.

Angiogenesis is an independent prognostic factor in malignant mesothelioma

Angiogenesis is essential for tumour growth beyond 1 to 2 mm in diameter. The clinical relevance of angiogenesis, as assessed by microvessel density (MVD), is unclear in malignant mesothelioma (MM). Immunohistochemistry was performed on 104 archival, paraffin-embedded, surgically resected MM samples with an anti-CD34 monoclonal antibody, using the Streptavidin-biotin complex immunoperoxidase technique. 93 cases were suitable for microvessel quantification. MVD was obtained from 3 intratumoural hotspots, using a Chalkley eyepiece graticule at x 250 power. MVD was correlated with survival by Kaplan-Meier and log-rank analysis. A stepwise, multivariate Cox model was used to compare MVD with known prognostic factors and the EORTC and CALGB prognostic scoring systems. Overall median survival from the date of diagnosis was 5.0 months. Increasing MVD was a poor prognostic factor in univariate analysis (P = 0.02). Independent indicators of poor prognosis in multivariate analysis were non-epithelial cell type (P = 0.002), performance status > 0 (P = 0.003) and increasing MVD (P = 0.01). In multivariate Cox analysis, MVD contributed independently to the EORTC (P = 0.006), but not to the CALGB (P = 0.1), prognostic groups. Angiogenesis, as assessed by MVD, is a poor prognostic factor in MM, independent of other clinicopathological variables and the EORTC prognostic scoring system. Further work is required to assess the prognostic importance of angiogenic regulatory factors in this disease.