Serologic responses in patients with malignant mesothelioma: evidence for both public and private specificities

Autoantibodies and cancer among asbestos-exposed cohorts in Western Australia

Asbestos exposure is associated with many adverse health conditions including malignant mesothelioma and lung cancer as well as production of autoantibodies. Autoantibodies may serve as biomarkers for asbestos exposure in patients with cancer, and autoimmune dysfunction has been linked to increased rates of various cancers. The aim of this study was to examine the hypothesis that autoantibodies are more frequent in asbestos-exposed individuals with either lung cancer or mesothelioma than those without these conditions. Asbestos-exposed individuals from Western Australia who had lung cancer (n = 24), malignant mesothelioma (n = 24), or no malignancy (n = 51) were tested for antinuclear autoantibodies (ANA) using indirect immunofluorescence and specific extractable nuclear autoantibodies (ENA) employing a multiplexed addressable laser bead immunoassay. Contrary to the hypothesis, data demonstrated that individuals without malignancy were more likely to be positive for ANA compared to those with cancer. However, autoantibodies to histone and Ro-60 were found to be associated with lung cancer. These results support a possible predictive value for specific autoantibodies in the early detection of lung cancer and/or in our understanding of the role of autoimmune processes in cancer. However, further studies are needed to identify specific target antigens for the antibodies.

Immune checkpoint inhibition for the treatment of mesothelioma

INTRODUCTION

Combination chemotherapy is currently standard care for advanced mesothelioma. Checkpoint blockade is a promising new treatment.

AREAS COVERED

This review covers clinical use and biomarkers of checkpoint blockade. Medline search used keywords 'mesothelioma' combined with 'checkpoint blockade' OR 'PD-L1' OR 'PD1' OR 'anti-CTLA4'; the search terms AND 'clinical trial' or AND 'biomarker*' were added. Handsearching covered abstracts from relevant meetings from 2016 to 2018 and reference lists. Data informed a narrative review.

EXPERT OPINION

Single agent anti-CTLA4 blockade is inactive in mesothelioma. Single agent PD-1 blockade as second or subsequent treatment gives 20-29% partial responses; no randomized comparisons against placebo or chemotherapy are available. Biomarkers of response have been difficult to identify. There is no consensus as to whether tumor PD-L1 expression predicts outcomes. Combination checkpoint inhibitors (CTLA4 and PD1 blockade) provide a small incremental increase in response rates and progression-free survival. Chemoimmunotherapy is the next frontier.

Immunotherapy strategies for mesothelioma - the role of tumor specific neoantigens in a new era of precision medicine

INTRODUCTION

Immunotherapy has long been considered a potential therapy for malignant mesothelioma and is currently being pursued as such. Some of the early phase clinical trials involving immunomodulators have demonstrated encouraging results and numerous clinical trials are underway to further investigate this treatment approach in various treatment settings and larger patient cohorts. Areas covered: This review summarizes the current and emerging clinical evidence for checkpoint blockade and other immunotherapeutic strategies in mesothelioma. The mesothelioma tumor immune microenvironment and mutational landscape are also discussed, including their impact on treatment strategies. We also provide an evaluation of the current evidence for neoantigen targeted personalized immunotherapy. Expert opinion: Immune checkpoint inhibitors work by unleashing the host immune response against probable neoantigens. Despite impressive activity in a small subset of patients and the potential for prolonged responses, most patients experience treatment failure. Neoantigen vaccines provide a potential complementary therapeutic strategy by increasing the immunogenic antigen load, which can lead to an increased tumor specific immune response. Further research is needed explore this treatment option in mesothelioma and technological advances are required to translate this concept into clinical practice.

Autoantibody biomarkers identified by proteomics methods distinguish ovarian cancer from non-ovarian cancer with various CA-125 levels

PURPOSE

CA-125 has been a valuable marker for detecting ovarian cancer, however, it is not sensitive enough to detect early-stage disease and not specific to ovarian cancer. The purpose of our study was to identify autoantibody markers that are specific to ovarian cancer regardless of CA-125 levels.

METHODS

Top-down and iTRAQ quantitative proteomics methods were used to identify high-frequency autoantibodies in ovarian cancer. Protein microarrays comprising the recombinant autoantigens were screened using serum samples from various stages of ovarian cancer with diverse levels of CA-125 as well as benign and healthy controls. ROC curve and dot blot analyses were performed to validate the sensitivity and specificity of the autoantibody markers.

RESULTS

The proteomics methodologies identified more than 60 potential high-frequency autoantibodies in ovarian cancer. Individual serum samples from ovarian cancer stages I-IV compared to control samples that were screened on a microarray containing native recombinant autoantigens revealed a panel of stage I high-frequency autoantibodies. Preliminary ROC curve and dot blot analyses performed with the ovarian cancer samples showed higher specificity and sensitivity as compared to CA-125. Three autoantibody markers exhibited higher specificity in various stages of ovarian cancer with low and normal CA-125 levels.

CONCLUSIONS

Proteomics technologies are suitable for the identification of protein biomarkers and also the identification of autoantibody biomarkers when combined with protein microarray screening. Using native recombinant autoantigen arrays to screen autoantibody markers, it is possible to identify markers with higher sensitivity and specificity than CA-125 that are relevant to early detection of ovarian cancer.

Identification of novel autoantibodies for detection of malignant mesothelioma

Background

The malignant mesothelioma (MM) survival rate has been hampered by the lack of efficient and accurate early detection methods. The immune system may detect the early changes of tumor progression by responding with tumor-associated autoantibody production. Hence, in this study, we translated the humoral immune response to cancer proteins into a potential blood test for MM.

Methodology/Principal Findings

A T7 phage MM cDNA library was constructed using MM tumor tissues and biopanned for tumor-associated antigens (TAAs) using pooled MM patient and normal serum samples. About 1008 individual phage TAA clones from the biopanned library were subjected to protein microarray construction and tested with 53 MM and 52 control serum samples as a training group. Nine candidate autoantibody markers were selected from the training group using Tclass system and logistic regression statistical analysis, which achieved 94.3% sensitivity and 90.4% specificity with an AUC value of 0.89 in receiver operating characteristic analysis. The classifier was further evaluated with 50 patient and 50 normal serum samples as an independent blind validation, and the sensitivity of 86.0% and the specificity of 86.0% were obtained with an AUC of 0.82. Sequencing and BLASTN analysis of the classifier revealed that five of these nine candidate markers were found to have strong homology to cancer related proteins (PDIA6, MEG3, SDCCAG3, IGHG3, IGHG1).

Conclusions/Significance

Our results indicated that using a panel of 9 autoantibody markers presented a promising accuracy for MM detection. Although the results need further validation in high-risk groups, they provided the potentials in developing a serum-based assay for MM diagnosis.

Triplex DNA-binding proteins are associated with clinical outcomes revealed by proteomic measurements in patients with colorectal cancer

Background

Tri- and tetra-nucleotide repeats in mammalian genomes can induce formation of alternative non-B DNA structures such as triplexes and guanine (G)-quadruplexes. These structures can induce mutagenesis, chromosomal translocations and genomic instability. We wanted to determine if proteins that bind triplex DNA structures are quantitatively or qualitatively different between colorectal tumor and adjacent normal tissue and if this binding activity correlates with patient clinical characteristics.

Methods

Extracts from 63 human colorectal tumor and adjacent normal tissues were examined by gel shifts (EMSA) for triplex DNA-binding proteins, which were correlated with clinicopathological tumor characteristics using the Mann-Whitney U, Spearman’s rho, Kaplan-Meier and Mantel-Cox log-rank tests. Biotinylated triplex DNA and streptavidin agarose affinity binding were used to purify triplex-binding proteins in RKO cells. Western blotting and reverse-phase protein array were used to measure protein expression in tissue extracts.

Results

Increased triplex DNA-binding activity in tumor extracts correlated significantly with lymphatic disease, metastasis, and reduced overall survival. We identified three multifunctional splicing factors with biotinylated triplex DNA affinity: U2AF65 in cytoplasmic extracts, and PSF and p54nrb in nuclear extracts. Super-shift EMSA with anti-U2AF65 antibodies produced a shifted band of the major EMSA H3 complex, identifying U2AF65 as the protein present in the major EMSA band. U2AF65 expression correlated significantly with EMSA H3 values in all extracts and was higher in extracts from Stage III/IV vs. Stage I/II colon tumors (p = 0.024). EMSA H3 values and U2AF65 expression also correlated significantly with GSK3 beta, beta-catenin, and NF- B p65 expression, whereas p54nrb and PSF expression correlated with c-Myc, cyclin D1, and CDK4. EMSA values and expression of all three splicing factors correlated with ErbB1, mTOR, PTEN, and Stat5. Western blots confirmed that full-length and truncated beta-catenin expression correlated with U2AF65 expression in tumor extracts.

Conclusions

Increased triplex DNA-binding activity in vitro correlates with lymph node disease, metastasis, and reduced overall survival in colorectal cancer, and increased U2AF65 expression is associated with total and truncated beta-catenin expression in high-stage colorectal tumors.

The Role of Regulatory T Cells in Mesothelioma

Malignant mesothelioma (MM) appears to be responsive to immunotherapy. The lack of complete tumour cure as a result of many immunotherapies tested to date suggests that the immune response to MM is complex and multi-parametric. Regulatory T (Treg) cells are prevalent within murine and human mesotheliomas with their removal shown to result in tumour growth inhibition and the release of anti-tumour effector T cells from immunosuppression. The targeting of immune checkpoints as treatments for various solid tumours has recently shown promise in clinical settings. In addition, synergy between chemotherapy and immunotherapy has been demonstrated for many cancers, including mesothelioma. Here we demonstrate Treg cells as critical mediators of the anti-tumour immune response to MM and potential targets for anti-tumour immunotherapy; though the timing and dosage of Treg cell manipulating immunotherapies need to be optimised.

Auto-antibodies to β-F1-ATPase and vimentin in malignant mesothelioma

Patients with Malignant Mesothelioma (MM) develop unidentified auto-antibodies to MM tumour antigens. This study was conducted to identify the targets of MM patient auto-antibodies in order to try to understand more of the anti-tumour response and to determine if these antibodies might be helpful for diagnosis or prognostication. Using MM patient sera in a Western immunoblott screening strategy, no common immunoreactive proteins were identified. The sera from one long-term survivor recognised a protein band of 50-60 kDa present in cell lysates from four of five MM cell lines tested. The immunoreactive proteins in this band were identified by 2D electrophoretic separation of a MM cell line protein lysate, followed by analysis of excised immunoreactive proteins on a MALDI TOF mass spectrometer and peptide mass fingerprinting. The immunoreactive proteins identified were vimentin (accession gi55977767) and the ATP synthase (F1-ATPase) beta chain (accession gi114549 and gi47606749). ELISA assays were developed for antibodies to these proteins. Neither vimentin (median and 95% CI 0.346; 0.32-0.468 for MM patients, 0.327; 0.308-0.428 for controls) nor ß-F1-ATPase (0.257; 0.221-0.453 for MM patients, 0.263; 0.22-0.35 for controls) showed significant differences in autoantibody levels between a group of MM patients and controls. Using a dichotomized antibody level (high, low) for these targets we demonstrated that vimentin antibody levels were not associated with survival. In contrast, high ß-F1-ATPase antibody levels were significantly associated with increased median survival (18 months) compared to low ß F1 ATPase antibody levels (9 months; p = 0.049). Immunohistochemical analysis on a MM tissue microarray showed cytoplasmic staining in 28 of 33 samples for vimentin and strong cytoplasmic staining in14 and weak in 16 samples for ß-F1-ATPase. Therefore antibodies to neither vimentin nor ß-F1-ATPase are useful for differential diagnosis of MM, however high antibody levels to ß-F1-ATPase may be associated with increased survival and this warrants further investigation.

Genetically engineered oncolytic Newcastle disease virus effectively induces sustained remission of malignant pleural mesothelioma

Malignant pleural mesothelioma is a highly aggressive tumor. Alternative treatment strategies such as oncolytic viral therapy may offer promising treatment options in the future. In this study, the oncolytic efficacy and induction of tumor remission by a genetically engineered Newcastle disease virus [NDV; NDV(F3aa)-GFP; GFP, green fluorescent protein] in malignant pleural mesothelioma is tested and monitored by bioluminescent tumor imaging. The efficacy of NDV(F3aa)-GFP was tested against several mesothelioma cell lines in vitro. Firefly luciferase-transduced MSTO-211H* orthotopic pleural mesothelioma tumor-bearing animals were treated with either single or multiple doses of NDV(F3aa)-GFP at different time points (days 1 and 10) after tumor implantation. Tumor burden was assessed by bioluminescence imaging. Mesothelioma cell lines exhibited dose-dependent susceptibility to NDV lysis in the following order of sensitivity: MSTO-211H > MSTO-211H* > H-2452 > VAMT > JMN. In vivo studies with MSTO-211H* cells showed complete response to viral therapy in 65% of the animals within 14 days after treatment initiation. Long-term survival in all of these animals was >50 days after tumor installation (control animals, <23 d). Multiple treatment compared with single treatment showed a significantly better response (P = 0.005). NDV seems to be an efficient viral oncolytic agent in the therapy of malignant pleural mesothelioma in an orthotopic pleural mesothelioma tumor model.

CD40-activated B cells contribute to mesothelioma tumor regression

Targeting CD40, a member of the tumor necrosis factor superfamily, using agonist antibodies (Abs) produces dramatic antitumor effects. Indeed, high-dose intravenous anti-CD40 Ab 'licenses' dendritic cells (DCs) that instruct activated CD8(+) cytotoxic T cells to leave lymph nodes (LNs) and penetrate the mesothelioma tumor microenvironment. However, toxic side effects and the potential of an 'overwhelmed' immune response warrant an alternative approach. In this study, we show that injecting lower doses of anti-CD40 Ab directly into the tumor bed avoided toxic side effects and prolonged survival in 60% of mice, with most cured. Unexpectedly, DCs in tumors and LNs 'disappeared', CD8(+) tumor-specific T-cell numbers and function were not enhanced, and T cells did not infiltrate regressing tumors. CD4(+) or CD8(+) depletion only marginally hindered anti-CD40 Ab efficacy implying another effector mechanism. B-cell numbers significantly increased in tumors, draining LNs and spleens during intratumoral anti-CD40 Ab treatment. CD40 targeting had no effect on splenic B-1 cells, obliterated marginal zone B cells and promoted follicular (FO) B-cell activity. Adoptive transfer of tumor antigen-experienced, CD40-activated B cells, or their immunoglobulin products, which recognized autoantigens on mesothelioma cells, protected against tumor challenge. Finally, studies using B-cell knockout mice showed that successful treatment of established tumors required the presence of B cells. Thus, these data suggest that CD40-activated FO B cells can become an important component of an effective antitumor immune response.

Low-dose cyclophosphamide synergizes with dendritic cell-based immunotherapy in antitumor activity

Clinical immunotherapy trials like dendritic cell-based vaccinations are hampered by the tumor's offensive repertoire that suppresses the incoming effector cells. Regulatory T cells are instrumental in suppressing the function of cytotoxic T cells. We studied the effect of low-dose cyclophosphamide on the suppressive function of regulatory T cells and investigated if the success rate of dendritic cell immunotherapy could be improved. For this, mesothelioma tumor-bearing mice were treated with dendritic cell-based immunotherapy alone or in combination with low-dose of cyclophosphamide. Proportions of regulatory T cells and the cytotoxic T cell functions at different stages of disease were analyzed. We found that low-dose cyclophosphamide induced beneficial immunomodulatory effects by preventing the induction of Tregs, and as a consequence, cytotoxic T cell function was no longer affected. Addition of cyclophosphamide improved immunotherapy leading to an increased median and overall survival. Future studies are needed to address the usefulness of this combination treatment for mesothelioma patients.

What's the place of immunotherapy in malignant mesothelioma treatments?

Malignant pleural mesothelioma (MPM) is a rare malignancy of the pleura with a very poor prognosis. Treatments evaluated for malignant mesothelioma, including chemotherapy, radiotherapy and surgery are of limited efficacy. However, the fact that the tumors of some patients with MPM regress spontaneously or respond to immunotherapy suggests that the immune system may respond to MPM under some circumstances. In this respect, animal studies have demonstrated immunoreactivity of MPM to different immunotherapies. In the case of MPM, several clinical studies have demonstrated a correlation between the presence of a lymphocyte infiltrate and a better prognosis and humoral response directed against specific antigens related to tumor. Thus, MPM immunotherapy is undoubtedly a highly promising but also very challenging approach to the treatment of this disease that has slipped through the defense lines of the immune system. This article reviews past and recent developments of the clinical strategies that concern immunotherapy of mesothelioma.

Malignant mesothelioma-associated antigens recognized by tumor-infiltrating B cells and the clinical significance of the antibody titers

Malignant pleural mesothelioma (MPM) is difficult to diagnose at an early stage. The present study attempted to obtain a tumor-specific antibody against MPM derived from tumor-infiltrating B lymphocytes in MPM by using a xenotransplanted severe combined immunodeficiency (SCID) mouse model, and to identify the antigens recognized by the antibodies. Among the antigen-antibody relationships, the clinical usefulness of antibody titers in the sera was evaluated from the viewpoint of diagnosis of MPM and monitoring of therapeutic effects. Tumor tissue specimens from two patients with MPM were engrafted subcutaneously in SCID mice and blood samples were obtained and pooled every 2 weeks after xenotransplantation until 14 weeks when the mice were killed. A cDNA library was constructed from the mRNA of a MPM cell line (K921MSO). Immunoscreening of the libraries was carried out by serological identification of antigens by a recombinant expression cloning method (SEREX) and four antigens were identified as MPM-associated antigens. Among them, antibody titers against two antigens, Gene-X and thrombospondin-2 (THBS-2), were analyzed by phage plaque assay as the first step. ELISA systems correlated with the phage plaque assay to detect antibody titers against the two antigens were constructed using 20-mer peptides of the antigen-coding genes. The cut-off value was decided by the average and standard deviation of normal healthy persons. Antibody against Gene-X was detected in 10 out of 18 (55.6%) mesothelioma patients and antibody against THBS-2 was detected in 16 out of 18 (88.9%) mesothelioma patients. No patients with lung cancer regardless of asbestos exposure exhibited positive antibody titer against the two antigens. Furthermore, the serum antibody titers decreased after surgical treatment of MPM and increased after recurrence of the disease. The titers of the antibodies against Gene-X and THBS-2 could be used as tumor markers for the diagnosis and follow up of patients with MPM.

Fluorescent nanocrystal-encoded microbeads for multiplexed cancer imaging and diagnosis

Bead-based assays on very large numbers of molecules in proteomics, genomics, drug screening and clinical diagnostics require encoding of each of the microbeads according to the particular ligand bound to its surface. The benefits of using optically encoded microbeads (instead of the solid-state two-dimensional arrays) are derived from the freedom of bead to move in three dimensions. Polymeric beads optically encoded with organic dyes allow for a limited number of unique codes whereas the use of semiconductor nanocrystals as fluorescent tags improves the beads multiplexed imaging capabilities, photostability and sensitivity of the antigen detection. Additionally, an employment of the recently demonstrated Förster resonance energy transfer (FRET) from the microbeads nanocrystal codes to the nearby antibody dye label allows for the very specific detection of the interaction between the microbead and the antibody. This interaction turns the fluorescence signal from dye label off and on thus effectively discriminating between the occurrence and the non-occurrence of antibody binding. The absence of fluorescent background from non-interacting with the beads dye-labelled antibodies additionally increases the sensitivity of detection and further facilitates the multiplexing capabilities of nanocrystals-based detection and diagnostics. This paper reviews the state-of-the-art results of development of microbeads optically encoded with the fluorescent nanocrystals "quantum dots" and their applications to proteomics for cancer antigens and autoantibodies imaging and diagnosis.

The La autoantigen is a malignancy-associated cell death target that is induced by DNA-damaging drugs

PURPOSE

To evaluate the La autoantigen as a target for specific monoclonal antibody (mAb) binding in dead cancer cells after use of DNA-damaging chemotherapy.

EXPERIMENTAL DESIGN

In vitro studies of La-specific 3B9 mAb binding to malignant and normal primary cells with and without cytotoxic drug treatment were done using immunoblotting and flow cytometry. Chromatin-binding studies and immunofluorescence detection of gammaH2AX as a marker of DNA double-stranded breaks together with 3B9 binding assays were done to measure DNA damage responses. Incorporation of a transglutaminase 2 (TG2) substrate and TG2 inhibition were studied to measure protein cross-linking in dead cells.

RESULTS

La was overexpressed in human cancer cell lines with respect to normal primary cells. Within 3 h of the DNA-damaging stimulus, La became chromatin bound when it colocalized with gammaH2AX. Later, after the stimulus produced cell death, La-specific 3B9 mAb bound specifically and preferentially in the cytoplasm of dead cancer cells. Moreover, 3B9 binding to dead cancer cells increased with increasing DNA damage. Both La and 3B9 became cross-linked in dead cancer cells via TG2 activity.

CONCLUSION

La autoantigen represents a promising cancer cell death target to determine chemotherapy response because its expression was selectively induced in dead cancer cells after DNA-damaging chemotherapy.

Shared immunoproteome for ovarian cancer diagnostics and immunotherapy: potential theranostic approach to cancer

Elimination of cancer through early detection and treatment is the ultimate goal of cancer research and is especially critical for ovarian and other forms of cancer typically diagnosed at very late stages that have very poor response rates. Proteomics has opened new avenues for the discovery of diagnostic and therapeutic targets. Immunoproteomics, which defines the subset of proteins involved in the immune response, holds considerable promise for providing a better understanding of the early-stage immune response to cancer as well as important insights into antigens that may be suitable for immunotherapy. Early administration of immunotherapeutic vaccines can potentially have profound effects on prevention of metastasis and may potentially cure through efficient and complete tumor elimination. We developed a mass-spectrometry-based method to identify novel autoantibody-based serum biomarkers for the early diagnosis of ovarian cancer that uses native tumor-associated proteins immunoprecipitated by autoantibodies from sera obtained from cancer patients and from cancer-free controls to identify autoantibody signatures that occur at high frequency only in cancer patient sera. Interestingly, we identified a subset of more than 50 autoantigens that were also processed and presented by MHC class I molecules on the surfaces of ovarian cancer cells and thus were common to the two immunological processes of humoral and cell-mediated immunity. These shared autoantigens were highly representative of families of proteins with roles in key processes in carcinogenesis and metastasis, such as cell cycle regulation, cell proliferation, apoptosis, tumor suppression, and cell adhesion. Autoantibodies appearing at the early stages of cancer suggest that this detectable immune response to the developing tumor can be exploited as early-stage biomarkers for the development of ovarian cancer diagnostics. Correspondingly, because the T-cell immune response depends on MHC class I processing and presentation of peptides, proteins that go through this pathway are potential candidates for the development of immunotherapeutics designed to activate a T-cell immune response to cancer. To the best of our knowledge, this is the first comprehensive study that identifies and categorizes proteins that are involved in both humoral and cell-mediated immunity against ovarian cancer, and it may have broad implications for the discovery and selection of theranostic molecular targets for cancer therapeutics and diagnostics in general.

Recombinant GM-CSF plus autologous tumor cells as a vaccine for patients with mesothelioma

Treatments evaluated for malignant mesothelioma (MM), including chemotherapy, radiotherapy and surgery are of limited efficacy. Immunotherapy has shown some promise in MM but optimal vaccination conditions are yet to be defined. Autologous tumour vaccines have the advantage of containing both 'self'- and 'neo'-tumor antigens but they are not commonly used in any cancer, and never in MM. We therefore evaluated the effect of an autologous MM tumor cell lysate, given s.c. with recombinant granulocyte-macrophage colony stimulating factor (GM-CSF), on anti-tumor immunity in patients with MM.

PATIENTS AND METHODS

An autologous tumor lysate vaccine was manufactured from surgically resected tumor and administered subcutaneously together with GM-CSF. Induction of tumor specific cellular immunity was assessed by delayed type hypersensitivy (DTH) skin testing using autologous tumor tissue and of humoral immune responses to shared MM antigens by western blotting of patients' sera against a panel of allogeneic human MM cell lines. CT scanning was used to evaluate tumor progression.

RESULTS

Twenty-two patients were enrolled onto the trial. Of these five developed positive delayed type hypersensitivity skin tests and five showed evidence of altered antibody specificities by western blotting. A total of seven patients developed at least one type of anti-MM immune response. On an intention-to-treat basis the median survival of all patients was 11.5 months, and the 1- and 2-year survival rates were 50% and 27%, respectively. Complete or partial CT responses were not seen, however seven patients had stable disease for the duration of the trial. Vaccination was safe with no severe adverse reactions.

CONCLUSION

Vaccination with autologous MM tumor cell lysate with GM-CSF induced tumor specific immunity in 32% of patients, was safe and was associated with stable disease but no major tumour regressions.

Malignant mesothelioma

Malignant mesothelioma is an aggressive, treatment-resistant tumour, which is increasing in frequency throughout the world. Although the main risk factor is asbestos exposure, a virus, simian virus 40 (SV40), could have a role. Mesothelioma has an unusual molecular pathology with loss of tumour suppressor genes being the predominant pattern of lesions, especially the P16INK4A, and P14ARF, and NF2 genes, rather than the more common p53 and Rb tumour suppressor genes. Cytopathology of mesothelioma effusions or fine-needle aspirations are often sufficient to establish a diagnosis, but histopathology is also often required. Patients typically present with breathlessness and chest pain with pleural effusions. Median survival is now 12 months from diagnosis. Palliative chemotherapy is beneficial for mesothelioma patients with high performance status. The role of aggressive surgery remains controversial and growth factor receptor blockade is still unproven. Gene therapy and immunotherapy are used on an experimental basis only. Patterns identified from microarray studies could be useful for diagnosis as well as prognostication.

Immunotherapy of Murine Malignant Mesothelioma Using Tumor Lysate–pulsed Dendritic Cells

RATIONALE

Exploiting the immunostimulatory capacities of dendritic cells holds great promise for cancer immunotherapy. Currently, dendritic cell-based immunotherapy is evaluated clinically in a number of malignancies, including melanoma and urogenital and lung cancer, showing variable but promising results.

OBJECTIVE

To evaluate if pulsed dendritic cells induce protective immunity against malignant mesothelioma in a mouse model.

METHODS

Malignant mesothelioma was induced in mice by intraperitoneal injection of the AB1 mesothelioma cell line, leading to death within 28 days. For immunotherapy, dendritic cells were pulsed overnight either with AB1 tumor cell line lysate, AB1-derived exosomes, or ex vivo AB1 tumor lysate, and injected either before (Days -14 and -7) at the day of (Day 0) or after (Days +1 and +8) tumor implantation.

MAIN RESULTS

Mice receiving tumor lysate-pulsed dendritic cells before tumor implantation demonstrated protective antitumor immunity with prolonged survival (> 3 months) and even resisted secondary tumor challenge. Tumor protection was associated with strong tumor-specific cytotoxic T-lymphocyte responses. Adoptive transfer of splenocytes or purified CD8+ T lymphocytes transferred tumor protection to unimmunized mice in vivo. When given after tumor implantation in a therapeutic setting, pulsed dendritic cells prevented mesothelioma outgrowth. With higher tumor load and delayed administration after tumor implantation, dendritic cells were no longer effective.

CONCLUSIONS

We demonstrate in this murine model that immunotherapy using pulsed dendritic cells may emerge as a powerful tool to control mesothelioma outgrowth. In the future, immunotherapy using dendritic cells could be used as adjuvant to control local recurrence after multimodality treatment for malignant mesothelioma.

Identification of autoantigens in psoriatic plaques using expression cloning

To search for autoantigens in psoriatic plaques, we screened cDNA libraries of plaque epidermis with psoriatic serum samples. This approach has been highly successful in identifying tumor antigens, but has not been widely applied to autoimmune disease. We identified 11 autoantigens including three with prominent reactivity and plausible disease relevance. These are keratin 13 (K13), heterogeneous nuclear ribonucleoprotein-A1 (hnRNP-A1), and a previously uncharacterized protein, FLJ00294. Serum antibody screening for these demonstrated reactivity in 40%, 38%, and 27% of psoriasis patients, respectively. Most positive samples reacted with all three, and we found that this was due to cross-reactivity among them. Enzyme-linked immunospot assay (ELISPOT) analysis of psoriatic peripheral blood T cells confirmed that these autoantigens are also recognized by T cells. This demonstrates that this is a feasible method to identify autoantigens in an autoimmune target tissue, and suggests that these antigens warrant further study in psoriasis. Furthermore, but peripheral blood of normal controls reacted to these autoantigens with essentially the same frequencies as patients, suggesting that psoriatics may have not only an immune system which is capable of reacting to certain autoantigens, but also to a skin immunoregulatory alteration which allows this normal reactivity to develop into abnormal inflammation.

Cell protection, resistance and invasiveness of two malignant mesotheliomas as assessed by 10K-microarray

Malignant pleural mesothelioma (MPM) is an aggressive serosal tumor, strongly associated with former exposure to asbestos fibers and for which there is currently no effective treatment available. In human, MPM is characterized by a high local invasiveness, poor prognosis and therapeutic outcomes. In order to assess molecular changes that specify this phenotype, we performed a global gene expression profiling of human MPM. Using a 10,000-element microarray, we analyzed mRNA relative gene expression levels by comparing a mesothelioma cell line to either a pleural cell line or tumor specimens. To analyze these gene expression data, we used various bioinformatics softwares. Hierarchical clustering methods were used to group genes and samples with similar expression in an unsupervised mode. Genes of known function were further sorted by enzyme, function and pathway clusters using a supervised software (IncyteGenomics). Taken together, these data defined a molecular fingerprint of human MPM with more than 700 up- or down-regulated genes related to several traits of the malignant phenotype, specially associated with MPM invasiveness, protection and resistance to anticancer defenses. This portrait is meaningful in disease classification and management, and relevant in finding new specific markers of MPM. These molecular markers should improve the accuracy of mesothelioma diagnosis, prognosis and therapy.

Integration of Multimodality Approaches in the Management of Malignant Pleural Mesothelioma

More than half a century after the first descriptions of mesothelioma as a pathologic entity, satisfactory treatment is still elusive. Although relatively uncommon, the incidence of mesothelioma will most likely increase over the next 10-20 years. Advances have been made in understanding the pathogenesis, diagnosis, and staging, but they have not translated into markedly improved survival. Some use palliative treatment as the primary means of therapy even now. On the other hand, a cadre of individuals have studied how surgery, chemotherapy, and radiation therapy affect the disease. Although each individual modality has had limited success by itself, a multimodality approach has been documented to improve survival and quality of life. In addition, intriguing discoveries in immunology and gene profiling and therapy promise hope for further improvement. In this article, we will illustrate the current views on integrating these different approaches and delineate areas of active research.

Identification of tumor-associated antigens by screening phage-displayed human cDNA libraries with sera from tumor patients

Screening cDNA libraries from solid human tumors with sera of autologous patients (SEREX) has proven to be a powerful approach to identifying tumor antigens recognized by the humoral arm of the immune system. In many cases, application of this methodology has led to the discovery of novel tumor antigens as unknown gene products. We tried to improve the potency of the SEREX approach by combining it with phage-display technology. We designed a new lambda vector to express protein fragments as N-terminal fusions to the D capsid protein and generated high-complexity cDNA libraries from human breast carcinoma cell lines and solid tumors. Screening these phage-displayed libraries required limited amounts of sera from patients and efficiently identified several tumor antigens specifically reacting with sera from breast cancer patients.

A panel of candidate tumor antigens in colorectal cancer revealed by the serological selection of a phage displayed cDNA expression library

In the last few years it has been shown that the humoral immune response in cancer patients is a rich source of putative cancer vaccine candidates. To fully explore the complex information present within the Ab repertoire of cancer patients, we have applied a method, serological Ag selection, to molecularly define tumor Ags recognized by the humoral immune response in colorectal cancer (CRC). First, we built a cDNA display library by cloning a cDNA library from CRC cell line HT-29 for expression as a fusion protein with a filamentous phage minor coat protein, pVI. This cDNA display library was then enriched on pooled sera from CRC patients who had undergone active specific immunization with autologous tumor. We identified a panel of 19 clones reactive with the serum pool. Seventeen of 19 (89%) clones showed reactivity with one or more of the eight Ag-reactive sera, conversely six of eight (75%) sera were reactive with at least one of the 19 clones. Sequencing revealed that these 19 clones represented 13 different Ags. A detailed serological analysis of the 13 different Ags showed preferential reactivity to sera of cancer patients for six different Ags. Four of these Ags displayed increased serum reactivity after the active specific immunization procedure. Furthermore, one of the six Ags, a novel Ag homologous to HSPC218, showed restricted expression in normal testis, suggesting that it belongs to the cancer-testis Ag family. Some of the Ags we have identified may be candidates for tumor vaccination, for sero-diagnosis of cancer, as prognostic markers, or as probes for monitoring tumor cell-based vaccination trials.

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.

Autoantibodies in cryptogenic fibrosing alveolitis

The pathogenesis of cryptogenic fibrosing alveolitis (CFA) involves injury, an immune/inflammatory response and fibrosis. The cause of the injury is unknown, but the identification of serum autoantibodies makes an autoimmune aetiology attractive. The core study on which this commentary is based used novel cloning and serum screening technologies in order to identify new public and private autoantibodies in sera from 12 patients with CFA. Largely negative conclusions were drawn from that study. However, we suggest that the prevalence of autoantibodies may have been underestimated, that the study was timely and that this approach is worth pursuing further.

Translation initiation factor eIF-4G is immunogenic, overexpressed, and amplified in patients with squamous cell lung carcinoma

BACKGROUND

Recently, the authors reported identification and cloning of several novel immunogenic antigens in squamous cell lung carcinoma. Of 14 corresponding genes, 9 mapped in an amplified chromosomal region with the gene for eIF-4G that was amplified most frequently.

METHODS

Recombinant eIF-4G was expressed in E. coli and screened with sera from patients with squamous cell carcinoma of the lung and of the head and neck. Protein extracts from squamous cell carcinoma tissues were analyzed for eIF-4G expression by Western blot analysis. Mutation analysis was performed using an automatic DNA sequencer.

RESULTS

The authors screened a spectrum of 33 heterologous sera from lung carcinoma patients and detected antibodies against eIF-4G in 5 of these sera (15%). They found no immune response to eIF-4G in 17 sera from squamous cell carcinoma tissues derived from the head and neck. In addition, no antibodies were found to eIF-4G in a group of 17 control sera from individuals without known tumor formation. Sequence analysis of the eIF-4G gave no indication of mutations. To analyze the expression of eIF-4G, a monoclonal antibody was used. Western blot analysis clearly showed overexpression in the tumor tissue compared with the corresponding normal lung tissues.

CONCLUSIONS

The translation initiation factor eIF-4G is the first protein in which the gene shows amplification, has increased expression in a human tumor, and induces an immune response in patients. eIF-4G lends itself as a marker for the diagnosis of and possibly as a future therapeutic target in patients with squamous cell lung carcinoma.

PHF3-specific antibody responses in over 60% of patients with glioblastoma multiforme

Glioblastoma multiforme (GBM), a malignant astrocytic tumour, represents the most frequent tumour of the human brain. Nevertheless, its molecular pathology is not well understood. We utilized the immune system, which contributes to cancer protection, to help identify new GBM-related genes. By screening a human GBM cDNA library with autologous patient serum (SEREX-approach), we isolated a gene termed PHF3 (PHD finger protein 3). The gene product of PHF3 is immunogenic in GBM as tested in an allogenic patient serum screening demonstrating antibodies in 24 of 39 (61.53%) sera, whereas none of the 14 healthy persons had antibodies against PHF3. While previous SEREX studies revealed allogenic antibody responses up to 40%, our results for PHF3 represent the highest reported rate for a specific antibody response. We show that GBM patients with an antibody response against PHF3 show significant better survival than patients without PHF3-specific antibodies. Because the amino acid sequence of PHF3 contains a PHD finger (also termed LAP motif), a TFIIS homology, a proline rich region and nuclear localization signals, it supposedly functions as a transcription factor. A polyclonal antibody generated against PHF3 shows nuclear expression in most investigated formalin-fixed, paraffin embedded tissues. In GBM, PHF3 expression is concentrated in cells surrounding necroses.

p53 autoantibodies in patients with malignant mesothelioma: stability through disease progression

Malignant mesothelioma (MM) generally occurs as a pleural tumour, related to the inhalation of asbestos fibres. It is highly aggressive and largely unresponsive to treatment. The incidence of MM is particularly high in Western Australia because of the extensive blue asbestos mining operations that occurred in the north of the state until 1966. MM is unusual in that mutations in the tumour suppressor gene p53 are rarely observed, whilst over-expression of p53 protein is common. As the level of antibodies directed against p53 is thought to be of prognostic value in some cancers and as MM is known to be immunogenic, we studied a cohort of Western Australian patients to determine the prevalence of anti-p53 antibodies and their value as diagnostic markers or prognostic indicators. 6/88 (7%) of patients had high titres (>2 SD above the mean of controls) of anti-p53 antibodies. There was no correlation between antibody titre and survival. Although 3/38 (8%) of sera obtained from patients exposed to asbestos but prior to a diagnosis of MM contained antibodies, the same proportion of sera obtained from patients exposed to asbestos but who remained disease free also contained antibodies (2/40; 8%). Sera collected sequentially demonstrated a profound temporal stability in the titre of anti-p53 antibodies in patients with MM throughout the course of their illness. These results show that anti-p53 antibodies are observed only at a low frequency in the sera of MM patients and where they do occur, their elicitation is an early event that may be unrelated to antigen load. The occurrence of anti-p53 antibodies does not serve as either a useful prognostic or diagnostic indicator in MM.

Private specificities can dominate the humoral response to self-antigens in patients with cryptogenic fibrosing alveolitis

BACKGROUND

The pathogenetic mechanisms that underlie the interstitial lung disease cryptogenic fibrosing alveolitis (CFA) may involve an immunological reaction to unidentified antigens in the lung, resulting in tissue damage.

METHOD

In order to identify the range of target autoantigens, we used expression cloning, employing serum from an index patient as the probe against an expressed cDNA library that was derived from a tumour cell line. We screened over 5 x 105 recombinants and obtained sequence information on three antigens that had provoked strong responses with immunoglobulin heavy chain class switching, presumably as a consequence of T-cell recognition.

RESULTS

All of the antigens were identifiable by comparison with sequence data from the US National Center for Biotechnology Information. Alanyl tRNA synthetase (ATS) was picked on six occasions; five of these incidences reflected independent recombination events, indicating that the library was not biased. Antibodies to ATS (anti-PL-12) represent the most common reactivity that defines the antisynthetase syndrome, which is typically expressed as polymyositis, dermatomyositis and interstitial lung disease (ILD). The index patient never showed symptoms other than those associated with alveolitis, even though sera obtained from him over a period of 2 years contained antibodies with the same specificity. Autoantibodies to ATS were never detected in serial bleeds from 11 other patients with CFA, and neither did we detect antibodies to the other two antigens identified from the serum of the index patient.

CONCLUSION

The humoral response in patients with CFA can be dominated by autoantibodies with private specificities. This suggests that the antibodies are epiphenomenal and are a secondary feature of tissue damage induced by some other mechanism.