Constitutive secretion of bioactive transforming growth factor beta 1 by small cell lung cancer cell lines

MiR-146b-5p/SEMA3G regulates epithelial-mesenchymal transition in clear cell renal cell carcinoma

OBJECTIVE

The primary purpose was to unveil how the miR-146b-5p/SEMA3G axis works in clear cell renal cell carcinoma (ccRCC).

METHODS

ccRCC dataset was acquired from TCGA database, and target miRNA to be studied was further analyzed using survival analysis. We performed miRNA target gene prediction through the database, and those predicted miRNAs were intersected with differential mRNAs. After calculating the correlation between miRNAs and mRNAs, we completed the GSEA pathway enrichment analysis on mRNAs. MiRNA and mRNA expression was examined by qRT-PCR. Western blot was introduced to detect SEMA3G, MMP2, MMP9 expression, epithelial-mesenchymal transition (EMT) marker proteins, and Notch/TGF-β signaling pathway-related proteins. Targeted relationship between miRNA and mRNA was validated using a dual-luciferase test. Transwell assay was employed to assess cell migration and invasion. Wound healing assay was adopted for evaluation of migration ability. The effect of different treatments on cell morphology was observed by a microscope.

RESULTS

In ccRCC cells, miR-146b-5p was remarkably overexpressed, yet SEMA3G was markedly less expressed. MiR-146b-5p was capable of stimulating ccRCC cell invasion, migration and EMT, and promoting the transformation of ccRCC cell morphology to mesenchymal state. SEMA3G was targeted and inhibited via miR-146b-5p. MiR-146b-5p facilitated ccRCC cell migration, invasion, morphology transforming to mesenchymal state and EMT process by targeting SEMA3G and regulating Notch and TGF-β signaling pathways.

CONCLUSION

MiR-146b-5p regulated Notch and TGF-β signaling pathway by suppressing SEMA3G expression, thus promoting the growth of ccRCC cells, which provides a possible target for ccRCC therapy and prognosis prediction.

Advances in the Lung Cancer Immunotherapy Approaches

Despite the progress in the comprehension of LC progression, risk, immunologic control, and treatment choices, it is still the primary cause of cancer-related death. LC cells possess a very low and heterogeneous antigenicity, which allows them to passively evade the anticancer defense of the immune system by educating cytotoxic lymphocytes (CTLs), tumor-infiltrating lymphocytes (TILs), regulatory T cells (Treg), immune checkpoint inhibitors (ICIs), and myeloid-derived suppressor cells (MDSCs). Though ICIs are an important candidate in first-line therapy, consolidation therapy, adjuvant therapy, and other combination therapies involving traditional therapies, the need for new predictive immunotherapy biomarkers remains. Furthermore, ICI-induced resistance after an initial response makes it vital to seek and exploit new targets to benefit greatly from immunotherapy. As ICIs, tumor mutation burden (TMB), and microsatellite instability (MSI) are not ideal LC predictive markers, a multi-parameter analysis of the immune system considering tumor, stroma, and beyond can be the future-oriented predictive marker. The optimal patient selection with a proper adjuvant agent in immunotherapy approaches needs to be still revised. Here, we summarize advances in LC immunotherapy approaches with their clinical and preclinical trials considering cancer models and vaccines and the potential of employing immunology to predict immunotherapy effectiveness in cancer patients and address the viewpoints on future directions. We conclude that the field of lung cancer therapeutics can benefit from the use of combination strategies but with comprehension of their limitations and improvements.

Infiltrating T lymphocytes in the tumor microenvironment of small cell lung cancer: a state of knowledge review

Immune checkpoint inhibitors (ICIs) have brought new hope for the treatment of patients with small cell lung cancer (SCLC) over the past decades. However, the overall response rate is limited, and is lower than that in non-small cell lung cancer (NSCLC). This is in part because of the lack of pre-existing tumor-infiltrating T lymphocytes (TITLs), especially cytotoxic T cells (CTLs), in the SCLC tumor microenvironment (TME), resulting in insufficient anti-tumor immune response. To unleash the full potential of ICIs, the trafficking and infiltration of TITLs to the tumor is necessary and tightly regulated, the highly immunosuppressive tumor microenvironment blunts the infiltration and function of TITLs that reach the tumor in SCLC. Here, we review the characteristics of TITLs, the effects of various factors on T cell infiltration, and possible strategies to restore or promote T cell infiltration in the TME of SCLC.

Identification of a prognostic immune-related signature for small cell lung cancer

Purpose

As a subgroup of lung cancer, small cell lung cancer (SCLC) is characterized by a short tumor doubling time, high rates of early occurred distant cancer spread, and poor outcomes. Despite its exquisite sensitivity to chemotherapy and radiotherapy, acquired drug resistance and tumor progression are typical. This study aimed to develop a robust signature based on immune‐related genes to predict the outcome of patients with SCLC.

Methods

The expression data of 77 SCLC patients from George's cohort were divided into training set and testing set, and 1534 immune‐related genes from ImmPort database were used to generate and validate the signature. Cox proportional hazards and the Kaplan–Meier analysis were used for developing and testing the prognostic signature. Single‐sample gene set enrichment analysis was used to determine immune cell infiltration phenotypes.

Results

A 10‐gene model comprising NR3C1, NR1D2, TANK, ARAF, HDGF, INHBE, LRSAM1, PLXNA1, PML, and SP1 with the highest frequency after 1000 interactions, was chosen to construct immune‐related signature. This signature showed robust predictive value for SCLC patients’ survival in both training and testing sets. This signature was weakly associated with the clinic pathological values like TNM stage. Furthermore, patients with low risk presented with activation of immune signal pathways, and specific immune cell infiltration with high levels of CD56^bright NK cells but low levels of CD8⁺ T cells, mast cells, and helper T cells.

Conclusion

The present study developed immune‐related signature that may help predict the prognosis of SCLC patients, which reflects an unappreciated level of heterogeneity of immunophenotype associated with diverse prognosis for specific subsets in this highly lethal cancer type.

DCision-making in tumors governs T cell anti-tumor immunity

The exploitation of T cell-based immunotherapies and immune checkpoint blockade for cancer treatment has dramatically shifted oncological treatment paradigms and broadened the horizons of cancer immunology. Dendritic cells have emerged as the critical tailors of T cell immune responses, which initiate and coordinate anti-tumor immunity. Importantly, genetic alterations in cancer cells, cytokines and chemokines produced by cancer and stromal cells, and the process of tumor microenvironmental regulation can compromise dendritic cell-T cell cross-talk, thereby disrupting anti-tumor T cell responses. This review summarizes how T cell activation is controlled by dendritic cells and how the tumor microenvironment alters dendritic cell properties in the context of the anti-tumor immune cycle. Furthermore, we will highlight therapeutic options for tailoring dendritic cell-mediated decision-making in T cells for cancer treatment.

Understanding the Complexity of the Tumor Microenvironment in K-ras Mutant Lung Cancer: Finding an Alternative Path to Prevention and Treatment

Kirsten rat sarcoma viral oncogene (K-ras) is a well-documented, frequently mutated gene in lung cancer. Since K-ras regulates numerous signaling pathways related to cell survival and proliferation, mutations in this gene are powerful drivers of tumorigenesis and confer prodigious survival advantages to developing tumors. These malignant cells dramatically alter their local tissue environment and in the process recruit a powerful ally: inflammation. Inflammation in the context of the tumor microenvironment can be described as either antitumor or protumor (i.e., aiding or restricting tumor progression, respectively). Many current treatments, like immune checkpoint blockade, seek to augment antitumor inflammation by alleviating inhibitory signaling in cytotoxic T cells; however, a burgeoning area of research is now focusing on ways to modulate and mitigate protumor inflammation. Here, we summarize the interplay of tumor-promoting inflammation and K-ras mutant lung cancer pathogenesis by exploring the cytokines, signaling pathways, and immune cells that mediate this process.

Potential immune escape mechanisms underlying the distinct clinical outcome of immune checkpoint blockades in small cell lung cancer

Small cell lung cancer (SCLC) is one of the deadliest cancer types in the world. Despite the high response rate to frontline platinum-containing doublets, relapse is inevitable for the majority of patients and the prognosis is poor. Topotecan, which has limited efficacy, has remained the standard second-line therapy for approximately three decades. Although SCLC has a high mutation burden, the clinical efficacy of immune checkpoint blockades (ICBs) in SCLC is far less pronounced than that in non-small cell lung cancer (NSCLC). Only atezolizumab in combination with chemotherapy improved overall survival over chemotherapy alone in the phase III CheckMate 133 trial and has recently received FDA approval as first-line therapy. Most studies concerning ICBs in SCLC are limited to early-phase studies and found that ICBs were not superior to traditional chemotherapy. Why is there such a large difference between SCLC and NSCLC? In this review, comparative analyses of previous studies indicate that SCLC is even more immunodeficient than NSCLC and the potential immune escape mechanisms in SCLC may involve the low expression of PD-L1 and the downregulation of major histocompability complex (MHC) molecules and regulatory chemokines. In consideration of these immune dysfunctions, we speculate that chemotherapy and radiotherapy prior to immunotherapy, the combination of ICBs with antiangiogenic treatment, and selecting tumor mutation burden in combination with PD-L1 expression as biomarkers could be promising strategies to improve the clinical efficacy of immunotherapy for SCLC.

Comparing progression molecular mechanisms between lung adenocarcinoma and lung squamous cell carcinoma based on genetic and epigenetic networks: big data mining and genome-wide systems identification

Non-small-cell lung cancer (NSCLC) is the predominant type of lung cancer in the world. Lung adenocarcinoma (LADC) and lung squamous cell carcinoma (LSCC) are subtypes of NSCLC. We usually regard them as different disease due to their unique molecular characteristics, distinct cells of origin and dissimilar clinical response. However, the differences of genetic and epigenetic progression mechanism between LADC and LSCC are complicated to analyze. Therefore, we applied systems biology approaches and big databases mining to construct genetic and epigenetic networks (GENs) with next-generation sequencing data of LADC and LSCC. In order to obtain the real GENs, system identification and system order detection are conducted on gene regulatory networks (GRNs) and protein-protein interaction networks (PPINs) for each stage of LADC and LSCC. The core GENs were extracted via principal network projection (PNP). Based on the ranking of projection values, we got the core pathways in respect of KEGG pathway. Compared with the core pathways, we found significant differences between microenvironments, dysregulations of miRNAs, epigenetic modifications on certain signaling transduction proteins and target genes in each stage of LADC and LSCC. Finally, we proposed six genetic and epigenetic multiple-molecule drugs to target essential biomarkers in each progression stage of LADC and LSCC, respectively.

The role of Foxp3 and Tbet co-expressing Treg cells in lung carcinoma

Despite the opposite roles of Tbet and Foxp3 in the immune system as well as in tumour biology, recent studies have demonstrated the presence of of CD4⁺ T cells, expressing both, Tbet and Foxp3. Although Tbet⁺Foxp3⁺ T cells are currently a subject of intense research, less is known about their biological function especially in cancer. Here we found a considerable accumulation of Tbet⁺Foxp3⁺CD4⁺ T cells, mediated by the immunosuppressive cytokine TGFβ in the lungs of tumour bearing mice. This is in line with previous studies, demonstrating the important role of TGFβ for the immunopathogenesis of cancer. By gathering results both in murine model and in human disease, we demonstrate that, the conversion of IFNγ producing anti-tumoral T-bet+Th1 CD4+ T cells into immunosuppressive Tbet and Foxp3-PD1 co-expressing regulatory cells could represent an additional important mechanism of TGFβ-mediated blockade of anti-tumour immunity.

Targeting myeloid cells in the tumor sustaining microenvironment

Myeloid cells are the most abundant cells in the tumor microenvironment (TME). The tumor recruits and modulates endogenous myeloid cells to tumor-associated macrophages (TAM), dendritic cells (DC), myeloid-derived suppressor cells (MDSC) and neutrophils (TAN), to sustain an immunosuppressive environment. Pathologically overexpressed mediators produced by cancer cells like granulocyte-macrophage colony-stimulating- and vascular endothelial growth factor induce myelopoiesis in the bone marrow. Excess of myeloid cells in the blood, periphery and tumor has been associated with tumor burden. In cancer, myeloid cells are kept at an immature state of differentiation to be diverted to an immunosuppressive phenotype. Here, we review human myeloid cells in the TME and the mechanisms for sustaining the hallmarks of cancer. Simultaneously, we provide an introduction into current and novel therapeutic approaches to redirect myeloid cells from a cancer promoting to a rather inflammatory, cancer inhibiting phenotype. In addition, the role of platelets for tumor promotion is discussed.

Reduced incidence of lung cancer in patients with idiopathic pulmonary fibrosis treated with pirfenidone

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a disease with a worse prognosis than some types of cancer. In patients with IPF, lung cancer is critical because of the associated high mortality rate from its progression and fatal complications from anticancer treatments. Therefore, preventing lung cancer in patients with IPF is primordial. Pirfenidone is an anti-fibrotic agent that reduces the decline in forced vital capacity. This study aimed to assess the effect of pirfenidone in the development of lung cancer in patients with IPF.

METHODS

Data from 261 patients with IPF with and without pirfenidone were retrospectively reviewed, and the incidence of lung cancer was analyzed.

RESULTS

In the pirfenidone group, the incidence of lung cancer was significantly lower than in the non-pirfenidone group (2.4% vs. 22.0%, P < 0.0001). Multivariate Cox proportional hazards regression analysis demonstrated that pirfenidone decreased the risk of lung cancer (hazard ratio, 0.11; 95% confidence interval, 0.03 to 0.46; P = 0.003), whereas coexisting emphysema increased the incidence of lung cancer (hazard ratio, 3.22; 95% confidence interval, 1.35 to 7.70; P = 0.009).

CONCLUSIONS

Pirfenidone might correlate with a decreased risk of lung cancer in patients with IPF. However, no definite conclusion can be drawn from this retrospective study, and a multicenter, prospective cohort study is still warranted to confirm the effect of pirfenidone on lung cancer in patients with IPF.

Transforming growth factor-β: A therapeutic target for cancer

Transforming growth factor-β (TGF-β) regulates cell growth and differentiation, apoptosis, cell motility, extracellular matrix production, angiogenesis, and cellular immunity. It has a paradoxical role in cancer. In the early stages it inhibits cellular transformation and prevents cancer progression. In later stages TGF-β plays a key role in promoting tumor progression through mainly 3 mechanisms: facilitating epithelial to mesenchymal transition, stimulating angiogenesis and inducing immunosuppression. As a result of its opposing tumor promoting and tumor suppressive abilities, TGF-β and its pathway has represented potential opportunities for drug development and several therapies targeting the TGF-β pathway have been identified. This review focuses on identifying the mechanisms through which TGF-β is involved in tumorigenesis and current therapeutics that are under development.

Mechanisms of immune response regulation in lung cancer

Lung cancer is a leading cause of cancer deaths. As a solid tumor with low antigenicity and heterogenic phenotype lung cancer evades host immune defense. The cytotoxic anticancer effect is suppressed by a complex mechanism in tumor microenvironment. The population of regulatory T cells (Tregs) plays a crucial role in this inhibition of immune response. Tregs are defined by presence of forkhead box P3 (Foxp3) molecule. The high expression of Foxp3 was found in lung cancer cells and in tumor infiltrating lymphocytes (TIL). Cytotoxic T-lymphocyte antigen 4 (CTLA4) is constitutively expressed on Tregs and suppresses T cell activation. The elevated CTLA4 expression in lymphocytes in patients with lung cancer was found. Recently the antibodies blocking CTLA4 showed some clinical efficacy in patients with lung cancer. Cancer cells and immune cells release many cytokines capable to show suppressive immune effect in cancer microenvironment. The most active are transforming growth factorβ (TGFβ) and IL-10. The pleiotropic function of Th17 population is TGFβ related. The myeloid lineage of suppressor cells in lung cancer is represented by tumor associated macrophages (TAM) with phenotype of M2 macrophages and some regulatory properties with releasing amounts of IL-10 and TGFβ. The myeloid derived suppressor cells (MDSCs) control cytotoxic T cell activity in mechanisms which are highly dependent on the context of tumor environment. The mechanisms of anticancer immune response regulation need further investigation as an important target to new way of treatment.

Bioinformatic approaches to augment study of epithelial-to-mesenchymal transition in lung cancer

Bioinformatic approaches are intended to provide systems level insight into the complex biological processes that underlie serious diseases such as cancer. In this review we describe current bioinformatic resources, and illustrate how they have been used to study a clinically important example: epithelial-to-mesenchymal transition (EMT) in lung cancer. Lung cancer is the leading cause of cancer-related deaths and is often diagnosed at advanced stages, leading to limited therapeutic success. While EMT is essential during development and wound healing, pathological reactivation of this program by cancer cells contributes to metastasis and drug resistance, both major causes of death from lung cancer. Challenges of studying EMT include its transient nature, its molecular and phenotypic heterogeneity, and the complicated networks of rewired signaling cascades. Given the biology of lung cancer and the role of EMT, it is critical to better align the two in order to advance the impact of precision oncology. This task relies heavily on the application of bioinformatic resources. Besides summarizing recent work in this area, we use four EMT-associated genes, TGF-β (TGFB1), NEDD9/HEF1, β-catenin (CTNNB1) and E-cadherin (CDH1), as exemplars to demonstrate the current capacities and limitations of probing bioinformatic resources to inform hypothesis-driven studies with therapeutic goals.

Emerging evidence of epithelial-to-mesenchymal transition in lung carcinogenesis

The epithelial-to-mesenchymal transition (EMT) is a developmental programme that regulates embryonic morphogenesis and involves significant morphological and molecular changes in cells. Experimental models have revealed that EMT also contributes to various malignant features of cancer cells, including motile, invasive, anti-apoptotic and stem-like phenotypes. Clinically, correlative studies have indicated that mesenchymal-like features of tumour cells are associated with poor tumour differentiation as well as worse patient prognosis. Nevertheless, due to its transitory nature, demonstration of an actual occurrence of EMT during human carcinogenesis is challenging, and most of the evidence to date has been limited to breast and colorectal cancers. However, recent studies suggest that EMT may occur during lung cancer development, although such evidence is still limited. We propose three approaches for obtaining direct evidence of EMT in human cancers and use these criteria to review the available data. We suggest that multiple intrinsic and extrinsic factors cooperatively induce EMT in lung cancer. Intrinsic factors include oncogenic genetic changes such as mutant K-RAS. Extrinsic factors are associated with a tumour microenvironment that is inflammatory and hypoxic. The induction of EMT is primarily mediated by various EMT-inducing transcription factors that suppress E-cadherin expression, including SLUG and ZEB1. miR-200 family expression can reverse EMT by suppressing EMT- inducing transcription factors. Obviously, more data demonstrating the clinical relevance of EMT in lung cancer are required, and further elucidation of how EMT is regulated in lung cancer will enable us to develop novel therapeutics that specifically target molecules with critical roles in EMT.

Lung cancer: a classic example of tumor escape and progression while providing opportunities for immunological intervention

Lung cancers remain one of the most common and deadly cancers in the world today (12.5% of newly diagnosed cancers) despite current advances in chemo- and radiation therapies. Often, by the time these tumors are diagnosed, they have already metastasized. These tumors demonstrate the classic hallmarks of cancer in that they have advanced defensive strategies allowing them to escape various standard oncological treatments. Immunotherapy is making inroads towards effectively treating other fatal cancers, such as melanoma, glioblastoma multiforme, and castrate-resistant prostate cancers. This paper will cover the escape mechanisms of bronchogenic lung cancer that must be overcome before they can be successfully treated. We also review the history of immunotherapy directed towards lung cancers.

Immunotherapies for non-small-cell lung cancer and mesothelioma

Non-small-cell lung cancer and mesothelioma are thoracic malignancies, which in their advanced stages are incurable and have poor prognosis. Advances in our understanding of immune responses to tumours, tumour immunosuppression mechanisms, and tumour-specific shared antigens enabled successful early clinical trials of several specific and non-specific immunotherapies. For non-small-cell lung cancer, phase 3 clinical trial results of Toll-like receptor agonists show little promise. However, ongoing phase 3 trials are assessing melanoma-associated antigen A3 vaccine, liposomal BLP25, belagenpumatucel-L, and talactoferrin. In mesothelioma, immunotherapies being investigated include dendritic cell-based and Listeria-based vaccines, and allogeneic tumour cell and WT1 analogue peptide vaccines. Selection of appropriate patients and disease stages for immunotherapy, measurement of tumour-specific immune responses, and understanding the association between immune and clinical responses are some of the major challenges for the development of immunotherapies for these malignancies.

Lung cancer vaccines

To date, in lung cancer, early attempts to modulate the immune system via vaccine-based therapeutics have been unsuccessful. An improved understanding of tumor immunology has facilitated the production of more sophisticated lung cancer vaccines. It is anticipated that it will likely require multiple epitopes of a diverse set of genes restricted to multiple haplotypes to generate a truly effective vaccine that is able to overcome the various immunologic escape mechanisms that tumors employ. Other issues to overcome include optimal patient selection, which adjuvant agent to use, and how to adequately monitor for an immunologic response. This review discusses the most promising vaccination strategies for non-small cell lung cancer including the allogeneic tumor cell vaccine belagenpumatucel-L, which is a mixture of 4 allogeneic non-small cell lung cancer cell lines genetically modified to secrete an antisense oligonucleotide to transforming growth factor β2 and 3 other target protein-specific vaccines designed to induce responses against melanoma-associated antigen A3, mucin 1, and epidermal growth factor.

Tumor associated regulatory dendritic cells

Immune effector and regulatory cells in the tumor microenvironment are key factors in tumor development and progression as the pathogenesis of cancer vitally depends on the multifaceted interactions between various microenvironmental stimuli provided by tumor-associated immune cells. Immune regulatory cells participate in all stages of cancer development from the induction of genomic instability to the maintenance of intratumoral angiogenesis, proliferation and spreading of malignant cells, and formation of premetastatic niches in distal tissues. Dendritic cells in the tumor microenvironment serve as a double-edged sword and, in addition to initiating potent anti-tumor immune responses, may mediate genomic damage, support neovascularization, block anti-tumor immunity and stimulate cancerous cell growth and spreading. Regulatory dendritic cells in cancer may directly and indirectly maintain antigen-specific and non-specific T cell unresponsiveness by controlling T cell polarization, MDSC and Treg differentiation and activity, and affecting specific microenvironmental conditions in premalignant niches. Understanding the mechanisms involved in regulatory dendritic cell polarization and operation and revealing pharmacological means for harnessing these pathways will provide additional opportunities for modifying the tumor microenvironment and improving the efficacy of different therapeutic approaches to cancer.

Targeting the immune system in non-small-cell lung cancer: bridging the gap between promising concept and therapeutic reality

Developing effective immunotherapy for lung cancer is a daunting but hugely attractive challenge. Until recently, non-small-cell lung cancer (NSCLC) was thought of as a nonimmunogenic tumor, but there is now evidence highlighting the integral role played by both inflammatory and immunologic responses in lung carcinogenesis. Despite recent encouraging preclinical and phase I/II data, there are a paucity of phase III trials showing a clear clinical benefit for vaccines in lung cancer. There are many difficulties to overcome before the development of a successful therapy. Perhaps a measurable immune response may not translate into a clinically meaningful or radiologic response. Patient selection may also be a problem for ongoing clinical studies. The majority of trials for lung cancer vaccines are focused on patients with an advanced stage of the disease; however, the ideal candidates may be patients with a lower tumor burden and stage I or II disease. Selecting the exact antigens to target is also difficult. It will likely require multiple epitopes of a diverse set of genes restricted to multiple haplotypes to generate a truly effective vaccine that is able to overcome the various immunologic escape mechanisms that tumors use. This review discusses the most promising active immunotherapy using protein/peptide vaccines, whole cell vaccines, and dendritic cell vaccines and examines current phase I and II clinical trial data on some novel nonspecific immunomodulating agents.

Transforming growth factor-beta: a target for cancer therapy

Transforming growth factor-beta (TGF-beta) is a pleiotropic growth factor that regulates cell growth and differentiation, apoptosis, cell motility, extracellular matrix production, angiogenesis, and cellular immune responses. TGF-beta demonstrates paradoxical action whereby it can function to suppress early tumorigenesis; however, it can also facilitate malignant transformation and stimulate tumor growth by manipulating a more hospitable environment for tumor invasion and the development of metastases. Given the integral role of TGF-beta in transformation and cancer progression, various components of the TGF-beta signaling pathway offer potentially attractive therapeutic targets for cancer treatment. This review focuses on the role of TGF-beta in cancer and discusses both small and large molecule drugs currently in development that target TGF-beta, its receptor and important down stream steps along its signaling pathway.

Transforming growth factor-beta and the immune response to malignant disease

Transforming growth factor-beta (TGF-beta) is a key player in malignant disease through its actions on host tissues and cells. Malignant cells often secrete large amounts of TGF-beta that act on nontransformed cells present in the tumor mass as well as distal cells in the host to suppress antitumor immune responses creating an environment of immune tolerance, augmenting angiogenesis, invasion and metastasis, and increasing tumor extracellular matrix deposition. Cells of the innate immune system contribute to the high concentrations of TGF-beta found in tumor masses. In addition, dendritic cell subpopulations secreting TGF-beta contribute to the generation of regulatory T cells that actively inhibit the activity of other T cells. Elevated levels of plasma TGF-beta are associated with advanced stage disease and may separate patients into prognostically high-risk populations. Anti-TGF-beta therapy could reverse the immunosuppressive effects of this cytokine on the host as well as decrease extracellular matrix formation, decrease angiogenesis, decrease osteolytic activity, and increase the sensitivity of the malignant cells to cytotoxic therapies and immunotherapies. Phase I clinical trials of an inhibitor of TGF-beta receptor type I kinase activity and a TGF-beta neutralizing antibody are under way.

Intratumoral cytokines/chemokines/growth factors and tumor infiltrating dendritic cells: friends or enemies?

The tumor microenvironment consists of a variable combination of tumor cells, stromal fibroblasts, endothelial cells and infiltrating leukocytes, such as macrophages, T lymphocytes, and dendritic cells. A variety of cytokines, chemokines and growth factors are produced in the local tumor environment by different cells accounting for a complex cell interaction and regulation of differentiation, activation, function and survival of multiple cell types. The interaction between cytokines, chemokines, growth factors and their receptors forms a comprehensive network at the tumor site, which is primary responsible for overall tumor progression and spreading or induction of antitumor immune responses and tumor rejection. Although the general thought is that dendritic cells are among the first cells migrating to the tumor site and recognizing tumor cells for the induction of specific antitumor immunity, the clinical relevance of dendritic cells at the site of the tumor remains a matter of debate regarding their role in the generation of successful antitumor immune responses in human cancers. While several lines of evidence suggest that intratumoral dendritic cells play an important role in antitumor immune responses, understanding the mechanisms of dendritic cell/tumor cell interaction and modulation of activity and function of different dendritic cell subtypes at the tumor site is incomplete. This review is limited to discussing the role of intratumoral cytokine network in the understanding immunobiology of tumor-associated dendritic cells, which seems to possess different regulatory functions at the tumor site.

Role of tumor-derived transforming growth factor-beta1 (TGF-beta1) in site-dependent tumorigenicity of murine ascitic lymphosarcoma

An ascitic lymphosarcoma (LS-A) of Swiss mice that regressed spontaneously on subcutaneous (s.c.) transplantation was investigated for the mechanism of its progressive growth and host mortality on intraperitoneal (i.p.) transplantation. In vitro studies indicated significant inhibition of LS-A proliferation seeded at higher cell density (>10(4)/ml). Culture supernatants of LS-A caused bi-modal growth effects, the early supernatants (24 h) caused stimulation and the late (72 h) supernatants inhibited LS-A proliferation. The 72-h supernatants also suppressed T and B cell response to mitogens in a dose-dependent manner. Pan anti-transforming growth factor-beta antibody abrogated the inhibitory effects of supernatants. The supernatants contained both latent as well as bio-active form of transforming growth factor-beta1 (TGF-beta1) as determined by ELISA. Mice bearing i.p. ascites tumor had elevated serum TGF-beta1, hemoglobulinemia, splenic lymphopenia, impaired response of the T cells to mitogen and reduced expression of transferrin receptor (CD71) on the bone marrow cells. However, mice which rejected s.c. transplants, did not show significant changes in these parameters. Our studies indicated profound influence of site of tumor growth on tumor progression and host immune system mediated by tumor-derived TGF-beta1. It is possible that human tumors which secrete TGF-beta1 may exhibit similar patho-physiological effects in the host depending on the anatomical site of the tumor.

Transforming growth factor beta can be a parameter of aggressiveness of pT1 colorectal cancer

AIM: To evaluate the significance of transforming growth factor beta (TGF β) expression, in correlation with histopathological parameters, at the front of invasion in T1 colorectal cancer (CRC) and presence of metastases.

METHODS: TGF β immunohistochemical expression was studied in 34 specimens of colorectal adenocarcinomas (pT1). A three-step avidin-biotinylated immuno-peroxidase (ABCu-NCL) staining technique was performed on 4-µm paraffin-embedded tissue sections with a monoclonal antibody to TGF β (Novocastra, NCL-TGFB, clone TGFB 17, dilution 1:40).

RESULTS: Seventeen (50%) out of 34 lesions were positive for TGF β expression. The TGF β-positive rate in patients with vascular invasion was significantly higher than in those without vascular invasion (11/14 cases, P<0.01, P = 0.005). The TGF β-positive rate was observed in 91.7% of patients with presence of tumor budding at the front of invasion (11/12 cases, P<0.01, P = 0.0003). A statistically significant correlation was found between the presence of lymph node metastases and positive expression of TGF β (14/16 cases, P<0.01, P = 0.0001). We also observed that the TGF β-positive rates in groups with distant and non-distant metastases were 92.8% and 20% respectively, and a significant correlation between TGF β expression and distant metastasis was shown (P<0.01, P = 0.00003).

CONCLUSION: The evaluation of TGF β expression of protein in association with histological parameters can be used as a parameter of the aggressiveness of pT1 CRC.

Validation of molecular and immunological factors with predictive importance in lung cancer

Histological classification and staging are cornerstones of diagnosis in lung cancer. Treatment options have been enriched in the last few years by the development of a number of new drugs, and therapy is now increasingly being carried out within multimodal concepts and at earlier stages. Still, outcome of the disease is far from satisfactory and progress in clinical and preclinical research is time-consuming. With the whole variety of potent new therapeutic compounds including classical cytostatics and biological factors at hand, many now believe that a clear improvement of treatment results will be derived from a better understanding of the biology of these tumours and a resulting improvement of diagnosis. Biological factors reflecting the underlying tumour biology and aspects of clinically important pathomechanisms may not only better predict outcome of the disease but also of its treatment, serving as surrogate markers for a more appropriate general intensification of therapy and ideally for specific "targeted" interventions. This article describes the different insights in the biology of these tumours in relation with the representing surrogate markers, and opens routes to possible diagnostic and therapeutic consequences.

Tumor-derived TGF-beta reduces the efficacy of dendritic cell/tumor fusion vaccine

Dendritic cell (DC)-based antitumor vaccine is a novel cancer immunotherapy that is promising for reducing cancer-related mortality. However, results from early clinical trials were suboptimal. A possible explanation is that many tumors secrete immunosuppressive factors such as TGF-beta, which may hamper host immune response to DC vaccine. In this study, we demonstrated that TGF-beta produced by tumors significantly reduced the potency of DC/tumor fusion vaccines. TGF-beta-secreting (CT26-TGF-beta) stable mouse colon cancer cell lines were generated using a retroviral vector expressing TGF-beta. A non-TGF-beta-secreting (CT26-neo) cell line was generated using an empty retroviral vector. The efficacies of DC/tumor fusion vaccines were assessed in vitro and in vivo. DC/CT26-TGF-beta fusion cells failed to induce a strong T cell proliferative response in vitro, mainly due to the effect of TGF-beta on T cell responsiveness rather than DC stimulatory capability. Animals vaccinated with DC/CT26-TGF-beta fusion vaccine had lower tumor-specific CTL activity and had significantly lower survival after tumor challenge as compared with animals immunized with DC/CT26-neo hybrids (45 vs 77%, p < 0.05). Ex vivo exposure of DCs to TGF-beta did not appear to lessen the efficacy of DC vaccine. These data suggest that tumor-derived TGF-beta reduces the efficacy of DC/tumor fusion vaccine via an in vivo mechanism. Neutralization of TGF-beta produced by the fusion cells may enhance the effectiveness of DC-based immunotherapy.

Active versus passive anti-cytokine antibody therapy against cytokine-associated chronic diseases

Current therapeutic vaccine trials in major chronic diseases including AIDS, cancer, allergy and autoimmunity, target antigenic pathogens but not the pathogenic stromal cytokines which can be major sources of histopathologic processes. Considering that the limited efficacy of these vaccines has been ascribed to local pathogen-induced cytokine dysfunction, we propose to antagonize pathogenic cytokine(s) by high affinity neutralizing auto-Abs triggered by specific anti-cytokine vaccines. As anticipated by theoretical considerations, animal experiments and initial clinical trials showed that anti-cytokine immunization was safe, well tolerated and triggered transient high titers Abs neutralizing pathogenic cytokines but, in contrast to conventional vaccines, no relevant cellular response was observed. Advantages of active versus passive anti-cytokine Ab therapy, particularly for long-term treatments, as those required in AIDS, cancer, allergy and autoimmunity include greater ease of maintaining high Ab titers, lack of anti-antibody responses and low cost.

Prognostic significance of cytokine modulation in non-small cell lung cancer

Increased production of immunosuppressive interleukin-10 (IL-10) by non-small cell lung cancer (NSCLC) and increased serum IL-10 concentrations in NSCLC-patients have recently been correlated to reduced survival. We earlier demonstrated suppression of IL-2 secretion in whole blood cell cultures of NSCLC-patients. We now analyzed the influence of IL-2 secretion on survival in NSCLC-patients and the influence of IL-10 on IL-2 secretion. The correlation of the IL-2 producing ability of whole blood cells in response to PHA in 90 NSCLC-patients at the time of diagnosis to survival was calculated by Crit-level, the Kaplan-Meier method and the log-rank test. With a cut-off value of IL-2 production of 1,100 pg/ml by whole blood cells the difference in survival was significant with a p-value of 0.014. In the group with high and low IL-2, median survival was 14.1 and 9.7 months, respectively. In the subgroup of 33 surgically-treated patients the difference in survival was significant with a p-value of 0.011. In 14 patients with surgical resection of the tumor and high IL-2 at diagnosis and 19 patients with surgical resection, but low IL-2 at diagnosis, median survival was 86.2 and 11.3 months, respectively. Secretion of IL-2 in whole blood cell cultures from healthy individuals was inhibited in a dose-dependent manner upon addition of IL-10. Taken together, suppression of IL-2 secretion has prognostic significance for survival of NSCLC-patients and may be mediated by tumor-derived IL-10.

Cytokine secretion: clinical relevance of immunosuppression in non-small cell lung cancer

Increased production of immunosuppressive IL-10 by non-small cell lung cancer (NSCLC) and increased plasma IL-10 concentrations in NSCLC-patients have recently been correlated to reduced survival. We earlier demonstrated suppression of IL-2 secretion in NSCLC-patients. We now analyzed the influence of IL-2 suppression on survival in NSCLC-patients and influence of IL-10 on IL-2 secretion. The correlation of the IL-2-concentration in whole blood cell cultures from 90 NSCLC-patients at the time of diagnosis to survival was analyzed by using crit-level, the Kaplan-Meier method and the log-rank test. IL-2 secretion capacity at the time of diagnosis significantly influenced survival in NSCLC-patients. With a cut-off value for IL-2 of 1100 pg/ml, the difference in survival was significant with a P-value of 0.014 in the whole patient group. In the subgroup of surgically treated patients (n=33), survival was different with a P-value of 0.011. Moreover, secretion of IL-2 was inhibited in a dose-dependent manner upon addition of IL-10 in whole blood cell cultures from normal individuals. Thus, suppression of IL-2 secretion is predictive for survival of NSCLC-patients and may be mediated by tumor-derived IL-10.

The role of extracellular matrix in small-cell lung cancer

Lung cancer is the most common fatal malignant disease in the western world, accounting for 42,000 deaths each year in the UK alone. Small-cell lung cancer (SCLC), accounts for 25% of all lung cancers. It is a particularly aggressive form of the disease, characterised by widespread metastases and the development of resistance to chemotherapy. Even with combination chemotherapy and radiotherapy treatments, the 5-year survival is only about 5%. We review recent insights into the mechanisms underlying the development of metastases and resistance to chemotherapeutic agents in SCLC, focusing on the role of the extracellular matrix (ECM). We discuss the regulation of the interactions between cells and the ECM and the effects of these interactions on cellular phenotypes, together with some of the new approaches for combating drug resistance and metastases in this disease.

Transforming growth factor-beta1 promotes invasiveness after cellular transformation with activated Ras in intestinal epithelial cells

Invasion is a defining event in carcinoma progression. In general, invasive carcinoma is characterized by an epithelial-fibroblastoid conversion associated with loss of cell-cell adhesion receptors such as E-cadherin and beta-catenin. We report here that TGF-beta1 promotes the invasiveness by modulating the alterations of cellular plasticity including a loss of cell-cell contact in Ras-transformed epithelial cells. In order to examine the role of TGF-beta1 in the Ras-induced responses, intestinal epithelial cells expressing a conditionally activated Ha-Ras(Val12) (RIE-iRas cells) were used in this study. Induced expression of activated Ha-Ras(Val12) caused morphologic transformation of the RIE-iRas cells with an increase in vimentin expression and a decrease of E-cadherin levels. There was also redistribution of beta-catenin from the cytoplasm to the nucleus after the induction of Ras. TGF-beta1 treatment enhanced both the decrease in E-cadherin levels and the redistribution of beta-catenin. Interestingly, the activation of Ras markedly decreased the level of TGF-beta receptor type II (TbetaRII) in RIE-iRas cells. However, the expression of plasminogen activator inhibitor-1, which is known to be transcriptionally induced by TGF-beta1, was strongly induced by TGF-beta1 despite the marked downregulation of TbetaRII. The induction of Ha-Ras(Val12) markedly increased the invasiveness in RIE-iRas cells, as evaluated by a collagen type I-coated Boyden-chamber assay, and the Ras-mediated invasiveness was significantly enhanced by TGF-beta1 treatment. Expression of a dominant-negative form of TbetaRII in the RIE-iRas cells abrogated both growth-inhibitory and invasion responses to TGF-beta1. Collectively, these results suggest that TGF-beta1 and oncogenic Ras collaborate in promoting cellular invasiveness in intestinal epithelial cells. The enhancement of invasiveness was correlated with decreased E-cadherin levels and subcellular distribution of beta-catenin. The enhancement of oncogenic Ras-mediated cell transformation by TGF-beta1 occurs via TbetaRII.

Analysis of type T1 and T2 cytokines in patients with prostate cancer

BACKGROUND

It has been proposed that a dysregulation in the balance between type T1 (IL-2, IFN-gamma) and type T2 (IL-4, IL-10) cytokines may be implicated in the development of cancer.

METHODS

We determined the expression of IL-2, IL-4, IL-10, and IFN-gamma in CD4 and CD8 lymphocytes by flow cytometry in 12 patients with prostate cancer and in 7 healthy subjects. In addition to the basal expression of these cytokines, their expression was also determined, following stimulation of lymphocytes with PMA (phorbol 12-mystirate 13 acetate) and ionomycin.

RESULTS

The basal expression of cytokines was scarce, while following stimulation this increased markedly. On the other hand, there was a dysregulation in the balance between T1 and T2 lymphocytes in patients with prostate cancer. To this effect, in relation to healthy subjects, we observed an increase in IL-10 expression and a decrease in IL-2 expression.

CONCLUSIONS

The disequilibrium observed in the balance between type T1 and type T2 cytokines may be implicated in the evolution of neoplastic disease.

Selective suppression of cytokine secretion in whole blood cell cultures of patients with colorectal cancer

We have investigated the secretion of interferon alpha (IFN-alpha), IFN-gamma, interleukin-1alpha (IL-1alpha), IL-1beta, IL-2 and tumour necrosis factor alpha (TNF-alpha) in whole blood cell cultures (WBCCs) of colorectal cancer patients upon mitogen stimulation. Whereas the values for IL-1beta and TNF-alpha remained virtually unchanged in comparison with healthy control subjects, WBCCs of colorectal cancer patients secreted significantly lower amounts of IFN-alpha (P < 0.005), IFN-gamma (P < 0.0001), IL-1alpha (P < 0.0001) and IL-2 (P < 0.05). This reduction correlated with the progression of the disease. The total leucocyte and monocyte population were almost identical in both groups. In contrast, a dramatic depletion of lymphocytes was observed in colorectal cancer patients, which affected both lymphocyte counts (P < 0.0005) and their distribution (P < 0.0001). Our results suggest a selective suppression of cytokines in colorectal cancer patients that is related to tumour burden. Several mechanisms might account for this phenomenon, one of which might be lymphocyte depletion.

Immunotherapy in lung cancer

More research and new treatment options are needed in all stages of lung cancer. To this end immunotherapy needs a revival in view of recent improved technologies and greater understanding of the underlying biology. In this review we discuss mechanisms of tumour immunotherapy, non-specific, specific and adoptive, with particular reference to a direct therapeutic action on all subtypes of lung cancer.

Subcutaneous interleukin-2 as initial therapy for patients with extensive small cell lung cancer: a phase II trial of Cancer and Leukemia Group B

In a prior Cancer and Leukemia Group B (CALGB), 16% of a small cohort of patients with extensive small call lung cancer who had failed to obtain a complete remission with chemotherapy did obtain a complete remission after therapy with interleukin-2 (IL-2). In this current trial, 10 patients with extensive small cell lung cancer who had had no prior therapy were treated with subcutaneous IL-2 as induction therapy and then standard chemotherapy with etoposide/cisplatin. Only one patient experienced an objective response to the IL-2 administered prior to chemotherapy. The factors governing response to IL-2 in the first trial but not in this trial are discussed.

Tumour-derived, endocrine, exogenous and therapeutic factors differentially modulate cytokine secretion in whole blood cell culture

Following our previous results which showed that TGF-beta 1 suppressed the secretion of certain cytokines, we investigated the effects of different endogenous and exogenous factors on cytokine secretion in whole blood cell culture by using an enzyme-linked immunosorbent assay (ELISA) for measurement of cytokine concentrations. Several molecules including dexamethasone, noradrenaline (NA) and ethanol differentially inhibited mitogen-induced cytokine secretion. Dexamethasone and noradrenaline suppressed secretion of IL-2, IFN alpha, IFN gamma, TNF alpha, IL-1 alpha and IL-1 beta. beta-Endorphin and Leu-Enkephalin had no significant influence on cytokine secretion. Suppression of cytokine secretion by TGF-beta 1 was further intensified significantly and dose dependently by addition of noradrenaline. GM-CSF stimulated the secretion of IL-1 alpha, IL-1 beta and TNF gamma, but had no influence on the secretion of IL-2, IFN alpha and IFN gamma. G-CSF, IL-3 and SCF did not significantly influence secretion of all cytokines tested. Thus, endogenous and exogenous factors differentially influence cytokine secretion by immunocompetent cells.

Transforming growth factor-beta in breast cancer: a working hypothesis

Transforming Growth Factor-beta (TGF beta) is the most potent known inhibitor of the progression of normal mammary epithelial cells through the cell cycle. During the early stages of breast cancer development, the transformed epithelial cells appear to still be sensitive to TGF beta-mediated growth arrest, and TGF beta can act as an anti-tumor promoter. In contrast, advanced breast cancers are mostly refractory to TGF beta-mediated growth inhibition and produce large amounts of TGF beta, which may enhance tumor cell invasion and metastasis by its effects on extracellular matrix. We postulate that this seemingly paradoxical switch in the responsiveness of tumor cells to TGF beta during progression is the consequence of the activation of the latent TGF beta that is produced and deposited into the tumor microenvironment, thereby driving the clonal expansion of TGF beta-resistant tumor cells. While tumor cells themselves may activate TGF beta, recent observations suggest that environmental tumor promoters or carcinogens, such as ionizing radiation, can cause stromal fibroblasts to activate TGF beta by epigenetic mechanisms. As the biological effects of the anti-estrogen tamoxifen may well be mediated by TGF beta, this model has a number of important implications for the clinical uses of tamoxifen in the prevention and treatment of breast cancer. In addition, it suggests a number of novel approaches to the treatment of advanced breast cancer.

Decrease of interleukin-2 secretion is a new independent prognostic factor associated with poor survival in patients with small-cell lung cancer

BACKGROUND

We have previously shown that suppression of interleukin-2 (IL-2) secretion was mediated by transforming growth factor (TGF) beta 1 secreted by small-cell lung cancer (SCLC) tumor cells. We have also shown that IL-2 secretion was significantly impaired in patients with SCLC at the time of diagnosis. Reconstitution of cytokine secretion correlated with reduction of tumor load. These data suggested that the immune system was suppressed by the tumor. To address the clinical relevance of cytokine suppression in SCLC, we investigated the correlation of the level of IL-2 secretion with survival.

PATIENTS AND METHODS

The significance of correlations between single parameters in the test groups was calculated by using the linear regression analysis, the Wilcoxon rank sum test and the exact test according to Fisher. Using the Kaplan-Meier method, the log-rank test and the Cox-regression model, we analysed the relation of IL-2 secretion in whole blood cell cultures from 52 patients with SCLC at the time of diagnosis to established prognostic factors relevant for survival in SCLC.

RESULTS

Impairment of IL-2 secretion significantly correlates to survival in SCLC (P = 0.004). Further univariate and multivariate analysis showed that this prognostic factor is independent from other factors of prognostic relevance in SCLC, namely stage of disease, neurone specific enolase (NSE), lactate dehydrogenase (LDH), age, and sex. More important, the prognostic value of IL-2 secretion is comparable to the most predominant prognostic factors for survival in SCLC identified so far. In the final model of the cox regression analysis, the P-value for IL-2 secretion in relation to stage of disease was 0.012 and 0.019, respectively.

CONCLUSIONS

IL-2 secretion at the time of diagnosis represents an independent prognostic factor for survival in SCLC. Although its prognostic value has to be confirmed in a larger group of patients, our results demonstrate that IL-2 secretion may play an important role in diagnosis and treatment of SCLC. Moreover, in contrast to other prognostic factors, impairment of IL-2 secretion may help to understand immunosuppression in SCLC and, thus, important elements of the pathogenesis of this disease.

Cytokines may influence tumor growth and spread. An in vitro study in two human cancer cell lines

Tumor spread may be favored by a reduced production and/or an enhanced degradation of extracellular matrix components (collagen, fibronectin, laminin). Most tumor cell behavior, from growth to spread, may be regulated by cytokines, the exact roles of which, however, are not yet fully understood. We here evaluate the effects of some cytokines (epidermal growth factor, transforming growth factor-beta 1, interleukin-1 alpha, and interleukin-1 beta) on both cell growth and the production of the aminoterminal peptide of type III procollagen, the urokinase plasminogen activator, and the plasminogen activator inhibitor-1 in neoplastic cell lines originating in the pancreas and colon. Cells were stimulated daily with the above cytokines and the aminoterminal peptide of type III procollagen, urokinase plasminogen activator, and plasminogen activator inhibitor-1 were measured in the conditioned media. Epidermal growth factor stimulated cell growth of both cell lines. Transforming growth factor-beta 1 counteracted cell proliferation and stimulated type III procollagen and plasminogen activator inhibitor-1 production only in the colon cancer cell line. Interleukin-1 alpha slightly stimulated cell growth, but inhibited plasminogen activator inhibitor-1 production in both cell lines; interleukin-1 beta did not affect cell growth, but stimulated plasminogen activator inhibitor-1 production by the colon cancer cell line. Our findings suggest that transforming growth factor-beta 1 and interleukin-1 beta may have an antidiffusive effect. These results confirm that cytokine-producing cells have a potential role in stimulating or counteracting tumor growth and spread and also confirm the pivotal role of host-tumor interactions in determining the outcome of a particular neoplasia.

Selective suppression of cytokine secretion in patients with small-cell lung cancer

BACKGROUND

Whether or not cytokine secretion is impaired in patients with small-cell lung cancer (SCLC), is unknown. We therefore investigated whether cytokine secretion by immunocompetent cells may be suppressed in patients with SCLC.

PATIENTS AND METHODS

We determined cytokine secretion by lymphocytes and monocytes in whole blood cell cultures from 58 patients with SCLC, 95 patients with non-small-cell lung cancer (NSCLC), 10 patients with nonmalignant lung disease and from 44 normal healthy individuals by using an enzyme-linked immunosorbent assay (ELISA) specific for the different cytokines measured.

RESULTS

Compares to normal controls, immunocompetent cells from patients with SCLC secreted significantly lower amounts of IL-2, IFN alpha, and IFN gamma upon mitogen stimulation. TNF alpha-secretion was significantly reduced in SCLC extensive disease but not in SCLC limited disease. In contrast, secretion of IL-1 alpha and IL-1 beta was not reduced. In patients with NSCLC, secretion of IL-2 and IFN alpha was significantly reduced. Reduction of IFN gamma secretion was significant in metastasized NSCLC and marginally significant in localized NSCLC. Secretion of TNF alpha, IL-1 alpha and IL-1 beta was not impaired. In addition, cytokine secretion in SCLC patients substantially improved upon successful reduction of tumor load by chemotherapy but not upon ineffective chemotherapy. Furthermore, TGF beta 1 suppressed secretion of IL-2, IFN alpha, IFN gamma, TNF alpha but not of IL-1 alpha and IL-1 beta in whole blood cell cultures from healthy individuals.

CONCLUSIONS

Suppression of cytokine secretion in patients with SCLC was selective, dependent on tumor load, different from immunosuppression in NSCLC and seemed to be reconstituted upon reduction of tumor load. These results may suggest interactions between tumor cells and the immune system. TGF beta 1 secreted by SCLC cell lines induced the same selective cytokine suppression as that found in SCLC patients. However, whether or not tumor-derived TGF beta 1 is a factor inducing selective immunosuppression in SCLC patients is presently unclear.