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Title: Modulation of immune cell responses by small cell lung cancer cells
Author: Wang, Wei
ISNI:       0000 0004 6058 1310
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2016
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Small Cell Lung Cancer (SCLC) accounts for 15-20% of all lung cancers and kills at least one person every 2 hours in the UK. There is no effective treatment and overall 2-year survival is less than 5%. Patients with SCLC have poorly understood local and systemic immune defects. Previous studies have shown several important defects in cell-mediated immune responses in patients with SCLC. A better understanding of interactions between SCLC tumour cells and immune cells may lead to the development of novel therapeutic approaches. There is increasing recognition that immunological biomarkers may add to traditional histological analyses and can be exploited in the management of multiple epithelial malignancies. There are currently no such markers used in the management of SCLC. In my PhD project, I have shown that cell lines from different SCLC patients have differential immunosuppressive capabilities. These properties are mediated by the secretion of differing levels of soluble molecules that can suppress the mixed leukocyte reaction (MLR) and CD4+ T cell proliferation, induce IL-10 secretion and differentiation of functional CD4+CD25+CD127+FoxP3+Helios- regulatory T cells (Tregs) from naïve CD4+ T cells. IL-15 is secreted by SCLC cells in culture in proportion to their immunosuppressive capability. Its in vivo relevance is supported by its presence in tumour biopsy samples. The suppressive effect on CD4+ T cell proliferation and the induction of Treg cell population was not affected by blocking IL-10 or TGF-β signalling but was partially reversed by blocking IL-15 activity. Therefore, IL-15 is one, though not the only, soluble molecule produced by SCLC cells to mediate immune suppression by inducing increased population of Treg cells. This may represent a mechanism by which SCLC cells can suppress the immune response. In addition, SCLC cells supressed TNF-α release from monocytes in response to LPS stimulation, down-regulated expression of CD16 and CD86 and upregulated expression of CD163 and CD206 on monocyte-derived macrophages (MDMs) upon activation. This M2-like phenotype poralization was associated with decreased TNF-α and IL-6 production and increased IL-10 secretion. These effects were abrogated by blocking the signalling of bombesin-like peptides (BLPs) that are neuropeptides produced by SCLC cells using a GRP receptor (GRP-R) antagonist. Therefore, the polarization of macrophages to an M2-like phenotype by SCLC cell-derived BLPs may represent another mechanism by which SCLC tumours suppress the immune response. Finally, SCLC tumour biopsies were shown to be infiltrated with various mononuclear immune cells and Treg cells. CD45 and FoxP3 were used as paninflammatory cell and Treg cell markers respectively. An elevated CD45+ infiltrate was predictive of prolonged survival in SCLC independent of age, sex, stage or treatment strategy. An elevated FoxP3+/CD45+ ratio was predictive of a significantly worse prognosis. This study identifies potential mechanisms by which SCLC tumour cells may downregulate local and systemic immune response, and also identifies an independent prognostic marker to predict patient survival in SCLC. Further, IL- 15 and BLPs are potential novel therapeutic targets in SCLC.
Supervisor: Sethi, Tariq Jabbar ; McCaughan, Frank Martin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available