Supervisors info:
Γεωργία Ξάνθου, Ερευνήτρια Β', ΙΙΒΕΑΑ
Νικολέττα Ροβίνα, Επίκουρη Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Γεώργιος Βασιλόπουλος, Καθηγητής, Ιατρική Σχολή, Πανεπιστήμιο Θεσσαλίας
Summary:
Lung cancer is the second most common cancer worldwide, with the highest cancer mortality. It is characterised by great heterogeneity and grouped by two types mainly; the small cell lung cancer (SCLC) and the non-small cell lung cancer (NSCLC), which comprises 85% of all cases. NSCLC exhibits a 5-year survival rate in approximately 15% of patients, with most of the patients presenting metastasis or disease recurrence despite treatment with cytotoxic chemotherapy regimens.
The immune system plays a crucial role in eliminating tumor cells. The adaptive immunity, comprising of T and B cells, has a specific immune response. An effective anti-tumor immune response is mainly determined by CD4+ T helper cells that inhibit tumor cell proliferation and survival through the stimulation of cytotoxic CD8+ T lymphocyte mediated cancer cell lysis, the release of effector cytokines and the activation of innate immune responses. However, tumor cells are able to avoid tumor immunosurveillance and often set an immunosuppressive environment, in a procedure called tumor immunoediting.
Activin-A is pleiotropic cytokine that regulates critical biological processes, such as, haematopoiesis, embryonic development, stem cell maintenance and pluripotency, tissue repair
and fibrosis. Studies by our group and others have revealed that, activin-A exerts both pro- and
anti-inflammatory effects depending on the site of expression, the cell activation status and the
immunological context, a status that is being observed in lung cancer too.
Our hypothesis is that activin-A has an impact on patrolling T effector cells and as a result, plays a crucial factor in the regulation of lung cancer initiation and progression. The aim of our study is to decipher the in vivo effect of activin-A on T cell-mediated immune responses in lung cancer and to explore whether activin-A enhances anti-tumor human T cell immune responses in lung cancer patients.
To address our hypothesis regarding the mouse studies, we used CD4CreERT2/Acvr1bFx mice and inoculated them with LLC cells. In brief, we disrupted Avcr1b expression on CD4+ T cells, using tamoxifen. Tumor infiltrated leukocytes were obtained from lung cancer tissues of these mice, and were cultured upon antigen stimulation. CD4+ T cells were isolated from the tumor infiltrating leukocyte fraction and analysed using FACS and ELISA. Pertinent to the human studies, we obtained primary human lung tumor tissue and adjacent lung healthy tissue from NSCLC patients. Tumor infiltrating leukocytes (TILs), obtained from tissues, were polyclonally stimulated with anti-CD3/anti-CD28 in the presence or absence of recombinant activin-A. In some experiments, CD4+ and CD8+ T cells were isolated from TILs and cultured as mentioned above. These cells, as well as, their culture supernatants were further analysed using FACS, ELISA and LDH cytotoxicity assays.
Our studies revealed that disruption of activin-A’s signalling on CD4+ T cells accelerates lung tumor progression and decreases the overall survival of lung-tumor bearing mice (CD4ALK4 KO mice). Notably, CD4+ T cells from CD4ALK4 KO mice produced less IFN-γ and TNF-α, concomitantly with increased levels of the immunoregulatory cytokine IL-10, compared to CD4+ T cells from wild type mice, upon antigenic stimulation. In human lung tissues, activin-A unveils different effects on CD4+ T cells that infiltrate the lung tumors, compared to CD4+ T cells from the adjacent healthy lung tissue. In brief, CD4+ T cells that infiltrated the lung tumors produced increased levels of the effector cytokines TNF-α and IL-2 and decreased levels of the immunosuppressive cytokine IL-10, whereas CD4+ T cells from the adjacent health tissue produce less IFN-γ and IL-2. Moreover, activin-A-treated human lung tumor infiltrating CD4+ T cells exhibited a less exhausted phenotype/profile and acquired a more immunostimulatory capacity towards autologous CD4+ responder T cells. Lastly, CD8+ T cells from the periphery supplemented with culture medium from act-A-CD4+ T cell cultures were more prominent in killing the targeted primary lung cancer cells.
Taking together our data uncover activin-A as an important orchestrator of anti-tumor T cell responses. Importantly, this study will also set the bases for further exploitation of activinA’s utilization as a prognostic tool and a potential target for immunotherapy devoid of potentially harmful side effects, in the setting of human lung cancer.
Keywords:
Activin A, Lung cancer, Anti-tumor immunity, CD4+ T cells, Cytokine(s)
