The human genome is constantly subjected to endogenous and exogenous sources of damage. Protection against these genotoxic insults is secured by the network of DDR pathways triggered by the detection of DNA lesions. The subsequent step is the initiation of a signal transduction cascade including molecules that activate genome-protection pathways, such as DNA repair, cell cycle control, apoptosis, transcription and chromatin remodeling. Failure to repair DNA damage can result in a variety of genomic alterations, such as point mutations, chromosomal translocations and gain or loss of chromosomal segments or entire chromosomes. Under certain conditions, these genomic aberrations induce changes in cellular physiology that drive disease initiation and progression. In this project, using established cell lines and primary biological samples from cancer patients (multiple myeloma, head and neck cancer, lung cancer) and autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, Behçet's disease, antiphospholipid syndrome) at different stages of the disease, we test the hypothesis that the deregulated DDR network plays a crucial role in the onset and progression of cancer and autoimmunity.

Major outcomes

• Systemic autoimmune diseases: The results presented in this study suggest that the deregulated DDR network plays a crucial role in the pathogenesis and progression of systemic autoimmune diseases.
  https://doi.org/10.3390/ijms21010055
• Systemic sclerosis (SSc): We found that SSc patients displayed increased endogenous DNA damage and oxidative stress, defective DSB repair but not NER capacity, and deregulated expression of DDR-associated genes.
  https://doi.org/10.3389/fimmu.2020.582401
• Rheumatoid arthritis (RA): We found that deregulated chromatin organization, deficient DNA repair capacity and augmented formation of DNA damage, which are reversible after treatment, contribute to the accumulation of endogenous DNA damage in RA.
  https://doi.org/10.1016/j.clim.2019.03.009
• RNA editing: We found that ADAR1p150-mediated A-to-I RNA editing is critically involved in type I IFN responses highlighting the importance of proinflammatory gene regulation at the post-transcriptional level in systemic autoimmunity.
  https://doi.org/10.1016/j.jaut.2021.102755
• Iron deposition and DDR activation in Systemic Sclerosis: In this study, we formulated the hypothesis that hemorrhagic tissue deposition of iron, due to microvasculopathy-related extravasation of erythrocytes, may be of pathogenetic importance in fibrosis in SSc, thus comprising an additional therapeutic target.
  https://doi.org/10.3390/life12030430
• Genomic instability/carcinogenesis: The current study broadens our understanding of how chronic p53-independent p21WAF1/Cip1 expression, seen in a sizeable fraction of advanced human tumors, impacts the global DNA repair landscape and undermines genomic stability.
  https://doi.org/10.1186/s13059-018-1401-9
• DDR in multiple myeloma: In this study, we tested the hypothesis that epigenetic alterations and changes in DDR signals are implicated in the transformation process of myelomagenesis. Indeed, we found that in bone marrow plasma cells from patients with MGUS, SMM and MM, significant progressive changes occur in chromatin structure, transcriptional activity and DDR signals during the transformation process of myelomagenesis. Interestingly, these changes were also present in PBMCs from the same patients and strongly correlated with those observed in corresponding bone marrow plasma cells.
  https://doi.org/10.1038/leu.2013.284

Since DNA damage response decides the cell's fate (either to repair DNA damage or to undergo apoptosis if there is too much damage), DNA damage response processes are also implicated in cancer therapy. Herein, we study epigenetic modifications, changes in the gene expression profiles, oxidative stress, abasic sites and DDR alterations in established cell lines and primary cells from cancer patients with different response rates using advanced genome-wide methodologies in combination with biochemical and new imaging technology based on confocal microscopy. The study of these alterations holds great promise for contributing to the outcome of therapy on an individual basis, thus providing unique tools for the discovery of biomarkers and therapeutic targets.

Major outcomes

• Head and neck squamous cell carcinoma (HNSCC): We found that aberrations in DDR signals are implicated in the response to HNSCC chemotherapy and can be exploited as novel therapeutic targets, sensitive/effective non-invasive biomarkers, as well as for the design of novel clinical trials.
  https://doi.org/10.1016/j.esmoop.2021.100075
• DDR in multiple myeloma I: To investigate the mechanistic basis for the link between DNA repair efficiency and response to antimyeloma therapy, we studied major DNA repair mechanisms in MM cell lines and malignant bone marrow plasma cells (BMPCs) from patients with MM before antimyeloma therapy. We found that BMPCs from responders to melphalan therapy are characterized by slower rates of NER and DSBs repair compared with nonresponders. Moreover, we provide evidence that inhibitors of DSBs repair might be proven efficient when they are used in combination with DNA-damaging chemotherapeutic drugs.
  https://doi.org/10.1182/blood-2016-01-691618
• DDR in multiple, to myeloma II: Here investigate the mechanism underlying differential response rates to melphalan therapy, we assessed the epigenetic changes and the alteration of DDR signals in malignant BMPCs and PBMCs of newly diagnosed MM patients. We found that changes in chromatin structure and transcriptional activity affect the drug sensitivity of myeloma cells via alteration of the repair efficiency of the transcribed strnd of the active genes and the associated persistence of lesions in this strand, and correlate with the clinical response to melphalan therapy.
  https://doi.org/10.1038/bjc.2014.410
• DDR in multiple myeloma III: In this study, we found that the extent of p53-specific damage formation/repair in PBMCs from MM patients following in vitro exposure to melphalan correlates with the respective results obtained in vivo, i.e. outcome after treatment with high-dose melphalan, and is of value in predicting clinical response and progression-free survival. Thus, measurement of the individual levels of DNA damage induced in vitro after melphalan treatment of PBMCs collected before chemotherapy may help in the selection of patients more likely to benefit from high-dose melphalan therapy.
  https://doi.org/10.3324/haematol.11435
• DDR in multiple myeloma IV: This study describes the in vivo kinetics of gene-specific damage formation and repair in human blood leukocytes of MM patients after therapeutic exposure to high-dose melphalan. Increased individual damage formation and slower repairing capacity in p53 gene within the first 24 hours after treatment of myeloma patients with high-dose melphalan correlate with an improved clinical outcome. These results suggest that quantitation of such biologic end points in a readily accessible tissue may be of predictive value for MM patients.
  https://doi.org/10.1200/JCO.2005.07.385
• DDR and ovarian cancer I: In this study we showed that deregulated DDR pathways play a crucial role in the cisplatin resistance in ovarian cancer. Thus, unravelling these molecular pathways can be exploited to discover new treatment opportunities in the field. This new knowledge is essential to design future strategies to circumvent the complex mechanisms of cisplatin resistance more effectively and to translate them into improved clinical responses.
  https://doi.org/10.3390/biomedicines10010082
• DDR and ovarian cancer II: Herein, we conducted a study to test the hypothesis that DDR, a crucial mechanism for cell survival, is involved in resistance to platinum chemotherapy. We found that ovary cancer patients are characterized by higher intrinsic DNA damage compared to healthy volunteers, and that the efficiency of DNA repair as measured in PBMCs from ovary cancer patients correlates with the drug sensitivity of these cells and reflects the individualized response to platinum-based chemotherapy.
  https://doi.org/10.1371/journal.pone.0117654

The deregulated interplay between the DDR network and the immune system plays a crucial role in the pathogenesis and progression of cancer and systemic autoimmune diseases. Thus, unraveling the molecular mechanisms of this interplay can be exploited for understanding pathogenesis and progression of these diseases, as well as to discover new treatment opportunities in the field. Interestingly, during recent years the blockade of the immune checkpoints, using monoclonal antibodies targeting the PD-1/PD-L1 and CTLA-4/B7 pathways, has led to impressive improvements in the effectiveness of immunotherapy against several cancers, including lung carcer, melanoma and several types of head and neck cancer. Our preliminary data have shown that in addition to direct cytotoxic effects on cancer cells, a proportion of DNA damaging agents and/or DDR modifiers may actually promote immunogenic cell death, alter the inflammatory milieu of the tumour microenvironment and/or stimulate neoantigen production, thereby activating an antitumour immune response. This evidence forms the basis of the current work to systematically examine the effects of genotoxic drugs on the immunogenicity of the tumor and the host immune defences against lung carcer, melanoma and several types of head and neck cancer, and assess the potential of such drugs to improve the efficiency of immune checkpoint blockade-based therapy. Moreover, in order to investigate how transient immune activation triggers the DDR network, we evaluate critical DDR parameters and factors leading to DNA damage formation in PBMCs from healthy controls following vaccination against Influenza and SARS-CoV-2.

Major outcomes

• SARS-CoV-2 vaccination I: Herein, we sought to investigate the hypothesis that augmented oxidative stress and/or increased DNA double-strand breaks in circulating immune cells may predict lower antibody titers after SARS-CoV-2 vaccination. We found that humoral responses to SARS-CoV-2 vaccination may be weaker when immune cells are under oxidative and/or genomic stress.
  https://doi.org/10.1016/j.bbadis.2022.166393
• SARS-CoV-2 vaccination II: By studying vaccinations against Influenza and SARS-CoV-2 (mRNA-based) we found acute increases of type-I interferon inducible gene expression, oxidative stress and DNA damage accumulation in blood mononuclear cells of healthy controls, coupled with effective anti-SARS-CoV-2 neutralizing antibody production in all healthy controls.
  https://doi.org/10.1016/j.clim.2021.108765

The members of the group participate in the administration/organization and teaching of the Master's Program “Oncology: from Oncogenesis to Therapy” in collaboration with the Medical School of the University of Crete. Website: www.oncologymaster.gr/

Geriatric physical frailty is a relatively novel concept established in routine medical practice over recent years, constructed to entify reduced physiologic function and decreased resilience to biological stressors which afflicts a subset of older adults, beyond the effects of chronic diseases. This study aims to investigate if physical frailty according to the Rockwood Clinical Frailty Scale is associated with oxidative stress and deregulated DDR network in PBMCs of older adults.

In collaboration with: the University of Athens Medical School

SARS-CoV-2 vaccination: As an extension to our published work we plan to investigate the hypothesis that oxidative stress and/or endogenous DNA damage in circulating immune cells may predict antibody titers after SARS-CoV-2 vaccination.

In collaboration with: the University of Athens Medical School

Antiphospholipid syndrome (APS): In this study, we plan to study the pathogenesis of APS by evaluating intracellular factors/processes that lead to the formation of DNA damage and/or its delayed/decreased removal in PBMCs from APS patients at diagnosis.

In collaboration with: the University of Athens Medical School

Systemic sclerosis: Since tissue iron deposition is a hallmark of fibrosis, in the current study we will test the hypothesis that iron accumulation originating from hemolytic red blood cells plays a crucial role in the pathogenesis of systemic sclerosis. Moreover, we aim to explore the role of ferroptosis (a newly discovered type of regulated cell death) on the onset and progression of systemic sclerosis.

In collaboration with: the University of Athens Medical School

Lung cancer: In lung cancer cell lines and primary cells from lung cancer patients we plan to characterize the effects of DNA damaging drugs and/or DNA repair inhibitors on key pathways and markers related to DDR signaling and tumor immunogenicity. In addition, in vivo murine models of lung cancer will be used to confirm the in vitro results and to evaluate the anti-tumor efficacy of combined treatment of genotoxic drugs (cisplatin) and/or DDR modifiers (olaparib) with immune checkpoint inhibitors.

In collaboration with: the University of Athens Medical School

Multiple myeloma I: Herein, we will test the hypothesis that endogenous DNA damage is involved in the malignant progression of multiple myeloma and the outcome of anti-myeloma therapy. For this purpose, we will evaluate critical DDR parameters and endogenous factors leading to DNA damage formation in bone marrow plasma cells and peripheral blood mononuclear cells from patients at different stages of myelomagenesis and from MM patients at different degrees of therapeutic response.

In collaboration with: the University of Athens Medical School

Multiple myeloma II: We plan to study the mechanistic basis for the action of the combination treatment of the HDAC inhibitor panobinostat with the genotoxic drug melphalan in MM. For this purpose, in bone marrow plasma cells and peripheral blood mononuclear cells from MM patients at diagnosis, we will evaluate the effect of this combined ex vivo treatment on critical DDR pathways, including fundamental DNA repair mechanisms and apoptosis rates.

In collaboration with: the University of Athens Medical School

Multiple myeloma III: DNA repair efficiency, along with MAPK mutational status in MM, influences the therapeutic outcome and the patients' survival. Understanding of the DDR network and its interplay with the MAPK signaling pathway is essential to optimize rational combinational therapies in MM.

In collaboration with: German Cancer Research Center (DKFZ), Heidelberg

Head and neck cancer (HNSCC): In HNSCC cell lines and primary cells from HNSCC patients we plan to characterize the effects of DNA damaging drugs and/or DNA repair inhibitors on key pathways and markers related to DDR signaling and tumor immunogenicity. In addition, in vivo murine models of HNSCC will be used to confirm the in vitro results and to evaluate the anti-tumor efficacy of combined treatment of genotoxic drugs (cisplatin) and/or DDR modifiers (olaparib) with immune checkpoint inhibitors.

In collaboration with: the University of Athens Medical School