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Coming theses from other universities

  • Circulating Biomarkers in Patients with Head and Neck Cancer and the Influence of Cigarette Smoking Author: Bengt-Åke Andersson Link: Publication date: 2019-11-19 09:58

    Head and neck cancer (HNC) is a collective name for heterogeneous tumors located in the head and neck regions for which smoking, alcohol and human papillomavirus (HPV) are documented risk factors. The survival of HNC patients has only improved marginally during the last decade. The most important prognostic factors are tumor size, local spread and distant metastases, tumor node metastasis (TNM) staging. Prognostic biomarkers are needed as a complement to TNM staging.

    The aim for this thesis was to investigate rapid and low cost blood based biomarkers which could indicate the risk of HNC, recurrence of the disease or the survival of HNC patients. Furthermore, the aim was to examine how cigarette smoking influences the levels of biomarkers.

    In paper I, a possible role of plasma cytokines or proteins associated with immune response or inflammation, as biomarkers for the survival of HNC patients was investigated. Higher levels of C-reactive protein (CRP) and tumor necrosis factor alpha (TNF-α) were detected in plasma of the patients compared with the levels in the controls. The elevated levels of these two biomarkers detected in patients were associated with decreased survival.

    In paper II, the influence of 45 single nucleotide polymorphisms (SNPs) located in 41 genes associated with cell cycle progression, cell death, DNA repair or immune response on cancer risk, tumor recurrence and survival in HNC patients were investigated. SNPs in immune response genes were associated with risk for HNC, an elevated risk for recurrence and a decreased survival in HNC patients.

    In paper III, the influence of cigarette smoking on levels of inflammatory cells, proteins or cytokines/chemokines, microRNAs (miRNAs) and SNPs was analysed in healthy smokers and non-smokers. Higher levels of total white blood cells (WBCs), neutrophils, monocytes, lymphocytes, neutrophil to lymphocyte ratio (NLR), CRP, monocyte chemoattractant protein- 1 (MCP-1) and interferon gamma (IFN-γ) were detected in smokers compared to non-smokers and indicate an inflammatory response. Also, a lower level of oncomiRNA miR-21was detected in smokers. This alteration, in combination with the elevated levels of IFN-γ in smokers could be a protective response to cigarette smoke. The higher levels of IFN-γ in smokers compared to non-smokers were however only detected in individuals with SNP rs2069705 genotype AG/GG. This indicates a genetic association of the levels of IFN-γ.

    In paper IV, the separate effects of cigarette smoking and HNC on inflammatory or immune biomarkers and the impact of high risk human papillomavirus, age and gender were investigated. Comparisons of circulating levels of WBCs and its subpopulations, plasma proteins or cytokines/chemokines between smoking and non-smoking patients, smoking and non-smoking controls and between the patient and control groups were analysed. Smoking had highest impact on elevated levels of WBCs, IFN-γ and MCP-1, and HNC had highest impact on elevated levels of neutrophils, monocytes, NLR, CRP, macrophage inflammatory protein 1 beta and TNF-α.

    In conclusion, host immune response associated parameters could be suitable as biomarkers for the risk of HNC, risk of recurrence or in predicting survival of HNC patients. This thesis show that HNC are associated with systemic inflammatory response and upregulated CRP and TNF-α is related to shorter survival in HNC patients. Additionally, SNPs in immune response genes such as rs1800629 in the TNF-α gene indicates a risk for HNC or an elevated risk for recurrence and a decreased survival in HNC patients. These rapid and low cost blood based biomarkers could be used in combination or as a supplement to established biomarkers in the clinic for a more personalized treatment modality.

  • Biogenesis, function and regulation of the type III secretion translocon of Yersinia pseudotuberculosis Author: Salah I. Farag Link: Publication date: 2019-11-15 06:00

    Many Gram negative bacteria use type III secretion systems to cross-talk with eukaryotic cells. Type III secretion system assembly and function is tightly regulated. It initiates with assembly of a basal body-like structure, and is followed by a cytoplasmic-located substrate sorting and export platform that first engages with early substrates required for needle assembly. At the needle tip, a translocon is formed upon eukaryotic cell contact to allow the translocation of effector proteins to the host cell. The focus of this thesis is on understanding aspects of biogenesis, regulation and function of the translocon and its interaction with the host cell. Research questions are addressed in enteropathogenic Yersinia pseudotuberculosis model.

    Prioritising the secretion of translocon components before effector proteins is a task given partly to the InvE/MxiC/HrpJ family of proteins. In Yersinia, homology to this protein family is partitioned over two proteins; YopN and TyeA. Certain Yersinia strains naturally produce a single YopN/TyeA polypeptide hybrid. To understand the implications of hybrid formation towards type III secretion control, a series of mutants were engineered to produce only a single hybrid peptide. Using in vitro assays revealed no difference in substrate secretion profiles between parent and mutants. Moreover, no obvious prioritisation of secretion between translocator and effector substrates was observed. Although these in vitro studies indicate that the YopN-TyeA single polypeptide is fully functionally competent, these mutants were attenuated in the mouse infection model. Hence, natural production of YopN and TyeA as a single polypeptide alone is unlikely to confer a fitness advantage to the infecting bacteria and is unlikely to orchestrate hierarchal substrate secretion.

    The YopB and YopD translocon components form a pore in the host cell plasma membrane to deliver the effectors into the host cell. To better understand how YopD contributes to the biogenesis, function and regulation of the translocon pore, a series of mutants were constructed to disrupt two predicted α-helix motifs, one lying at the N-terminus and the other at the C-terminus. Based upon phenotypes associated with environmental control of Yop synthesis and secretion, effector translocation, evasion of phagocytosis, killing of immune cells and virulence in a mouse infection model, the mutants were grouped into three phenotypic classes. A particularly interesting mutant class maintained full T3SS function in vitro, but were attenuated for virulence in a murine oral-infection model. To better understand the molecular basis for these phenotypic differences, the effectiveness of RAW 264.7 cells to respond to infection by these mutants was scrutinised. Sixteen individual cytokines were profiled with mouse cytokine screen multiplex analysis. Signature cytokine profiles were observed that could again separate the different YopD mutants into distinct categories. The activation and supression of certain cytokines that function as central innate immune response modulators correlated well with the ability of mutant bacteria to modulate programmed cell death and antiphagocytosis pathways. Hence, the biogenesis of sub-optimal translocon pores alters host cell responsiveness and limits the ability of Yersinia to fortify against attack by both early and late arms of the host innate immune response.

    The amount of bacteria now resistant to multiple antibiotics is alarming. By providing insights into a common virulence process, this work may ultimately facilitate the design of novel broad-acting inhibitors of type III secretion, and thereby be useful to treat an array of bacterial infections.

  • Studies on the biological functions of interaction between components in Wnt, TGF-β and HIF pathways for cancer progression Author: Karthik Aripaka Link: Publication date: 2019-11-08 06:00

    Cancer is a disease that involves aggressive changes in the genome and aberrant signals between the living cells. Signalling pathways such as TGF-β (Transforming growth factor-β), Wnt, EGF (epidermal growth factor) and HIF (Hypoxia-inducible factor) evolved to regulate growth and development in mammals. These factors are also implicated for tumorigenesis due to failure or aberrant expression of components in these pathways. Cancer progression is a multistep process, and these steps reflect genetic alterations driving the progressive transformation of healthy human cells into highly malignant derivatives. Many types of cancers are diagnosed in the human population, such as head & neck, cervical, brain, liver, colon, prostate, uterine, breast, and renal cell cancer.

    Prostate cancer is the second most common cancer and one of the foremost leading cancer-related deaths in men in the world. Aberrant Wnt3a signals promote cancer progression through the accumulation of β-Catenin. In the first paper, we have elucidated intriguing functions for Tumour necrosis factor receptor-associated factor 6 (TRAF6) as a coregulatory factor for the expression of Wnt-target genes which was confirmed in vivo by using CRISPR/Cas9 genomic editing, in zebrafish. Our data suggest that Wnt3a promotes TRAF6 interaction with Wnt components, and TRAF6 is required for gene expression of β-Catenin as well as for the Wnt-ligand co-receptor LRP5. From the in vivo studies, we elucidated positive regulation of TRAF6, which is crucial for survival and development of zebrafish. This study identifies TRAF6 as an evolutionary conserved co-regulatory protein in the Wnt pathway that also promotes the progression of prostate and colorectal cancer due to its positive effects on Wnt3a signalling.

    Hypoxia is a condition due to O2 deprivation, and Hypoxia-inducible factors (HIF) transcription factors are responsible for the maintenance of oxygen homeostasis in living cells. Irregularities in these HIF transcription factors trigger pathological cellular responses for initiation and progression of malignant cancers. Renal cell carcinoma, malignant cancer arising in renal parenchyma and renal pelvis and, hypoxia plays a vital role in its progression. In the second paper, we have investigated the clinicopathological relevance of several hypoxic and TGF-β component proteins such as HIF-1α/2α/3α, TGF-β type 1 receptor (ALK5-FL) and the intracellular domain of ALK5 (ALK5-ICD), SNAI1 and PAI-1 with patient survival in clear cell renal cell carcinoma (ccRCC). We showed that HIF-2α associated with low cancer-specific survival. HIF-2α and SNAI1 positively correlated with ALK5-ICD, pSMAD2/3, PAI-1 and SNAI1 with HIF-2α; HIF-1α positively correlated with pSMAD2/3. Further, under normoxic conditions, our data suggest that ALK5 interacts with HIF-1α and HIF-2α, and promotes their expression and target genes such as GLUT1 and CA9, in a VHL dependent manner through its kinase activity. These findings shed light on the critical aspect of cross-talk between TGF-β signalling and hypoxia pathway, and also the novel finding of an interaction between ALK5 and HIF-α might provide a more in-depth understanding of mechanisms behind tumour progression

    In the third paper, an ongoing study, we investigated the role of HIF-3α in the progression of Renal cell carcinoma and its association with the components of TGF-β and HIF pathways. We have observed increased levels of HIF-3α in ccRCC and pRCC (papillary renal cell carcinoma) which are associated with advanced tumour stage, metastasis and larger tumours. Also, we found HIF-3α show a significant positive association with pro-invasive gene SNAI1, which is a crucial regulator of epithelial to mesenchymal transition. TRAF6 an E3 ligase known to be a prognostic marker in RCC and we observed HIF-3α associates with TRAF6.