Coming dissertations at MedFak
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Tertiary lymphoid structures in glioblastoma : Discovery, Characterization and Therapeutic Induction
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-523782
Glioblastoma (GBM) is an incurable brain cancer with a median survival of less than two years from diagnosis. The tumor microenvironment plays a major role in GBM progression through sustaining immunosuppression and poor lymphocytic infiltration. Tertiary lymphoid structures (TLS) are ectopic lymphoid aggregates that form in inflamed tissues and are associated with positive prognosis in numerous cancers outside the central nervous system. Prior to this work, TLS had not been reported or studied in GBM. In this thesis, we aimed to characterize TLS in glioma patients, and to investigate immunotherapeutic approaches that could reprogram the GBM microenvironment to induce these structures, promote anti-tumor responses and prolong survival.
In Paper I, we discovered the presence of TLS in low grade and high grade glioma tissues, and found that they correlated with increased T cell infiltration inside the tumor. Moreover, we demonstrated that agonistic CD40 therapy (αCD40) induced the formation of TLS with a follicle-like organization in murine glioma models. αCD40 also promoted a population of CD11b+ regulatory B cells, which inhibited T cell activation. These cells were not present within the TLS, indicating that TLS formation and the induction of CD11b+ B cells were likely two independent processes.
In Paper II, we employed murine glioma models to study the therapeutic effect of cytokines involved in lymphoid tissue development, and selected LIGHT as the most promising candidate. To therapeutically deliver LIGHT to the tumor microenvironment, we engineered an AAV vector targeted to the brain endothelial cells to express LIGHT (AAV-LIGHT). AAV-LIGHT promoted the formation of TLS and functional high endothelial venules. Moreover, AAV-LIGHT strengthened effector and memory CD8+ T cell responses, and boosted a population of TCF1+CD8+ stem-like T cells. This was associated with a prolonged survival, indicating that AAV-LIGHT is a promising therapeutic candidate for the treatment of GBM.
In Paper III, we coupled advanced spatial transcriptomics of human GBM tissue and time point experiments in murine glioma models to investigate the stages of TLS assembly. We found that TLS formation is a step-wise process, where each stage is characterized by specific cell components and pathways. Understanding the steps underlying TLS assembly will be critical to develop efficient TLS-inducing immunotherapies.
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Pitfalls in β-cell ion imaging with fluorescent indicators and their use for real-time detection of somatostatin secretion
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-523019
Fluorescent ion indicators have become indispensable tools in cell physiology. Dye indicators can easily be loaded into most types of cells, while genetically encoded indicators are advantageous in allowing specific cellular or subcellular targeting. Comparing responses of dye and protein-based indicators may provide useful insights into indicator properties and cellular processes. Here, a few genetically encoded Ca2+ indicators and fluorescent Ca2+ dyes were compared in insulin-secreting β-cells. Recordings of depolarization-triggered changes of the cytoplasmic Ca2+ concentration ([Ca2+]i) beneath the plasma membrane with total internal reflection fluorescence microscopy demonstrated distinct [Ca2+]i spikes with protein-based indicators, while the dyes mainly reported stable [Ca2+]i elevations. The spikes reflected Ca2+ release from the endoplasmic reticulum, triggered by autocrine purinergic receptor activation from exocytotic release of ATP. The indicator-dependent differences were unrelated to Ca2+ binding affinity and buffering and probably reflected slower Ca2+ dissociation kinetics of the protein indicators. In glucose-stimulated mouse islets, the dye Fura-2 reported the characteristic [Ca2+]i response with an initial lowing followed by rapid increase, which was abolished by hyperpolarization with the K+-channel opener diazoxide. The simultaneously present genetically encoded indicator R-GECO1 failed to detect the lowering and reported a spurious [Ca2+]i elevation also in the presence of diazoxide, responses that could be ascribed to pH sensitivity of the indicator. Recordings with fluorescent H+ indicators demonstrated that glucose increases cytoplasmic pH in β-cells. Elevations of [Ca2+]i counteracted the alkalinization and [Ca2+]i oscillations in glucose-stimulated islets were associated with anti-phasic oscillations of [Ca2+]i and pH. A [Ca2+]i imaging-based reporter cell assay for real-time detection of the islet hormone somatostatin was generated by transfecting HeLa cells with somatostatin receptor 2, the G-protein Gα15 and R-GECO1. The reporter cells detected somatostatin secretion from islets imaged in the same view-field as dose-dependent [Ca2+]i elevations. Mouse and human islets released somatostatin in response to high K+, glucose, and the hormones GLP-1 and ghrelin. In glucose-stimulated mouse islets, bursts of somatostatin release were synchronized with islet [Ca2+]i oscillations. Analyses of islets from human donors indicated that type 2 diabetes is associated with hypersecretion of somatostatin. In conclusion, this thesis highlights potential pitfalls with fluorescent ion indicators in β-cell signalling studies and provides new insights into β-cell regulation of [Ca2+]i and pH. Moreover, it introduces an assay for real-time detection of somatostatin secretion from islets that holds promise for studies of the role of this hormone under normal conditions and in diabetes.
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Prognostic and Predictive Factors in Metastatic Colorectal Cancer
Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-522642
The outcome for metastatic colorectal cancer (mCRC) patients has improved substantially in recent decades. This has chiefly been observed in study populations, and predominantly in left-sided primary tumours, which is why we wanted to study if and how survival has improved in the background population. It has also been seen that certain molecular subtypes are more common in population-based materials, and, thus, we studied the prevalence and effects of different molecular alterations.
Paper I is a national population-based material of all 19 566 Swedish patients with a diagnosis of mCRC 2007-2016, 55% were male and 70% had synchronous metastases. Median overall survival (OS) for all patients was 14.0 months. An improvement could be seen over time, also in stratified analyses. OS was influenced by presentation of metastases, age, primary tumour location, and sex. All except sex remained statistically significant in a multivariable analysis. Differences of about one month in median OS were seen between healthcare regions, but these diminished over time.
Paper II included all 765 patients from the Uppsala Region with a mCRC diagnosis 2010-2020. Right colon primary tumours were seen in 38%, left colon in 27% and rectum in 34%. BRAF-V600E mutations (mt) and deficient mismatch repair (dMMR) had a poor OS and were more common in right colon primary tumours. Primary tumour location did not affect OS in subgroups according to mutations in RAS or BRAF, nor in a multivariable analysis. Molecular alterations seem to be more important than primary tumour location for prognosis.
Paper III studied KRAS-G12Cmt in three population-based and one real-world material. KRAS-G12C was seen in 2-4% of all tested and in 4-8% of all KRASmt. No differences in patient characteristics were observed between KRAS-G12C and other KRASmt. No differences in OS were seen between KRAS-G12C and other KRASmt, neither for all patients, nor in different treatment groups.
Paper IV studied atypical BRAFmt (aBRAFmt) in two population-based and one real-world cohort. aBRAFmt was seen in 1-4% of the adequately tested patients in the different cohorts. aBRAFmt patients were predominantly male, had dMMR less often, more rectal primary tumours, and less peritoneal metastases compared with BRAF-V600Emt. Serrated adenocarcinomas were seen in about half of the aBRAFmt. OS was significantly better for aBRAFmt than in BRAF-V600Emt, but worse than for RASmt and RAS&BRAFwt patients. Nine aBRAFmt received epidermal growth factor receptor inhibitors without responses.