Prostatacancer utgör idag den vanligaste cancerformen bland män i västvärlden och enbart i Sverige diagnostiseras cirka 10 000 män årligen med sjukdomen. Immunförsvaret och mer specifikt CD8+ T-cellerna spelar en viktig roll i förmågan att eliminera tumöromvandlade celler innan en klinisk relevant cancer uppstår. T-cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif domain (TIGIT) är ett inhibitoriskt checkpoint protein som har visat sig ha en dämpande effekt på CD8+ T-celler vilket tumörceller utnyttjar för att öka sin tillväxt. Detta protein har identifierats i hög grad i flera olika cancertyper samt kan användas som prognostisk markör för ett antal olika cancersjukdomar. Ett immunohistokemiskt protokoll optimerades och användes för att detektera TIGIT-uttryck i formalinfixerad och paraffininbäddad prostatatumörer från män med eller utan lymfkörtelmetastas vid diagnostillfället. Resultatet var att av patienter med lymfkörtelmetastas hade 17 (77,3 %) TIGIT-uttryck i sin primärtumör och för män utan lymfkörtelmetastas hade 27 (79,4 %) TIGIT-uttryck. Fisher’s exact test användes för att studera associationen mellan TIGIT-uttryck i primärtumören hos prostatacancerpatienter och lymfkörtelmetastas. Testet visade ingen signifikant skillnad mellan dessa grupper, p = 1,00. Vår slutsats är att TIGIT inte kan användas som prognostisk markör för prostatacancermetastasering, men ytterligare studier krävs för att definitivt kunna dra några slutsatser. / Prostate cancer constitutes the most common form of cancer among men in the western world today and, in Sweden alone, about 10,000 men are diagnosed with the disease annually. The immune system and specifically CD8+ T cells play an important role in the ability to eliminate tumour cells before a clinically significant cancer occurs. T-cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif domain (TIGIT) is an inhibitory checkpoint protein that has been shown to have a suppressing effect on CD8+ T cells in which tumour cells exploit to increase in size. This protein has been identified in several types of cancer and can be used as a prognostic biomarker in a range of different cancer diseases.  A protocol for immunohistochemistry was optimized and used for detecting TIGIT expression in formalin-fixed and paraffin-embedded tissues of prostate tumour from men either with lymph node metastases or not by the time of diagnosis.  The results from patients with lymph node metastases was that 17 (77,3 %) had TIGIT expression in their primary tumour while for men without lymph node metastases 27 (79,4 %) had TIGIT expression. Fisher’s exact test was used to study the association between TIGIT expression in the primary tumour of prostate cancer patients and lymph node metastases. The test showed no significant difference between these groups, p = 1,00. Our conclusion is that TIGIT can not be used as a prognostic biomarker for prostate cancer metastases, but further study is needed to definitely draw any conclusions.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19594号 / 医博第4101号 / 新制||医||1014(附属図書館) / 32630 / 京都大学大学院医学研究科医学専攻 / (主査)教授 竹内 理, 教授 河本 宏, 教授 朝長 啓造 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Endemic Burkitt lymphoma (eBL) is the leading pediatric cancer in sub-Saharan Africa and is associated with Epstein-Barr virus (EBV) and Plasmodium falciparum malaria co-infections. Current treatment options in Africa are combination chemotherapy with a survival rate hovering around 50%. Relapsed or refractory eBL patients have failed to receive any targeted treatments in the clinic. Our focus was to delineate immune responses in eBL, interrogate the tumor variation in responses to targeted treatments and develop mouse models that can be used to target essential mediators of tumor pathogenesis. Immune-based treatments including immune checkpoint inhibition have recently become an effective therapeutic modality in oncology. However, some B cell lymphomas such as Hodgkin Lymphoma (HL), are more receptive to checkpoint inhibition than others suggesting a need to understand the efficacy of checkpoint inhibition on different lymphoma subtypes. Checkpoint inhibitors act by blocking inhibitory receptors on T cells and improving anti-tumor responses. One of the goals of this thesis was to characterize checkpoint inhibitors on Tumor-infiltrating lymphocytes (TILs) in eBL tumors and to identify T cell subsets that exhibit increased expression of inhibitory receptors, poor cytokine production, poor proliferation and express transcription factors associated with exhaustion. Using scRNA seq, we identified T cell clusters that co-expressed inhibitory receptors, poor proliferative markers but also sustained costimulatory signals, as well as cytokine expression suggesting a pre dysfunctional state and not terminally exhausted state. Furthermore, we quantified the dominant co-inhibitory receptors PD1 and TIGIT that are upregulated in the tumor microenvironment via immunohistochemistry (IHC) and in peripheral blood of eBL patients via flow cytometry. We compared eBL patients with healthy pediatric cohorts with a history of persistent malaria exposure to those who had little to no malaria infections, to understand uniquely T cell mediated responses in BL children. Tumors had high co-expression of PD1 and TIGIT but fewer PD1 only populations, suggesting that both ligands may play a role in restraining immune activation via IHC. Next, we investigated if PD1 ligands or TIGIT ligands were overexpressed in eBL tumors. Nectin-2, TIGIT ligand was highly expressed in eBL tumors but was not highly correlated with TIGIT expression. These studies provide insights for PD1/ TIGIT blockade in Burkitt lymphoma patients. Additionally, we established new patient-derived cell lines from eBL tumors to study tumor variation and to study targeted treatments. We established five new patient-derived eBL lines BL717, BL 719, BL720, BL725, and BL740 that were interrogated for their inter-patient variation by studying their gene expression profiles. Further, we developed a patient cell-line derived xenograft (CDX) mouse model by injecting newly patient-derived BL cell lines in immunodeficient mice (NSG BL) and studying BL tumorigenesis. Having successfully established NSG BL tumors, we observed differences in tumor growth sensitivity and survival. We tested rituximab efficacy, one of the most established treatments for B cell lymphomas in our mouse model. We also identified pathways associated with unfolded protein response (UPR) and the mammalian target of rapamycin (mTOR) signaling, as well as apoptosis in one of the cell line xenografts, BL740, in response to rituximab. BL717, BL720 cell line xenograft failed to control tumor growth and was enriched in IFN-ɑ signature genes. This mouse model will prove to be useful to study combination therapy against eBL tumors as well as mechanisms of resistance to drug targets. Collectively, these studies provide insights into intratumoral variation including subtypes during tumor progression and expression profiles of TILs in eBL tumors. This will be important in designing new therapeutic strategies as well as help pose novel therapeutic targets.

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