| Summary: | Liver cancer comprises a heterogeneous group of malignant tumors with different histological features that include hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), among other neoplasms. HCC and CCA present limited options for effective therapeutic strategies, being ablation, surgical resection and/or transplantation the only curative treatments applied so far. In addition, these carcinomas are characterized by a high recurrence rate after surgical resection. Therefore, novel treatment strategies and/or mechanism to determine therapy response are needed to improve the prognosis of HCC and CCA patients. Immunotherapybased approaches represent an alternative very promising for liver cancer. However, predicting responders and non-responders to immune therapies remains a challenge. The present Thesis had as main objective to advance and deepen the current knowledge on the relationship between cancer and immunity as well as to characterize the immune and the lipidomic context in liver cancer patients. To do so, a deep functional and phenotypical characterization of tumorinfiltrating leukocyte (TIL) subsets and circulating immune cells was performed by multi-color flow cytometry. Purification of immune cell populations by cell sorting was carried out for subsequent analysis of mRNA expression of immune mediators by qRT-PCR. ELISA techniques were used to quantify immune mediators in patients’ sera. Additionally, highresolution LC-MS base lipidomic approach was applied to monitor peripheral changes in the phospholipidome of cancer patients, before and after tumor resection, providing an indirect read of the lipid changes induced by the surgical procedure. A higher infiltration of protumor macrophages in HCC classified into high-grades or into highrisk was detected. A pro-inflammatory state was observed both in HCC and CCA patients, and functional defects of some circulating monocyte subsets and myeloid dendritic cells were also detected, displaying partial recovery after tumor resection. TNFα mRNA expression by circulating monocytes as well as serum TNFα levels were associated to the presence of highgrade tumors. The frequency of circulating Treg cells in HCC and CCA patients was decreased, being partially recovered after tumor resection. Moreover, the frequency of circulating Tc17 cells as well as CD4 T lymphocytes with the plasticity to produce both IFNγ and IL-17 cytokines were decreased in CCA and HCC patients, suggesting a specific migration to the tumor microenvironment. Furthermore, it was revealed that the alterations identified in the phospholipidome of liver cancer patients were affected by tumor resection procedure. The results obtained showed that the alterations observed in the phospholipidic profile of liver cancer patients were reverted after surgery. Overall, the studies presented in this Thesis reported the utility of multi-color flow cytometry to detect functional and phenotypic differences in TIL subsets from patients with different types of cancer (CCA vs. HCC), different tumor histopathological grades, and different risk stratification classifications, in addition to monitoring functional competence of circulating immune cells to better evaluate immune dysfunctions in cancer patients. Besides, high-resolution LC-MS was demonstrated as being a usefulness technique to monitor peripheral changes in the phospholipid profile of liver cancer patients that could be used to predict patients’ outcomes after surgery.
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