Investigation of factors affecting pre-metastatic niche development

Cancer is a group of diseases characterized by uncontrolled growth and abnormal spread of cells throughout the body. In the world, one of each seven deaths ıs due to cancer. According to the International Agency for Research on Cancer (IARC), cancer is the second leading cause of death in the world after cardiovascular diseases and was responsible for about 18.1 million new cases and 9.6 million deaths in 2018. Most of these deaths are due to the formation of metastases, known as, secondary tumors. Vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2) are known to have critical roles in tumor angiogenesis. There is also evidence that due to the formation of new blood vessels and having a role in the induction of metastasis-related cytokines it may be associated with tumor growth and metastasis as well. VEGF-A inhibits the development of APC cells and T-cells and organizes undeveloped APC cells to recruit immune-suppressing cells (MDSC, TAM, and Tregs) to the environment. On the other hand, it has been shown that VEGF receptors present on many cell types, causing them to release metastasis-related cytokines such as TGF-β, NO, IL-17 and IL-6. It was also shown that PD-L1, synthesized by tumor cells and immune suppressor cells, plays a role in epithelial-mesenchymal transition (EMT), metastasis and treatment resistance, as well as its role in escape from the immune response. In this study, we mainly planed to investigate the effect of VEGF pathway on the formation of pre-metastatic niches in the lung. For this purpose, we aimed to investigate the effects of anti-VEGF (axitinib) and anti-PDL1 (anti-hPD-L1-mlgG1) treatments, routinely used in cancer treatment, on the secretion of metastasis-related cytokines, immune cells, and immune suppressor cells. Our study was planned in-vitro and in-vivo. During in-vitro experiments, melanoma cancer cell line was used. The metastasis-related cytokine secretion were determined at the gene level by the qPCR method and the immune system-associated cells by the Western Blot method. On the other hand, during the in-vivo experiments, the mice were sacrificed and their lung were mapped, then from different part of the lung tissue the metastasis-related cytokines were investigated at the gene level by qPCR method at protein level by Western Blot method. On the other hand the immune system-related cells were investigated through İmmunohistochemistry method. This study is a further step of my master thesis. This project is specific because Axitinib and atezolizumab both solo and in combination were used during in-vitro and in-vivo experiments to map the lung tissue. Possible pre-metastatic niche mapping on the lung were made with the data obtained with this study. In addition, the effect of using anti-angiogenic and immune checkpoint inhibitors in combination on metastasis were determined and provide us with a rationale for the use of them in combination.