Abstract
The prognosis of metastatic gastric cancer is poor. Despite the use of VEGF-, EGFR-, and HER2-targeting agents, prognosis is still poor in advanced gastric cancer. Although cancer immunotherapy responds well in some patients, clinical use is limited due to unanswered patients. For this reason, it is necessary to know the characteristics of primary and metastatic cancer cells for patient selection for immunotherapy and additional criteria are required. MHC-1 downregulation is most frequently observed in the tumor escape mechanism of cancer cells from the immune system. MHC-1 downregulation with increased PDL-1 expression of cancer cells has an important role in immune escape. MHC-1 downregulation and PDL-1 expression have been shown in many types of cancers. However, there is no study on the status of MHC-1 and PDL-1 in primary and metastatic tumor tissue. In this study, MHC-1 and PDL-1 score in primary and metastatic tumor cells was evaluated in 43 gastric cancer patients with lymph node metastasis. According to our results, the primary tumor PDL-1 score was correlated with the number of metastatic lymph nodes (r = 0.258; p = 0.024) and primary tumor size (r = 0.341; p = 0.045). A similar correlation was found between the primary tumor PDL-1 score and the metastatic tumor PDL-1 score (r = 0.213; p = 0.015). In our study, MHC-1 was found to be higher in primary tumors than metastatic tumors, although not statistically significant (p = 0.054). The results of our study showed high MHC-1 and low PDL-1 expression in primary tumors and low MHC-1 and high PDL-1 expression in metastatic tumors. These results reveal different biological characteristics of primary and metastatic tumor cells.
Highlights
Gastric cancer is the third most frequent cause of deaths from cancer in the world [1, 2]
No staining with Programmed cell death ligand-1 (PDL-1) was found in 25 primary tumors (58.1%) and 17 metastatic lymph nodes (39.5%)
Though no treatment on this case currently exists, it still is an important target for the immunotherapies since it might be playing an important role in terms of activating T cells against the tumor cells
Summary
Gastric cancer is the third most frequent cause of deaths from cancer in the world [1, 2]. As in all cancer types, knowing the features of metastatic cells is important to determine the treatment for gastric cancer. Metastatic tumor cells can have different phenotypical and biological characteristics from primary tumor cells [3, 4] The determination of these characteristics is significant to use and develop effective treatment methods. MHC class 1 downregulation is the most common mechanism of tumor escape from the host immune system. An MHC class 1 downregulation over 90% was reported to be observed in certain types of cancers. This situation might arise as a result of various mechanisms related with the regulation
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