GC, as one of the common malignant tumors of the digestive system, poses a serious threat to human health as well as smart cancer and colorectal cancer[12]. Although its morbidity and mortality have shown a downward trend globally, it has been in major malignancies. Cancer still ranks second in mortality and fourth in new cases worldwide, and its new cases and deaths in developing countries are higher than in developed countries[13]. In China, the current incidence of GC is 29.9 per 100,000 (male 41.3/100,000 vs. female 18.5/100,000), and the mortality rate is 22.3 per 100,000 (male 30.1/100,000). (VS. Women 14.6/100,000)[14, 15]. The current treatment method for GC is comprehensive surgery (including adjuvant chemotherapy, molecular report drug treatment)[16]. Although surgical resection and adjuvant chemotherapy have made great progress in the treatment of GC, some GC can be cured at an early stage[17, 18]. Unfortunately, most patients are already in an incurable stage when they are discovered. Originally effective treatments have become ineffective or ineffective, and the overall prognosis is poor. Over the years, countless scholars have contributed their lives in the pathogenesis and improvement of prognosis of GC. The detection of EGF, cycInE, p27, E-caerin, CD44v6, MMP-1, TIMP-1, HER-2, HER-3, and VEGF may have important significance for the individualized treatment of GC patients[19, 20]. However, the mechanism of gastric cancer has not been fully clarified so far, and there is no effective indicator for early diagnosis, early treatment, improved prognosis, and prolonged patient survival. Therefore, whether or not to find an effective tumor marker for early diagnosis and improve the treatment effect has become an urgent need for clinicians and laboratory researchers.
Recently, a new candidate oncogene, tumor necrosis factor-a-inducing protein 8 (Tumorcrosis factor-a-induce protein 8, TNFAJP8), has gradually come into the sight of scholars and has attracted widespread attention. Members of this family include TNFAIP8, TNFAIP1 (TNF-induceprotein8-lick1, TIPE1), TIPE2 and TIPE3. The first to be found was TNFAIP8, also known as GG2-1, SCC-S2, MDC-3.13[21, 22]. The gene is located on chromosome 5q23.1 and is expressed in most malignant tumor tissues. This gene is involved in many gestational processes such as immune homeostasis, signal transduction, and apoptosis, and therefore plays an important role in tumorigenesis, invasion and metastasis. In recent years, a series of roles of TNFAIP8 in tumor formation have been continuously confirmed. These results show that TNFAIP8 plays a vital role in the development of tumors. They are involved in the regulation of cell proliferation in different tumor types, and tumor invasion, migration, death, and drug resistance. Xing et al. measured the expression of TNFAIP8 in non-small cell lung cancer tissues and adjacent normal lung tissues using real-time quantitative PCR, Western blotting, and immunohistochemical methods[23]. Among 25 lung cancer tissues, 18 (72%) of them were lung cancer tissues. We can detect the high expression of TNFAIP8mRNA. Compared with cancer tissue, TNFAIP8 protein is more highly expressed in lung cancer tissues. Miao et al. analyzed the expression pattern of TNFAIP8 in 92 colon cancer tissues by immunohistochemistry, and found that TNFAIP8 was overexpressed in 45 patients (48.9%). There is a significant correlation between TNFAIP8 overexpression and TNM staging, lymphatic metastasis and appreciation index. Although TNFAIP8 plays a vital role in the genesis and development of tumors, the expression of TNFAIP8 in gastric cancer and its role in regulating the growth, invasion and migration of gastric cancer cells have not been determined. In our study, PCR results found that compared with normal tissues, the TNFAIP8 gene was significantly increased in gastric cancer tissues. In addition, compared with normal gastric mucosa tissue, T genes were significantly increased in the four gastric cancer tissues. This result indicates that TNFAIP8 gene is involved in the pathological process of gastric cancer.
At present, there are few studies on the role of TNFAIP8 in gastric cancer, and it is difficult to determine whether down-regulation of TNFAIP8 will affect the biological characteristics of gastric cancer cells. In the first experiment, we have confirmed that TNFAIP8 is expressed in gastric cancer tissues and tissues, and its expression is higher than that of adjacent tissues and normal gastric mucosal cells, suggesting that TNFAIP8 is closely related to the occurrence and development of gastric cancer. There is also a correlation between expression and the clinicopathological features and poor prognosis of gastric cancer. However, its effect on the colonization of gastric cancer cells and its ability to affect invasion and migration has not been determined. For this study, we explored the correlation between TNFAIP8 and autophagy.
At present, a type of cell death that does not depend on the apoptotic pathway-cell autophagy has become a research hotspot. On the one hand, autophagy can play an anti-tumor and anti-aging effect; but on the other hand, the autophagy process can provide cells with nutrients to help them survive the harsh environment and also play a role in promoting the development of tumors[24]. It is a "double-edged sword" in the process of tumorigenesis and development. Hypoxia, ischemia, and radiation therapy can cause tumor cell autophagy to increase, tumor tissue lacks blood supply, and metastasis is prone to place tumor cells in a metabolic stress state[25]. At this time, autophagy could help tumors with defective apoptosis cells continue to survive under this metabolic stress condition. In this study, over-expression of the TNFAIP8 significantly increased cell viability, decreased apoptotic rate and increased migration ability. However, autophagy inhibitor and activator significantly reversed these changes. The above phenomenon is very interesting, suggesting that the TNFAIP8 gene may have effect on tumor cells by activating autophagy signals and regulated the pathophysiology of gastric cancer.
Akt is a key molecule downstream of PI3K. It binds to PI3K through its N-terminal PH domain. At the same time, it can regulate the proliferation and survival of many types of cells[26]. Akt acts as a key regulator of multiple cell proliferation, differentiation and survival. mTOR is an important substrate of ATK, as a large protein with a C-terminal serine/threonine PI3K-related kinase domain. The mTOR signal pathway, as an important cell signal transduction pathway, is involved in physiological activities such as cell growth, survival, and autophagy. Studies have also shown that abnormal mTOR signals have profound effects on cell homeostasis, and may even lead to the development of pathological conditions, such as gastric cancer[27]. Tian et al used immunohistochemistry to detect the expression of AKT in tumor tissues and adjacent tissues of 128 patients with gastric cancer, and found that the expression level of AKT in tumor tissues was significantly higher than that in adjacent tissues and was related to the T stage[28]. The expression of phosphorylated AKT (phospho-AKT, p-AKT) was detected in tissue samples from 231 patients with gastric cancer. It was found that p-AKT was expressed in 119 samples (53%). Statistical analysis showed that p-AKT Poor patient prognosis. Li et al. detected the expression of mTOR in 33 patients with GC and 30 healthy controls by immunohistochemistry, and found that the expression rate of mTOR in patients with GC was 51.5%. There is almost no mTOR expression, suggesting that mTOR activation occurs during the occurrence and development of GC[29]. In addition, the study also found that mTOR expression is associated with late tumor stage, poor differentiation, and lymph node metastasis. ULK1 (Unc-51. Like. Autophage. Akinting. Kinase) complex can initiate the formation of autosome. ULK1 can be regulated by mTORC1 and MAPK-related kinases. mTORC1 can integrate growth factors, regulate oxygen content, amino acids and energy, and promote the synthesis of proteins related to cell growth metabolism[30]. When mTORC1 is activated, it can reduce the activity of ULK1 kinase by phosphorylating ULK1 and ATG13. In this study, we investigated the relationship between the TNFAIP8 and the mTOR-Akt-ULK1signaling pathway and its role in gastric cancer. Our results show that over-expressing the TNFAIP8 significantly reduced p-Akt and p-mTOR levels and increases p-ULK1 level. In contrast, silenced TNFAIP8 significantly increased p-Akt and p-mTOR levels, and significantly reduced p-ULK1 level. Even more interesting was that when autophagy activators are added, these changes are significantly reversed. The above results show that the TNFAIP8 could inhibit the mTOR-Akt-ULK1 and involved in the physiological and pathological processes of gastric cancer.