Tumor necrosis factor-α-inducible protein 8-like protein 3 (TIPE3): a novel prognostic factor in colorectal cancer

Colorectal cancer (CRC) is the most common malignant tumor of the digestive system and is associated with a high mortality rate [1, 2]. The occurrence and development of CRC are closely related to patients’ age, gender, lifestyle, dietary habits, and genetic factors [3].

The tumor necrosis factor-α-induced protein 8 family (TNFAIP8/TIPE) is induced by tumor necrosis factor-α (TNF-α), which is closely related to immune regulation and tumorigenesis [4]. It has been reported that this family contains four members, namely, TNFAIP8/TIPE, TIPE1, TIPE2, and TIPE3 [5]. TIPE is a negative regulator of apoptosis, which can lead to the occurrence of cancer. TIPE1 is an enhancer of cell apoptosis, which can induce cell apoptosis and which has an anti-tumor effect. As a negative regulator of inflammation and immunity, TIPE2 can prevent the occurrence of some tumors [6]. Among these, TIPE3, identified in 2008, is the least studied member of the TIPE family [7]. TIPE3 is highly expressed in most human tumor cell lines, such as lung cancer cell line NCI-H727, bladder cancer cell line T24, and colon adenocarcinoma cell line HT-29, but with a low expression in the gastric cancer cell line. At the same time, it is significantly up-regulated in lung cancer, esophagus cancer, cervical cancer, and colon cancer [8]; it was found that TIPE3 overexpression significantly increased the migration, invasion, and proliferation of MCF-7 and MDA-MB-231 tumor cells in human breast cancer cell lines. On the contrary, knockdown of TIPE3 in MDA-MB-231 cells can significantly reduce the migration, invasion, and proliferation of tumor cells [9]. In human non-small-cell lung cancer (NSCLC), some researchers have found that the expression of TIPE3 on the plasma membrane is positively correlated with the T stage of NSCLC, indicating that TIPE3 located in the plasma membrane may play a role in promoting tumor development, whereas cytoplasmic TIPE3 may exert a negative effect [10]. Meanwhile, in human glioblastoma (GBM), overexpressed TIPE3 inhibits p38 phosphorylation and blocks p38 nuclear translocation, leading to the negative regulation of the p38 MAPK pathway and resulting in GBM cell survival [11]. These results suggest that the role of TIPE3 in different tumors is heterogeneous.

In this work, we mainly used clinical/surgical specimens, focusing on the correlation between the TIPE3 expression and tumor-immune infiltration and the prognosis of CRC patients. The expression level of TIPE3 in the cancer and adjacent tissues of 110 CRC patients was detected by immunohistochemistry (IHC). According to the score statistics of the IHC results, combined with the patients’ prognosis information, the survival curve of the TIPE3 expression in CRC tissues and the prognosis of patients were determined, and the correlation between the TIPE3 expression and prognosis was analyzed. At the same time, we investigated the relationship between the TIPE3 expression level and tumor immune invasion: IHC was used to detect the positive cell numbers of CD8+ T cells, CD20+ B cells, and CD66b+ neutrophils in the cancer and adjacent tissues of 110 CRC patients. Combined with the prognosis information of the patients, a corresponding survival curve was drawn, and we found that patients with a high TIPE3 expression had a lower survival rate, while patients with a low TIPE3 expression had a higher survival rate.

The most effective form of prevention and early treatment of CRC is colonoscopy, which can detect precancerous lesions and early cancers to improve survival and prognosis rates significantly [16]. Current evidence suggests that through early screening, diagnosis, and treatment, patients with rectal cancer have a better prognosis, with a five-year survival rate of about 90% and a metastasis rate of only 14% [17]. In recent years, researchers have achieved significant strides in bringing awareness to the importance of early screening [18], made improvements to surgical techniques [19], and developed targeted therapy [20], which have significantly improved the survival rate of CRC patients. In our work, we found that patients with a high TIPE3 expression had a lower survival rate, while patients with a low TIPE3 expression had a higher survival rate. However, the type of TIPE positive cells was not analyzed in detail. Univariate regression analysis showed that the expression of TIPE3 and the number of CD66b+ neutrophils were risk factors for the OS of CRC patients; and the number of CD8+ T cells, the number of CD20+ B cells, and tumor grade were protective factors for the OS of CRC patients. These prognostic factors were then subjected to multivariate regression analysis, and the results show that the expression of TIPE3, the number of CD8+ T cells, and the number of CD66b+ neutrophils are prognostic factors affecting the OS rate of CRC patients, and TIPE3 is correlated with survival rate.

Our study found that the TIPE3 expression in CRC cancer tissues was significantly higher than in adjacent normal tissues, which may be related to the fact that TIPE3 can promote the occurrence and development of tumors. It is widely thought that at the cancerous site, TIPE3 is stimulated by the tumor environment, resulting in a higher TIPE3 expression, which in turn accelerates the transport rates of PIP2 and PIP3, two lipid second messengers; this activates the PI3K/AKT and MEK-ERK signaling pathways, which further promotes the growth, proliferation, and migration of tumor cells, accounting for the malignancy and poor prognosis. Combined with the prognostic information of CRC patients, it is suggested that a high TIPE3 expression predicts a poor prognosis, and the survival rate of these patients is significantly lower than that of patients with a low TIPE3 expression, consistent with the results of the TCGA database analysis (Supplementary Fig. 1). We noted that Zhong’s analysis of 49 CRC samples showed no correlation between TIPE3 mRNA expression levels and patients’ clinicopathological features, while the TIPE3 protein expression level in the tumor group was lower than that in the adjacent group [21]. This contrasts our current results, possibly because of the different number of samples tested or the existence of tumor heterogeneity. In our work, 110 samples were used, and IHC staining was performed to count the number of TIPE3-positive cells in the tumor and adjacent tissues, and two conditions—high and low TIPE3 expressions—in tumor tissues were found, among which the number of high-expression samples was 76 and the number of low-expression samples was 34. This result is consistent with most studies [22, 23].

Tumor-infiltrating immune cells are an important component of tumor tissue and play a crucial role in tumor occurrence and development. T cells are key tumor-infiltrating immune cells [24], and CD8+ T cells, a T-cell subtype, participate in the immune surveillance of tumor antigens during tumor development. T cell antigen receptors activate CD8+ T cells, rapidly proliferate and differentiate into cytotoxic T lymphocytes, and finally eliminate cancer cells through cellular immunity. Ample literature suggests that the extensive infiltration of CD8+ T cells in tumors is associated with good patient prognosis [25‐28]. In our work, we found that the expression of TIPE3 and the number of CD8+ T cells were prognostic factors affecting the OS rate of CRC patients. Although our study did not find a significant correlation between the TIPE3 expression and the number of tumor-infiltrating immune cells, a Cox regression analysis showed that the TIPE3 expression and CD8+ T cells jointly affect patient survival (Table 3 and Supplementary Fig. 2), suggesting they have significant prospects for clinical applications as prognostic indicators.

Using clinical samples from 110 CRC patients, we found the TIPE3 protein to be upregulated in CRC cancer tissues and to be significantly correlated with patients’ OS rate. The high TIPE3 expression correlated with poor overall survival of the patients.