With the in-depth study of tumor immunotherapy, tumor immune had been found that it played an increasingly important role in the recurrence and metastasis of PTC[20, 21]. LncRNAs were confirmed to serve as an important role in immune process activities, such as antigen exposure, antigen recognition, immune activation, immune cell infiltration and tumor clearance by regulating the expression of immune genes5,12. In our study, we defined 325 immune-related lncRNAs closely associated with PTC. Moreover, many of these lncRNAs were impacted on the prognosis of PTC.
In further analysis, the IRLPI established by 7 immune-related lncRNAs was a promising biomarker closely related to the prognosis of PTC through complex analysis. It was an independent factor for predicting the prognosis of PTC. High IRLPI group predicted a poor prognosis compared with low IRLPI. Many scholars also proposed different prognosis models for PTC in previous studies[22, 23], but our index was focused on immune-related lncRNAs of PTC. This had not explored at previous. As the deepening of the research on lncRNAs, it was confirmed that lncRNAs played an important control factor in tumor immune[7]. Therefore, we believed that IRLPI model based on immune-related lncRNA would show stronger predictive power and value in PTC.
CRNDE and LINC01614 were considered to be oncogenes in previous studies. CRNDE could promote cell proliferation, invasion and migration by competitively binding miR-384, and the CRNDE/miR-384/PTN played an important role in the regulation of PTC progression[24]. The results were consistent with our analysis. In Colorectal cancer, CRNDE had been demonstrated as a novel serum-based marker for the diagnosis and prognosis of colorectal cancer[25]. Furthermore, CRNDE also had been shown to be elevated in glioma[26], hepatocellular carcinoma[27], lung cancer[28] and other tumors[29, 30]. For LINC01614, it could promote expression of FOXP1 to impact the prognosis of lung cancer by inhibiting the expression of mir-217[31]. The same was true for breast cancer[32]. LINC01614 could affect the survival of breast cancer associated with TGF - and focal adhesion kinase (FAK) signaling. Choi et al[33] also found that LINC01614 could enhance the proliferation, colony formation and migration ability of gastric cancer cells. Unfortunately, only CRNDE and LINC01614 of 7 immune-related lncRNAs had been explored in cancers so far. Our study broadened the understanding of between lncRNAs and PTC, and also gave us some new insight into immune aspect.
The 7 immune-related lncRNAs could use to better divide PTC patients into two different directions in our analysis. The result indicated that various of signal pathways and biological processes were associated with the IRLPI in our result. Activation of cGMP-PKG signaling pathway could inhibit the proliferation and induce apoptosis of colon cancer[34]. Wang et.al indicated activation of Calcium signaling pathway could induce autophagy to promote apoptosis of tumor[35]. Glutamatergic synapse could promote Ca2+ entry into cells or regulate the PI3K/AKT pathway to impact tumor[36, 37]. In cancer patients, the nutrient metabolism pathways existed changes. Ciavardelli et al. indicated that there was metabolic heterogeneity between tumor cells and stromal cells[38]. In addition, adhesion and invasion-related pathways such as focal adhesion, could affect the invasion and metastasis of tumor. Previously studies were declared that the adhesion kinase was difference in follicular thyroid carcinoma with distant metastases[16, 39, 40]. Furthermore, IRLPI was associated with immune system development, which was a biological process with immune-related biological progress. This result manifested that IRLPI was related with immune status and immune microenvironment of PTC.
To explore the immune mechanism of IRLPI, ssGSEA analysis and Pearson correlation analysis were performed. Our result showed that IRLPI was closely associated with the PTC immune microenvironment. The infiltration of pDCs, APC and regulation of two types of IFN response were considered as anti-tumor component of IRLPI with negative correlation. pDCs might induce the differentiation of naive CD4+ T cells into ICOS+Foxp3+Tregs and was one of the mechanisms underlying tumor escape in PTC plus multinodular non-toxic goiter patients[41]. However, other studies showed a significant reduction in pDCs in cancer tissues[42]. T cells required at least two signals for their full activation in immune response. The interaction of between T cell receptor with an MHC antigenic peptide complex was the first factor. The interaction of between T cells receptors and co-stimulatory molecules of antigen presenting cells (e.g.LFA-3, CD40, ICOS, CD80 or CD86) was the second factor[43, 44]. APC co-stimulus molecules served as the second factor for anti-tumor in PTC by our analysis. Li et al[45] declared that IFN-a (type I IFN) could induce Fas expression and apoptosis in hedgehog pathway through inhibiting Ras-Erk signaling in Basal cell carcinoma, which indicated IFN-a was Anti-cancer agent. This was consistent with our result. There was controversial for IFN-γ (Type II IFN) in PTC. IFN-γ (Type II IFN) could mediate the activation of T lymphocytes and played an anti-cancer role[46]. And in PTC, IFN-γ could induce the secretion of CXCL10 and inhibit the proliferation of PTC cells significantly. But in funnily, LV et al[47] found that TNF-a and IFN-γ could induce epithelia mesenchymal transition of the three PTC cell lines and malignant progression in human PTC cells. The topic of between immune and tumor was complex and still unclear at present. In our study, we identified the anti-tumor immune components associated with IRLPI in PTC. Our preliminary analysis result could broaden our understanding of the immunological aspects of PTC and provide a perspective to explore for further.
This research comprehensively explored the impact on between IRLPI established by 7 immune-related and prognosis of PTC in R platform. IRLPI was novel index for the prognosis of PTC. Meanwhile, we investigated the latent mechanism of IRLPI by applying multiple analytical methods. However, some limitations still needed to be considered in our study. First, the lack of validation in another independent cohort was a limitation of our study. Second, the reliability of molecular mechanism and immune-related analysis results faced challenged because of the lack of in vivo and in vitro experiments.