Tumor-infiltrating immune cells are a critical part of the tumor microenvironment. These cells regulate tumor growth, invasion, and metastasis by altering the immune status of tumor cells. In this study, we evaluated the status of the nine TIICs related to OS in 291 patients with pRCC and found that patients with high-risk scores had a shorter overall survival time. Nine immune-related markers for pRCC were screened out via multiple analyses by comparing the differences between the high-risk and low-risk groups.
In this study, nine TIICs related to OS, including T cells follicular helper, Macrophages M1, Dendritic cells activated, T cells regulatory (Tregs), B cells memory, T cells CD8, Macrophages M2, B cells naïve, T cells CD4 memory activated, and T cells CD4 memory resting, were identified via univariate Cox analysis. Previous studies have shown that macrophages are one of the most abundant cell types in the tumor microenvironment, contributing to tumor progression [25, 26]. In our study, correlation analysis with clinical traits showed that macrophages affected the tumor type, pathological stage, TNM stage, and prognosis of patients with pRCC. Moreover, we found that macrophages were also the most abundant cell types in pRCC and were significantly associated with the nine hub genes we obtained (TOP2A, BUB1B, BUB1, TPX2, PBK, CEP55, ASPM, RRM2, and CENPF). Therefore, the results of previous studies are consistent with the results obtained in this study [25, 26].
Functional enrichment analysis showed that the DEGs in the high- and low-risk groups were significantly associated with tumor cell infiltration-related pathways. Both the cytokine-cytokine receptor and cAMP signaling pathways were significantly enriched, based on our analyses. Cytokines play an important role in cancer-related immune responses and promote tumor angiogenesis, tumor cell invasion, and tumor cell metastasis [27, 28]. IFN-γ is one of the cytokines necessary in immunomodulation and anticancer immunity, which also induces the expression of PD-L1 in most tumor cells . The cAMP signaling pathway is a critical modulator of specific tumor cell properties such as proliferation, differentiation, and migration . Dou A-X et al. showed that regulatory T cells might suppress the antitumor immune response through the intercellular transport of cAMP and the activation of the cAMP-protein kinase A signaling pathway . Furthermore, the GSEA found that regulatory T cells were significantly enriched in pRCC, which was consistent with the KEGG enrichment results.
Currently, researchers have reported that hub genes such as TPX2, TOP2A, and BUB1 are closely associated with pRCC progression [32–34]. A study based on computer modeling showed that TPX2 was a potential risk biomarker involved in cell proliferation in pRCC . Further, bioinformatics analyses showed that both TOP2A and BUB1 were predicted to be related to the occurrence and development of pRCC [32, 33]. In addition, some studies have also reported the effect of the expression of these genes in other tumors [35, 36]. TOP2A cleavage is a broad DNA damage mechanism found in oncogenic translocations . MiR-139-5 upregulates the expression of its target gene TOP2A and promotes the progression of ccRCC . Downregulation of TPX2 inhibits the proliferation and invasion of endometrial cancer cells and promotes the apoptosis of EC-derived cells . It also suppresses the growth of liver cancer by regulating the PI3K/AKT signaling pathway . A dysregulated expression of BUB1 leads to aberrant chromosomal replication and aneuploidy, contributing to the development of tumors . Previous studies have demonstrated that these three genes play an important role in tumorigenesis and cancer development, and verified the role of these genes in pRCC through computer models and bioinformatics analyses.
The underlying mechanism of the other hub genes such as BUB1B, PBK, CEP55, ASPM, RRM2, and CENPF remains unclear in pRCC. However, we found that these hub genes strongly correlated with macrophages and had clinical significance in pathological staging, survival, and diagnostic value. A nomogram obtained containing these hub genes had good predictability, suggesting that these genes are significantly associated with prognosis. Therefore, these hub genes are potential immune-related biomarkers for pRCC. Additionally, our conclusions are supported by the results of previous studies. Mechanistically, it modulates the transcriptional activation of the mitotic checkpoint kinase BUB1B, which also promotes tumor growth and chemoresistance, leading to poor outcomes for patients with lung adenocarcinoma . An in vitro study showed that the overexpression of BUB1B enhanced the proliferation, migration, and invasion of prostate cancer cell lines, while the removal of BUB1B did not affect these cell functions . PBK is a novel serine-threonine kinase related to the mitogen-activated protein kinase (MAPK) family. It is an important link in many carcinogenic signaling pathways, including p38, extracellular signal-regulated kinase 1/2 (ERK1/2), and the FAK/Src-MMP signal pathways . CEP55 is a key regulatory factor of the cytoplasmic split and is associated with genomic instability; genomic instability is a hallmark of cancer . Carcinogenic CEP55 regulates the proliferation, migration, and invasion of tumor cells as mediated by the PI3K/AKT/mTOR pathway and is related to poor prognosis . The potential role of ASPM on pRCC is still unclear; however, it was highly expressed in various cancers such as endometrial cancer and lung squamous cell carcinoma and is related to poor clinical prognosis and an increased risk of cancer recurrence [45, 46]. RRM2 is essential for DNA synthesis and repair and is frequently overexpressed in various cancers . The oncogenic role of RRM2 has been linked to the promotion of epithelial-mesenchymal transition (EMT) and angiogenesis . CENPF is a critical regulator of cancer metabolism, and the silencing of CENPF has been shown to increase the expression of inactive forms of pyruvate kinase M2, a rate-limiting enzyme indispensable for an irreversible reaction in glycolysis and reduces global bio-energetic capacity, acetyl-CoA production, histone acetylation, and lipid metabolism . The above analysis mainly reveals that the hub genes obtained play an important role in tumor development and may be potential therapeutic targets in the treatment of pRCC.
In summary, nine prognostic-related immune cells and nine hub genes were identified, providing compelling insights into the pathogenesis of pRCC and may serve as potential therapeutic targets for pRCC. These nine types of immune cells may also provide important clues so we can better understand the immune microenvironment in pRCC. The hub genes obtained can be considered as biomarkers for the prognosis of pRCC and may also serve as key targets for immunotherapy in pRCC. However, it is important to point out that the evidence presented in this study was obtained indirectly from bioinformatics analyses, which is its major limitation.