AQP9 Is a Prognostic Factor for Kidney Cancer and a Promising Indicator for M2 TAM Polarization and CD8+ T-Cell Recruitment

Jibo Jing; Jin Sun; Yuqing Wu; Nieke Zhang; Chunhui Liu; Saisai Chen; Wenchao Li; Cheng Hong; Bin Xu; Ming Chen

doi:10.3389/fonc.2021.770565

AQP9 Is a Prognostic Factor for Kidney Cancer and a Promising Indicator for M2 TAM Polarization and CD8+ T-Cell Recruitment

Front Oncol. 2021 Nov 5:11:770565. doi: 10.3389/fonc.2021.770565. eCollection 2021.

Authors

Jibo Jing^{1

2

3}, Jin Sun⁴, Yuqing Wu^{1

2

3}, Nieke Zhang^{1

2

3}, Chunhui Liu^{1

2

3}, Saisai Chen^{1

2

3}, Wenchao Li^{1

2

3}, Cheng Hong^{1

2

3}, Bin Xu^{1

2

3}, Ming Chen^{1

2

3}

Affiliations

¹ Institute of Urology, Surgical Research Center, Institute of Urology, Medical School of Southeast University, Nanjing, China.
² Department of Urology, Medical School of Southeast University, Nanjing, China.
³ Department of Urology, Affiliated Zhongda Hospital of Southeast University, Nanjing, China.
⁴ Department of Urology, People's Hospital of Xuyi County, Nanjing, China.

Abstract

Background: It is undeniable that the tumor microenvironment (TME) plays an indispensable role in the progression of kidney renal clear cell carcinoma (KIRC). However, the precise mechanism of activities in TME is still unclear.

Methods and results: Using the CIBERSORT and ESTIMATE calculation methods, the scores of the two main fractions of tumor-infiltrating immune cells (TICs) from The Cancer Genome Atlas (TCGA) database of 537 KIRC patients were calculated. Subsequently, differentially expressed genes (DEGs) were drawn out by performing an overlap between Cox regression analysis and protein-protein interaction (PPI) network. Aquaporin 9 (AQP9) was identified as a latent predictor through the process. Following research revealed that AQP9 expression was positively correlated with the pathological characteristics (TNM stage) and negatively connected with survival time. Then, by performing gene set enrichment analysis (GSEA), it can be inferred that genes with high expression level of AQP9 were mainly enriched in immune-related activities, while low AQP9 group was associated with functions of cellular metabolism. Further studies have shown that regulatory T cells (Tregs), macrophages M2, macrophages M0, CD4+ T cells, and neutrophils were positively correlated with AQP9 expression. While the levels of mast cells, natural killer (NK) cells, and CD8+ T cells are negatively correlated with AQP9. The result of multiple immunohistochemistry (mIHC) suggests a negative relevance between AQP9 and CD8+ T cells and reveals a trend of consistent change on AQP9 and M2 macrophages.

Conclusion: The expression level of AQP9 may be helpful in predicting the prognosis of patients with KIRC, especially to the TME state transition, the mechanism of which is possibly through lipid metabolism and P53, Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways that affect M2 polarization. AQP9 was associated with the expression levels of M2, tumor-associated macrophages (TAMs), and the recruitment of CD8+ T cells in tumor environment. The research result indicates that AQP9 may be an obstacle to maintain the immune activity of TME.

Keywords: AQP9; TCGA; extracellular matrix (ECM); renal clear cell carcinoma (KIRC); tumor microenvironmental; tumor-associated macrophages (TAMs).