Identification of CCL4 as an Immune-Related Prognostic Biomarker Associated With Tumor Proliferation and the Tumor Microenvironment in Clear Cell Renal Cell Carcinoma.

Xiao Liang,Jianlong Li,Qiuya Shao,Lu Wang,Jinhai Fan,Tao Yang,Minxuan Jing,Mengzhao Zhang,Lu Zhang,Minghai Ma,Rundong Song,Nan Zhang

doi:10.3389/fonc.2021.694664

Abstract

The last decade has witnessed revolutionary advances taken in immunotherapy for various malignant tumors. However, immune-related molecules and their characteristics in the prediction of clinical outcomes and immunotherapy response in clear cell renal cell carcinoma (ccRCC) remain largely unclear. C-C Motif Chemokine Ligand 4 (CCL4) was extracted from the intersection analysis of common differentially expressed genes (DEGs) of four microarray datasets from the Gene Expression Omnibus database and immune-related gene lists in the ImmPort database using Cytoscape plug-ins and univariate Cox regression analysis. Subsequential analysis revealed that CCL4 was highly expressed in ccRCC patients, and positively correlated with multiple clinicopathological characteristics, such as grade, stage and metastasis, while negatively with overall survival (OS). We performed gene set enrichment analysis (GSEA) and gene set variant analysis (GSVA) with gene sets coexpressed with CCL4, and observed that gene sets positively related to CCL4 were enriched in tumor proliferation and immune-related pathways while metabolic activities in the negatively one. To further explore the correlation between CCL4 and immune-related biological process, the CIBERSORT algorithm, ESTIMATE method, and tumor mutational burden (TMB) score were employed to evaluate the tumor microenvironment (TME) characteristics of each sample and confirmed that high CCL4 expression might give rise to high immune cell infiltration. Moreover, correlation analysis revealed that CCL4 was positively correlated with common immune checkpoint genes, such as programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA4), and lymphocyte activating 3 (LAG3). Overall, this study demonstrated that CCL4 might serve as a potential immune-related prognostic biomarker to predict clinical outcomes and immunotherapy response in ccRCC. Moreover, CCL4 might contribute to TME modulation, indicating the mechanism CCL4 involved in tumor proliferation and metastasis, which could provide novel therapeutic perceptions for ccRCC patients.

Highlights

Kidney cancer ranks among the top 10 cancer killers [1], while malignant kidney tumors contribute to 2% of the cancer burden in the world with increasing incidence [2]
The “GOChord” package was employed to visualize Gene Ontology (GO) terms, which were divided into three categories: biological processes (BP), cellular component (CC) and molecular function (MF) (Figures 2A–C)
To investigate whether C Motif Chemokine Ligand 4 (CCL4) is involved in modulating the tumor microenvironment (TME), we extended the “CIBERSORT” algorithm to estimate the relative infiltration proportion of 22 immune cell types from TCGA-KIRC samples, which were divided into CCL4 high and low groups according to the median value of CCL4 expression

Summary

Introduction

Kidney cancer ranks among the top 10 cancer killers [1], while malignant kidney tumors contribute to 2% of the cancer burden in the world with increasing incidence [2]. Several small molecule agents targeting VEGF or mTOR have been approved for clinical use, such as bevacizumab, sunitinib, cabozantinib, everolimus and temsirolimus [8]. Most of these agents are multitargeted resulting in multiple drug resistance and serious adverse effects. A recent study identified a mixed subgroup in ccRCC with comprehensive bioinformatics tools. The patients in this mixed group were characterized by upexpression of mitochondrial and weakened angiogenesisrelated genes, making them a distinct therapy stratification compared to the traditional ccRCC patients [9]. Several clinical trials have proposed that antiangiogenics combined with immunotheraputic strategies can achieve greater therapeutic efficacy compared with traditional tyrosine kinase inhibitors targeting VEGF or mTOR inhibitors alone, which has become an alternative first-line treatment for ccRCC in the clinic, emphasizing the crucial status of the tumor microenvironment (TME) [13, 14]

Methods

Results

Discussion

Conclusion