The Comprehensive Role of High Mobility Group Box 1 (HMGB1) Protein in Different Tumors: A Pan-Cancer Analysis

Abstract

Background: HMGB1 is a highly conserved nuclear protein widely expressed in mammalian cells. This study aimed to comprehensively investigate the roles and mechanisms of HMGB1 in different tumors.

Methods: Original data on HMGB1 expression, localization, potential interacting proteins, genetics were obtained from The Cancer Genome Atlas, Genotype-Tissue Expression, Cancer Cell Line Encyclopedia, Human Protein Atlas, Compartmentalized Protein-Protein Interaction and cBioPortal databases. Then, correlation between HMGB1 expression levels and tumor stage, prognosis, potential pathways, tumor microenvironment, ESTIMATE score, immune-related genes, immune cell infiltration, microsatellite instability, tumor mutation burden, or anti-tumor drug resistance was investigated. The above results consistently indicated that high expression of HMGB1 protein may be related to clinical prognosis of HCC patients. Therefore, clinical tissues of HCC patients were selected to verify the differential expression of HMGB1 protein in HCC. The sensitivity of HMGB1-siRNA transfected HepG2 cells to sorafenib was assessed.

Results: HMGB1 was found to be differentially expressed in many tumors and normal tissues. HMGB1 was mainly located in the nucleus and might interact with proteins such as TLR2 and TLR4. Furthermore, HMGB1 expression was closely related to tumor stage, prognosis, tumor microenvironment, immune-related genes, immune cell infiltration, microsatellite instability, tumor mutation burden, and anti-tumor drug resistance and might be involved in different pathways of various tumors. Immunohistochemistry results further verified the differential expression of HMGB1 in HCC and paracancerous tissues. HMGB1-siRNA transfected HepG2 cells had a tendency to be more insensitive to sorafenib treatment compared to the control group.

Conclusions: HMGB1 was differentially expressed in most tumors and normal tissues, and was closely related to the clinical stage, prognosis, immune infiltration, tumor microenvironment, and drug resistance of tumors. Therefore, HMGB1 may serve as a novel biomarker for predicting tumor prognosis, efficacy of immune checkpoint inhibitors, and a potential target for anti-tumor therapy.

Keywords: bioinformatics; high mobility group box 1; pan-cancer analysis; prognosis; tumor.

Figure 1

HMGB1 expression levels in tumors, cancer cell lines, and normal tissues. HMGB1 expression levels in normal tissues (A), cancer cell lines (B), and tumors (C). (D) Comparison of HMGB1 expression levels between tumors and normal tissues. (E) Comparison of HMGB1 expression levels in tumors and matched paracancerous tissues. (F) Comparison of HMGB1 levels in different tumor stages. P > 0.05, < 0.05, < 0.01, < 0.001, and < 0.0001 were presented as “ns”, “*”, “**”, “***”, “****”, respectively.

Figure 2

Genetic alterations, cellular localization, and interaction of HMGB1. (A) Mutation status of HMGB1 in different tumors. (B) Correlation between HMGB1 expression levels and copy number in different tumors. (C) Correlation between HMGB1 expression levels and methylation in different tumors. (D) Proteins that might interact with HMGB1 through ComPPI database. (E) Intracellular localization of HMGB1 protein in cell lines through HPA database.

Figure 3

Forest map of univariate Cox regression model for the impact of HMGB1 expression on prognosis in different tumors. The impacts of HMGB1 expression on (A) overall survival, (B) progression-free interval, (C) disease-specific survival, and (D) disease-free interval in different tumors.

Figure 4

Correlation between HMGB1 expression and tumor microenvironment. (A) The correlation between HMGB1 expression and possible pathways in different tumors by GSVA method. (B) The correlation between HMGB1 expression and tumor microenvironment. (C) The correlation between HMGB1 expression and tumor microenvironment by ESTIMATE method. P > 0.05, < 0.05, < 0.01, < 0.001, and < 0.0001 were presented as “ns”, “*”, “**”, “***”, “****”, respectively.

Figure 5

Correlation between HMGB1 expression and tumor immune infiltration. (A) Correlation between HMGB1 expression and immune cell infiltration by CIBERSORT method. (B) Correlation between HMGB1 expression and immunosuppressive genes. (C) Correlation between HMGB1 expression and immune-activation genes. (D) Correlation between HMG1B expression and chemokines. P > 0.05, < 0.05, < 0.01, < 0.001, and < 0.0001 were presented as “ns”, “*”, “**”, “***”, “****”, respectively.

Figure 6

Correlation between HMGB1 expression and tumor mutation. (A) Correlation between HMGB1 expression and tumor mutation burden. (B) Correlation between HMGB1 expression and microsatellite instability. (C) Correlation between HMGB1 expression and mismatch repair. P > 0.05, < 0.05, < 0.01, < 0.001, and < 0.0001 were presented as “ns”, “*”, “**”, “***”, “****”, respectively.

Figure 7

Correlation between HMGB1 expression and immune cells infiltration by TIMER2 database.

Figure 8

Association between HMGB1 expression and anti-tumor drug sensitivity. (A) Association between HMGB1 expression levels and IC50 of anti-tumor drugs. (B) Comparison of IC50 of anti-tumor drugs between HMGB1 high and low expression subgroup. (C) Comparison of HMGB1 levels in advanced non-small cell lung cancer patients with response and non-response to bevacizumab combined with erlotinib therapy. (D) Proportion of HMGB1 response to bevacizumab combined with erlotinib in high and low HMGB1 expression subgroups of advanced non-small cell lung cancer. (E) The survival probabilities of HMGB1-high and low expressing subgroups in patients with advanced non-small cell lung cancer receiving bevacizumab combined erlotinib therapy. (F) ROC analysis for HMGB1 to predict drug efficacy in patients with advanced non-small cell lung cancer receiving bevacizumab combined erlotinib therapy. P > 0.05, < 0.05, < 0.01, < 0.001, and < 0.0001 were presented as “ns”, “*”, “**”, “***”, “****”, respectively.

Figure 9

Association between HMGB1 expression and hepatocellular carcinoma. (A) Immunohistochemical results showed HMGB1 expression in hepatocellular carcinoma and pericarcinomatous tissues. (B) Expression levels of HMGB1 in hepatocellular carcinoma and pericarcinomatous tissues. (C) Expression of HMGB1 in HepG2 cells after transfection with HMGB1-siRNA. (D) HMGB1/β-actin ratios of both NC-siRNA and HMGB1-siRNA groups in HepG2 cells. (E) Effect of silencing HMGB1 on cell viability in HepG2 cells. P < 0.05 and P < 0.01 were presented as “*” and “**”, respectively.