The Expression/Methylation Profile of Adipogenic and Inflammatory Transcription Factors in Adipose Tissue Are Linked to Obesity-Related Colorectal Cancer

Abstract

Obesity is well accepted as crucial risk factor that plays a critical role in the initiation and progression of colorectal cancer (CRC). More specifically, visceral adipose tissue (VAT) in people with obesity could produce chronic inflammation and an altered profile expression of key transcription factors that promote a favorable microenvironment to colorectal carcinogenesis. For this, the aim of this study was to explore the relationship between adipogenic and inflammatory transcription factors in VAT from nonobese, obese, and/or CRC patients. To test this idea, we studied the expression and methylation of CCAAT-enhancer binding protein type alpha (C/EBP-α), peroxisome proliferator-activated receptor gamma (PPAR-γ), peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) in VAT from non-obese control, non-obese CRC subjects, overweight/obese control, and overweight/obese CRC patients and their correlation with anthropometric and biochemical variables. We found decreased expression of C/EBP-α in overweight/obese CRC patients in comparison with overweight/obese control subjects. PGC-1α and NF-κB were overexpressed in CRC patients independently of the BMI. NF-κB promoter was hypomethylated in overweight/obese CRC patients when compared to overweight/obese control individuals. In addition, multiple significant correlations between expression, methylation, and biochemical parameters were found. Finally, linear regression analysis showed that the expression of C/EBP-α and NF-κB and that NF-κB methylation were associated with CRC and able to explain up to 55% of CRC variability. Our results suggest that visceral adipose tissue may be a key factor in tumor development and inflammatory state. We propose C/EBP-α, PGC-1α and NF-κB to be interesting candidates as potential biomarkers in adipose tissue for CRC patients.

Keywords: C/EBP-α; NF-κB; PGC-1α; PPAR-γ; colorectal cancer; obesity; visceral adipose tissue.

Figure 1

Gene expression and methylation analyses of CCAAT-enhancer binding protein type alpha (C/EBP-α) and peroxisome proliferator-activated receptor gamma (PPAR-γ) in visceral adipose tissue (VAT): Quantitative RT-PCR of C/EBP-α (a) and PPAR-γ (b) expression analyses and methylation analyses at specific CpG dinucleotides for C/EBP-α (c) and PPAR-γ (d) promoters was used to compare the nonobese control (N = 53), nonobese CRC (N = 27), overweight/obese control (N = 81), and overweight/obese CRC groups (N = 58). The mRNA expression of C/EBP-α and PPAR-γ were normalized to Peptidylprolyl Isomerase A (PPIA) expression. The results are given as the mRNA relative mean expression ± SD and methylation average ± SD. Significant differences between the means of the different groups of subjects was performed according to the Wilcoxon test (p < 0.05). Abbreviations: C/EBP-α: CCAAT/enhancer-binding protein type alpha; PPAR-γ2: peroxisome proliferator-activated receptor gamma; VAT: Visceral adipose tissue.

Figure 2

Correlation between gene expression and methylation analyses of C/EBP-α and PPAR-γ in VAT: Pearson’s correlation between gene expression and methylation analyses of C/EBP-α in VAT from the overweight/obese CRC groups (N = 58) (a) and of PPAR-γ in VAT from the overweight/obese control (N = 81) (b) and overweight/obese CRC groups (N = 58) (c) (p < 0.05). Abbreviations: C/EBP-α: CCAAT/enhancer-binding protein type alpha; PPAR-γ2: peroxisome proliferator-activated receptor gamma; VAT: Visceral adipose tissue.

Figure 3

Gene expression and methylation analyses of PGC-1α and NF-κB in VAT: Quantitative RT-PCR of PGC-1α (a) and NF-κB (b) expression analyses and methylation analyses at specific CpG dinucleotides for PGC-1α (c) and NF-κB (d) promoters was used to compare the nonobese control (N = 53), nonobese CRC (N = 27), overweight/obese control (N = 81), and overweight/obese CRC groups (N = 58). The mRNA expression of PGC-1α and NF-κB was normalized to the PPIA expression. The results are given as the mRNA relative mean expression ± SD and methylation average ± SD. Significant differences between the means of the different groups of subjects was performed according to the Wilcoxon test (p < 0.05). Abbreviations: PGC-1α: peroxisome proliferator-activated receptor gamma coactivator 1-α; NF-κB: nuclear factor κ-light-chain-enhancer of activated B cells; VAT: Visceral adipose tissue.

Figure 4

Correlation between gene expression and methylation analyses of C/EBP-α, PPAR-γ, PGC-1α, and NF-κB in VAT and anthropometric and biochemical data. Pearson’s correlation between Gene expression and methylation analyses of C/EBP-α, PPAR-γ, PGC-1α, and NF-κB in VAT from the nonobese CRC (N = 27) (a), nonobese control (N = 53) (b), overweight/obese CRC (N = 58) (c) overweight/obese control (N = 81) (d) groups. the square that are not crossed out with a cross are significant (* p < 0.05). Abbreviations: C/EBP-α: CCAAT/enhancer-binding protein type alpha; PPAR-γ2: peroxisome proliferator-activated receptor gamma; PGC-1α: peroxisome proliferator-activated receptor gamma coactivator 1-α; NF-κB: nuclear factor κ-light-chain-enhancer of activated B cells; VAT: Visceral adipose tissue.