Background
Many studies have shown an elevated level of cholesterol in colon tumors as compared to normal tissue. Obesity and high low-density lipoprotein cholesterol (LDL-C) are known risk factors for colon cancer. However, the role of LDL-C in colon cancer patients with normal body mass index (BMI) remains elusive.
Conclusions
Our study supports the idea that LDL-C regulates the expression of CCL5 and CCL11 chemokines, which may have predictive values for survival in colon cancer patients with normal BMI, especially for patients in TNM stage II.
Methods
Levels of serum cholesterol and oxysterols were quantified by ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) from 129 individuals with normal BMI, including 32 with solitary polyp, 36 with multiple polyps, and 31 with adenocarcinoma as well as 32 healthy controls. In vitro, colon cancer cells were treated with LDL-C and assayed for chemokines via RNA-Seq and mitochondrial morphology via transmission electron microscopy and immunofluorescence. Additionally, correlation analysis was performed between LDL-C-induced chemokines and the overall survival of colon cancer patients from the Cancer Genome Atlas (TCGA), the Genotype-Tissue Expression (GTEx), and the Human Protein Atlas (HPA) database.
Results
The serum cholesterol level was significantly higher in colon adenocarcinoma patients with normal BMI than that in healthy controls (P<0.001). LDL-C potentiated colon cancer cell invasion and resistance to glucose-deprivation in vitro via chemokine-mediated signaling, mainly upregulation of CC chemokine ligand (CCL) 5 and downregulation of CCL 11. By analyzing the RNA expression data of colorectal cancer from TCGA, GTEx, and HPA, we demonstrated that the CCL5 level in colorectal adenocarcinoma tissues was significantly increased relative to adjacent normal tissues (P=0.01) while the CCL11 level was decreased (P=0.01). Both increased CCL5 and decreased CCL11 showed a negative correlation with the 5-year overall survival in tumor node metastasis (TNM) stage II colon cancer patients (P=0.0032, 0.026 for CCL5 and CCL11, respectively). Conclusions: Our study supports the idea that LDL-C regulates the expression of CCL5 and CCL11 chemokines, which may have predictive values for survival in colon cancer patients with normal BMI, especially for patients in TNM stage II.