Novel SFRP2 DNA Methylation Profile Following Neoadjuvant Therapy in Colorectal Cancer Patients with Different Grades of BMI

Abstract

The relationship between body weight and different cancers is now well-recognized and among such cancers, colorectal cancer (CRC) is reported most frequently. Our group recently published findings, through an epigenome-wide association study, suggesting that body mass index (BMI) could act as a relevant risk factor in the CRC. In addition, aberrant SFRP2 methylation is one of the major mechanisms for Wnt signaling activation in CRC. Conversely, neoadjuvant chemo-radiotherapy appears to alter the rectal cancer epigenome. This study was aimed to evaluate the effect of obesity, measured by BMI, on the methylation of SFRP2 in tumor samples of patients with CRC. Non-treated CRC patients and CRC patients treated with pre-operative neoadjuvant therapy from 2011 to 2013 were included and classified by BMI < 25.0 kg/m² and BMI > 25.0 kg/m². SFRP2 DNA methylation in tumor samples was measured by pyrosequencing. Our findings suggest a possible interaction between SFRP2 methylation levels and BMI in CRC tumor samples. The correlation of SFRP2 hypomethylation with an elevated BMI was stronger within the non-treated CRC patient group than within the treated CRC patient group. We have successfully demonstrated that the beneficial association of tumor SFRP2 hypomethylation is dependent on patient BMI in non-treated CRC, suggesting a possible tumor suppressor role for SFRP2 in overweight and obese patients. Additional studies of clinical pathologies would be necessary to strengthen these preliminary results.

Keywords: BMI; DNA methylation; SRFP2; colorectal cancer; location; therapy.

Figure 1

Methylation status of SFRP2 in tumoral tissue of patients with CRC. (a) A representative picture of the genomic structure of the human SFRP2 gene on chromosome 4q31 and the CpG island included in this study. Bioinformatic analysis demonstrated seven CpG-rich islands located at the −1500 position, relating to the transcription start site (+1). (b) Methylation levels of the SFRP2 and LINE-1 genes in 75 tumor tissue biopsies of CRC and adjacent tumor-free areas were analyzed by bisulfite treatment and pyrosequencing. Comparison through paired t-test (c) Quantitative RT-PCR was used to determine the expression of SFRP2 in HTC116, after treatment with AZA, during 72 h. The mRNA expression of SFRP2 was normalized to the PPIA expression. The results are displayed as mRNA relative mean expression ± SD. Abbreviations: SFRP2—secreted frizzled-related protein type 2; LINE-1—long interspersed element type 1; PPIA—peptidylprolyl Isomerase A; HTC116—Homo sapiens colon colorectal carcinoma; AZA—5-aza-2′-deoxycytidine; ND—not detected.

Figure 2

Relationship between BMI and SFRP2 methylation in colorectal cancer. Methylation levels of the SFRP2 (a) and LINE-1 (b) genes, in 75 tumor tissue biopsies of CRC and adjacent tumor-free areas, in BMI < 25 and BMI > 25 kg/m², analyzed by Mann–Whitney U-test. (c) Correlations between global methylation in SFRP2 and LINE-1 genes in all subjects (d) in individuals with BMI < 25 kg/m² and (e) those with BMI > 25 kg/m² subjects. Abbreviations: SFRP2—Secreted frizzled-related protein type 2; LINE-1—Long interspersed element type 1; BMI—body mass index.

Figure 3

Analysis of abdominal location and therapy of CRC on the SRFP2 methylation. Analysis of location and CRC patients treated on SFRP2 methylation status. Methylation levels of the SFRP2 divided by the treated versus the non-treated patients in areas with tumor and in tumor-free areas (a), and rectum separated by BMI in the treated versus the non-treated patients only in the samples with tumors (b). Mann-Whitney U-test was performed to compare the means. Abbreviations: SFRP2—Secreted frizzled-related protein type 2; BMI—body mass index.