Title:
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Expression and DNA methylation of TNF, IFNG and FOXP3 in colorectal cancer, and association with clinico-pathological features
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Colorectal cancer (CRC) progression is associated with suppression of host cell mediated
immunity (CMI) and local immune escape mechanisms. Suppression of CMI associated
cytokines (IFN-y & TNF-a) has been demonstrated in CRC. Immunosuppressive effect of T
regulatory cells in solid cancers has been demonstrated with FOXP3 being identified as the
most specific T regulatory cell marker.
To assess the impact of immunological function upon survival in CRC and investigate the
expression of TNF, IFNG & FOXP3 and their epigenetic regulation in CRC.
Methods
Sixty patients with CRC were recruited. TaqMan quantitative PCR (qRT-PCR) was performed
for relative quantitation of expression of TNF, IFNG and FOXP3 in the PBMC and tumour
samples. Methylation specific PCR (MSPCR) was performed to determine the DNA
methylation status. Survival analysis was performed using Kaplan-Meier method and Cox
regression models.
Results
TNF was suppressed in tumour tissue and IFNG was suppressed in the PBMC of patients
with CRC. IFNG suppression in PBMC was significant in recurrent CRC. Tumour tissue
showed enhanced expression of FOXP3 and had a positive correlation with tumour size.
Methylated TNFprom0 ter, TNFexonl and FOXP3cpg correlated significantly with
suppression of TNF and FOXP3 respectively. Significant TNF suppression was noted in the
PBMC of patients with MSI. A suppressed FOXP3 in PBMC was associated with poor overall
survival. Tumour vascular invasion (VI) was associated with enhanced expression of TNF.
While VI is associated with adverse prognosis in CRC, its presence is an independent
predictor of poor survival in younger patients.
Conclusion
Specific patterns of TNF, IFNG and FOXP3 expression correlate with tumour progression.
DNA methylation appears to influence the expression of TNF and FOXP3. Further
quantitative analyses are needed to confirm the findings. We have detected changes in the
immunomodulatory genes that could act as biomarkers for prognosis and future
immunotherapeutic strategies.
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