Pre-Operative Decitabine in Colon Cancer Patients: Analyses on WNT Target Methylation and Expression.

Janneke F Linnekamp,Pieter J Tanis,Cornelis J A Punt,Jan Paul Medema,Evelyn Fessler,Lianne Koens,Willem A Bemelman,Frans O The,Evelien Dekker,Hanneke W M Van Laarhoven,Elles M Kemper,Raju Kandimalla,Gregor G W Van Bochove,Joan H De Jong,Anthony W H Van De Ven,Hans M Rodermond,Louis Vermeulen

doi:10.3390/cancers13102357

Janneke F Linnekamp, Pieter J Tanis + Show 15 more

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https://doi.org/10.3390/cancers13102357

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Abstract

Simple SummaryColon cancer is one of the leading causes of cancer-related death worldwide. Therefore, the development of new therapeutic strategies is of the utmost importance. Previously, we identified a subset of colon cancers that are characterised by DNA methylation and have a poor prognosis. In this study, we therefore treated ten colon cancer patients with a demethylating agent, decitabine, to investigate if reversal of methylation is feasible and can be used as a novel therapy. Unfortunately, this study revealed that while decitabine treatment is effective in vitro, it only marginally decreased global methylation in patients and had no effect on the specific regions of DNA methylation in the tumours. Future studies should therefore focus on optimisation of treatment schedules in patients with highly methylated tumours.DNA hypermethylation is common in colon cancer. Previously, we have shown that methylation of WNT target genes predicts poor prognosis in stage II colon cancer. The primary objective of this study was to assess whether pre-operative treatment with decitabine can decrease methylation and increase the expression of WNT target genes APCDD1, AXIN2 and DKK1 in colon cancer patients. A clinical study was conducted, investigating these potential effects of decitabine in colon cancer patients (DECO). Patients were treated two times with 25 mg/m2 decitabine before surgery. Methylation and expression of LINE1 and WNT target genes (primary outcome) and expression of endogenous retroviral genes (secondary outcome) were analysed in pre- and post-treatment tumour samples using pyrosequencing and rt-PCR. Ten patients were treated with decitabine and eighteen patients were used as controls. Decitabine treatment only marginally decreased LINE1 methylation. More importantly, no differences in methylation or expression of WNT target or endogenous retroviral genes were observed. Due to the lack of an effect on primary and secondary outcomes, the study was prematurely closed. In conclusion, pre-operative treatment with decitabine is safe, but with the current dosing, the primary objective, increased WNT target gene expression, cannot be achieved.

Highlights

The genetic aberrations in colon cancer have been extensively studied and are traditionally described by “the Vogelgram”, starting with loss of functional APC, followed by mutations in other genes including KRAS, TP53 and SMAD4 [1]
DNA hypermethylation occurs in CpG islands in promotor regions of specific genes, resulting in transcriptional silencing, methylation of CDKN2A in many cancers being an example [3,6,7]
A subsequent decrease in tumour growth was observed [14]. These findings suggest that DNA methylation could be a therapeutic target in colon cancer and inducing re-expression could potentially lead to improved patient outcomes, especially in tumours characterised by extensive WNT target gene methylation

Summary

Introduction

The genetic aberrations in colon cancer have been extensively studied and are traditionally described by “the Vogelgram”, starting with loss of functional APC, followed by mutations in other genes including KRAS, TP53 and SMAD4 [1]. In addition to genetic events, epigenetic alterations are frequently found and have been shown to be essential for the initiation and progression of colon cancer [2]. DNA methylation is associated with changes in the chromatin structure and results in altered gene expression without permanently changing the DNA sequence itself [3]. In various types of tumours, genomewide hypomethylation mainly occurs in repetitive sequences and can lead to genomic instability [4,5]. DNA hypermethylation occurs in CpG islands in promotor regions of specific genes, resulting in transcriptional silencing (e.g., tumour suppressor genes), methylation of CDKN2A in many cancers being an example [3,6,7]. Besides being an important step in tumourigenesis, DNA hypermethylation has been suggested to cause resistance to systemic therapy [8,9]

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