WRN Promoter CpG Island Hypermethylation Does Not Predict More Favorable Outcomes for Patients with Metastatic Colorectal Cancer Treated with Irinotecan-Based Therapy

Abstract

PURPOSE WRN promoter CpG island hypermethylation in colorectal cancer (CRC) has been reported to increase sensitivity to irinotecan-based therapies. We aimed to characterize methylation of the WRN promoter; determine the effect of WRN promoter hypermethylation upon expression; and validate a previous report that WRN promoter hypermethylation predicts improved outcomes for metastatic colorectal cancer (mCRC) patients treated with irinotecan-based therapy. DESIGN WRN methylation status was assessed using methylation-specific PCR and bisulfite sequencing assays. WRN expression was determined using qRT-PCR and Western blotting. WRN methylation status was correlated with overall survival (OS) and progression-free survival (PFS) in 183 patients with mCRC. Among these patients 90 received capecitabine monotherapy (CAP) as first line therapy and 93 received capecitabine plus irinotecan (CAPIRI) therapy as part of the CAIRO Phase III clinical trial. RESULTS WRN mRNA and WRN protein expression levels were low in CRC cell lines and in primary CRC, and were largely independent of WRN methylation status. Patients with methylated WRN CRC had a shorter OS compared to patients who had unmethylated WRN CRC (hazard ratio [HR]=1.6 (95%CI1.2–2.2), p=0.003). Patients with unmethylated WRN showed a significantly longer PFS when treated with CAPIRI compared to CAP alone (HR=0.48 (95%CI 0.32–0.70), p=0.0001). In contrast, patients did not benefit from adding irinotecan to CAP when WRN was methylated (HR=1.1 (95%CI 0.69–1.77), p=0.7). CONCLUSION WRN expression is largely independent of WRN promoter hypermethylation in CRC. Moreover, we could not validate previous finding that WRN promoter hypermethylation predicts improved clinical outcomes of mCRC treated with irinotecan-based therapy and found instead the opposite result.

A Phase I Trial of a Guadecitabine (SGI-110) and Irinotecan in Metastatic Colorectal Cancer Patients Previously Exposed to Irinotecan

“…Similar preclinical and early phase clinical studies in ovarian cancer have shown DNMTi reversing resistance to platinum agents (8). In preclinical CRC models, DNMTis can induce re-expression of tumor suppressor genes (9). Our group has reported DNMTi can both induce sensitivity and reverse chemoresistance to irinotecan in in vitro and in vivo models (10).…”

“…There is no well-agreed upon mechanism that has explained irinotecan resistance (23,24). It has been hypothesized that that methylation of DCR1 and WRN, the latter being a DNA helicase, may affect sensitivity to irinotecan, but confirmatory studies to validate these findings in clinical data sets have not been successful (9,(25)(26)(27). The multifocal effects of epigenetic therapies, such as guadecitabine, that result in widespread changes in gene expression across hundreds of cellular pathways, may well be responsible for reversing resistance to cytotoxic chemotherapies, but also create great barriers in understanding the mechanisms behind these effects (28)(29)(30).…”

Modulation of the Endothelin System in Colorectal Cancer Liver Metastasis: Influence of Epigenetic Mechanisms?

“…Hypomethylating agents can reverse this resistance mechanism by promotor demethylation and subsequent gene expression reactivation (Lee et al, 2018). In fact, tumor suppressor genes were found re-expressed by DNA methyltransferase enzyme inhibitors (DNMTi) in colorectal cancer cell lines (Bosch et al, 2016). In line with this, DNMTinhibitors-reversed irinotecan chemotherapy resistance in colorectal cancer models, in vitro and in vivo (Sharma et al, 2017).…”

Recent Advances in Understanding Werner Syndrome

“…Irinotecan (CPT-11), a semi-synthetic derivative of CPT, which is routinely used in colorectal cancer therapy, enhances the survival of colorectal cancer patients with hypermethylated WRN promoter 90 . In contrast, Bosch et al reported that hypermethylation of the WRN promoter does not have predictive value for personalized irinotecan-based therapy 91 . The observed differences could be due to the complex nature of promoter hypermethylation and varied expression of WRN.…”

“…Primary tumors of colorectal cancer patients and cell lines display decreased WRN mRNA and protein expression 90 , 91 ; however, no WRN mutations have been associated with colorectal cancer risk 92 , 93 . Irinotecan (CPT-11), a semi-synthetic derivative of CPT, which is routinely used in colorectal cancer therapy, enhances the survival of colorectal cancer patients with hypermethylated WRN promoter 90 .…”