Identification of a potent epigenetic biomarker for resistance to camptothecin and poor outcome to irinotecan-based chemotherapy in colon cancer

Abstract

Abstract. Drug resistance remains a major obstacle to successful cancer treatment. Genome-wide comprehensive analysis identified a novel gene, glucocorticoid-induced protein-coding gene (DEXI), which was frequently methylated in colorectal (CRC; 36 of 73 patients; 49%) and gastric (28 of 89 patients; 31%) cancer patients. Here, we show that DEXI methylation is implicated in mechanisms facilitating resistance to camptothecin (CPT) via inhibition of apoptosis. Silencing of DEXI by siRNA significantly reduced CPT-induced apoptosis in a fibroblast cell line (1/6-fold; p<0.01) originally expressing endogenous DEXI. Restored expression of DEXI by 5-aza-2'-deoxycytidine (DAC) significantly enhanced susceptibility to CPT (3-fold; p<0.01) in a colon cancer cell line originally suppressing endogenous DEXI due to almost complete methylation. Exogenous induction of DEXI confirmed that DEXI per se contributed to enhanced susceptibility to CPT. 5-Fluorouracil (5-FU) did not exhibit these synergistic effects by DEXI restoration. Further, to estimate the clinical usefulness of DEXI methylation status as biomarker for drug resistance to irinotecan (CPT-11), 16 CRC patients who underwent FOLFIRI (5-FU + CPT-11) therapy because they were refractory to FOLFOX (5-FU + oxaliplatin) were analyzed. Significantly poor response and outcome were observed in 8 CRC patients harboring DEXI methylation. In 8 CRC patients harboring DEXI methylation disease control rate, progression-free survival and overall survival were 25.0%, 2 and 11.8 months, respectively, whereas in 8 CRC patients without DEXI methylation they were 62.5%, 5.3 and 15 months, respectively (p<0.01). These significant differences were not observed in patients undergoing treatment with FOLFOX. In conclusion, silencing of DEXI leads to resistance, but restored expression enhances susceptibility to CPT in vitro and DEXI methylation results in poor response and outcome to CPT-11-based chemotherapy, suggesting that DEXI is a potent therapeutic target and an epigenetic biomarker for the selection of patients more likely to benefit from CPT-11-based chemotherapy. IntroductionMetastatic colorectal cancer (CRC) varies greatly in clinical outcome, depending on the response to chemotherapies despite recent advances achieved by combining new anticancer agents. One of the key drugs for metastatic CRC is irinotecan (CPT-11), a derivative drug of camptothecin (CPT) (1-4) and potent DNA topoisomerase I (top I) inhibitor that blocks the rejoining step of the cleavage/religation reaction of top I (5). CPT-11 is indispensable to chemotherapy in various cancer treatments and is widely used in combination treatment using 5-fluorouracil (5-FU) and CPT-11 (FOLFIRI) (5), which yields a high response rate (>50%) in first-line treatment for metastatic CRC patients (6). However, progression-free survival (PFS) was estimated to be only 8-9 months when this regimen was given as first-line therapy (6), suggesting that most patients acquired resistance to CPT-11 within <1 year after initial treatment.Seque...

Fine Mapping and Functional Studies of Risk Variants for Type 1 Diabetes at Chromosome 16p13.13

“…There are no identifiable domains in DEXI that might suggest a possible function for the protein. However, Miyaki et al ( 54 ) showed that small interfering RNA–mediated knockdown of DEXI reduced the incidence of apoptosis in cells treated with the chemotherapy agent camptothecin. A role in a basic cellular function, such as apoptosis, would be consistent with the involvement of DEXI in multiple autoimmune diseases with different target tissues.…”

DNA methylation alterations of AXIN2 in serrated adenomas and colon carcinomas with microsatellite instability

“…Bisulfite modification was performed using the Epitect Bisulfite kit (Qiagen), as described previously [36]. Genomic DNA (1 μg) was used for conversion with the bisulfite reagent.…”

“…DNA sequencing was performed after bisulfite modification, as previously described [36]. The primers for the bisulfite sequencing were 5′-TTGTATATAGTTTAGYGGTTGGG-3′ (forward) and 5′-AAATCTAAACTCCCTACACACTT -3′ (reverse).…”

Cellular irinotecan resistance in colorectal cancer and overcoming irinotecan refractoriness through various combination trials including DNA methyltransferase inhibitors: a review

“…Bcl-2/adenovirus E1B 19 kDa protein-interacting protein (BNIP3), a pro-apoptotic gene, was methylated in human colon cancer cell lines. BNIP3 upregulation led to the enhancement of irinotecan sensitivity [68,69] . Clinically, it has been suggested that BNIP3 methylation is associated with poor OS and shorter time to cancer progression [69] .…”