Assessment of chromosomal imbalances in CIMP-high and CIMP-low/CIMP-0 colorectal cancers

Data presented in a number of recent studies have revealed a negative correlation between CpG island methylator phenotype (CIMP) and chromosomal instability (CIN) measured by a loss of heterozygosity (LOH) of selected loci, suggesting that CIN and CIMP represent two independent mechanisms in sporadic colorectal cancer (CRC) carcinogenesis. However, CIN is a heterogeneous phenomenon, which may be studied not only by employing LOH analysis but also by observing chromosomal imbalances (gains and deletions). The current study aimed to investigate the relationship between CIMP and chromosomal gains and deletions (assessed by comparative genomic hybridization) in a group of 20 CIMP-high and 79 CIMP-low/CIMP-0 CRCs. Our results revealed that the mean numbers of gains and of total chromosomal imbalances were significantly greater (p = 0.004 and p = 0.007, respectively) in the CIMP-low/CIMP-0 group compared to the CIMP-high group, while no significant difference was observed between the mean numbers of losses (p = 0.056). The analysis of copy number changes of 41 cancer-related genes by multiplex ligation-dependent probe amplification showed that CRK gene was exclusively deleted in CIMP-low/CIMP-0 tumors (p = 0.02). Given that chromosomal losses play an important role in tumor suppressor inactivation and chromosomal gains, in the activation of proto-oncogenes, we hypothesize that tumor suppressor inactivation plays similar roles in both CIMP-high and CIMP-low/CIMP-0 CRCs, while the predominance of chromosomal gains in CIMP-low/CIMP-0 tumors may suggest that the activation of proto-oncogenes is the underlying mechanism of CIMP-low/CIMP-0 CRC progression.     

LINE-1 hypomethylation is inversely associated with microsatellite instability and CpG island methylator phenotype in colorectal cancer

Two pathways leading to vulvar squamous cell carcinoma (SCC) exist. The expression of proliferation- and cell-cycle-related biomarkers and the presence of high-risk (hr) HPV might be helpful to distinguish the premalignancies in both pathways. Seventy-five differentiated vulvar intra-epithelial neoplasia (VIN)-lesions with adjacent SCC and 45 usual VIN-lesions (32 solitary and 13 with adjacent SCC) were selected, and tested for hr-HPV DNA, using a broad-spectrum HPV detection/genotyping assay (SPF(10)-LiPA), and the immunohistochemical expression of MIB1, p16(INK4A) and p53. All differentiated VIN-lesions were hr-HPV- and p16-negative and in 96% MIB1-expression was confined to the parabasal layers. Eighty-four percent exhibited high p53 labeling indices, sometimes with parabasal extension. Eighty percent of all usual VIN-lesions were hr-HPV-positive, p16-positive, MIB1-positive and p53-negative. Five (of seven) HPV-negative usual VIN lesions, had an expression pattern like the other HPV-positive usual VIN lesions. In conclusion, both pathways leading to vulvar SCC have their own immunohistochemical profile, which can be used to distinguish the 2 types of VIN, but cannot explain differences in malignant potential.     

APC gene methylation is inversely correlated with features of the CpG island methylator phenotype in colorectal cancer

The notion of a CpG island methylator phenotype (CIMP) was proposed to describe a subset of colorectal cancers (CRC) displaying frequent and concordant methylation of CpG islands located within gene promoter regions. Some workers have failed to observe associations between CIMP and specific clinicopathological features of CRC, possibly because of the choice of genes used to define this phenotype. The aim of the current study was to determine whether the aberrant methylation of 6 genes implicated in CRC development was associated with the same phenotypic features of this tumour type. The MethyLight assay was used to provide quantitative estimates of MLH1, P16, TIMP3, P14, DAPK and APC methylation levels in 199 unselected colorectal tumours. The methylation of MLH1, P16, TIMP3 and P14 was highly concordant (p < 0.0001 for each pair) but that of DAPK and APC was not. An inverse association was observed between the methylation of APC and TIMP3 (p = 0.004). Methylation of the MLH1, P16, TIMP3 and P14 genes was associated with tumour infiltrating lymphocytes (p < 0.05), microsatellite instability (p < 0.001), BRAF mutation (p < 0.0001) and elevated concentrations of the methyl group carriers tetrahydrofolate (THF) and 5,10-methylene THF (p < 0.05). In contrast, APC methylation was associated with wildtype BRAF (p = 0.003) and with lower concentrations of methyl group carriers (p < 0.05). These findings highlight the importance of gene selection in studies that aim to characterize the biological features and clinical behaviour of CIMP+ tumours.     

Long interspersed nuclear element-1 hypomethylation is a potential biomarker for the prediction of response to oral fluoropyrimidines in microsatellite stable and CpG island methylator phenotype-negative colorectal cancer

We investigated the clinical value of methylation of long interspersed nuclear element-1 (LINE-1) for the prognosis of colorectal cancer (CRC) and for the survival benefit from adjuvant chemotherapy with oral fluoropyrimidines. LINE-1 methylation in tumor DNA was measured by quantitative methylation-specific PCR in 155 samples of stage II and stage III CRC. The presence of microsatellite instability and CpG island methylator phenotype (CIMP) were assessed and 131 microsatellite stable/CIMP- cases were selected for survival analysis, of which 77 patients had received postoperative adjuvant chemotherapy with oral fluoropyrimidines. The CRC cell lines were used to investigate possible mechanistic links between LINE-1 methylation and effects of 5-fluorouracil (5-FU). High LINE-1 methylation was a marker for better prognosis in patients treated by surgery alone. Patients with low LINE-1 methylation who were treated with adjuvant chemotherapy survived longer than those treated by surgery alone, suggestive of a survival benefit from the use of oral fluoropyrimidines. In contrast, a survival benefit from chemotherapy was not observed for patients with high LINE-1 methylation. The CRC cell lines treated with 5-FU showed increased expression of LINE-1 mRNA. This was associated with upregulation of the phospho-histone H2A.X in cells with low LINE-1 methylation, but not in cells with high LINE-1 methylation. The 5-FU-mediated induction of phospho-histone H2A.X, a marker of DNA damage, was inhibited by knockdown of LINE-1. These results suggest that LINE-1 methylation is a novel predictive marker for survival benefit from adjuvant chemotherapy with oral fluoropyrimidines in CRC patients. This finding could be important for achieving personalized chemotherapy.     

CpG island methylator phenotype associates with low-degree chromosomal abnormalities in colorectal cancer

PURPOSE: Aberrant promoter methylation and genomic instability occur frequently during colorectal cancer development. CpG island methylator phenotype (CIMP) has been shown to associate with microsatellite instability, and BRAF mutation and is often found in the right-side colon. Nevertheless, the relative importance of CIMP and chromosomal instability (CIN) for tumorigenesis has yet to be thoroughly investigated in sporadic colorectal cancers. EXPERIMENTAL DESIGN: We determined CIMP in 161 primary colorectal cancers and 66 matched normal mucosae using a quantitative bisulfite/PCR/ligase detection reaction (LDR)/Universal Array assay. The validity of CIMP was confirmed in a subset of 60 primary tumors using MethyLight assay and five independent markers. In parallel, CIN was analyzed in the same study cohort using Affymetrix 50K Human Mapping arrays. RESULTS: The identified CIMP-positive cancers correlate with microsatellite instability (P = 0.075) and the BRAF mutation V600E (P = 0.00005). The array-based high-resolution analysis of chromosomal aberrations indicated that the degree of aneuploidy is spread over a wide spectrum among analyzed colorectal cancers. Whether CIN was defined by copy number variations in selected microsatellite loci (criterion 1) or considered as a continuous variable (criterion 2), CIMP-positive samples showed a strong correlation with low-degree chromosomal aberrations (P = 0.075 and P = 0.012, respectively). Similar correlations were observed when CIMP was determined by MethyLight assay (P = 0.001 and P = 0.013, respectively). CONCLUSION: CIMP-positive tumors generally possess lower chromosomal aberrations, which may only be revealed using a genome-wide approach. The significant difference in the degree of chromosomal aberrations between CIMP-positive and the remainder of samples suggests that epigenetic (CIMP) and genetic (CIN) abnormalities may arise from independent molecular mechanisms of tumor progression.     

BRAF mutation is associated with the CpG island methylator phenotype in colorectal cancer from young patients

This study investigated the relationship between BRAF mutation, the CpG island methylator phenotype (CIMP+) and APC methylation in colorectal cancer (CRC) from young patients. The V600E BRAF mutation was found in 7% of cases and was strongly associated with the tumour features of proximal site, advanced stage and poor histological grade. More than half (53%) the tumours with BRAF mutation were also CIMP+ as evaluated by a standard panel of markers, compared to only 4% of tumours with wildtype BRAF (P<0.0001). In contrast to CIMP+, APC methylation was inversely correlated with BRAF mutation (P=0.02). BRAF mutation and CIMP+ are therefore likely to be involved in an alternate, albeit rare, pathway to APC inactivation during the development of CRC in younger patients.     

CpG island methylator phenotypes in aging and cancer.

CpG islands are short stretches of CpG rich regions that are frequently associated with the promoter region of genes. Aberrant methylation of CpG islands is one mechanism of inactivating tumor suppressor genes (TSGs) in neoplasia, and there is growing evidence that altered cytosine methylation play important roles in cancer development. However, the differences in global CpG island methylation patterns between normal and cancer cells remain poorly understood. By examining a large number of loci in a series of cancers, global methylation profiles can be constructed. Such studies revealed that in colorectal cancer, there appears to be two types of methylation that are associated with cancer progression: type A (for age-related) methylation, and type C (for cancer-specific) methylation. Initially, type A methylation arises as a function of age in normal colorectal epithelial cells. By affecting genes that regulate the growth and/or differentiation of these cells, such methylation may result in a predisposition state that precedes tumor formation in the colon. Type C methylation, by contrast, was found exclusively in a subset of cancers, which display a CpG island methylator phenotype (CIMP). CIMP is a novel molecular instability pathway that appears to be responsible for most cases of aberrant TSG methylation in colorectal cancer, and which has important interactions with genetic pathways as well. In fact, CIMP+ tumors account for the majority of sporadic colorectal cancers with microsatellite instability, through methylation of the mismatch repair gene hMLH1. This model whereby age-related methylation increases cell-susceptibility to transformation and cancer-specific methylation results in neoplastic progression in a subset of cases may be applicable to many human neoplasms.     

CpG island methylator phenotype (CIMP) in cancer: causes and implications

Strong evidence exists for a subgroup of tumours, from a variety of tissue types, exhibiting concordant tumour specific DNA methylation: the "CpG island methylator phenotype" (CIMP). Occurrence of CIMP is associated with a range of genetic and environmental factors, although the molecular causes are not well-understood. Both increased expression and aberrant targeting of DNA methyltransferases (DNMTs) could contribute to the occurrence of CIMP. One under-explored area is the possibility that DNA damage may induce or select for CIMP during carcinogenesis or treatment of tumours with chemotherapy. DNA damaging agents can induce DNA damage at guanine rich regions throughout the genome, including CpG islands. This DNA damage can result in stalled DNA synthesis, which will lead to localised increased DNMT1 concentration and therefore potentially increased DNA methylation at these sites. Chemotherapy can select for cells which have increased tolerance to DNA damage due to increased lesion bypass, in some cases by mechanisms which involve inactivation of genes by CpG island methylation. CIMP has been associated with worse patient prognosis, probably due to increased epigenetic plasticity. Therefore, further clinical testing of the diagnostic and prognostic value of the current CIMP markers, as well as increasing our understanding of the molecular causes underlying CIMP are required.     

Association of the CpG island methylator phenotype with family history of cancer in patients with colorectal cancer

Methylation of promoter CpG islands in colorectal cancer (CRC) falls into two categories: age related and cancer specific. Most cancer-specific methylation at CpG islands occurs in a subset of cases that display the CpG island methylator phenotype (CIMP). The underlying cause of CIMP is not known. Using methylation-specific PCR, we studied 47 CRC patients for methylation at five loci to determine whether the methylation status of CpG islands is associated with family history of cancer. Four of the loci were differentially methylated between the CRC cases with a family history and those with no family history. Patients with methylation at all four loci were 14 times more likely to have a family history of cancer than patients with methylation at none of the four loci. These findings suggest that there may be a genetic component to CIMP in CRC.     

BRAF mutation, CpG island methylator phenotype and microsatellite instability occur more frequently and concordantly in mucinous than non-mucinous colorectal cancer

Mucinous colorectal cancer (CRC) has been reported to have distinct clinicopathological and genetic characteristics. However, the incidence and the relationship among microsatellite instability (MSI), CpG island methylator phenotype (CIMP) and BRAF and KRAS mutations in mucinous and non-mucinous CRC are not known. Activating mutations of BRAF and KRAS and their relationship with MSI and CIMP were examined in 83 sporadic CRC specimens (26 mucinous and 57 non-mucinous CRC). MSI, CIMP, BRAF and KRAS mutation were observed in 17, 24, 25 and 36% of the tumors, respectively. BRAF mutation was highly correlated with MSI (p < 0.001) and CIMP (p < 0.001). A higher incidence of MSI (27% vs. 12%), CIMP (38% vs. 18%, p < 0.05) and BRAF mutation (46% vs. 16%, p < 0.01) was observed in mucinous CRC. KRAS mutation (27% vs. 40%) was observed more frequently in non-mucinous CRC. Significantly higher percentages of mucinous CRC (54%, p < 0.05) had MSI or CIMP or BRAF mutations. Concordant occurrence of 2 or more of these alterations was observed in 39% of mucinous CRC and only 11% of non-mucinous CRC (p < 0.01). The more frequent occurrence and closer association among MSI, CIMP and BRAF mutation in mucinous CRC observed in our study further supports the idea that its pathogenesis may involve distinct genetic and epigenetic changes.     

Low expression of gamma-glutamyl hydrolase mRNA in primary colorectal cancer with the CpG island methylator phenotype

The CpG island methylator phenotype (CIMP+) in colorectal cancer (CRC) is defined as concomitant and frequent hypermethylation of CpG islands within gene promoter regions. We previously demonstrated that CIMP+ was associated with elevated concentrations of folate intermediates in tumour tissues. In the present study, we investigated whether CIMP+ was associated with a specific mRNA expression pattern for folate- and nucleotide-metabolising enzymes. An exploratory study was conducted on 114 CRC samples from Australia. mRNA levels for 17 genes involved in folate and nucleotide metabolism were measured by real-time RT-PCR. CIMP+ was determined by real-time methylation-specific PCR and compared to mRNA expression. Candidate genes showing association with CIMP+ were further investigated in a replication cohort of 150 CRC samples from Japan. In the exploratory study, low expression of gamma-glutamyl hydrolase (GGH) was strongly associated with CIMP+ and CIMP+-related clinicopathological and molecular features. Trends for inverse association between GGH expression and the concentration of folate intermediates were also observed. Analysis of the replication cohort confirmed that GGH expression was significantly lower in CIMP+ CRC. Promoter hypermethylation of GGH was observed in only 5.6% (1 out of 18) CIMP+ tumours and could not account for the low expression level of this gene. CIMP+ CRC is associated with low expression of GGH, suggesting involvement of the folate pathway in the development and/or progression of this phenotype. Further studies of folate metabolism in CIMP+ CRC may help to elucidate the aetiology of these tumours and to predict their response to anti-folates and 5-fluorouracil/leucovorin.     

High CpG island methylator phenotype is associated with lymph node metastasis and prognosis in gastric cancer

Several studies have found that the promoter CpG island is frequently methylated in gastric cancer. The CpG island methylator phenotype (CIMP) defines concordant methylation of multiple promoter CpG island loci in a subset of gastric cancer. However, the relationship between CIMP and lymph node metastasis in gastric cancer is unknown. Our study aimed to characterize the role of CIMP in lymph node metastasis. Clinical specimens from 120 patients were analyzed and PCR was used to detect the methylation status of five genes (ALX4, TMEFF2, CHCHD10, IGFBP3, and NPR1). We measured the level of mRNA for the five genes by real-time RT-PCR. Microsatellite instability and Helicobacter pylori infection status were assayed by capillary electrophoresis and real-time PCR, respectively. DNA methylation in the five genes was correlated with low expression of the respective mRNA. With CIMP as the dependent variable, CIMP-high gastric cancer tended to show more distant lymph node metastasis, higher pathologic tumor classification, more pathologic metastasis, and higher pathologic TNM status. Microsatellite instability and H. pylori status were not significant predictors of prognosis. CIMP-high gastric cancer showed significantly worse survival compared with that of CIMP-low/CIMP-negative gastric cancer (P < 0.001). Our results show that there is an association between CIMP status and lymph node metastasis in gastric cancer and CIMP-high was an independent prognostic factor.     

Phase II study of nab-paclitaxel in refractory small bowel adenocarcinoma and CpG island methylator phenotype (CIMP)-high colorectal cancer

BackgroundHypermethylation of promoter CpG islands [CpG island methylator phenotype (CIMP)] represents a unique pathway for the development of colorectal cancer (CRC), characterized by lack of chromosomal instability and a low rate of adenomatous polyposis coli (APC) mutations, which have both been correlated with taxane resistance. Similarly, small bowel adenocarcinoma (SBA), a rare tumor, also has a low rate of APC mutations. This phase II study evaluated taxane sensitivity in SBA and CIMP-high CRC.Patients and methodsThe primary objective was Response Evaluation Criteria in Solid Tumors version 1.1 response rate. Eligibility included Eastern Cooperative Oncology Group performance status 0/1, refractory disease, and SBA or CIMP-high metastatic CRC. Nab-paclitaxel was initially administered at a dose of 260 mg/m² every 3 weeks but was reduced to 220 mg/m² owing to toxicity.ResultsA total of 21 patients with CIMP-high CRC and 13 with SBA were enrolled from November 2012 to October 2014. The efficacy-assessable population (patients who received at least three doses of the treatment) comprised 15 CIMP-high CRC patients and 10 SBA patients. Common grade 3 or 4 toxicities were fatigue (12%), neutropenia (9%), febrile neutropenia (9%), dehydration (6%), and thrombocytopenia (6%). No responses were seen in the CIMP-high CRC cohort and two partial responses were seen in the SBA cohort. Median progression-free survival was significantly greater in the SBA cohort than in the CIMP-high CRC cohort (3.2 months compared with 2.1 months, P = 0.03). Neither APC mutation status nor CHFR methylation status correlated with efficacy in the CIMP-high CRC cohort. In vivo testing of paclitaxel in an SBA patient-derived xenograft validated the activity of taxanes in this disease type.ConclusionAlthough preclinical studies suggested taxane sensitivity was associated with chromosomal stability and wild-type APC, we found that nab-paclitaxel was inactive in CIMP-high metastatic CRC. Nab-paclitaxel may represent a novel therapeutic option for SBA.     

The CpG island methylator phenotype is not associated with a personal or family history of cancer

Colorectal cancers with widespread CpG island methylation display a number of distinct clinicopathological features, and it has been suggested that the condition has an inheritable genetic component. To address this possibility, histories of cancer were obtained from 562 individuals undergoing curative surgery for unselected colorectal cancer at one institution. Microsatellite status and methylation at p16, MINT1, 2, 12, and 31 loci were determined on fresh tumor tissue using standard methods. Fifty-five of 562 probands in this study provided a personal history of at least one other colorectal cancer, 10 reported at least one extracolonic cancer of hereditary nonpolyposis colorectal cancer type, and 84 individuals had another type of cancer. Age was strongly associated with the risk of multiple cancers, but there was no evidence that microsatellite instability or the CpG island methylator phenotype were independent risk factors for their development, either in the colorectum or elsewhere. Of the 547 individuals with knowledge of their family history, 80 (14.6%) reported a family history of colorectal cancer in a first-degree relative, and 60% of individuals reported a history of any cancer in a first-degree relative. Neither tumor CpG island methylator phenotype status nor microsatellite instability was predictive of a positive history of cancer in first- or second-degree relatives. The probability of a positive family or personal history of cancer did not increase with increasing number of methylated loci. Epigenetic silencing of multiple genes seen in some tumors is at best rarely the result of an inherited defect in the methylation apparatus. There is no justification for altering the personal or family cancer screening recommendations on the basis of tumor CpG island methylator phenotype status.     

CpG island methylator phenotype is an independent predictor of survival benefit from 5-fluorouracil in stage III colorectal cancer.

PURPOSE: The CpG island methylator phenotype (CIMP) is observed in approximately 30% of colorectal cancer (CRC) cases and is characterized by the concurrent methylation of multiple CpG islands in tumor DNA. This phenotype (CIMP+) is more frequently observed in tumors with proximal location, microsatellite instability, and normal p53. Because it has previously been observed that each of these features is associated with a good survival benefit from 5-fluorouracil (5-FU)-based adjuvant chemotherapy, we investigated in the present study whether CIMP+ has independent predictive value. Experimental Design: CIMP+ status was evaluated in 103 stage III CRCs from patients treated with surgery alone and for an additional 103 cases from patients treated with surgery and adjuvant 5-FU-based chemotherapy. The two cohorts were randomly pair-matched for age, sex, and tumor site, and the median length of follow-up time was 39 months. RESULTS: CIMP+ status predicted survival benefit from 5-FU treatment independently of microsatellite instability and p53 mutation status (relative risk = 0.22; 95% confidence interval, 0.06-0.84; P = 0.027). Unmeasured, high-risk confounding factors could only account for this association if they were unequally distributed between the two patient cohorts by a factor of at least 2-fold. CONCLUSIONS: CIMP+ has independent predictive significance for the survival benefit from 5-FU chemotherapy in CRC. This molecular marker should be incorporated into prospective clinical trials of fluorouracil-based therapies to confirm its clinical value.     

Aberrant methylation in gastric cancer associated with the CpG island methylator phenotype.

Aberrant methylation of 5' CpG islands is thought to play an important role in the inactivation of tumor suppressor genes in cancer. In colorectal cancer, a group of tumors is characterized by a hypermethylator phenotype termed CpG island methylator phenotype (CIMP), which includes methylation of such genes as p16 and hMLH1. To study whether CIMP is present in gastric cancer, the methylation status of five newly cloned CpG islands was examined in 56 gastric cancers using bisulfite-PCR. Simultaneous methylation of three loci or more was observed in 23 (41%) of 56 cancers, which suggests that these tumors have the hypermethylator phenotype CIMP. There was a significant concordance between CIMP and the methylation of known genes including p16, and hMLH1; methylation of p16 was detected in 16 (70%) of 23 CIMP+ tumors, 1 (8%) of 12 CIMP intermediate tumors, and 1 (5%) of 21 CIMP- tumors (P<0.0001). Methylation of the hMLH1 gene was detected in three of five tumors that showed microsatellite instability, and all three of the cases were CIMP+. The CIMP phenotype is an early event in gastric cancer, being present in the normal tissue adjacent to cancer in 5 of 56 cases. These results suggest that CIMP may be one of the major pathways that contribute to tumorigenesis in gastric cancers.     

Left-Sided microsatellite unstable colorectal cancers show less frequent methylation of hMLH1 and CpG island methylator phenotype than right-sided ones

CONDENSED ABSTRACT: We compared the methylation status of several loci between right-sided and left-sided colorectal cancers (CRCs). To the best of our knowledge, this is the first to report that left-sided CRCs show significantly less frequent methylation at several loci and CpG island methylator phenotype (CIMP) than right-sided ones. BACKGROUND AND OBJECTIVES: MSI CRC occurs in 10-20% of unselected series of patients with CRC. Somatic hMLH1 promoter methylation is reported to cause MSI in sporadic cases. Many researchers report that MSI CRCs are more frequently located in the right-side colon than MSS CRCs. Though the number is very small, some MSI CRCs are located in the left-side colorectum. We focused on the existence of left-sided MSI CRCs and investigated whether they arise through hMLH1 methylation as they do in right-sided ones. METHODS: Thirty-eight sporadic MSI CRCs were included in the study. The methylation status of the promoter of hMLH1, p16, MINT1, 2 and 31 were examined and the proportions of methylated samples for each locus were compared. RESULTS: The left-sided group showed significantly less frequent methylation in hMLH1, p16, MINT1, 2 and 31. The frequency of CIMP+ samples in the left-sided group was significantly lower than the right-sided group. CONCLUSIONS: Left-sided MSI CRCs show significantly less frequent methylation of hMLH1. They also showed significantly less frequent occurrence of CIMP+ than right-sided ones. It is possible that left-sided MSI CRCs differ from the right-sided ones in the way of acquiring MSI.     

CpG island methylator phenotype is associated with the efficacy of sequential oxaliplatin- and irinotecan-based chemotherapy and EGFR-related gene mutation in Japanese patients with metastatic colorectal cancer

Background

The CpG island methylator phenotype (CIMP) with multiple promoter methylated loci has been observed in a subset of human colorectal cancer (CRC) cases. CIMP status, which is closely associated with specific clinicopathological and molecular characteristics, is considered a potential predictive biomarker for efficacy of cancer treatment. However, the relationship between the effect of standard chemotherapy, including cytotoxic drugs and anti-epidermal growth factor receptor (EGFR) antibodies, and CIMP status has not been elucidated.

Methods

In 125 metastatic colorectal cancer (mCRC) patients, we investigated how clinical outcome of chemotherapy was related to CIMP status as detected by methylation-specific PCR (MSP) and to genetic status in five EGFR-related genes (KRAS, BRAF, PIK3CA, NRAS, and AKT1) as detected by direct sequencing.

Results

CIMP-positive status was significantly associated with proximal tumor location and peritoneum metastasis (all P values <0.05). The progression-free survival of patients with CIMP-positive tumors receiving sequential therapy with FOLFOX as the first-line treatment followed by irinotecan-based therapy as the second-line treatment (median = 6.6 months) was inferior to that of such patients receiving the reverse sequence (median = 15.2 months; P = 0.043). Furthermore, CIMP-positive tumors showed higher mutation frequencies for the five EGFR-related genes (74.1 %) than the CIMP-negative tumors did (50.0 %). Among the KRAS wild-type tumors, CIMP-positive tumors were associated with a worse clinical outcome than CIMP-negative tumors following anti-EGFR antibody therapy.

Conclusion

Sequential FOLFOX followed by an irinotecan-based regimen is unfavorable in patients with CIMP-positive tumors. High frequencies of mutation in EGFR-related genes in CIMP-positive tumors may cause the lower response to anti-EGFR antibody therapy seen in patients with wild-type KRAS and CIMP-positive tumors.