Sensitive and Noninvasive Detection of Aberrant SFRP2 and MGMT-B Methylation in Iranian Patients with Colon Polyps

Epigenetic Alteration in Colorectal Cancer: A Biomarker for Diagnostic and Therapeutic Application

Colorectal cancer (CRC) is the leading cause of cancer death worldwide. A crucial process that initiates and progresses CRC is various epigenetic and genetic changes occurring in colon epithelial cells. Recently, huge progress has been made to understand cancer epigenetics, especially regarding DNA methylation changes, histone modifications, dysregulation of miRNAs and noncoding RNAs. In the “epigenome” of colon cancer, abnormal methylation of genes that cause gene alterations or expression of miRNA has been reported in nearly all CRC; these findings can be encountered in the average CRC methylome. Epigenetic changes, known as driving events, are assumed to play a dominant part in CRC. Furthermore, as epigenetic changes in CRC become properly understood, these changes are being established as clinical biomarkers for therapeutic and diagnostic purposes. Progression in this area indicates that epigenetic changes will often be utilized in the future to prevent and treat CRC.

Technical considerations in PCR-based assay design for diagnostic DNA methylation cancer biomarkers

Background

DNA methylation biomarkers for early detection, risk stratification and treatment response in cancer have been of great interest over the past decades. Nevertheless, clinical implementation of these biomarkers is limited, as only < 1% of the identified biomarkers is translated into a clinical or commercial setting. Technical factors such as a suboptimal genomic location of the assay and inefficient primer or probe design have been emphasized as important pitfalls in biomarker research. Here, we use eleven diagnostic DNA methylation biomarkers for colorectal cancer (ALX4, APC, CDKN2A, MGMT, MLH1, NDRG4, SDC2, SFRP1, SFRP2, TFPI1 and VIM), previously described in a systematic literature search, to evaluate these pitfalls.

Results

To assess the genomic assay location, the optimal genomic locations according to TCGA data were extracted and compared to the genomic locations used in the published assays for all eleven biomarkers. In addition, all primers and probes were technically evaluated according to several criteria, based on literature and expert opinion. Both assay location and assay design quality varied widely among studies.

Conclusions

Large variation in both assay location and design hinders the development of future DNA methylation biomarkers as well as inter-study comparability.

Circulating cell-free nucleic acids as biomarkers in colorectal cancer screening and diagnosis - an update

Introduction: Screening methods for one of the most frequently diagnosed malignancy, colorectal cancer (CRC), have limitations. Circulating cell-free nucleic acids (cfNA) hold clinical relevance as screening, prognostic and therapy monitoring markers. Area covered: In this review, we summarize potential CRC-specific cfNA biomarkers, the recently developed sample preparation techniques, their applications, and pitfalls. Expert opinion: Automated extraction of cfDNA is highly reproducible, however, cfDNA yield is less compared to manual isolation. Quantitative and highly sensitive detection techniques (e.g. digital PCR, NGS) can be applied to analyze genetic and epigenetic changes. Detection of DNA mutations or methylation in cfDNA and related altered levels of mRNA, miRNA, and lncRNA may improve early cancer recognition, based on specific, CRC-related patterns. Detection of cfDNA mutations (e.g. TP53, KRAS, APC) has limited diagnostic sensitivity (40-60%), however, methylated DNA including SEPT9, SFRP1, SDC2 can be applied with higher sensitivity (up to 90%) for CRC. Circulating miRNAs (e.g. miR-21, miR-92, miR-141) provide comparably high sensitivity for CRC as the circulating tumor cell mRNA markers (e.g. EGFR, CK19, CK20, CEA). Automation of cfNA isolation coupled with quantitative analysis of CRC-related, highly sensitive biomarkers may enhance CRC screening and early detection in the future.

Genetic and molecular origins of colorectal Cancer among the Iranians: an update

BACKGROUND

Colorectal cancer (CRC) is one the leading causes of cancer related deaths among Iranians. Despite the various progresses in new therapeutic methods, it has still a low rate of survival. This high ratio of mortality is mainly related to the late diagnosis, in which the patients refer for treatment in advanced stages of tumor. MAIN BODY: colorectal cancer progression is largely associated with molecular and genetic bases. Although Iran has a high ratio of CRC mortality, there is not an efficient genetic panel for detection and prognosis. Therefore, it is critical to introduce new diagnostic markers with ability to detect in early stages.

CONCLUSION

Present review summarizes all of the genetic and epigenetic factors which are reported in CRC until now among the Iranian patients to pave the way of incorporation of new ethnic specific markers into the clinical practice and development of new targeted therapeutic methods.

O6-Methyguanine-DNA Methyl Transferase (MGMT) Promoter Methylation in Serum DNA of Iranian Patients with Colorectal Cancer

Introduction:

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide but current molecular targeted therapy is not providing major success in CRC treatment, so early detection by non-invasive methods continues to be vital. Aberrant methylation of CpG islands in promoter regions is associated with inactivation of various tumor suppressor genes. O6-methyguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that removes mutagenic and cytotoxic adducts from O6-guanine in DNA. Aberrant hypermethylation of the MGMT promoter has been associated with lack of mRNA expression, with concomitant loss of protein content and enzyme activity.

AIM:

Our aim was to determine whether MGMT promoter methylation might be detectable in circulating free DNA in the serum of CRC patients and normal individuals using a methylation specific (MSP) polymerase chain reaction (PCR) method.

Methods:

A total of 70 subjects were enrolled in the study. Of these, 30 patients who were diagnosed previously as untreated colon adenocarcinoma by a gastroenterologist and the other 40 were nearly age-matched individuals who had a normal colonoscopic evaluation (except for hemorrhoids or fissures) and normal pathologic reports. After bisulphite modification of DNA, serum samples were examined for MGMT promoter methylation using MSP.

Results:

Ninety percent of CRC patients had MGMT promoter hypermethylation as compared to no methylation in normal subjects’ serum. Most of the cancers were stage П and moderately differentiated adenocarcinomas; nearly 60% were found in the left colon. No statistically significant correlation was found between the promoter methylation status and gender and age.

Discussion and Conclusions:

MGMT hypermethylation can be detected in free circulating DNA in serum of CRC patients and can be used “as a clinical biomarker” for early diagnosis and prognostic assessment of the disease. Our data confirm previous studies indicating utility for free circulating DNA as a serum biomarker for early detection, diagnosis and monitoring of CRC patients.

Epigenetic biomarkers in colorectal cancer: premises and prospects

CONTEXT

Colorectal cancer is one of the most common cancers worldwide. Epigenetic alterations play an important role in the pathogenesis of the colorectal cancer.

OBJECTIVE

This review has focused on the most recent investigations, which has suggested potential epigenetic biomarkers in colorectal cancer.

METHODS

Evidences were achieved by searching online medical databases including Google scholar, Pubmed, Scopus and Science Direct.

RESULTS

Extensive studies have indicated that aberrant epigenetic modifications could serve as potential biomarkers for diagnosis, prognosis and prediction of colorectal cancer.

CONCLUSION

Advances in aberrant epigenetic modifications can open new avenues for exploration of reliable and robust biomarkers to improve the management of CRC patients.