Cancer is a result of unregulated cell growth. For all types of cancer currently studied, the transition from a healthy cell to a malignant tumor cell is a step-by-step process which requires mutation in at least several oncogenes and tumor suppressor genes together. Another cancer early event is DNA methylation. Cancer-related DNA methylation focuses on promoter hypermethylation of the certain genes. The DNA mutation and methylation profile can serve as biomarkers for diagnosing early stage of cancer.
Colorectal cancer is the third most common cancer type in the United States and has been well studied. The essential mechanism of cancer development is becomeing clear, so there are more approaches to diagnose early stage cancer and improve cancer treatment, which benefits colorectal cancer screening in recent years.
The current mutation/methylation detection techniques generally have two major categories which rely on the 1) physical property of double strand DNA or 2) enzyme
selectivity to survey the target sequence. Chapters I and III summarize the major methods used in the present DNA mutation and methylation analysis.
High Resolution Melting (HRM) is a simple, PCR-based method for detecting DNA sequence variation by measuring the melting temperature of a DNA duplex. In Chapter II, a robust and lower cost HRM assay for screening P53 and Kras mutations is discussed. In Chapter IV we developed Probe Enrichment Mutation/Methylation-High Resolution Melting (PEMM-HRM) assay. PEMM-HRM analysis is a simple and high sensitive post PCR technique which can be used for high throughput mutation scanning, genotyping and methylation analysis. PEMM-HRM analysis with enhanced sensitivity and specificity can have broad applications in clinical research.
In chapter V, We studied adenylosuccinate lyase deficiency, which is a defect of purine metabolism. We developed a method combining ESI-MS with solid-phase extraction to detect succinyladenosine (SA) and succinylamino-imidazolecarboxamide riboside (SAICAr) of patients with adenylosuccinate lyase (ADSL) deficiency urine samples. For the first time, we demonstrated that both SAICAr and SA biomarkers can be detected by Electrospray Ionization Mass Spectrometry.