Molecular Detection of Codon 12 K-RAS Mutations in Circulating DNA from Serum of Colorectal Cancer Patients

Point mutations of the K-RAS gene at codon 12 are found in about 40% of cases with colorectal cancer. The diagnostic implications of the detection of these mutations and their clinical utility are still unclear. The aim of this study was to test both the feasibility of the detection of the mutated K-RAS gene in serum and its potential role in colorectal cancer detection and monitoring.

Codon 12 K-RAS mutations were examined in DNA extracted from the serum of 35 patients with colorectal cancer and were compared with the K-RAS status in the corresponding primary tumor. Molecular detection was performed by the mutant-enriched PCR (ME-PCR) assay, a sensitive method capable of distinguishing a small quantity of mutated DNA in the presence of abundant wild-type DNA. The occurrence of mutations was compared with clinicopathological parameters as well as CEA and CA19.9 serum levels.

We found codon 12 K-RAS mutations in the tissue of 13/35 (37%) patients. Serum mutations were detected in 5/13 (38.5%) patients with mutated K-RAS in the tissue. 26/35 (74%) patients showed an identical K-RAS pattern in tissue and serum. No codon 12 K-RAS alterations were found in serum samples of 22 patients with benign gastrointestinal diseases. Elevated serum CEA levels were detected in 16 patients, four of whom also presented serum RAS mutations.

Our results confirm that K-RAS mutations can be found in circulating DNA extracted from serum samples of patients with colorectal cancer and show that there is a correspondence between serum and tissue K-RAS patterns.

Origin of multifocal carcinomas of the bladder and upper urinary tract: molecular analysis and clinical implications

The simultaneous or metachronous development of multifocal tumors with identical or variable histological features in the urothelial tract in a single patient is a well-known characteristic of urothelial cancer. To explain this phenomenon, two distinct concepts have been proposed: the 'field defect' hypothesis according to which urothelial cells in patients are primed to undergo transformation by previous carcinogenic insults and the 'single progenitor cell' hypothesis, which asserts that the multifocal development is caused by the seeding or intraepithelial spread of transformed cells. Results of recent molecular genetic studies support the 'single progenitor cell' hypothesis, and indicate that the genetic and phenotypic diversity observed in multifocal urothelial tumors is a consequence of clonal evolution from a single transformed cell. An understanding of the mechanism of the heterotopic recurrence of urothelial cancer may provide new prospects for early molecular detection and prevention of heterotopic recurrence of urothelial cancer.

A method to quantitatively detect H-ras point mutation based on electrochemiluminescence

Conventional methods for point mutation detection are usually multi-stage, laborious, and need to use radioactive isotopes or other hazardous materials, and the assay results are often semi-quantitative. In this work, a protocol for quantitative detection of H-ras point mutation was developed. Electrochemiluminescence (ECL) assay was coupled with restriction endonuclease digestion directly from PCR products. Only the wild-type amplicon containing the endonuclease's recognition site can be cut off, and thus cannot be detected by ECL assay. Using the PCR-ECL method, 30 bladder cancer samples were analyzed for possible point mutation at codon 12 of H-ras oncogene. The results show that the detection limit for H-ras amplicon is 100 fmol and the linear range is more than three orders of magnitude. The point mutation was found in 14 (46.7%) out of 30 bladder cancer samples. The experiment results demonstrate that the PCR-ECL method is a feasible quantitative approach for point mutation detection due to its safety, high sensitivity, and simplicity.

Telomerase activity detected by quantitative assay in bladder carcinoma and exfoliated cells in urine

Early diagnosis is one of the most determining factors for patient survival. The detection of telomerase activity is a potentially promising tool in the diagnosis of bladder and other types of cancer due to the high expression of this enzyme in tumor cells. We carried out a quantitative evaluation of telomerase activity in urine samples in an attempt to determine a cut-off capable of identifying cancer patients. Telomerase activity was quantified by fluorescence TRAP assay in urine from 50 healthy volunteers and in urine and bioptic tumor samples from 56 previously untreated bladder cancer patients and expressed in arbitrary enzymatic units (AEU). Telomerase activity in urine ranged from 0 to 106 AEU (median 0) in healthy donors and from 0 to 282 AEU (median 87) in patients with cancer. A telomerase expression higher than the cut off value determined by receiver operating characteristic (ROC) analysis was observed in 78% of cases, regardless of tumor grade and in 71% (15/21) of cases of nonassessable or negative cytology. The quantitative analysis of telomerase activity in urine enabled us to define cut-off values characterized by different sensitivity and specificity. Cytologic and telomerase determination, used sequentially, enabled us to detect about 90% of tumors.