title: Persistence of K-ras mutations in plasma after colorectal tumor resection.
abstract: Free DNA in the circulation is increased five-to ten-fold in patients with solid tumours compared to healthy controls. A range of tumor-specific mutated DNA has been shown to be readily extractable and possible to analyse from plasma and serum in these patients. K-ras oncogene mutations are an early event in a subset of colorectal tumors and have been found in 30-60% of patients with colorectal carcinoma (CRC). The presence of tumor-derived k-ras gene mutations in the circulation has previously been described before surgery. The aim of this study was to characterize the presence of mutant k-ras in plasma in the short-term postoperative period after radical surgery of CRC patients, and further to characterize this in relation to relapse of the disease. Tumors and corresponding plasma pre- and postoperatively on day three after surgery were collected from 25 patients with CRC (Dukes' stage A-D). Biopsies for DNA extraction from the tumors were collected from the most invasive parts microscopically. After PCR amplification of the k-ras gene (codon 12 and 13), the presence of mutations was analysed by TGGE (temperature gradient gel electrophoresis). Twenty four/25 patients underwent putatively curative resections. Sixteen of the 25 patients (64%) expressed k-ras mutations in their tumor. Of these, 9 patients (56%) also had detectable k-ras mutations in preoperative plasma samples. On day three postoperatively, 8 of these patients persistently were found to have mutant k-ras in the plasma. This was not correlated with tumor stage. None of the 9 tumor mutation-negative cases expressed mutated k-ras in their plasma pre- or postoperatively. The results indicate that plasma mutant k-ras can be detected pre- and early postoperatively in all stages of colorectal neoplasia. No correlation between short-term postoperative persistence of mutant plasma-DNA and disease recurrence at follow-up was found. However, the use of k-ras as a marker during postoperative follow-up and as a possible tool for early detection of recurrent disease must be further characterized.
authors.affiliation: Karolinska University Hospital, Huddinge, Sweden. Ulrik.Lindforss@cfss.ki.se
authors.forename: Ulrik
authors.initials: U
authors.lastname: Lindforss
authors.forename: Henrik
authors.initials: H
authors.lastname: Zetterquist
authors.forename: Nikos
authors.initials: N
authors.lastname: Papadogiannakis
authors.forename: Hans
authors.initials: H
authors.lastname: Olivecrona
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D002277:Carcinoma / Q000097:blood / Q000235:genetics / Q000601:surgery; D015179:Colorectal Neoplasms / Q000097:blood* / Q000235:genetics* / Q000601:surgery*; D004247:DNA / Q000097:blood / Q000378:metabolism; D004273:DNA, Neoplasm; D004586:Electrophoresis; D005260:Female; D011905:Genes, ras; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012008:Recurrence; D013997:Time Factors
chemical_list: D004273:DNA, Neoplasm; D004247:DNA