Novel multiple, monoallelic KRAS mutations at codon 12 and 13

Multipoint Kras oncogene mutations potentially indicate mucinous carcinoma on the entire spectrum of mucinous ovarian neoplasms

Kras mutation is a common phenomenon in many human neoplasms. We aimed to assess the Kras mutational status along the histological continuum from normal ovaries to the development of benign, borderline and malignant ovarian mucinous neoplasms. We analyzed 41 cases of malignant, 10 cases of borderline, 7 cases of benign mucinous ovarian tumors and 7 cases of normal ovarian tissue. The prevalence of Kras mutations in the normal ovary was 0.00% (n=0/7), while the prevalence in benign, borderline and malignant mucinous neoplasms was 57.14% (n=4/7), 90.00% (n=9/10) and 75.61% (n=31/41), respectively. Multiple Kras mutations were detected in 6 cases of mucinous carcinoma, including 5 double mutations with G13D/V14I (n=1), G12V/G13S (n=1), G12D/G13S (n=3) and one triple mutation with A11V/G13N/V14I (n=1). We identified six cases with 3 novel Kras mutations not previously described in the COSMIC database, which included A11V (n=3) and V14I (n=2) in mucinous carcinomas, and A11T (n=1) in a mucinous borderline tumor. In conclusion, Kras mutation appears to be one of the imperative events in the ovarian mucinous adenoma–borderline tumor–carcinoma sequence, as increased numbers of Kras mutations have been shown to be the strongest predictor of unequivocal malignancy in ovarian mucinous neoplasms.

The usability of allele-specific PCR and reverse-hybridization assays for KRAS genotyping in Serbian colorectal cancer patients

BACKGROUND

Colorectal cancers (CRCs) with wild-type KRAS respond to EGFR-targeted antibody treatment. Analysis of the hotspot clustered mutations in codons 12 and 13 is compulsory before therapy and no standardized methodology for that purpose has been established so far. Since these mutations may have different biological effects and clinical outcome, reliable frequency and types of KRAS mutations need to be determined for individual therapy.

AIMS

The purpose of this study was to describe the KRAS mutation spectrum in a group of 481 Serbian mCRC patients and to compare the general performances of allele-specific PCR and reverse-hybridization assays.

METHODS

KRAS testing was performed with two diagnostic analyses, DxS TheraScreen K-RAS PCR Kit and KRAS StripAssay™.

RESULTS

KRAS mutations in codons 12 and 13 were present in 37.6 % of analyzed formalin-fixed paraffin-embedded (FFPE) DNA samples. The seven most frequent mutation types were observed with both assays: p.G12D 34.6 %, p.G12V 24.9 %, p.G12A 10.3 %, p.G12C 8.1 %, p.G12S 5.4 %, p.G12R 1.6 %, and p.G13D 15.1 %. Regarding double mutants, 0.8 % of them were present among all tested samples and 2.2 % among KRAS mutated ones.

CONCLUSIONS

Two screening approaches that were used in this study have been shown as suitable tests for detecting KRAS mutations in diagnostic settings. In addition, they appear to be good alternatives to methods presently in use. In our experience, both methods showed capacity to detect and identify double mutations which may be important for potential further subgrouping of CRC patients.

Multiple mutations in the Kras gene in colorectal cancer: review of the literature with two case reports

PURPOSE

Kras mutations are negative predictors of anti-EGFR therapy, occurring in 40% of colorectal carcinomas (CRCs). Point substitutions in codon 12 or 13 are the most frequent mutations in Kras, but multiple mutations (MMs) in other codons can also develop. Few data exist on MMs with regard to their frequency and the codons and amino acids that are affected. We report two cases of Kras double mutations in codons 12 and 13 and review Kras MMs in primary CRC in PubMed databases.

CASE REPORT

A 53-year-old woman and a 70-year-old man presented with deep, invasive, moderately differentiated CRC at an advanced clinical stage. The former had regional lymph node involvement and vaginal wall neoplastic implantation, and the latter had liver metastasis. Primary tumors were examined for Kras mutations by pyrosequencing, which were confirmed by direct sequencing. Both tumors had a mutation in codons 12 and 13, wherein codon 12 was mutated to GAT, and codon 13 became GAC.

CONCLUSIONS

We identified 69 reported cases of Kras MMs and reported two other cases, representing 2.1% of all mutated tumors; the incidence of such mutations is 1.0% in CRC patients. In most cases (59%), MMs develop in a single codon, usually codon 12. Codons 12 and 13 are affected simultaneously in only 27% of cases. These findings add information about the impact of specific amino acid changes in the Kras gene.