Circulating cell-free DNA from colorectal cancer patients may reveal high KRAS or BRAF mutation load

Florent Mouliere, Safia El Messaoudi, Celine Gongora, Anne Sophie Guedj, Bruno Robert, Maguy del Rio, Franck Molina, Pierre Jean Lamy, Evelyne Lopez-Crapez, Muriel Mathonnet, Marc Ychou, Denis Pezet, Alain R. Thierry

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Abstract

We used a novel method based on allele-specific quantitative polymerase chain reaction (Intplex) for the analysis of circulating cell-free DNA (ccfDNA) to compare total ccfDNA and KRAS- or BRAF-mutated ccfDNA concentrations in blood samples from mice xenografted with the human SW620 colorectal cancer (CRC) cell line and from patients with CRC. Intplex enables single-copy detection of variant alleles down to a sensitivity of ≥0.005 mutant to wild-type ratio. The proportion of mutant allele corresponding to the percentage of tumor-derived ccfDNA was elevated in xenografted mice with KRAS homozygous mutation and varied highly from 0.13% to 68.7% in samples from mutationpositive CRC patients (n = 38). Mutant ccfDNA alleles were quantified in the plasma of every patient at stages II/III and IV with a mean of 8.4% (median, 8.4%) and 21.8% (median, 12.4%), respectively. Twelve of 38 (31.6%) and 5 of 38 (13.2%) samples showed a mutation load higher than 25%and 50%, respectively. This suggests that an important part of ccfDNA may originate from tumor cells. In addition, we observed that tumor-derived (mutant) ccfDNA was more fragmented than ccfDNA from normal tissues. This observation suggests that the form of tumor-derived and normal ccfDNA could differ. Our approach revealed that allelic dilution is much less pronounced than previously stated, considerably facilitating the noninvasive molecular analysis of tumors.

Original languageEnglish
Pages (from-to)319-328
Number of pages10
JournalTranslational Oncology
Volume6
Issue number3
DOIs
Publication statusPublished - 1 Jan 2013

Cite this

Mouliere, F., Messaoudi, S. E., Gongora, C., Guedj, A. S., Robert, B., del Rio, M., ... Thierry, A. R. (2013). Circulating cell-free DNA from colorectal cancer patients may reveal high KRAS or BRAF mutation load. Translational Oncology, 6(3), 319-328. https://doi.org/10.1593/tlo.12445