Mutagenicity of N-ethyl-N-nitrosourea, N-methyl-N-nitrosourea, methyl methanesulfonate and ethyl methanesulfonate in the developing Syrian hamster fetus

In-utero exposure to nelfinavir-ethyl methyl sulfone

Ethyl methyl sulfone contained in nelfinavir between 2007 and 2008 accidentally exposed embryos and fetuses to a powerful mutagen. We report data for 101 HIV-uninfected children exposed in utero included in the French prospective national cohort. The incidence of malformation was similar to that in the cohort as a whole with different drug exposures; no children had developed cancer after 9 years of follow-up.

Microsatellite instability detected in tumor-related genes in C57BL/6J mice with thymic lymphoma induced by N-methyl-N-nitrosourea

Microsatellite instability (MSI) has been observed within tumors and found to be closely associated with the degree of malignancy and prognosis in tumors. However, whether MSI in tumor-related genes can be induced by a chemical and whether a connection exists between MSI and tumors remain unclear. In the present study, we detected MSI in the tissues of N-methyl-N-nitrosourea (MNU) treated mice by targeting to 5, 29, 30 microsatellite loci in 3 mismatch repair (MMR) genes, 1 DNA repair gene, and 5 tumor suppressor (TS) genes, respectively. Among 26 mice survived in the MNU-group, 18 (69%) mice presented thymic lymphomas. Moreover, 61% (11/18) of the tumors metastasized to the other organs, including the liver, spleen, and kidney. We examined 104 tissues from MNU-treated mice using the 64 loci, and found 8 MSI events involved 4 loci in 4 tissues types. The MSI incidence in MMR, DNA repair, and TS genes was 67% (2/3), 0% (0/1) and 40% (2/5), respectively. MSI occurrence in tumor and non-tumor tissues was 5.6% (1/18) and 0% (0/8) and that in metastasis and non-metastasis tissues was 7.1% (1/14) and 9.4% (6/64), showing no significant difference. MSI loci in intronic regions of Atm, Msh6 and p21 and MSI in the 3'UTR of Pms2 were detected in MNU-treated mice. Specifically, we found a loss of heterozygosity in intron of Atm (ATM-8) in one metastasis mouse. Four similar events occurred in p21 gene intron (P21-1) of another non-metastasis mouse. Another MSI was a heterozygous mutation existed in an Msh6 allele (MSH6-2) in metastasis mouse. We also found a homozygous 2-bp insertion in the 3'UTR of Pms2 in two non-metastasis mice. These results imply that MNU can induce MSI in MMR and TS genes in C57BL/6J mice. MSI frequency does not seem to be associated with tumorigenesis or metastasis.

Ethyl methanesulfonate induces mutations in Caenorhabditis elegans embryos at a high frequency

Mutagenesis protocols typically call for exposure of late-stage larvae or adults to a mutagen with the intention of inducing mutations in a robust germ line. Instead, ca. 16,000 CB665 [unc-58(e665)] one- to four-cell embryos of the nematode Caenorhabditis elegans were hand selected and exposed to ethyl methanesulfonate (EMS) for 50min. Twenty-one reversion mutants were recovered, of which 17 were intragenic suppressors of the e665 mutation. The mutation frequency was 6.5-fold higher than when CB665 adults were similarly mutagenized, which was predicted given that cell-cycle checkpoints are muted in C. elegans embryos. The mutation spectrum was similar to that obtained after standard EMS mutagenesis.