Hussein Mahmoud R, Wood Gary S
Department of Dermatology, University of Wisconsin, William S Middleton Veteran Hospital, Madison, WI 53705, USA.
Exp Dermatol. 2003 Dec;12(6):872-5. doi: 10.1111/j.0906-6705.2003.00104.x.
Microsatellite instability and reduced expression of mismatch repair proteins were reported in melanomas. However, little is known about mutational changes of the mismatch repair genes in radial growth-phase melanoma especially following UVB irradiation. To investigate these changes, an in vitro system consisting of radial growth-phase Wistar melanoma cell lines (WM35, WM3211 and WM1650) was established. The cells were UVB irradiated (10 mJ/cm(2)), and evaluated for mutational changes of exon regions 13,16 and 19 (hMLH1) and 6,7 and 12 (hMLH2) of these genes before and after irradiation. The genomic DNAs were PCR amplified and the products were directly sequenced. Transition (C-->T, G-->A, T-->C) and transversion (G-->, A-->T) mutations were found in exons 6,16 and 19. Some were present in both the sham-irradiated and UV-irradiated cells but others were only detected after UVB irradiation. hMLH1 and hMLH2 gene mutations occur early in melanoma tumorigenesis. The ability of UVB irradiation to induce additional mutations in these repair genes suggests its possible role in melanoma pathogenesis. Further investigation will be needed to determine whether mutations such as these contribute to the development of microsatellite instability in melanoma.
黑色素瘤中存在微卫星不稳定性和错配修复蛋白表达降低的情况。然而，对于辐射生长期黑色素瘤尤其是紫外线B（UVB）照射后错配修复基因的突变变化知之甚少。为了研究这些变化，建立了一个由辐射生长期Wistar黑色素瘤细胞系（WM35、WM3211和WM1650）组成的体外系统。对细胞进行UVB照射（10 mJ/cm²），并在照射前后评估这些基因外显子区域13、16和19（hMLH1）以及6、7和12（hMLH2）的突变变化。对基因组DNA进行聚合酶链反应（PCR）扩增，并对产物进行直接测序。在第6、16和19外显子中发现了转换（C→T、G→A、T→C）和颠换（G→、A→T）突变。有些突变在假照射和UVB照射的细胞中均有出现，但其他一些突变仅在UVB照射后才被检测到。hMLH1和hMLH2基因突变在黑色素瘤肿瘤发生的早期就会出现。UVB照射诱导这些修复基因产生额外突变的能力表明其在黑色素瘤发病机制中可能发挥的作用。需要进一步研究来确定这些突变是否会导致黑色素瘤中微卫星不稳定性的发展。
