在癌症治疗中，包括黑色素瘤在内，使用免疫检查点抑制剂（ICI）和化疗药物的联合治疗方案的疗效已得到研究。在引入ICIs之前，达卡巴嗪或替莫唑胺（TMZ）被用于治疗黑色素瘤。一些使用胶质瘤或结直肠癌细胞的研究表明，TMZ能增加肿瘤突变负荷（TMB）并诱导与微卫星不稳定（MSI）相关的错配修复（MMR）缺陷。这些可能增加对ICI的免疫反应性，但在黑色素瘤细胞中尚未进行评估。我们研究了TMZ对黑色素瘤细胞的MSI状态和TMB的影响。为评估TMB，我们对来自人类黑色素瘤细胞系Mel18、A375、WM266-4、G361和TXM18的基因组DNA进行了全外显子测序，分别在TMZ治疗前后进行。我们进行了五个单核苷酸重复标记物（BAT25、BAT26、NR21、NR24和MONO27）的聚合酶链式反应扩增，并分析了MSI状态的变化。在所有细胞系中，即使在无明显细胞学损伤的情况下，TMZ治疗后TMB均有增加（≤ 5%变异等位基因频率[VAF]的TMB变化量为每兆碱基对18.0-38.3个突变）。在任何细胞中，TMZ治疗后未观察到MSI。TMZ增加了黑色素瘤细胞的TMB，但未改变MSI状态。© 2023日本皮肤科学会。

The efficacy of combination therapy with an immune checkpoint inhibitor (ICI) and cytotoxic chemotherapeutic agents has been investigated in cancer, including melanoma. Before ICIs were introduced, dacarbazine or temozolomide (TMZ) were used to treat melanoma. Several studies using glioma or colorectal cancer cells showed that TMZ can increase the tumor mutation burden (TMB) and induce mismatch repair (MMR) deficiency associated with microsatellite instability (MSI). These could increase immunoreactivity to an ICI, but this has not been evaluated in melanoma cells. We investigated the effects of TMZ on MSI status and TMB in melanoma cells. To evaluate the TMB, we performed whole-exome sequencing using genomic DNA from the human melanoma cell lines Mel18, A375, WM266-4, G361, and TXM18 before and after TMZ treatment. Polymerase chain reaction amplification of five mononucleotide repeat markers, BAT25, BAT26, NR21, NR24, and MONO27, was performed, and we analyzed changes in the MSI status. In all cell lines, the TMB was increased after TMZ treatment (the change amount of TMB with ≤ 5% variant allele frequency [VAF] was 18.0-38.3 mutations per megabase) even in the condition without obvious cytological damage. MSI after TMZ treatment was not observed in any cells. TMZ increased TMB but did not change MSI status in melanoma cells.© 2023 Japanese Dermatological Association.