Melanoma arises from pigment-producing cells called melanocytes located in the basal layers of the epidermis of the skin. Cytoglobin (CYGB) is a ubiquitously expressed hexacoordinated globin that is highly enriched in melanocytes and frequently downregulated during melanomagenesis. Previously, we showed that non-thermal plasma (NTP)-produced reactive oxygen and nitrogen species (RONS) lead to the formation of an intramolecular disulfide bridge that would allow CYGB to function as a redox-sensitive protein. Here, we investigate the cytotoxic effect of indirect NTP treatment in two melanoma cell lines with divergent endogenous CYGB expression levels, and we explore the role of CYGB in determining treatment outcome. Our findings are consistent with previous studies supporting that NTP cytotoxicity is mediated through the production of RONS and leads to apoptotic cell death in melanoma cells. Furthermore, we show that NTP-treated solutions elicit an antioxidant response through the activation of nuclear factor erythroid 2–related factor 2 (NRF2). The knockdown and overexpression of CYGB respectively sensitizes and protects melanoma cells from RONS-induced apoptotic cell death. The presence of CYGB enhances heme-oxygenase 1 (HO-1) and NRF2 protein expression levels, whereas the absence impairs their expression. Moreover, analysis of the CYGB-dependent transcriptome demonstrates the tumor suppressor long non-coding RNA maternally expressed 3 (MEG3) as a hitherto undescribed link between CYGB and NRF2. Thus, the presence of CYGB, at least in melanoma cells, seems to play a central role in determining the therapeutic outcome of RONS-inducing anticancer therapies, like NTP-treated solutions, possessing both tumor-suppressive and oncogenic features. Hence, CYGB expression could be of interest either as a biomarker or as a candidate for future targeted therapies in melanoma.

黑色素瘤由位于皮肤表皮基底层的称为黑色素细胞的色素产生细胞产生。细胞珠蛋白（CYGB）是一种普遍表达的六配位珠蛋白，在黑色素细胞中高度富集，并在黑色素瘤发生过程中经常下调。此前，我们表明非热等离子体 (NTP) 产生的活性氧和氮物种 (RONS) 导致分子内二硫键的形成，从而使 CYGB 能够充当氧化还原敏感蛋白。在这里，我们研究了间接 NTP 治疗对两种具有不同内源 CYGB 表达水平的黑色素瘤细胞系的细胞毒性作用，并探讨了 CYGB 在确定治疗结果中的作用。我们的研究结果与之前的研究一致，即 NTP 细胞毒性是通过 RONS 的产生介导的，并导致黑色素瘤细胞凋亡。此外，我们还发现，经 NTP 处理的溶液通过激活核因子红细胞 2 相关因子 2 (NRF2) 来引发抗氧化反应。CYGB 的敲低和过表达分别使黑色素瘤细胞敏感并保护其免受 RONS 诱导的细胞凋亡。CYGB 的存在会增强血红素加氧酶 1 (HO-1) 和 NRF2 蛋白的表达水平，而缺乏则会损害它们的表达。此外，对 CYGB 依赖性转录组的分析表明，肿瘤抑制因子长链非编码 RNA 母体表达 3 (MEG3) 是 CYGB 和 NRF2 之间迄今为止未被描述的联系。因此，至少在黑色素瘤细胞中，CYGB 的存在似乎在决定 RONS 诱导抗癌疗法的治疗结果方面发挥着核心作用，例如 NTP 处理的溶液，具有肿瘤抑制和致癌特性。因此，CYGB 表达可能作为生物标志物或作为未来黑色素瘤靶向治疗的候选者。