Inorganic arsenic is a known human skin carcinogen. Chronic arsenic exposure results in various human skin lesions, including hyperkeratosis and squamous cell carcinoma (SCC), both characterized by distorted cytokeratin (CK) production. Prior work shows the human skin keratinocyte HaCaT cell line, when exposed chronically for >25 weeks to a low level of inorganic arsenite (100nM) results in cells able to produce aggressive SCC upon inoculation into nude mice. In the present study, CK expression analysis was performed in arsenic-exposed HaCaT cells during the progressive acquisition of this malignant phenotype (0-20 weeks) to further validate this model as relevant to epidermal carcinogenesis induced by arsenic in humans. Indeed, we observed clear evidence of acquired cancer phenotype by 20 weeks of arsenite exposure including the formation of giant cells, a >4-fold increase in colony formation in soft agar and a approximately 2.5-fold increase in matrix metalloproteinase-9 secretion, an enzyme often secreted by cancer cells to help invade through the local extra-cellular matrix. During this acquired malignant phenotype, various CK genes showed markedly altered expression at the transcript and protein levels in a time-dependent manner. For example, CK1, a marker of hyperkeratosis, increased up to 34-fold during arsenic-induced transformation, while CK13, a marker for dermal cancer progression, increased up to 45-fold. The stem cell marker, CK15, increased up to 7-fold, particularly during the later stages of arsenic exposure, indicating a potential emergence of cancer stem-like cells with arsenic-induced acquired malignant phenotype. The expression of involucrin and loricrin, markers for keratinocyte differentiation, increased up to 9-fold. Thus, during arsenic-induced acquired cancer phenotype in human keratinocytes, dramatic and dynamic alterations in CK expression occur which are consistent with the process of epidermal carcinogenesis helping validate this as an appropriate model for the study of arsenic-induced skin cancer.

中文翻译：

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砷诱导的人 HaCaT 角质形成细胞获得性恶性表型期间的异常细胞角蛋白表达与表皮致癌作用一致。

无机砷是一种已知的人类皮肤致癌物。慢性砷暴露会导致各种人类皮肤病变，包括角化过度和鳞状细胞癌 (SCC)，两者的特征都是细胞角蛋白 (CK) 产生扭曲。先前的工作表明，当人类皮肤角质形成细胞 HaCaT 细胞系长期暴露于低水平的无机亚砷酸盐 (100nM) 超过 25 周时，会导致细胞在接种到裸鼠中后产生侵袭性 SCC。在本研究中，在这种恶性表型（0-20 周）的逐渐获得过程中，在暴露于砷的 HaCaT 细胞中进行了 CK 表达分析，以进一步验证该模型与人类砷诱导的表皮致癌作用相关。的确，我们通过亚砷酸盐暴露 20 周观察到获得性癌症表型的明确证据，包括巨细胞的形成、软琼脂中集落形成增加 4 倍以上以及基质金属蛋白酶 9 分泌增加约 2.5 倍，这是一种常见的酶由癌细胞分泌，帮助侵入局部细胞外基质。在这种获得性恶性表型期间，各种 CK 基因在转录本和蛋白质水平上以时间依赖性方式显示出显着改变的表达。例如，CK1，一种角化过度的标志物，在砷诱导的转化过程中增加了 34 倍，而 CK13，一种皮肤癌进展的标志物，增加了 45 倍。干细胞标志物 CK15 增加了 7 倍，特别是在砷暴露的后期阶段，表明具有砷诱导的获得性恶性表型的癌症干细胞样细胞的潜在出现。外皮蛋白和 loricrin（角质形成细胞分化的标志物）的表达增加了 9 倍。因此，在人类角质形成细胞中砷诱导的获得性癌症表型期间，CK 表达发生戏剧性和动态变化，这与表皮致癌过程一致，有助于验证其作为研究砷诱导皮肤癌的合适模型。