Bredfeldt Tiffany G, Jagadish Bhumasamudram, Eblin Kylee E, Mash Eugene A, Gandolfi A Jay
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, 1703 E. Mabel St., Tucson, AZ 85721, USA.
Toxicol Appl Pharmacol. 2006 Oct 1;216(1):69-79. doi: 10.1016/j.taap.2006.04.011. Epub 2006 Jun 27.
Arsenic is a human bladder carcinogen. Arsenic is methylated to both monomethyl and dimethyl metabolites which have been detected in human urine. The trivalent methylated arsenicals are more toxic than inorganic arsenic. It is unknown if these trivalent methylated metabolites can directly cause malignant transformation in human cells. The goal of this study is determine if monomethylarsonous acid (MMA(III)) can induce malignant transformation in a human bladder urothelial cell line. To address this goal, a non-tumorigenic human urothelial cell line (UROtsa) was continuously exposed to 0.05 muM MMA(III) for 52 weeks. Hyperproliferation was the first phenotypic change observed in exposed UROtsa (URO-MSC). After 12 weeks of exposure, doubling time had decreased from 42 h in unexposed control cells to 27 h in URO-MSC. Hyperproliferation continued to be a quality possessed by the URO-MSC cells after both 24 and 52 weeks of exposure to MMA(III), which had a 40-50% reduction in doubling time. Throughout the 52-week exposure, URO-MSC cells retained an epithelial morphology with subtle morphological differences from control cells. 24 weeks of MMA(III) exposure was required to induce anchorage-independent growth as detected by colony formation in soft agar, a characteristic not found in UROtsa cells. To further substantiate that malignant transformation had occurred, URO-MSC cells were tested after 24 and 52 weeks of exposure to MMA(III) for the ability to form tumors in SCID mice. Enhanced tumorigenicity in SCID mouse xenografts was observed after 52 weeks of treatment with MMA(III). These observations are the first demonstration of MMA(III)-induced malignant transformation in a human bladder urothelial cell line and provide important evidence that MMA(III) may be carcinogenic in human tissues.
砷是一种人类膀胱致癌物。砷会甲基化形成一甲基和二甲基代谢产物，这些代谢产物已在人类尿液中被检测到。三价甲基化砷比无机砷毒性更强。目前尚不清楚这些三价甲基化代谢产物是否能直接导致人类细胞发生恶性转化。本研究的目的是确定一甲基亚砷酸（MMA(III)）是否能诱导人膀胱尿路上皮细胞系发生恶性转化。为实现这一目标，将一种非致瘤性人尿路上皮细胞系（UROtsa）持续暴露于0.05μM的MMA(III)中52周。细胞过度增殖是在暴露的UROtsa（URO-MSC）中观察到的第一个表型变化。暴露12周后，倍增时间从未暴露的对照细胞中的42小时降至URO-MSC中的27小时。在暴露于MMA(III) 24周和52周后，URO-MSC细胞持续具有过度增殖的特性，其倍增时间减少了40 - 50%。在整个52周的暴露过程中，URO-MSC细胞保持上皮形态，与对照细胞存在细微形态差异。暴露于MMA(III) 24周后，通过软琼脂中的集落形成检测到诱导了不依赖贴壁生长，这是UROtsa细胞中未发现的特征。为进一步证实发生了恶性转化，在暴露于MMA(III) 24周和52周后，对URO-MSC细胞进行检测，以确定其在SCID小鼠中形成肿瘤的能力。在用MMA(III)处理52周后，观察到SCID小鼠异种移植瘤的致瘤性增强。这些观察结果首次证明了MMA(III)可诱导人膀胱尿路上皮细胞系发生恶性转化，并提供了重要证据表明MMA(III)可能在人体组织中具有致癌性。
