Bishak Yaser Khaje, Payahoo Laleh, Osatdrahimi Alireza, Nourazarian Alireza
Student Research Committee, Nutrition Research Center, Department of Nutrition, Tabriz University of Medical sciences, Tabriz, Iran E-mail :
Asian Pac J Cancer Prev. 2015;16(1):9-21. doi: 10.7314/apjcp.2015.16.1.9.
Cancer, a serious public health problem in worldwide, results from an excessive and uncontrolled proliferation of the body cells without obvious physiological demands of organs. The gastrointestinal tract, including the esophagus, stomach and intestine, is a unique organ system. It has the highest cancer incidence and cancer- related mortality in the body and is influenceed by both genetic and environmental factors. Among the various chemical elements recognized in the nature, some of them including zinc, iron, cobalt, and copper have essential roles in the various biochemical and physiological processes, but only at low levels and others such as cadmium, lead, mercury, arsenic, and nickel are considered as threats for human health especially with chronic exposure at high levels. Cadmium, an environment contaminant, cannot be destroyed in nature. Through impairment of vitamin D metabolism in the kidney it causes nephrotoxicity and subsequently bone metabolism impairment and fragility. The major mechanisms involved in cadmium carcinogenesis could be related to the suppression of gene expression, inhibition of DNA damage repair, inhibition of apoptosis, and induction of oxidative stress. In addition, cadmium may act through aberrant DNA methylation. Cadmium affects multiple cellular processes, including signal transduction pathways, cell proliferation, differentiation, and apoptosis. Down-regulation of methyltransferases enzymes and reduction of DNA methylation have been stated as epigenetic effects of cadmium. Furthermore, increasing intracellular free calcium ion levels induces neuronal apoptosis in addition to other deleterious influence on the stability of the genome.
癌症是全球范围内严重的公共卫生问题，它是由身体细胞在无明显器官生理需求的情况下过度且不受控制地增殖所导致的。胃肠道，包括食管、胃和肠道，是一个独特的器官系统。它在人体中具有最高的癌症发病率和癌症相关死亡率，并且受到遗传和环境因素的双重影响。在自然界中已被确认的各种化学元素中，其中一些元素，包括锌、铁、钴和铜，在各种生化和生理过程中发挥着重要作用，但仅在低水平时如此，而其他元素，如镉、铅、汞、砷和镍，则被视为对人类健康的威胁，尤其是在长期高剂量接触的情况下。镉作为一种环境污染物，在自然界中无法被破坏。它通过损害肾脏中的维生素D代谢，导致肾毒性，进而引起骨代谢损害和骨质脆弱。镉致癌的主要机制可能与基因表达的抑制、DNA损伤修复的抑制、细胞凋亡的抑制以及氧化应激的诱导有关。此外，镉可能通过异常的DNA甲基化起作用。镉影响多种细胞过程，包括信号转导通路、细胞增殖、分化和凋亡。甲基转移酶的下调和DNA甲基化的减少已被认为是镉的表观遗传效应。此外，细胞内游离钙离子水平的升高除了对基因组稳定性产生其他有害影响外，还会诱导神经元凋亡。
