维生素D3结构上属于甾体激素，它的主要生理功能是调节钙磷代谢和维持正常血钙水平、调节骨代谢和多种细胞的生理反应。近年来很多研究表明维生素D3在多种肿瘤中扮演重要角色，影响肿瘤细胞的增殖、凋亡等活动。维生素D3作用于不同癌细胞类型的细胞机制，有力地表明维生素D3可以发挥保护和抗肿瘤作用，延缓细胞转化、增生和肿瘤进展。流行病学研究发现血清维生素D水平与胃肠道肿瘤发病风险呈负相关，血清维生素D水平与胃肠道肿瘤患者预后正相关。进一步研究表明维生素D3可以通过多种途径诱导细胞凋亡、阻滞细胞周期、抑制胃肠道肿瘤细胞增殖。维生素D3能够与化疗药物协同作用促进肿瘤细胞凋亡、抑制肿瘤细胞增殖。维生素D3类似物不产生高血钙的副作用，也能够发挥其抑制肿瘤细胞生长的作用。维生素D3可能通过维生素D3受体VDR发挥其抗肿瘤作用。结合这些研究表明维生素D3有希望做为治疗和预防胃肠道肿瘤的新思路，更多的维生素D3抗肿瘤机制研究及临床实验能够为胃肠道肿瘤患者带来福音。

The structure of vitamin D3belongs to steroid hormone. Its main physiological function is regulating calcium and phosphorus metabolism and maintaining normal blood calcium levels, regulating bone metabolism and physiological reaction of many cells. In recent years, many studies have shown that vitamin D3plays an important role in many kinds of tumors, affecting tumor cell proliferation, apoptosis and other activities. The mechanisms by which vitamin D3acts on different cancer cell types strongly suggest that vitamin D3may play a protective and antitumor role, delaying cell transformation, proliferation, and cancer progression. Epidemiological studies have found that serum vitamin D levels are negatively correlated with the risk of gastrointestinal cancer, and serum vitamin D levels are positively correlated with the prognosis of patients with gastrointestinal cancer. Further studies have shown that vitamin D3can induce apoptosis, block cell cycle and inhibit proliferation of gastrointestinal cancer cells in a variety of ways. Vitamin D3 can cooperate with chemotherapeutic drugs to promote tumor cell apoptosis and inhibit tumor cell proliferation. Compared with vitamin D3, vitamin D3has less side effects and can play its role in inhibiting the growth of tumor cells. Vitamin D3may exert its antitumor effect through vitamin D3 receptor VDR. In combination with these studies, vitamin D3is expected to become a new approach for the treatment and prevention of gastrointestinal tumors, and more vitamin D3 anti-tumor mechanisms and clinical trials can bring good news for patients with gastrointestinal cancer.