State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, China.
School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
Int J Mol Sci. 2020 Jan 31;21(3):957. doi: 10.3390/ijms21030957.
The tumor microenvironment has been recently recognized as a critical contributor to cancer progression and anticancer therapy-resistance. Cyclophosphamide (CTX) is a cytotoxic agent commonly used in clinics for the treatment of cancer. Previous reports demonstrated that CTX given at low continuous doses, known as metronomic schedule, mainly targets endothelial cells and circulating Tregs with unknown mechanisms. Here, we investigated the antitumor activity of two different metronomic schedules of CTX along with their corresponding MTD regimen and further explored their effect on immune function and tumor microenvironment. Toxicity evaluation was monitored by overall survival rate, weight loss, and histopathological analysis. A nude mouse model of Lewis lung cancer was established to assess the anti-metastatic effects of CTX in vivo. CD4, CD8, and CD4CD25FoxP3 T cells were selected by flow cytometry analysis. Low and continuous administration of CTX was able to restore immune function via increase of CD4/CD8 T cells and depletion of T regulatory cells, not only in circulatory and splenic compartments, but also at the tumor site. Low-dose CTX also reduced myofibroblasts, accompanied with an increased level of E-cadherin and low N-cadherin, both in the primary tumor and lung through the TGF-β pathway by the downregulated expression of TGF-β receptor 2. Our data may indicate that several other molecular mechanisms of CTX for tumor may be involved in metronomic chemotherapy, besides targeting angiogenesis and regulatory T cells.
肿瘤微环境最近被认为是癌症进展和抗癌治疗耐药的关键因素。环磷酰胺（CTX）是一种临床常用的细胞毒性药物，用于治疗癌症。先前的报告表明，以低连续剂量给予 CTX，称为节拍化疗，主要针对内皮细胞和循环 Tregs，其机制尚不清楚。在这里，我们研究了两种不同的 CTX 节拍化疗方案及其相应的最大耐受剂量方案的抗肿瘤活性，并进一步探讨了它们对免疫功能和肿瘤微环境的影响。通过总生存率、体重减轻和组织病理学分析监测毒性评估。建立了裸鼠 Lewis 肺癌模型，以评估 CTX 在体内的抗转移作用。通过流式细胞术分析选择 CD4、CD8 和 CD4CD25FoxP3 T 细胞。低剂量和连续给予 CTX 能够通过增加 CD4/CD8 T 细胞和耗尽 T 调节细胞来恢复免疫功能，不仅在循环和脾脏部位，而且在肿瘤部位。低剂量 CTX 还通过下调 TGF-β 受体 2 的表达，降低肌成纤维细胞的数量，同时增加 E-钙黏蛋白的水平，降低 N-钙黏蛋白的水平，从而减少原发性肿瘤和肺部的 TGF-β 通路。我们的数据可能表明，CTX 除了靶向血管生成和调节性 T 细胞外，还有几种其他针对肿瘤的分子机制可能参与节拍化疗。
