A Review of Herbal Resources Inducing Anti-Liver Metastasis Effects in Gastrointestinal Tumors via Modulation of Tumor Microenvironments in Animal Models

SIMPLE SUMMARY: Based on the importance of the tumor microenvironment and liver environment in liver metastases, we conducted a systematic review to discover herbal candidates inhibiting the liver metastasis of tumors originating from the digestive system. We produced a list of potent herbs such as Curcuma longa Linn and single compounds such as curcumin and tanshinone II-A, along with their underlying mechanisms. The list of herbal agents and their mechanisms produced in this study is helpful for the development of anti-liver metastasis drugs in the future via modulation of liver environments. ABSTRACT: Liver metastases remain a major obstacle for the management of all types of tumors arising from digestive organs, and the tumor microenvironment has been regarded as an important factor in metastasis. To discover herbal candidates inhibiting the liver metastasis of tumors originating from the digestive system via the modulation of the tumor microenvironment and liver environment, we searched three representative public databases and conducted a systematic review. A total of 21 studies that employed experimental models for pancreatic (9), colon (8), and stomach cancers (4) were selected. The herbal agents included single-herb extracts (5), single compounds (12), and multiherbal decoctions (4). Curcuma longa Linn was most frequently studied for its anti-colon–liver metastatic effects, and its possible mechanisms involved the modulation of tumor microenvironment components such as vascular endothelial cells and immunity in both tumor tissues and circulating cells. The list of herbal agents and their mechanisms produced in this study is helpful for the development of anti-liver metastasis drugs in the future.