Exosomal miR-29a-3p in the immune microenvironment of spleen deficiency promotes hepatocellular carcinoma lung metastasis by activating FAM167A-α1-integrin-NF-κB signaling axis

Abstract Background Hepatocellular carcinoma (HCC), a common type of cancer, has a strong metastatic ability and poor prognosis. The tumor microenvironment is the “soil” for the occurrence and development of tumors, with exosomes playing an important role in these processes. In traditional Chinese medicine(TCM), the tumor microenvironment corresponds to the internal environment of the syndrome known as spleen deficiency (SD). Numerous studies have shown that exosomes contain high levels of miRNAs, which have been shown to contribute to tumor immune regulation and metastasis. The aim of this study was to explore the mechanisms underlying the changes in the tumor microenvironment under the condition of spleen deficiency in order to find better treatments for cancer. Methods The effects of exosomal miR-29a-3p on lung metastasis from hepatocellular carcinoma (HCC) were evaluated using the scratch test, migration test, mouse SD model, HCC model, and tail-vein injection model of lung metastasis. The western blot assay, ELISA, flow cytometry, luciferase reporter gene analysis, qRT-PCR and immunofluorescence staining were among the methods used to study the molecular mechanism of lung metastasis promotion under the SD internal environment. Results Compared with the mice with HCC only, the mice with HCC and SD symptoms secreted more miR-29a- 3p-enriched exosomes, and their tumor tissue expressed significantly higher levels of α1-integrin and lower levels of FAM167A. These changed the immune microenvironment of mice (Decreased infiltration of T cells (CD3 + CD4 + and CD3 + CD8 + ), activated α1-integrin-NF-κB signaling pathway, and secreted more interleukin inflammatory factors(IL-1β, IL-6, and IL-8), which promoted the invasion and infiltration of HCC and its lung metastasis both in vivo and in vitro . In a series of patients with liver cancer, SD was found to have affected their overall survival and relapse-free survival. Conclusion Our study showed that under conditions of SD, the body releases more miRNA-containing exosomes, changes the immune microenvironment of the body, and ultimately promotes tumor metastasis and growth. These results highlight potential therapeutic targets and methods for the prevention of cancer metastasis, which may help to screen possible anticachexia TCMs and elucidate its mechanism in the future.