Tumor-derived GABA promotes lung cancer progression by influencing TAMs polarization and neovascularization.

BACKGROUND: Gamma-aminobutyric acid (GABA), a common neurotransmitter, has been found in various cancers but its origin and its role in the tumor immune microenvironment remains unclear. METHODS: Here, we reported the expression of glutamate decarboxylase 1 (GAD1, converting glutamate into GABA) in lung cancer tissues based on the publicly available database, and explored the effects and underlying mechanism of GABA on lung cancer progression. RESULTS: Compared with normal tissues, GAD1 was aberrantly overexpressed in lung adenocarcinoma (LUAD) based on TCGA database. Furthermore, the LUAD patients' overall survival was negatively correlated with the GAD1 expression levels. Our work found that a GABAa receptor inhibitor had a therapeutic effect on mouse tumors and significantly reduced tumor size and weight. Further experiments showed that GABA derived from tumor cells promoted tumor progression not by directly affecting cancer cells but by affecting macrophages polarization in the tumor microenvironment. We found that GABA inhibited the NF-κB pathway and STAT3 pathway to prevent macrophages from polarizing towards M1 type, while promoting macrophage M2 polarization by activating the STAT6 pathway. GABA was also found to promote tumor neovascularization by increasing the expression of FGF2 in macrophages. CONCLUSIONS: These results suggest that GABA affects tumor progression by regulating macrophage polarization, and targeting GABA and its signaling pathway may represent a potential therapy for lung cancer.

Correction: Immunogenicity of mammary tumor cells can be induced by shikonin via direct binding-interference with hnRNPA1.

[This corrects the article DOI: 10.18632/oncotarget.9660.].

Induction of IL-25 secretion from tumour-associated fibroblasts suppresses mammary tumour metastasis.

Tumour-associated fibroblasts (TAFs), as a functionally supportive microenvironment, play an essential role in tumour progression. Here we investigate the role of IL-25, an endogenous anticancer factor secreted from TAFs, in suppression of mouse 4T1 mammary tumour metastasis. We show that a synthetic dihydrobenzofuran lignan (Q2-3), the dimerization product of plant caffeic acid methyl ester, suppresses 4T1 metastasis by increasing fibroblastic IL-25 activity. The secretion of IL-25 from treated human or mouse fibroblasts is enhanced in vitro, and this activity confers a strong suppressive effect on growth activity of test carcinoma cells. Subsequent in vivo experiments showed that the anti-metastatic effects of Q2-3 on 4T1 and human MDA-MD-231 tumour cells are additive when employed in combination with the clinically used drug, docetaxel. Altogether, our findings reveal that the release of IL-25 from TAFs may serve as a check point for control of mammary tumour metastasis and that phytochemical Q2-3 can efficiently promote such anticancer activities.

Immunogenicity of mammary tumor cells can be induced by shikonin via direct binding-interference with hnRNPA1.

Immunogenic cell death (ICD) of tumor cells occurs via various pathways that activate immune cell systems against cancer. Previous studies have demonstrated that shikonin (SK), a plant secondary metabolite, can confer strong pharmacological activities that activate ICD and strong immunogenicity of tumor cells. However, the exact hierarchical regulatory mechanisms including the molecular targets of SK-activated immunogenicity are still unknown. Here, the heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was revealed to serve as a specific protein target for SK. This binding plays a key role in SK-stimulated ICD activity and the suppression of post-transcriptional mRNA processing, including nuclear export activity of newly synthesized mRNAs in mammary carcinoma cells in vitro. Moreover, it also mechanistically mediates the anti-metastatic effect of a tumor cell lysate (TCL) vaccine, which can be readily generated from SK-treated 4T1 tumor cells (SK-TCL), and the derived tumor-immunogenicity of SK-TCL-treated dendritic cells in vivo. Together, the identification of hnRNPA1 as the intracellular molecular target provides compelling pharmacology-based knowledge for the potential clinical use of SK-induced immunogenicity. In addition, SK may also serve as a potent suppressor that interferes with specific post-transcriptional activities, a mechanism which may be useful for exploitation in cancer therapeutics.

Therapeutic applications of herbal medicines for cancer patients.

Medicinal herbs and their derivative phytocompounds are being increasingly recognized as useful complementary treatments for cancer. A large volume of clinical studies have reported the beneficial effects of herbal medicines on the survival, immune modulation, and quality of life (QOL) of cancer patients, when these herbal medicines are used in combination with conventional therapeutics. Here, we briefly review some examples of clinical studies that investigated the use of herbal medicines for various cancers and the development of randomized controlled trials (RCTs) in this emerging research area. In addition, we also report recent studies on the biochemical and cellular mechanisms of herbal medicines in specific tumor microenvironments and the potential application of specific phytochemicals in cell-based cancer vaccine systems. This review should provide useful technological support for evidence-based application of herbal medicines in cancer therapy.