Salmonella alters heparanase expression and reduces tumor metastasis

The Mycobacterium ulcerans toxin mycolactone causes destructive Sec61-dependent loss of the endothelial glycocalyx and vessel basement membrane to drive skin necrosis

The drivers of tissue necrosis in Mycobacterium ulcerans infection (Buruli ulcer disease) have historically been ascribed solely to the directly cytotoxic action of the diffusible exotoxin, mycolactone. However, its role in the clinically evident vascular component of disease aetiology remains poorly explained. We have now dissected mycolactone's effects on human primary vascular endothelial cells in vitro. We show that mycolactone-induced changes in endothelial morphology, adhesion, migration, and permeability are dependent on its action at the Sec61 translocon. Unbiased quantitative proteomics identified a profound effect on proteoglycans, driven by rapid loss of type II transmembrane proteins of the Golgi, including enzymes required for glycosaminoglycan (GAG) synthesis, combined with a reduction in the core proteins themselves. Loss of the glycocalyx is likely to be of particular mechanistic importance, since knockdown of galactosyltransferase II (beta-1,3-galactotransferase 6; B3GALT6), the GAG linker-building enzyme, phenocopied the permeability and phenotypic changes induced by mycolactone. Additionally, mycolactone depleted many secreted basement membrane components and microvascular basement membranes were disrupted in vivo during M. ulcerans infection in the mouse model. Remarkably, exogenous addition of laminin-511 reduced endothelial cell rounding, restored cell attachment and reversed the defective migration caused by mycolactone. Hence supplementing mycolactone-depleted extracellular matrix may be a future therapeutic avenue, to improve wound healing rates.

Hinokitiol reduces tumor metastasis by regulating epithelial cell adhesion molecule via protein kinase-B/mammalian target of rapamycin signaling pathway

Tumor metastasis is the leading cause of death in cancer patients. Epithelial cell adhesion molecule (EpCAM) is abundantly expressed in various malignant tumors and plays a crucial role in cell adhesion, metastasis, proliferation, and differentiation. This study investigated the effects of hinokitiol, a natural tropolone compound known for its antiviral, anti-inflammatory, and antibacterial properties, on tumor growth and metastasis. Specifically, the study focused on the expression of EpCAM in mouse tumor cells treated with hinokitiol. Hinokitiol was administered to mouse melanoma cells (B16F10) and mouse colorectal carcinoma cells (CT26), resulting in a significant decrease in EpCAM expression. Additionally, the protein levels involved in the protein kinase-B/mammalian target of rapamycin (AKT/mTOR) signaling pathway were reduced following hinokitiol treatment. Using wound healing and Transwell assays, the study demonstrated that hinokitiol effectively inhibits cancer cell migration. In vivo experiments were conducted using mice, which were injected intravenously with B16F10 or CT26 cells to induce tumor metastasis. The tumor cells were either treated with hinokitiol or left untreated. The results showed that tumor cells treated with hinokitiol exhibited significantly reduced tumor size and weight in the lungs, as well as prolonged survival, compared to untreated tumor cells. This study concludes that hinokitiol inhibits tumor migration by downregulating EpCAM via the AKT/mTOR signaling pathway and exhibits positive effects in vivo.

Harnessing the Engineered Probiotic-Nanosystem to Remodulate Tumor Extracellular Matrix and Regulate Tumor-Colonizing Bacteria for Improving Pancreatic Cancer Chemo-Immunotherapy

Poor chemotherapy efficacy in pancreatic cancer is attributed to limited drug permeation caused by the dense extracellular matrix (ECM) and drug degradation induced by tumor-colonizing bacteria. Here, a tumor-targeting probiotic-nanosystem is elaborately designed to remodulate ECM and selectively regulate tumor-colonizing bacteria for improving chemo-immunotherapy against pancreatic cancer. Specifically, drug-loaded liposomes are conjugated with Clostridium Butyricum (CB) via matrix metalloproteinase-2 (MMP-2)-responsive peptide to construct a probiotic-nanosystem. Particularly, vactosertib (VAC, a transforming growth factor-β1 receptor inhibitor) is delivered by probiotic-nanosystem to silence the active pancreatic stellate cells (PSCs) for inhibiting the development of ECM, resulting in a loosened ECM and providing a golden opportunity for the deep penetration of chemotherapy drugs and immune cells. Subsequently, gemcitabine (GEM) is efficiently delivered into the core of tumors via probiotic-nanosystem, achieving an enhanced chemotherapy efficacy. Noteworthily, CB can alleviate γ-proteobacteria-mediated GEM degradation through competitively reducing the contents of γ-proteobacteria and promoting the amounts of tumor-inhibiting bacteria, thereby significantly potentiating the therapeutic effect of GEM. The engineered probiotic-nanosystem can not only enhance the GEM-induced immunogenic cell death (ICD) of a pancreatic tumor to activate antitumor immune responses but also markedly increase the tumor-infiltration of effector immune cells to heighten tumoricidal immunity, offering a promising strategy for chemo-immunotherapy of pancreatic cancer.

Mycolactone causes destructive Sec61-dependent loss of the endothelial glycocalyx and vessel basement membrane: a new indirect mechanism driving tissue necrosis in Mycobacterium ulcerans infection

The drivers of tissue necrosis in Mycobacterium ulcerans infection (Buruli ulcer disease) have historically been ascribed solely to the directly cytotoxic action of the diffusible exotoxin, mycolactone. However, its role in the clinically-evident vascular component of disease aetiology remains poorly explained. We have now dissected mycolactone's effects on primary vascular endothelial cells in vitro and in vivo. We show that mycolactone-induced changes in endothelial morphology, adhesion, migration, and permeability are dependent on its action at the Sec61 translocon. Unbiased quantitative proteomics identified a profound effect on proteoglycans, driven by rapid loss of type II transmembrane proteins of the Golgi, including enzymes required for glycosaminoglycan (GAG) synthesis, combined with a reduction in the core proteins themselves. Loss of the glycocalyx is likely to be of particular mechanistic importance, since knockdown of galactosyltransferase II (beta-1,3-galactotransferase 6; B3GALT6), the GAG linker-building enzyme, phenocopied the permeability and phenotypic changes induced by mycolactone. Additionally, mycolactone depleted many secreted basement membrane components and microvascular basement membranes were disrupted in vivo. Remarkably, exogenous addition of laminin-511 reduced endothelial cell rounding, restored cell attachment and reversed the defective migration caused by mycolactone. Hence supplementing mycolactone-depleted extracellular matrix may be a future therapeutic avenue, to improve wound healing rates.

A tellurium-based small compound ameliorates tumor metastasis by downregulating heparanase expression

Tellurium is a rare element, and ammonium trichloro (dioxoethylene-o,o') tellurate (AS101) is the most bioactive molecule among several synthetic tellurium compounds. AS101 was found to be immunomodulatory and can modulate types of cytokines. However, the effect of AS101 on tumor metastasis remains unclear. Heparanase, an endo-glucuronidase, cleaves heparin sulfate side chains of proteoglycans on the cell surface, further leading to the degradation of the extracellular matrix. Heparanase also releases angiogenic factors in the extracellular matrix, is overexpressed in tumor cells, and promotes tumor metastasis and angiogenesis. In this study, we investigated the effect of AS101 in 4T1 and CT26 cells, especially heparanase. Heparanase expression was downregulated in 4T1 and CT26 cells after treatment with AS101 in vitro. The protein level involved in the protein kinase-B/mammalian target of rapamycin (AKT/mTOR) signaling pathway also declined. Cell migration assays revealed the inhibitory effect of AS101 on migration. The results of this study indicate that AS101 inhibits tumor migration by downregulating heparanase through the AKT/mTOR signaling pathway and has positive effects in vivo.

Salmonella-induced inhibition of β3-adrenoceptor expression in tumors and reduces tumor metastasis

The β3-adrenoceptor is a protein responsible for regulating the body's response to the neurotransmitter adrenaline and the hormone norepinephrine. It is critical in various physiological processes, including metabolism, thermogenesis, and cardiovascular function. Recently, researchers have discovered that the β3-adrenoceptor is also implicated in tumor progression and metastasis. Infections caused by Salmonella can lead to gastroenteritis; however, intriguingly, Salmonella is associated with tumor inhibition. In this study, Salmonella treatment resulted in the downregulation of β3-adrenoceptor expression and a decrease in the phosphorylation of the Protein Kinase-B (AKT)/Mammalian Target of Rapamycin (mTOR) pathway, as observed through immunoblotting in a dose-dependent manner. Notably, Salmonella treatment significantly reduced tumor cell migration, as demonstrated by wound healing and Transwell assays. Moreover, tumor-bearing mice that received Salmonella-pre-treated tumor cells exhibited improved survival rates compared to those injected with tumor cells without prior Salmonella treatment. The observed anti-metastatic effect in this study suggests that Salmonella treatment could hold promise as a potential therapeutic approach to combat tumor metastasis. Further research is warranted to explore its full therapeutic potential.

Downregulation of AKT/mTOR signaling pathway for Salmonella-mediated autophagy in human anaplastic thyroid cancer

Thyroid cancer has been known as the most common endocrine malignancy. Although majority of thyroid cancer types respond well to conventional treatment including surgery and radioactive iodine therapy, about 10% of those with differentiated thyroid cancer will present distant metastasis and will have persistent or recurrent disease. Even more serious is a rare type of thyroid cancer called anaplastic thyroid cancer (ATC), which accounts for about 1%, has been demonstrated as the most lethal and aggressive form of human malignancy. Unfortunately, these tumors are also frequently resistant to traditional therapy. Previous study have shown that Salmonella inhibits tumor growth, in part, by inducing autophagy - a cellular process that is important in the innate and adaptive immunity in response to viral or bacterial infection. In our study, we intended to investigate whether Salmonella can inhibit tumor growth by inducing autophagy, specifically in thyroid cancer and elucidate the possible molecular mechanism. In order to determine the signaling pathway involved in tumor cell autophagy, we used Salmonella to treat ATC cells line ASH-3 and KMH-2 in vitro. The autophagic markers, particularly autophagy-related gene 6 (Beclin-1), microtubule-associated protein 1A/1B-light chain 3 (LC3) and p62, were observed to be differentially expressed after infection with Salmonella indicating an activated autophagy in ATC cells. In addition, the protein expression levels of phospho-protein kinase B (P-AKT), phospho-mammalian targets of rapamycin (P-mTOR), phospho-p70 ribosomal s6 kinase (P-p70S6K) in tumor cells were decreased after Salmonella infection. In vivo, we also found that substantial cell numbers of Salmonella targeted tumor tissue, and regulated anti-tumor mechanisms. Our findings showed that Salmonella activated autophagic signaling pathway and inhibited ATC tumor growth via downregulation of AKT/mTOR pathway.