Smectite promotes probiotic biofilm formation in the gut for cancer immunotherapy.

Administration of probiotics to regulate the immune system is a potential anti-tumor strategy. However, oral administration of probiotics is ineffective because of the poor inhabitation of exogenous bacteria in host intestines. Here we report that smectite, a type of mineral clay and established anti-diarrhea drug, promotes expansion of probiotics (especially Lactobacillus) in the murine gut and subsequently elicits anti-tumor immune responses. The ion-exchangeable microstructure of smectite preferentially promotes lactic acid bacteria (LABs) to form biofilms on smectite in vitro and in vivo. In mouse models, smectite laden with LAB biofilms (Lactobacillus and Bifidobacterium) inhibits tumor growth (when used alone) and enhances the efficacy of chemotherapy or immunotherapy (when used in combination with either of them) by activating dendritic cells (DCs) via Toll-like receptor 2 (TLR2) signaling. Our findings suggest oral administration of smectite as a promising strategy to enrich probiotics in vivo for cancer immunotherapy.

Effect of cadmium stress on inorganic and organic components in xylem sap of high cadmium accumulating rice line (Oryza sativa L.).

Physiological properties involved in cadmium (Cd) transport were investigated in the high Cd accumulating rice line (Lu527-8) in comparison with the normal rice line (Lu527-4) through a soil culture experiment. The results showed that Cd contents in xylem saps of Lu527-8 were 1.68-2.55 times higher than those of Lu527-4 under Cd stress. A high-positive correlation between Cd contents in xylem saps and Cd contents in shoots was observed. Lu527-8 owned a more rapid and effective transport of Cd to above-ground part. By analyzing the relationship between inorganic anions, organic components and Cd contents in xylem saps, the lower HPO42- and oxalate contents were considered to be related to the higher Cd transport in xylem sap of Lu527-8. As for citrate, tartaric and histidine content, significant increases were observed with the increasing Cd contents in xylem saps of two rice lines, and their contents of Lu527-8 were significantly higher than those of Lu527-4. Citrate, tartaric and histidine could take part in root-to-shoot Cd transport in xylem.

Influence of cadmium stress on root exudates of high cadmium accumulating rice line (Oryza sativa L.).

A hydroponic experiment with two different cadmium (Cd) accumulating rice lines of Lu527-8 (the high Cd accumulating rice line) and Lu527-4 (the normal rice line) was carried out to explore the links among Cd stress, root exudates and Cd accumulation. The results showed that (1) Cd stress increased quantities of organic acids, but had no effect on composition in root exudates of the two rice lines. In Cd treatments, the contents of every detected organic acid in root exudates of Lu527-8 were 1.76-2.43 times higher than those of Lu527-4. Significant positive correlations between organic acids contents and Cd contents in plants were observed in both rice lines, except that malic acid was only highly relevant to Lu527-8, but not to Lu527-4. (2) Both composition and quantities of amino acids in root exudates changed a lot under Cd stress and this change differed in two rice lines. In control, four amino acids (glutamic acid, glycine, tyrosine and histidine) were detected in two rice lines. Under Cd stress, eight amino acids in Lu527-8 and seven amino acids in Lu527-4 could be detected, among which phenylalanine was only secreted by Lu527-8 and alanine, methionine and lysine were secreted by both rice lines. The contents of those four newly secreted amino acids from Lu527-8 increased significantly with the increase of Cd dose and each had a high-positive correlation with Cd contents, but the same change did not appear in Lu527-4. The difference between two rice lines in secretion of organic acids and amino acids may be related to their different Cd uptake properties.