Euglena gracilis Extract Protects From Tobacco Smoke Carcinogen-Induced Lung Cancer by Altering Gut Microbiota Metabolome.

Extracts from Euglena gracilis have been shown to prevent cancer growth in mouse models. However, the molecular mechanism of this anti-cancer activity has not been determined nor has the effect of Euglena extracts on tobacco smoke carcinogen-induced carcinogenesis. Here, we investigate the hypothesis that this anti-cancer activity is a result of changes in the intestinal microbiota induced by oral administration of the extract. We found that a Euglena gracilis water extract prevents lung tumorigenesis induced by a tobacco smoke-specific carcinogen (NNK) in mice treated either 2 weeks before or 10 weeks after NNK injection. Both of these treatment regimens are associated with significant increases in 27 microbiota metabolites found in the mouse feces, including large increases in triethanolamine, salicylate, desaminotyrosine, N-acetylserine, glycolate, and aspartate. Increases in the short-chain fatty acids (SCFAs) including acetate, propionate and butyrate are also observed. We also detected a significant attenuation of lung carcinoma cell growth through the induction of cell cycle arrest and apoptosis caused by low levels of SCFAs. This study provides strong evidence of anti-cancer activity in Euglena gracilis extracts against tobacco smoke carcinogen-induced tumorigenesis and demonstrates that this activity is linked to increased production of specific gut microbiota metabolites and the resultant induction of cell cycle arrest and apoptosis of lung carcinoma cells.

Cell Wall Membrane Fraction of Chlorella sorokiniana Enhances Host Antitumor Immunity and Inhibits Colon Carcinoma Growth in Mice.

A colon cancer growth inhibitor partially purified from the isolated cell wall membrane fraction of Chlorella sorokiniana, here referred to as Chlorella membrane factor (CMF), was evaluated for its antitumor and immunomodulatory effects in cell culture and in a colon carcinoma mouse model. The CMF treatment dose- and time-dependently inhibited colon carcinoma cell growth in 2-dimensional cultures. Treatment with CMF also significantly inhibited the growth of colon carcinoma spheroids in 3-dimensional cell culture in coculture with T lymphocytes. In a mouse CT26 colon carcinoma peritoneal dissemination model, intraperitoneal injection of CMF (10 or 30 mg dry weight/kg body weight, every other day) dose-dependently and significantly attenuated the growth of tumor nodules via induction of tumor cell apoptosis. Evaluation of immune cell populations in ascites showed that CMF treatment tended to increase T lymphocytes but lower granulocyte populations. The present study suggests that the cell wall membrane fraction of Chlorella sorokiniana contains a bioactive material that inhibits colon carcinoma growth via direct cell growth inhibition and stimulation of host antitumor immunity. Hence, it is suggested that the Chlorella cell wall membrane extract or a bioactive substance in the extract is an attractive complementary medicine for cancer therapy.