Colorectal cancer (CRC), which ranks among the top 10 most prevalent cancers, can obtain a good outcome with appropriate surgery and/or chemotherapy. However, the global numbers of both new cancer cases and death from CRC are expected to increase up to 2030. Diet-induced lifestyle modification is suggested to be effective in reducing the risk of human CRC; therefore, interventional studies using diets or diet-derived compounds have been conducted to explore the prevention of CRC. Fucoxanthin (Fx), a dietary carotenoid, is predominantly contained in edible brown algae, such as Undaria pinnatifida (wakame) and Himanthalia elongata (Sea spaghetti), which are consumed particularly frequently in Asian countries but also in some Western countries. Fx is responsible for a majority of the anticancer effects exerted by the lipophilic bioactive compounds in those algae. Interventional human trials have shown that Fx and brown algae mitigate certain risk factors for CRC; however, the direct mechanisms underlying the anti-CRC properties of Fx remain elusive. Fx and its deacetylated type “fucoxanthinol” (FxOH) have been reported to exert potential anticancer effects in preclinical cancer models through the suppression of many cancer-related signal pathways and the tumor microenvironment or alteration of the gut microbiota. We herein review the most recent studies on Fx as a potential candidate drug for CRC prevention.

Fucoxanthin (Fx) is a marine carotenoid with anti-inflammatory and anti-cancer properties in various animal models of carcinogenesis. However, there is currently no information on the effects of Fx in animal models of pancreatic cancer. We investigated the chemopreventive effects of Fx in C57BL/6J mice that received allogenic and orthotopic transplantations of cancer cells (KMPC44) derived from a pancreatic cancer murine model (Ptf1a^Cre/+; LSL-kras^G12D/+). Using microarray, immunofluorescence, western blot, and siRNA analyses, alterations in cancer-related genes and protein expression were evaluated in pancreatic tumors of Fx-administered mice. Fx administration prevented the adenocarcinoma (ADC) development of pancreatic and parietal peritoneum tissues in a pancreatic cancer murine model, but not the incidence of ADC. Gene and protein expressions showed that the suppression of chemokine (C-C motif) ligand 21 (CCL21)/chemokine receptor 7 (CCR7) axis, its downstream of Rho A, B- and T-lymphocyte attenuator (BTLA), N-cadherin, αSMA, pFAK(Tyr³⁹⁷), and pPaxillin(Tyr³¹) were significantly suppressed in the pancreatic tumors of mice treated with Fx. In addition, Ccr7 knockdown significantly attenuated the growth of KMPC44 cells. These results suggest that Fx is a promising candidate for pancreatic cancer chemoprevention that mediates the suppression of the CCL21/CCR7 axis, BTLA, tumor microenvironment, epithelial mesenchymal transition, and adhesion.

Fucoxanthinol (FxOH), the main metabolite of the marine carotenoid fucoxanthin, exerts anti-cancer effects. However, fragmentary information is available on the growth-inhibiting effects of FxOH on breast cancer (BC). We investigated the growth-inhibiting effects of FxOH on human BC cells (MCF-7 and MDA-MB-231 cells), and the underlying mechanisms, differently from previous studies, by using comprehensive transcriptome analysis. The molecular mechanisms of FxOH were evaluated using flow cytometry, microarray, Western blotting, and gene knockdown analyses. FxOH (20 μM) significantly induced apoptosis in MCF-7 and MDA-MB-231 cells. Transcriptome analysis revealed that FxOH modulated the following 12 signaling pathways: extracellular matrix (ECM), adhesion, cell cycle, chemokine and cytokine, PI3K/AKT, STAT, TGF-β, MAPK, NF-κB, RAS/Rho, DNA repair, and apoptosis signals. FxOH downregulated the levels of laminin β1, integrin α5, integrin β1, integrin β4, cyclin D1, Rho A, phosphorylated (p)paxillin (Tyr³¹), pSTAT3(Ser⁷²⁷), and pSmad2(Ser^465/467), which play critical roles in the 12 signaling pathways mentioned above. Additionally, FxOH upregulated the levels of pERK1/2(Thr²⁰²/Tyr²⁰⁴) and active form of caspase-3. Integrin β1 or β4 knockdown significantly inhibited the growth of MCF7 and MDA-MB-231 cells. These results suggest that FxOH induces apoptosis in human BC cells through some core signals, especially the ECM–integrins axis, and the downstream of cell cycle, STAT, TGF-β, RAS/Rho, MAPK, and/or DNA repair signals.

Introduction: 5-Aminosalicylic acid (5-ASA) is widely used as a key drug in inflammatory bowel disease. It has been recently reported that 5-ASA induces CD4 + Foxp3 + regulatory T cells (Tregs) in the colon via the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that regulates inflammation. However, the role of 5-ASA as an AhR agonist that induces Tregs in the spleen remains unknown. Methods: In the present study, we investigated these themes using an AhR-mediated transactivation assay and flow cytometry analysis. The experiments were conducted by using DR-EcoScreen cells and C57BL/6 mice. Results: The DR-EcoScreen cell-based transactivation assay revealed that 5-ASA acted as a weak AhR agonist at concentrations of ≥300 μM (1.31–1.45-fold), and that a typical AhR agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), activated AhR at a concentration of 0.1 nM (22.8-fold). In addition, the treatment of mouse splenic cells with 300 μM 5-ASA in a primary culture assay significantly induced CD4+CD25 + Foxp3 + Tregs (control vs. 5-ASA: 9.0% vs. 12.65%, p < 0.05), while 0.1 nM TCDD also showed significant induction of Tregs (control vs. TCDD: 9.0% vs. 14.1%, p < 0.05). Interestingly, this induction was eliminated by co-treatment with an AhR antagonist, CH-223191. Discussion: These results suggest that 5-ASA is a weak agonist of AhR and thereby induces Tregs in spleen cells. Our findings may provide useful insights into the mechanism by which 5-ASA regulates inflammation.

Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation and its treatment varies widely; however, when inflammation is high, a complete nutrient containing pre-digested elemental diet (ED) is used to preserve the intestinal tract. In this study, we investigated the mechanisms underlying the effectiveness of EDs for IBD using mice. C57BL/6 mice were orally treated with the ED (5 mL/day) and its ingredient L-tryptophan (Trp) (1–100 mg/kg), respectively. Flow cytometry analysis revealed that treatment with the ED and Trp (10 and 100 mg/kg) significantly increased the percentage of splenic CD4+-/CD25+-/Foxp3+ regulatory T cells (Tregs). In the 2% DSS-induced colitis-mouse model, Trp administration (100 mg/kg) led to a significant decrease in TNF-α and increase in IL-10 in the serum as well as a significant decrease in the inflammation score. Furthermore, the aryl hydrocarbon receptor (AhR) agonistic activity, which is a key function of Treg induction, of Trp and 15 Trp metabolites was characterized using a highly sensitive DR-EcoScreen cell assay. Five Trp metabolites, including L-kynurenine, acted as AhR agonists, while Trp did not. Taken together, these results suggest that the ED treatment has a Trp-dependent immunoregulatory effect, and several Trp metabolites that activate the AhR might contribute to induction of remission in patients with IBD.