The chemical composition of fucoidan, a kind of sulfated polysaccharide mainly derived from brown seaweed, includes a substantial percentage of l‐fucose. Fucoidan has various biological and pharmacological activities, such as anti‐cancer/anti‐tumor, anti‐proliferation, anti‐inflammatory and immune‐modulatory functions, and fucoidan‐related dietary supplements and nutraceuticals have recently drawn considerable attention. In this review, we aim to provide a current view of different aspects of fucoidan biological activity, with a focus on the anti‐cancer regulatory effects of fucoidan on growth signaling mechanisms. First, we discuss historical aspects of fucoidan and fucoidan products, as well as the anti‐cancer effects of fucoidan on various cancer cells. Second, we discuss fucoidan's biological activities and induction of cell death in cancer cells, including multiple mechanisms and signal transduction pathways related to its anti‐cancer effects. Next, we focus on fucoidan and fucoidan‐derived products that have been marketed as dietary supplements or nutraceuticals for cancer, including anti‐cancer effects of fucoidan when combined as an adjuvant with clinical drugs. Finally, case studies of fucoidan in complementary therapy and as an alternative medicine in animal and mouse models and human clinical trials to alleviate side effects of anti‐cancer chemotherapy are discussed. Combining fucoidan with clinical therapeutic agents in the treatment of cancer patients, dissecting the related signal transduction pathways and investigating their dynamic interactions may reveal potential molecular targets in cancer prevention, therapies and key obstacles in the current development of anti‐cancer strategies.

Fucoidan, a polysaccharide extracted from brown seaweeds, reduces tumor cell proliferation. Fucoidan inhibits the growth of breast cancer cells such as 4T1 and MDA-MB-231 and decreases their cell colony formation. Moreover, fucoidan reduces metastatic lung nodules in 4T1 xenograft female Balb/c mice. The molecular network of transforming growth factor β (TGFβ) receptors (TGFRs) plays an important role in the regulation of the epithelial to mesenchymal transition (EMT) in cancer cells. Using 4T1 and MDA-MB-231 cells, we found that fucoidan effectively reverses TGFR-induced EMT morphological changes, upregulates epithelial markers, downregulates mesenchymal markers and decreases the expression of transcriptional repressors Snail, Slug and Twist. Moreover, fucoidan inhibits migration and invasion during the EMT, suggesting the involvement of TGFR-mediated signaling in breast cancer cells. Fucoidan decreases TGFRI and TGFRII proteins and affects downstream signaling molecules, including Smad2/3 phosphorylation and Smad4 expression. In order to elucidate how fucoidan decreases TGFRI and TGFRII proteins in MDA-MB-231 cells, we investigated ubiquitination activity downregulation of TGFRs. It was found that fucoidan enhances proteasome-mediated degradation/ubiquitination of TGFR. This study is the first to identify a novel mechanism for fucoidan antitumor activity, namely regulation of the EMT via modulation of TGFR/Smad-dependent signaling, which leads to an inhibition of breast cancer cell growth in vitro and in vivo. Our current findings indicate that fucoidan is a potential therapeutic agent for breast cancer and acts via an ubiquitin-dependent degradation pathway that affects the TGFR/Smad/Snail, Slug, Twist and EMT axes.

Fucoidan, a sulfated polysaccharide extracted from brown algae, exhibits anti-cancer activity. However, the effects and mechanism of fucoidan-induced apoptosis via endoplasmic reticulum (ER) stress is unclear. In this study, we demonstrated that fucoidan prevents tumorigenesis and reduces tumor size in LLC1-xenograft male C57BL/6 mice. Fucoidan induces an ER stress response by activating the PERK-ATF4-CHOP pathway, resulting in apoptotic cell death in vitro and in vivo. Furthermore, ATF4 knockdown abolishes fucoidan-induced CHOP expression and rescues cell viability. Specifically, fucoidan increases intracellular reactive oxygen species (ROS), which increase ATF4 and CHOP in lung cancer cells. Using the ROS scavenger N-acetyl-l-cysteine (NAC), we found that ROS generation is involved in fucoidan-induced ER stress-mediated apoptosis. Moreover, via Toll-like receptor 4 (TLR4) knockdown, we demonstrated that fucoidan-induced ROS and CHOP expression were attenuated. Our study is the first to identify a novel mechanism for the antitumor activity of fucoidan. We showed that fucoidan inhibits tumor viability by activating the TLR4/ROS/ER stress axis and the downstream PERK-ATF4-CHOP pathway, leading to apoptosis and suppression of lung cancer cell progression. Together, these results indicate that fucoidan is a potential preventive and therapeutic agent for lung cancer that acts via activation of ROS-dependent ER stress pathways.

Fucoidan, a polysaccharide extracted from brown seaweeds, reduces tumor cell proliferation. In this study, we demonstrate that fucoidan reduces tumor size in LLC1-xenograft male C57BL/6 mice. Moreover, we found that LLC1-bearing mice continuously fed fucoidan showed greater antitumor activity than mice with discontinuous feeding. Fucoidan inhibited the in vitro growth of lung cancer cells. Transforming growth factor β (TGFβ) receptors (TGFRs) play important roles in the regulation of proliferation and progression, and high TGFRI expression in lung cancer specimens is associated with a worse prognosis. Herein, using lung cancer cells, we found that fucoidan effectively reduces TGFRI and TGFRII protein levels in vivo and in vitro. Moreover, fucoidan reduces TGFR downstream signaling events, including those in Smad2/3 and non-Smad pathways: Akt, Erk1/2, and FAK phosphorylation. Furthermore, fucoidan suppresses lung cancer cell mobility upon TGFβ stimulation. To elucidate how fucoidan decreases TGFR proteins in lung cancer cells, we found that fucoidan enhances the ubiquitination proteasome pathway (UPP)-mediated degradation of TGFRs in A549 and CL1-5 cells. Mechanistically, fucoidan promotes Smurf2 and Smad7 to conjugate TGFRs, resulting in TGF degradation; however, Smurf2-shRNA abolishes fucoidan-enhanced UPP-mediated TGFR degradation. Our study is the first to identify a novel mechanism for the antitumor activity of fucoidan, namely decreasing tumor growth by modulating the TGFR/Smad7/Smurf2-dependent axis, leading to TGFR protein degradation and inhibition of lung cancer cell progression in vitro and in vivo. Our current findings indicate that fucoidan is a potential therapeutic agent or dietary supplementation for lung cancer, acting via the Smurf2-dependent ubiquitin degradation of TGFβ receptors.

Ling Zhi-8 (LZ-8), an immunomodulatory protein, is derived from and has been cloned from the medicinal mushroom Ganoderma lucidum (Reishi or Ling Zhi); this protein exhibits immunomodulating and antitumor properties. We investigated the effects of recombinant LZ-8 protein (rLZ-8) on the proliferation of A549 human lung cancer cells. Here, we showed that rLZ-8 inhibits cell growth and that this is correlated with increased G₁ arrest. The treatment of A549 cells with rLZ-8 activated p53 and p21 expression, and both the G₁ arrest and the antigrowth effect were found to be p53 dependent. It was further demonstrated that rLZ-8 inhibited tumor growth in mice transplanted with Lewis lung carcinoma cells. Interestingly, rLZ-8 treatment was found to lead to nucleolar stress (or ribosomal stress) as evidenced by inhibition of precursor ribosomal RNA synthesis and reduced polysome formation in A549 cells. These changes resulted in an increasing binding of ribosomal protein S7 to MDM2 and a decreased interaction between MDM2 and p53. Taking these results together, we have identified a novel rLZ-8 antitumor function that positively modulates p53 via ribosomal stress and inhibits lung cancer cell growth in vitro and in vivo. Our current results suggest that rLZ-8 may have potential as a therapeutic intervention for the treatment of cancers that contain wild-type p53 and high expression of MDM2.