Molecular Mechanisms Associated with the Inhibitory Role of Long Chain n-3 PUFA in Colorectal Cancer.

Colorectal cancer (CRC) is the third leading cause of cancer-related death in the world. Multiple evidence suggests that there is an association between excess fat consumption and the risk of CRC. The long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential for human health, and both in vitro and in vivo studies have shown that these fatty acids can prevent CRC development through various molecular mechanisms. These include the modulation of arachidonic acid (AA) derived prostaglandin synthesis, alteration of growth signaling pathways, arrest of the cell cycle, induction of cell apoptosis, suppression of angiogenesis and modulation of inflammatory response. Human clinical studies found that LC n-3 PUFA combined with chemotherapeutic agents can improve the efficacy of treatment and reduce the dosage of chemotherapy and associated side effects. In this review, we discuss comprehensively the anti-cancer effects of LC n-3 PUFA on CRC, with a main focus on the underlying molecular mechanisms.

Krill Oil and Its Bioactive Components as a Potential Therapy for Inflammatory Bowel Disease: Insights from In Vivo and In Vitro Studies.

Krill oil is extracted from krill, a small crustacean in the Antarctic Ocean. It has received growing attention because of krill oil's unique properties and diverse health benefits. Recent experimental and clinical studies suggest that it has potential therapeutic benefits in preventing the development of a range of chronic conditions, including inflammatory bowel disease (IBD). Krill oil is enriched with long-chain n-3 polyunsaturated fatty acids, especially eicosapentaenoic and docosahexaenoic acids, and the potent antioxidant astaxanthin, contributing to its therapeutic properties. The possible underlying mechanisms of krill oil's health benefits include anti-inflammatory and antioxidant actions, maintaining intestinal barrier functions, and modulating gut microbiota. This review aims to provide an overview of the beneficial effects of krill oil and its bioactive components on intestinal inflammation and to discuss the findings on the molecular mechanisms associated with the role of krill oil in IBD prevention and treatment.

The comparative anti-cancer effects of krill oil and oxaliplatin in an orthotopic mouse model of colorectal cancer.

BACKGROUND: Our in vitro studies demonstrated that krill oil (KO) has anti-cancer potential. This study aimed to compare the anti-cancer effects of KO with a commonly used chemotherapeutic drug, oxaliplatin and to identify the molecular mechanisms associated with KO supplementation in a mouse model of colorectal cancer (CRC). METHODS: Thirty-six male Balb/c mice were randomly divided into six groups. Five groups received standard chow diet supplemented with KO (150 g/kg)), corn oil (150 g/kg), KO combined with ½ dose of oxaliplatin (1.5 mg/kg body weight/3 times per week), corn oil combined with ½ dose of oxaliplatin (1.5 mg/kg body weight/3 times per week), or a full dose of oxaliplatin (3 mg/kg body weight/3 times per week). The control (sham) group received a standard chow diet. Treatments started three weeks before and continued for three weeks after orthotopic CRC induction. The number of metastases, tumour weight and volume were quantified ex-vivo. The expression of cytochrome c, cleaved caspase-9 and -3, DNA damage, PD-L1, PD-L2 and HSP-70 were determined. RESULTS: A significant reductions in the weight and volume of tumours were observed in mice treated with KO and KO plus a ½ dose of oxaliplatin compared to the sham group, similar to oxaliplatin-treated mice. KO, and KO plus ½ dose of oxaliplatin significantly increased the expression of cytochrome c, cleaved caspase-9 and -3, and DNA damage and decreased expression of PD-L1, PD-L2 and HSP-70 in tumour tissues compared to the sham group. CONCLUSIONS: The in vivo anti-cancer effects of KO are comparable with oxaliplatin. Thus, dietary KO supplementation has a great potential as a therapeutic/adjunctive agent for CRC treatment.

Krill oil supplementation reduces the growth of CT-26 orthotopic tumours in Balb/c mice.

BACKGROUND: We have previously reported that the free fatty acid extract (FFAE) of krill oil (KO) significantly inhibits the proliferation and migration, and induces apoptosis of colorectal cancer (CRC) cells. This study aimed to investigate the in vivo efficacy of various doses of KO supplementation on the inhibition of CRC tumour growth, molecular markers of proliferation, angiogenesis, apoptosis, the epidermal growth factor receptor (EGFR) and its downstream molecular signalling. METHODS: Male Balb/c mice were randomly divided into four groups with five in each group. The control (untreated) group received standard chow diet; and other three groups received KO supplementation at 5%, 10%, and 15% of their daily dietary intake respectively for three weeks before and after the orthotopic implantation of CT-26 CRC cells in their caecum. The expression of cell proliferation marker Ki-67 and angiogenesis marker CD-31 were assessed by immunohistochemistry. The expression of EGFR, phosphorylated EGFR (pEGFR), protein kinase B (AKT), pAKT, extracellular signal-regulated kinase (ERK1/2), pERK1/2, cleaved caspase-7, cleaved poly (ADP-ribose) polymerase (PARP), and DNA/RNA damage were determined by western blot. RESULTS: KO supplementation reduced the CRC tumour growth in a dose-dependent manner; with 15% of KO being the most effective in reduction of tumour weight and volume (68.5% and 68.3% respectively, P < 0.001), inhibition of cell proliferation by 69.9% (P < 0.001) and microvessel density by 72.7% (P < 0.001). The suppressive effects of KO on EGFR and its downstream signalling, ERK1/2 and AKT, were consistent with our previous in vitro observations. Furthermore, KO exhibited pro-apoptotic effects on tumour cells as indicated by an increase in the expression of cleaved PARP by 3.9-fold and caspase-7 by 8.9-fold. CONCLUSIONS: This study has demonstrated that KO supplementation reduces CRC tumour growth by inhibiting cancer cell proliferation and blood vessel formation and inducing apoptosis of tumour cells. These anti-cancer effects are associated with the downregulation of the EGFR signalling pathway and activation of caspase-7, PARP cleavage, and DNA/RNA damage.

Krill oil extract suppresses the proliferation of colorectal cancer cells through activation of caspase 3/9.

BACKGROUND: Currently available treatments for colorectal cancer (CRC) associate with numerous side-effects that reduce patients' quality of life. The effective nutraceuticals with high anti-proliferative efficacy and low side-effects are desirable. Our previous study has reported that free fatty acids extract (FFAE) of krill oil induced apoptosis of CRC cells, possibly associated with changes in mitochondrial membrane potential (MMP). The aims of this study were to compare the anti-proliferative efficacy of FFAE from krill oil on CRC cells with commonly used chemotherapeutic drug, Oxaliplatin, and to investigate the molecular mechanisms underlying the anti-proliferative effects of krill oil with a focus on intrinsic mitochondrial death pathway. METHODS: Three human CRC cell lines, including DLD-1, HT-29 and LIM-2405, and one mouse CRC cell line, CT-26, were treated with FFAE of KO and the bioactive components of krill oil, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 24 h and 48 h. Similarly, these cell lines were treated with Oxaliplatin, a commonly used drug for CRC treatment, for 24 h. The effects of FFAE of KO, EPA, DHA and Oxaliplatin on cell proliferation, mitochondrial membrane potential and reactive oxygen species (ROS) were determined via WST-1, JC-10, and ROS assays respectively. The expression of caspase-3, caspase-9 and DNA damage following treatments of FFAE of KO was investigated via western blotting and immunohistochemistry. RESULTS: The FFAE of KO, EPA and DHA significantly inhibited cell proliferation and increased formation of ROS in all four cell lines (P < 0.01). A small dose of FFAE from KO ranged from 0.06 µL/100 µL to 0.12 µL/100 µL containing low concentrations of EPA (0.13-0.52 µM) and DHA (0.06-0.26 µM) achieved similar anti-proliferative effect as Oxaliplatin (P > 0.05). Treatments with the FFAE of KO, EPA and DHA (2:1 ratio) resulted in a significant increase in the mitochondrial membrane potential (P < 0.001). Furthermore, the expression of active forms of caspase-3 and caspase-9 was significantly increased following the treatment of FFAE of KO. CONCLUSIONS: The present study has demonstrated that the anti-proliferative effects of krill oil on CRC cells are comparable with that of Oxaliplatin, and its anti-proliferative property is associated with the activation of caspase 3/9 in the CRC cells.

Krill oil extract suppresses cell growth and induces apoptosis of human colorectal cancer cells.

BACKGROUND: Colorectal cancer (CRC) is the third most common cancer in the world. The current available treatments for CRC include surgery, chemotherapy and radiotherapy. However, surgery is only useful when the disease is diagnosed at the earlier stage. Chemotherapy and radiotherapy are associated with numerous side effects that decrease the patients' quality of life. Safer, effective alternatives, such as natural compounds, to chemotherapy are desirable. This study assessed the efficacy of free fatty acid (FFA) extract of krill oil on three human CRC cells lines. METHODS: HCT-15, SW-480 and Caco-2 cells were treated with the FFA extracts of krill oil and fish oil for 48 h while treatments with the bioactive omega-3 polyunsaturated fatty acids (LC n-3 PUFA) of these marine oils, eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C22:6n-3) in comparison with a n-6 PUFA, arachnoid acid (AA, C20:4n-6) were up to 72 h at the concentrations of 50, 100, 150 and 200 µM. Effects of all the treatments on cell proliferation were assessed using a water-soluble tetrazolium-1 (WST-1) assay kit at 24, 48 and 72 h. Effects of FFA extract of krill oil and EPA on apoptosis and mitochondrial membrane potential were determined using commercial kits after 48 h of treatment. RESULTS: Krill oil extract inhibited cell proliferation of all three cell lines in the similar manner as fish oil extract. A significant cell apoptosis and increase in mitochondrial membrane potential were observed after the treatment with krill oil extract. EPA at the concentration of 200 µM reduced significantly the proliferation of HCT-15 and SW-480 at 24, 48 and 72 h. In addition, EPA treatment (100 and 200 µM) resulted in significant cell apoptosis in all three cell lines. No significant changes were observed after treatment with DHA and AA. CONCLUSIONS: Our results indicate that the FFA extract of krill oil maybe an effective chemotherapeutic agent to suppress proliferation and induce apoptosis in CRC cells through its bioactive constitute EPA. Although the exact mechanism of the pro-apoptotic properties of krill oil extract is unclear, mitochondrial pathway seems to be implicated.