In vitro and in vivo anti-tumor efficacy of krill oil against bladder cancer: Involvement of tumor-associated angiogenic vasculature

[Display omitted] •Krill oil (KO) exhibits anticancer effect in vitro and in vivo.•KO inhibited VEGF-induced angiogenic responses in vitro and ex vivo.•Anticancer efficacy of KO is linked to its antiangiogenic properties.•Oral administration of KO did not induce toxicity.•Chemical composition of KO obtained by alcalase hydrolysis was determined. Krill oil (KO) obtained from Euphausia superba is nutrient-rich and has a positive effect on human health. Here, we explored the efficacy of KO in inhibiting tumor progression and tumor vascularization. KO (100–300 μg/mL) repressed the proliferation of bladder tumor cell lines MBT-2 and T24. Treatment of cells with KO raised cell-cycle arrest at G0/G1-phase via modulation of positive regulators and negative regulators in bladder cancer cells. KO treatment regulated phosphorylation of proteins involved in PI3K/AKT and MAPK signaling pathways, including ERK, JNK, and p38 MAPK. Additionally, KO hampered the invasion and migration of both cell lines via reduction of MMP-9 expression levels by disrupting transcriptional binding of Sp-1, AP-1, and NF-κB motifs. Moreover, in animal studies, KO (150–300 mg/kg) significantly decreased tumor growth in xenograft mice bearing T24 tumor cells. No significant toxic effects were observed in acute toxicity tests, including biological analysis and H&E staining. The reduced level of CD31 expression in KO-treated tumor tissues prompted us to investigate the effect of KO on tumor angiogenesis. KO (5–40 μg/mL) treatment impeded VEGF-induced capillary tube formation and proliferation by inhibiting VEGFR2-modulated eNOS/AKT/ERK1/2 signaling axis in HUVECs. Treatment of HUVECs with KO inhibited VEGF-stimulated migration and invasion by reducing MMP-2 expression level. VEGF-driven sprouting capacity of neo-microvessels was suppressed in the presence of KO (20–40 μg/mL), as determined via an ex vivo aortic ring assay. Our results indicated that KO can regulate both tumor growth and tumor-associated angiogenesis via a novel mechanism. Thus, KO may be a promising antitumor candidate, potentially useful to prevent or treat bladder cancer.