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

Abilasha Gayani Jayathilake; Elif Kadife; Nyanbol Kuol; Rodney Brain Luwor; Kulmira Nurgali; Xiao Qun Su

doi:10.1186/s12906-022-03521-4

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

BMC Complement Med Ther. 2022 Feb 4;22(1):34. doi: 10.1186/s12906-022-03521-4.

Authors

Abilasha Gayani Jayathilake¹, Elif Kadife¹, Nyanbol Kuol¹, Rodney Brain Luwor², Kulmira Nurgali^#^{1

3

4}, Xiao Qun Su^#⁵

Affiliations

¹ Institute for Health and Sport, Victoria University, Melbourne, 8001, Australia.
² Department of Surgery, The Royal Melbourne Hospital, The University of Melbourne, Parkville, Australia.
³ Department of Medicine, Western Health, The University of Melbourne, Melbourne, Australia.
⁴ Regenerative Medicine and Stem Cells Program, Australian Institute for Musculoskeletal Sciences (AIMSS), Melbourne, Australia.
⁵ Institute for Health and Sport, Victoria University, Melbourne, 8001, Australia. xiao.su@vu.edu.au.

^# Contributed equally.

Abstract

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.

Keywords: AKT; CD-31; CRC tumour growth; Caspase-7; Colorectal cancer; EGFR; ERK 1/2; Ki-67; Krill oil supplementation; PARP.

MeSH terms

Animals
Colorectal Neoplasms*
Dietary Supplements
Euphausiacea*
Male
Mice
Mice, Inbred BALB C
Tomography, X-Ray Computed