Abstract 1606: The ethyl ester forms of the n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid decrease the proliferation, invasion, and matrixmetalloproteinase activity of colorectal cancer cells
Authors: Pfister Eric , Lane Michelle A. 
Published: August 2019

More than half of individuals diagnosed with colorectal cancer (CRC) will die from their cancer. The 5-year survival rate for patients diagnosed metastatic CRC is only 14%. Effective and well-tolerated therapies, such as dietary supplements, that prevent metastasis may increase the survival of these patients. The ability of the n-3 fatty acids (n-3FAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to decrease the proliferation of a variety of cancers in vitro, including CRC, is well established; however, the efficacy of n-3FAs with respect to inhibition of CRC metastasis has received little attention. EPA- and DHA ethyl esters (EE) are alternative forms of n-3FAs that may be more efficacious than free, non-esterified n-3FAs due to their ability to resist degradation allowing them to exert their effects for longer durations. Our objectives were to (1) compare the efficacy of free vs EE-n-3FAs with respect to inhibition of CRC cell proliferation, (2) to determine if EE-n-3FAs decreased CRC cell invasion, and (3) to begin to elucidate the mechanism through which EE-n-3FAs decrease cell invasion. We used two human invasive CRC cell lines, HCT-116 and SW620. To examine the effects of each n-3FA on cellular proliferation, cells were treated with 12.5, 25, 50 and 100 µM free or EE- EPA or DHA for 72 h [CAS numbers: free EPA (10417-94-4), free DHA (6217-54-5), EE-EPA (86227-47-6), EE-DHA (81926-94-5)]. All cells received equal volumes of ethanol vehicle. Data shown are mean +/- n=3 unless indicated. As n-3FA concentration increased, cellular proliferation decreased, regardless of n-3 FA type. Importantly, the IC50 (inhibitory concentration) for EE-EPA (7.7 ± 1.6 µM) was lower than that of free EPA (24.5 ±4.2 µM). The ability of EE-EPA and -DHA to decrease the invasion of CRC cells through Matrigel coated Boyden chambers was assessed following treatment with 12.5 µM EE-EPA or -DHA for 24 h. EE-EPA and EE-DHA inhibited the invasion of HCT-116 cells to 37.1 ± 13.5% and 50.6 ± 17.5% of control, respectively (n=4). Similarly, SW620 cell invasion was decreased to 27.5 ± 9.7% of control by EE-EPA and 24.2 ± 6.7% of control by EE–DHA. The decrease in metalloproteinase-2 (MMP-2) activity, assessed via zymography following EE-n-3FA treatment, reflected the decrease in CRC cell invasion. Finally, EE-n-3FAs failed to inhibit the invasion of HCT-116 cells expressing two alleles of constitutively active phosphatidylinositol 3-kinase, suggesting their ability to decrease cell invasion is conferred by inhibition of PI3K activity. In conclusion, EE-n-3FAs are likely more effective inhibitors of CRC proliferation than free n-3FAs, potentially because they are more stable. Additionally, EE-n-3FAs also inhibit CRC invasion and decrease MMP-2 activity through a mechanism that may involve PI3K.

Citation Format: Eric Pfister, Michelle A. Lane. The ethyl ester forms of the n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid decrease the proliferation, invasion, and matrixmetalloproteinase activity of colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1606.