Introduction: Colorectal cancer (CRC) is the third leading cause of cancer deaths worldwide. Recently, much attention has been given to nutraceuticals. They are being investigated for prevention and treatment of cancer. It has been shown that they have antitumoral properties without secondary effects, and could be used as a complement to conventional therapy for CRC. Orexin-A (OXA) is a hypothalamic neuropeptide with various functions in central nervous system and peripheral tissues. Orexin receptor 1 (OX1R) is expressed in CRC tissues. Activation of OX1R by OXA in CRC cell lines triggers apoptosis and was proposed as a new alternative for therapy. The aim of this study was to evaluate different nutraceuticals that could decrease survival and increase apoptosis of CRC cells lines in synergism with OXA.

Material and Methods: Two CRC cell lines were obtained from ATCC: Caco2 and SW480. Cell lines were treated with Honokiol (HK) or Indol-3-carbinol (I3C) for 24h at different doses with or without 100nM OXA. Cell viability was determined using CellTiter Kit (Promega). Caspase 3/7 mediated apoptosis activity was assessed using ApoOne Kit (Promega). Real-time qPCR was performed to determine the effect of nutraceuticals on OX1R expression.

Results: In this study, HK decreases cellular viability on average of 47% in Caco2 and 80% SW480 cells lines, at 25uM, 50uM or 100uM. In Caco2 cell line an increase in caspase 3/7 mediated apoptosis of 60% and 76% was observed at 25uM and 50uM, respectively, unlike what was observed in SW480 in which there was an inhibition of 80% at the different doses used. The combined treatment of 50uM HK with 100nM OXA does not produce a synergistic effect in cell viability or apoptosis compared to use of HK alone in both cell lines. HK produces an inhibition in the OX1R expression that explains the lack of synergism with OXA. I3C produces a decrease of 25% to 95% of cell viability according to doses used with an increase in apoptosis of 6 % to 38% in Caco2 cell lines. The combined effect of 500uM I3C with 100nM OxA produces a synergistic effect of 95% decrease on cell viability, with an increase of OX1R expression, which is not explained by an increase in apoptosis mediated by caspase 3/7.

Conclusions: We found that HK and I3C can inhibit viability and induce apoptosis in Caco2 and SW480 cells. In Caco2 cell line this can be explained by an increase in 3/7 caspase-mediated apoptosis, unlike that observed for SW480 treated with HK. Only 13C has a synergistic effect with OXA on cell viability in Caco2 cell lines but was independent of caspase 3/7 mediated apoptosis at doses and times used. Treatments using new doses and times are necessary to improve response. In our results, I3C might be a better therapeutic agent than HK for CRC. In vivo studies and clinical trials are further required to evaluate physiologic efficacies of the combination treatment.

Fondecyt 1140012.

Citation Format: Ana Maria Wielandt, Cyntia Villarroel, Elea Gros, Mauricio Moreno, Claudia Hurtado, Udo Kronberg, Francisco Lopez-Kostner. Effect of Honokiol and Indol-3-carbinol in viability and apoptosis of colorectal cancer cell lines treated with Orexin-A [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2337.