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Reversal of Oxaliplatin Resistance by New Zealand Manuka Honey Extracts in Gastrointestinal Cancer Cells

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Date

2024

Authors

Supervisor

Li, Yan
Kam, Rothman
Seale, Brent

Item type

Thesis

Degree name

Doctor of Philosophy

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Publisher

Auckland University of Technology

Abstract

Gastrointestinal (GI) cancers remain among the leading causes of cancer-related deaths worldwide. GI cancer is one of the leading causes of cancer mortality in New Zealand with over 4,000 new cases and more than 1,000 deaths by GI cancers reported annually in NZ. Therefore, GI cancer is a big health burden to the health system. Although oxaliplatin-based chemotherapy has been widely adopted as the standard and preferred regimen for treating GI cancers including colorectal cancer (CRC), tumour resistance is one of the major limitations for many patients in clinical practice. Recently, our team has reported that MRP2 (a member of ATP-Binding Cassete (ABC) transporter protein) confers oxaliplatin resistance and a phytochemical MRP2 inhibitor myricetin increased cellular platinum accumulation and oxaliplatin cytotoxicity in several human GI cancer cell lines (Biswas et al., 2019; Khine et al., 2019). However, myricetin is not a potent MRP2 inhibitor and it only marginally enhanced oxaliplatin sensitivity in tumour xenograft mouse model (Khine et al., 2019). Manuka honey is produced from the nectar of the Manuka tree (Leptospermum scoparium), a native of New Zealand. Previous studies have shown that the content of Manuka honey contains more phenolic and flavonoid antioxidants in comparison to other types of honey worldwide. The strong antioxidant capacities of Manuka honey make them promising sources for further extraction/development of anticancer and chemopreventive compounds. Treatment with Manuka honey alone resulted in significant inhibition of colorectal tumour growth (Maria, Rkia, & Fawaz et al., 2013). Our team and others also discovered the anti-proliferation effects of NZ Manuka honey in several CRC cell lines but not in normal cells (Chan, 2016). However, the exact anti-cancer compound(s) in NZ Manuka honey remain unknown. Given the fact that NZ Manuka honey contains abundant myricetin analogues and more than 90% of ABC transporter inhibitors are derived from phytochemicals, this project aims to identify novel and potent MRP2 inhibitors/modulators from NZ Manuka honey. In Chapter 3, a comprehensive LC–MS/MS method has been developed and validated for the relative quantitation of 14 fingerprint phenolic compounds. NZ Manuka honey contains a significant amount of quercetin, methyl syringate, DL-3-phenyllactic acid, chlorogenic acid, chrysin, myrecitin, and 2-hydroxy-3-(4-methoxyphenyl) propanoic acid. A Mass Spectrometry Data Independent AnaLysis (MS-DIAL) approach was also explored to identify novel phytochemicals by aligning with the data from MS/MS libraries. To evaluate potential interactions between MRP2 and the NZ Manuka honey-derived fingerprint phenolic compounds, three-dimensional molecular docking of multiple ligands with MRP2 using an AutoDock Vina software was undertaken to identify MRP2 inhibitors based on the binding affinity and hydrogen bond interactions (Chapter 4). AutoDock Vina-based in silico screening identified chrysin as a potential MRP2 inhibitor. To further build on in silico findings, heterogeneous expression systems using human embryonic kidney 293 cells (HEK293) overexpressing MRP2 were adapted in Chapter 5. The isogenic pair was employed to identify whether ligands that showed low binding affinities (Chapter 4) can inhibit the MRP2-mediated transport of a model substrate CDCF and reverse MRP2-conferred oxaliplatin resistance. Our results demonstrated that chrysin (10 µM) increased the accumulation of CDCF and enhanced oxaliplatin cytotoxicity, in HEK-MRP2 cells, but not in HEK293 cells. In Chapter 6, further studies were carried out to evaluate the concentration-dependant effect of chrysin on the cellular accumulation of CDCF in vitro in two GI cancer cell lines, Caco-2 and PANC-1, which overexpress ABCC2 (MRP2) endogenously. Chrysin reversed MRP2-mediated oxaliplatin resistance in both GI lines tested but only enhanced oxaliplatin-induced apoptosis in Caco-2 cell line. The findings provide critical insights into the mechanisms of chemoresistance in GI cancers and suggest potential strategies for enhancing oxaliplatin efficacy by combination treatment with chrysin. In conclusion, chrysin exerted concentration-dependent sensitization of oxaliplatin on ABCC2-expressing GI cancer cell lines (endogenously in Caco-2 and PANC-1) and these results may broaden our options to develop a novel combination therapy to sensitise tumour MDR in patients with GI cancers.

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http://hdl.handle.net/10292/19015

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