Multidrug resistance (MDR) is a major challenge in cancer treatment, and the breast cancer resistance protein (BCRP) is an important target in the search for new MDR-reversing drugs. With the aim of discovering new potential BCRP inhibitors, the crude extract of leaves of Eremophila galeata, a plant endemic to Australia, was investigated for inhibitory activity of parental (HT29_par) as well as BCRP-overexpressing HT29 colon cancer cells resistant to the chemotherapeutic SN-38 (i.e., HT29_SN38 cells). This identified a fraction, eluted with 40% acetonitrile on a solid-phase extraction column, which showed weak growth-inhibitory activity on HT29_SN38 cells when administered alone, but exhibited concentration-dependent growth inhibition when administered in combination with SN-38. The major constituent in this fraction was isolated and found to be 5,3′,5′-trihydroxy-3,6,7,4′-tetramethoxyflavone (2), which at a concentration of 25 μg/mL potentiated the growth-inhibitory activity of SN-38 to a degree comparable to that of the known BCRP inhibitor Ko143 at 1 μM. A dye accumulation experiment suggested that 2 inhibits BCRP, and docking studies showed that 2 binds to the same BCRP site as SN-38. These results indicate that 2 acts synergistically with SN-38, with 2 being a BCRP efflux pump inhibitor while SN-38 inhibits topoisomerase-1.

SUMMARY: In a cross‐continental research initiative, including researchers working in Australia and Denmark, and based on joint external funding by a 3‐year grant from the Novo Nordisk Foundation, we have used DNA sequencing, extensive chemical profiling and molecular networking analyses across the entire Eremophila genus to provide new knowledge on the presence of natural products and their bioactivities using polypharmocological screens. Sesquiterpenoids, diterpenoids and dimers of branched‐chain fatty acids with previously unknown chemical structures were identified. The collection of plant material from the Eremophila genus was carried out according to a ‘bioprospecting agreement’ with the Government of Western Australia. We recognize that several Eremophila species hold immense cultural significance to Australia's First Peoples. In spite of our best intentions to ensure that new knowledge gained about the genus Eremophila and any potential future benefits are shared in an equitable manner, in accordance with the Nagoya Protocol, we encounter serious dilemmas and potential conflicts in making benefit sharing with Australia's First Peoples a reality.

Purpose: Adherence to 6-mercaptopurine (6-MP)/methotrexate maintenance treatment for acute lymphoblastic leukemia (ALL) is pivotal to preventing relapse, and the 6-MP metabolite DNA-incorporated thioguanine (DNA-TG) is associated with relapse risk. In the ALLTogether-1 (A2G1) Maintenance sub-study (EU CT nr 2022-501050-11-01), DNA-TG, thioguanine nucleotides (TGN), and methylated mercaptopurine metabolites (MeMP) are analyzed regularly. Upon levels below preset limits (TGN < 50, or MeMP < 200 or < 100 nmol/mmol hemoglobin for thiopurine S-methyltransferase (TPMT) wild type and heterozygous patients, respectively), the treating physician is informed of potential non-adherence. We investigated the feasibility of using DNA-TG as the primary flagging of potential non-adherence. Methods: We analyzed 6-MP metabolites in 3,074 blood samples from 368 children enrolled in the A2G1 Maintenance sub-study. Results: In 6% of samples, TGN (median 212, 95% range 40–642), MeMP (median 4,959, 95% range 135–23,880) or both were below the flagging potential non-adherence limits. DNA-TG was associated with TGN (estimate = 1.72, p < 0.0001), MeMP (estimate = 1.10, p < 0.0001), and prescribed 6-MP dose (estimate = 1.083 and 1.132, p < 0.0001, for TPMT wild type and heterozygous patients) in linear effects models, and the predicted probability of treatment interruption in logistic regression models. DNA-TG was below 200 fmol TG/µg DNA (13th percentile of all measurements, median 569, 95% range 73–1,823) in all samples with both TGN and MeMP below the flagging potential non-adherence limits. Conclusion: DNA-TG can provide a cost-effective guidance on when to measure TGN and MeMP to determine whether non-adherence should be suspected, which is an additional benefit to monitoring DNA-TG during maintenance therapy.