PURPOSE: This study outlines CuE's cytotoxic activity against drug-resistant tumor cell lines. Three members of ABC transporters superfamily, P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and ABCB5 were investigated, whose overexpression in tumors is tightly linked to multidrug resistance. Further factors of drug resistance studied were the tumor suppressor TP53 and the epidermal growth factor receptor (EGFR).
METHODS: Cytotoxicity assays (resazurin assays) were used to investigate the activity of Citrullus colocynthis and CuE towards multidrug resistant cancer cells. Molecular docking (In silico) has been carried out to explore the CuE's mode of binding to ABC transporters (P-gp, BCRP and ABCB5). The visualization of doxorubicin uptake was done by a Spinning Disc Confocal Microscope. The assessment of proteins expression was done by western blotting analysis. COMPARE and hierarchical cluster analyses were applied to identify, which genes correlate with sensitivity or resistance to cucurbitacins (CuA, CuB, CuE, CuD, CuI, and CuK).
RESULTS: Multidrug-resistant cells overexpressing P-gp or BCRP were cross-resistant to CuE. By contrast, TP53 knock-out cells were sensitive to CuE. Remarkably, resistant cells transfected with oncogenic ΔEGFR or ABCB5 were hypersensitive (collateral sensitive) to CuE. In silico analyses demonstrated that CuE is a substrate for P-gp and BCRP. Immunoblot analyses highlighted that CuE targeted EGFR and silenced its downstream signaling cascades. The most striking result that emerged from the doxorubicin uptake by ABCB5 overexpressing cells is that CuE is an effective inhibitor for ABCB5 transporter when compared with verapamil. The COMPARE analyses of transcriptome-wide expression profiles of tumor cell lines of the NCI identified common genes involved in cell cycle regulation, cellular adhesion and intracellular communication for different cucurbitacins.
CONCLUSION: CuE represents a potential therapeutic candidate for the treatment of certain types of refractory tumors. To best of our knowledge, this is the first time to identify CuE and verapamil as inhibitors for ABCB5 transporter.
METHODS: Between December 2020 and February 2023, we recruited patients with ARM and HD aged 3-17 years at four tertiary referral centres, who had primary corrective surgery done >12 months prior. Healthy controls were age-matched and sex-matched. All participants completed the Pediatric Quality of Life Inventory Generic Core Scales 4.0, General Well-Being (GWB) Scale 3.0 and Family Impact (FI) Module 2.0 Questionnaires. Bowel Function Score (BFS) Questionnaires were also administered. We also performed subgroup analysis according to age categories. Appropriate statistical analysis was performed with p<0.05 significance. Ethical approval was obtained.
RESULTS: There were 306 participants: 101 ARM, 87 HD, 118 controls. Patients with ARM and HD had significantly worse Core and FI Scores compared with controls overall and in all age categories. In the GWB Scale, only ARM and HD adolescents (13-17 years) had worse scores than controls. ARM and HD had significantly worse BFSs compared with controls overall and in all age categories. There was significant positive correlation between BFS and Core Scores, GWB Scores and FI Scores.
CONCLUSION: Patients with ARM and HD had worse QOL than controls. Lower GWB Scores in adolescents suggests targeted interventions are necessary. Bowel function influences QOL, indicating the need for continuous support into adulthood.