Characterization of a New Peptidomimetic Compound Modulating Sam68 Functions in Human Colon Cancer Stem Cells
Creators: name: Masibag, Angelique Noelline
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2021
Subjects: Sam68
CBP
CRC
CSCs
Peptidomimetic Compound

description: Background: Conventional chemotherapeutics target bulk tumour cells and generally leave cancer stem cell (CSC) populations unaffected. Recent literature characterized the presence and the role of CSC in several types of solid tumors, including colorectal cancer. Colorectal CSCs (CCSCs) display enhanced WNT/β-catenin pathway activity, sustaining self-renewal and tumor-initiating capacity. Thus, CCSCs are crucial for tumour recurrence and metastasis. As one of the main contributors to sustained self-renewal activity in CCSCs, enhanced formation of β-catenin/CBP complex is fostering transactivation of canonical WNT target genes such as c-myc. However, maintenance of healthy intestinal stem cells also dependents on the canonical WNT pathway. Thus, selective targeting CCSCs while sparring normal intestinal cells is still a significant challenge. Interestingly, Sam68 is a key mediator of the interaction between β-catenin and CBP. It has been reported as a “druggable” target to selectively disrupt β-catenin/CBP in CSCs. Indeed, CWP232228 successfully targets CSCs in AML by facilitating Sam68/CBP complex formation, and consequently lowering the abundance of β-catenin/CBP complexes. CWP232228 was clinically tested on multiple human cancers. Unfortunately, such clinical trials were halted due to unknown causes, and limited information was released on clinical safety and benefits. Consequently, developing more potent pharmacological modulators of Sam68/CBP complex formation is still highly relevant to eradicate CCSCs. Here we describe the discovery and characterization of a new CWP analog, known as YB-0158, which displays enhanced potency and neoplastic selectivity against CCSC. Methods and Results: Following the confirmation that ICG/CWP class of compounds bind to Sam68 in CSCs, I used in silico docking methods to screen for CWP analogs having high predicted affinity for Sam68 Cterminal proline-rich domain. Using high content imaging techniques, I confirmed our top candidate (YB-0158) as more potent vs. CWP parent molecule to compromise cell growth, to induce loss of pluripotency, and to increase Sam68 nuclear localization in a surrogate model of human CSCs. YB-0158 also displayed enhanced selective toxicity in colorectal cancer models vs. normal intestinal epithelium progenitor cells. Moreover, I confirmed that YB-0158 exert negative impact on cancer cell growth by inducing apoptosis and reducing proliferation. Lentiviral-based knockdowns explicitly displayed decrease in drug effectivity in the absence of Sam68, reinforcing the essential role of Sam68 mediating ICG-001/CWP response in CSCs. I demonstrated that Sam68 expression is enriched in tumor-initiating cell fractions derived from primary colorectal tumor tissues vs. bulk heterogeneous tumor organoids. Therefore, YB-0158 showed striking efficacy at supressing tumor-initiation activity in a patient-based serial organoid formation assay. Finally, YB-0158 eradicated CSCs activity in vivo as demonstrated by a syngeneic mouse-to-mouse serial transplantation assay. Conclusion: Overall, YB-0158 is a novel analog of CWP232228 with superior potency to target CCSCs activity through facilitation of Sam68 nuclear localization, thus reducing the interaction frequency between CBP and β-catenin.