Synthesis and evaluation of thiadiazole thioether analogs for hedgehog signaling pathway inhibition and malignant biological behavior against medulloblastoma cells

Medulloblastoma (MB), a prevalent pediatric malignant neoplasm that arises in the cerebellum. It demonstrates a pathogenesis fundamentally linked to dysregulated Hedgehog (HH) pathway activation. Smoothened (SMO), a core component of the Hh pathway, undergoes abnormal activation that triggers hypertranscription of the downstream target gene GLI1 , resulting in sustained activation of the HH pathway and subsequently accelerating tumor cell proliferation and invasion. Unfortunately, vismodegib, approved by the FDA, has encountered the challenge of drug resistance in MB treatment. Therefore, developing novel HH pathway inhibitors to precisely block this abnormal signaling conduction has become a critical issue that the scientific community urgently needs to address, holding great significance for the innovation of treatment strategies for MB. This study is dedicated to designing, synthesizing, and evaluating a series of HH pathway inhibitors targeting SMO, based on the thiadiazole thioether scaffold. Through rigorous GLI luciferase reporter gene assay screening, we have successfully identified a promising analog, 2-((2-methoxyphenyl)thio)-5-(pyridin-4-yl)-1,3,4-thiadiazole (WMC03). This compound exhibits a competitive action similar to cyclopamine at the binding site of the SMO protein, reducing cilium formation by binding to SMO, and thereby inhibiting the activation of the HH pathway. Molecular modeling approaches have provided deeper insights into the interaction mechanism between WMC03 and the SMO protein, shedding light on the collaborative contributions of hydrogen bonding, hydrophobic interactions, and electrostatic forces. Notably, WMC03 demonstrated a robust ability to suppress GLI1 expression, exerting its inhibitory effects at both the transcriptional and translational stages. This suppression subsequently led to the effective inhibition of Daoy cell proliferation and migration, ultimately triggering apoptosis in these cells. These findings not only emphasize the remarkable efficacy of WMC03 in MB cells but also provide new ideas and approaches for the development of efficient and specific Hh pathway inhibitors for the clinical treatment of MB.