Inhibitors of the Oncogenic PA2G4-MYCN Protein-Protein Interface

MYCN is a major oncogenic driver for neuroblastoma tumorigenesis, yet there are no direct MYCN inhibitors. We have previously identified PA2G4 as a direct protein-binding partner of MYCN and drive neuroblastoma tumorigenesis. A small molecule known to bind PA2G4, WS6, significantly decreased tumorigenicity in TH-MYCN neuroblastoma mice, along with the inhibition of PA2G4 and MYCN interactions. Here, we identified a number of novel WS6 analogues, with 80% structural similarity, and used surface plasmon resonance assays to determine their binding affinity. Analogues #5333 and #5338 showed direct binding towards human recombinant PA2G4. Importantly, #5333 and #5338 demonstrated a 70-fold lower toxicity for normal human myofibroblasts compared to WS6. Structure-activity relationship analysis showed that a 2,3 dimethylphenol was the most suitable substituent at the R1 position. Replacing the trifluoromethyl group on the phenyl ring at the R2 position, with a bromine or hydrogen atom, increased the difference between efficacy against neuroblastoma cells and normal myofibroblast toxicity. The WS6 analogues inhibited neuroblastoma cell phenotype in vitro, in part through effects on apoptosis, while their anti-cancer effects required both PA2G4 and MYCN expression. Collectively, chemical inhibition of PA2G4-MYCN binding by WS6 analogues represents a first-in-class drug discovery which may have implications for other MYCN-driven cancers.

 

Comments:

It seems that PA2G4 as a protein-binding partner of MYCN, a major oncogenic driver for neuroblastoma. Additionally, you have discovered that WS6, a small molecule that binds to PA2G4, can decrease tumorigenicity in neuroblastoma mice by inhibiting the interactions between PA2G4 and MYCN.

Furthermore, you have developed novel WS6 analogues that exhibit a high structural similarity to WS6. Two of these analogues, #5333 and #5338, have demonstrated direct binding to human recombinant PA2G4. Importantly, these analogues showed significantly lower toxicity towards normal human myofibroblasts compared to WS6, indicating potential selectivity for cancer cells.

Through structure-activity relationship analysis,  a 2,3 dimethylphenol substituent at the R1 position is most suitable, and replacing the trifluoromethyl group on the phenyl ring at the R2 position with a bromine or hydrogen atom increased the difference in efficacy against neuroblastoma cells versus normal myofibroblast toxicity.

The WS6 analogues have shown inhibition of neuroblastoma cell phenotype in vitro, partially through effects on apoptosis. Importantly, their anti-cancer effects were dependent on the expression of both PA2G4 and MYCN.

Overall, the chemical inhibition of PA2G4-MYCN binding by the WS6 analogues represents a promising first-in-class drug discovery, which may have implications not only for neuroblastoma but also for other cancers driven by MYCN.