Identification of a non-phosphorylated, cell permeable, small molecule ligand for the Stat3 SH2 domain

Area of Science:

• Medicinal Chemistry
• Molecular Biology
• Oncology

Background:

• Signal transducer and activator of transcription 3 (Stat3) is a transcription factor frequently activated in human cancers.
• Targeting aberrant Stat3 activation presents a promising therapeutic strategy for cancer treatment.

Purpose of the Study:

• To design and synthesize novel Stat3 inhibitors based on salicylic acid derivatives.
• To evaluate the efficacy of these inhibitors in disrupting Stat3-Stat3 protein interactions and inhibiting Stat3 signaling.

Main Methods:

• Synthesis of a focused library of salicylic acid-containing compounds targeting the Stat3 SH2 domain.
• Biochemical assays to determine inhibitor potency against Stat3-phosphopeptide complex formation and Stat3-Stat3 interactions.
• Cell-based assays to assess inhibition of intracellular Stat3 phosphorylation, target gene expression, and induction of cancer cell death.

Main Results:

• The lead compound, 17o, demonstrated potent inhibition of Stat3-phosphopeptide complexes (K(i)=13 μM) and Stat3-Stat3 interactions (IC(50)=19 μM).
• 17o effectively suppressed Stat3 phosphorylation and downstream target gene expression in cancer cells.
• Inhibition of Stat3 signaling by 17o led to significant cancer cell death in breast and multiple myeloma (MM) cell lines (EC(50)=10 and 16 μM, respectively).

Conclusions:

• Salicylic acid derivatives can be effectively designed to inhibit Stat3 SH2 domain interactions.
• The potent Stat3 inhibitor 17o demonstrates anti-cancer activity by disrupting Stat3 signaling and inducing apoptosis in relevant cancer models.
• 17o holds potential as a therapeutic agent for cancers characterized by aberrant Stat3 activation.