Bi-steric mTORC1 inhibitors induce apoptotic cell death in tumor models with hyperactivated mTORC1

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• The phosphoinositide 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway is frequently dysregulated in various cancers.
• Rapalogs offer limited clinical benefits, potentially due to their insufficient inhibition of 4EBP1, a key downstream target of mTORC1.

Purpose of the Study:

• To investigate the therapeutic potential of bi-steric mTORC1-selective inhibitors compared to rapalogs in preclinical cancer models.
• To determine if bi-steric inhibitors offer superior efficacy in tumors characterized by mTORC1 hyperactivity.

Main Methods:

• In vitro and in vivo assessment of bi-steric mTORC1-selective inhibitors in tumor models with elevated mTORC1 activity.
• Comparative analysis of bi-steric inhibitors, rapamycin, and MLN0128 regarding tumor growth inhibition, 4EBP1 phosphorylation, and apoptosis induction.
• Multiomics analysis to elucidate the molecular mechanisms of bi-steric inhibitor action.

Main Results:

• Bi-steric inhibitors demonstrated potent tumor growth inhibition and induced significant apoptosis, exceeding the effects of rapamycin and MLN0128.
• Bi-steric inhibitors effectively eliminated phosphorylated 4EBP1, unlike rapalogs.
• Multiomics analysis revealed extensive molecular alterations induced by bi-steric inhibitors, including the selective inhibition of de novo purine synthesis via reduction of JUN and PRPS1.

Conclusions:

• Bi-steric mTORC1-selective inhibitors represent a promising therapeutic strategy for cancers driven by mTORC1 hyperactivation.
• Targeting mTORC1 with bi-steric inhibitors, which effectively inhibit 4EBP1 and de novo purine synthesis, offers a potential advantage over current rapalog therapies.