Dual mTORC2/mTORC1 targeting results in potent suppressive effects on acute myeloid leukemia (AML) progenitors

Area of Science:

• Oncology
• Molecular Biology
• Cell Signaling

Background:

• The mechanistic target of rapamycin (mTOR) pathway is crucial in cell growth and proliferation.
• Aberrant mTOR signaling is implicated in the pathogenesis of acute myeloid leukemia (AML).
• Specific mTOR complexes, mTORC1 and mTORC2, play distinct roles in cellular regulation.

Purpose of the Study:

• To investigate the presence and activity of mTORC2 and rapamycin-insensitive (RI)-mTORC1 complexes in AML cells.
• To evaluate the therapeutic potential of dual mTORC1/mTORC2 inhibition in primitive AML leukemic progenitors.

Main Methods:

• Immunoblotting to detect activated mTOR pathway components in AML cell lines and primary blasts.
• Cell proliferation assays to measure cellular growth.
• Assessment of mRNA translation and colony formation assays to evaluate leukemic progenitor activity.

Main Results:

• mTORC2 complexes are active and play a critical role in AML leukemogenesis.
• RI-mTORC1 complexes are present and regulate the translational repressor 4E-BP1 in AML cells.
• OSI-027, a dual mTORC1/mTORC2 inhibitor, suppressed mRNA translation and proliferation in AML cells, outperforming rapamycin in vitro.

Conclusions:

• Dual inhibition of mTORC2 and mTORC1 demonstrates potent suppressive effects on primitive AML leukemic progenitors.
• Targeting the mTOR catalytic site with OSI-027 effectively inhibits both mTORC2 and RI-mTORC1 complexes.
• OSI-027 elicits significantly more potent anti-leukemic responses compared to selective mTORC1 inhibition with rapamycin.