mTOR inhibition promotes ATRA-induced cancer cell differentiation by overcoming a metabolic hyperactive state

All-trans retinoic acid (ATRA), a derivative of vitamin A, potently induces cell maturation in acute promyelocytic leukemia (APL). However, this therapeutic effect is attenuated or absent in non-APL acute myeloid leukemia (AML) and solid tumors. This study aims to elucidate the mechanisms underlying ATRA resistance and identify strategies to overcome it.

Integrated high-throughput sequencing-including single-cell multiomics, digital RNA with pertUrbation of genes (DRUG)-seq, bulk RNA-seq, ATAC-seq and CUT&Tag-was performed on AML and solid tumor cell lines treated with ATRA and the mTOR inhibitor PP242. Functional validation was conducted using flow cytometry, siRNA transfection, morphological assessment, Western Blotting and cell line derived xenografts (CDX). Pan-cancer analysis leveraged the Tahoe-100 M pharmacological perturbation dataset to assess metabolic responses across 50 cancer cell lines.

ATRA simultaneously activates myeloid differentiation programs and a hyperactive metabolic state that impedes terminal maturation in non-APL AML cells. Pharmacological inhibition of the mechanistic target of the mTOR pathway with PP242 suppresses this metabolic surge and redirects transcriptional output toward effective differentiation. The Tahoe-100 M analysis reveals that cancers harboring oncogenic RAS mutations exhibit heightened metabolic responsiveness to ATRA, a vulnerability confirmed in RAS-mutant lung and colon carcinoma cell lines. In these models, ATRA and PP242 synergistically promotes cell maturation and reduces viability.

These findings uncover a conserved metabolic barrier that limits ATRA-induced differentiation beyond APL. mTOR acts as a critical node governing the balance between pro-differentiation and pro-metabolic signals. Co-targeting mTOR overcomes this barrier, particularly in RAS-mutant malignancies, providing a genotype-informed rationale for extending differentiation therapy to broader cancer contexts.