Disrupting the Myc-Tfeb circuit confers vulnerabilities targeting amino acid homeostasis and provokes metabolic anergy
Metabolic reprogramming sustains cancer cell anabolism, and MYC oncoproteins control many aspects of this response. Normal cells adapt to nutrient-limiting conditions by activating autophagy, which is required for amino acid (AA) homeostasis. Surprisingly, here we report the autophagy-lysosomal pathway is suppressed by Myc in normal B cells, in premalignant and neoplastic B cells of Eµ-Myc transgenic mice, and in MYC-driven human Burkitt lymphoma. Myc suppresses autophagy by antagonizing expression and function of TFEB, a master regulator of autophagy/lysosome genes. Notably, compensatory mechanisms that sustain AA pools in MYC-expressing B cells include marked increases in AA transport and coordinate induction of the proteasome. Finally, reactivation of the autophagy-lysosomal pathway by constitutively active TFEB disables the malignant state, by perturbing mitochondrial functions and disrupting proteasome activity, amino acid transport, and disrupts amino acid and nucleotide metabolism, leading to growth arrest and apoptosis. This scenario provides therapeutic opportunities that disable MYC-driven tumorigenesis, including AA restriction and treatment with proteasome inhibitors. Overall design: A B-cell lymphoma isolated from Eµ-Myc;Eµ-rtTA transgenic moused was transduced with either a bicistronic retrovirus expressing the selection marker puromycin or a mutated form of the TFEB gene at Ser-211 to Ala fused to a mutated ligand domain of the human estrogen Receptor domain (ER-T2) and puromycin. The lymphoma was selected with 1 µg/mL and puromycin-resistant cells were plated in vehicle or  250 ng/mL 4-hydroxytamoxifen (4-OHT) to induced TFEB activity for 4 days. Lymphomas were collected, in triplicate, and processed for subsequent RNA purification, labeling and samples processed in a Nugen_Ovation_Mouse RNASeq Kit. .