Project description: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.
Project description:This study investigates the role of ADAM17 (a disintegrin and metalloproteinase 17) in skin homeostasis. Here, we show that mice lacking ADAM17 in keratinocytes have a normal epidermal barrier and skin architecture at birth, but develop pronounced defects in epidermal barrier integrity soon after birth and chronic dermatitis as adults. The dysregulated expression of epidermal differentiation proteins becomes evident 2 days after birth, followed by transepidermal water loss and inflammatory immune cell infiltration. Our results identify a previously unappreciated critical role of the ADAM17/EGFR signaling axis in maintaining the homeostasis of the postnatal epidermal barrier. The genome-wide effects of ADAM17 deficiency were analyzed using Agilent Whole Mouse Genome microarrays. Conditional keratinocyte-specific ADAM17 knockout mice were generated by crossing Adam17flox/flox mice with keratin-14-Cre (Krt14-Cre) transgenic mice. Adam17flox/+Krt14-Cre mice were mated with Adam17flox/flox mice to generate pups of Adam17flox/flox Krt14-Cre positive (cKO) and Krt14-Cre negative (wild-type) control littermates. The genetic background was a mix of 129Sv and C57BL/6. As material, back skin tissue biopsies (postnatal day 10) from n = 2 wild-type skin and n = 2 ADAM17 epidermal KO skin (matched WT-cKO pairs from two different litters) were used in this study.
Project description:Oncogenic MYC selectively activates Slc7a5 and Slc43a1 transcription and thus promotes essential amino acids (EAAs) uptake in Daudi cells. Elevated EAAs in turn stimulate Myc mRNA translation, prompting us to investigate whether Slc7a5/Slc43a1 inhibition affects MYC-dependent transcription. We performed microarrays to profile global gene expression and to identify Slc7a5-regulated genes.
Project description:Analysis of murine model of T cell acute lymphoblastic leukemia (T-ALL) caused by deletion of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) reveals that primary T-ALL cells have high transport rates for multiple nutrients. In particular, high levels of leucine transport in T-ALL fuels mammalian target of rapamycin complex 1 (mTORC1) activity which then sustains expression of hypoxia inducible factor-1a (HIF1a) and c-Myc, the drivers of glucose transport. A key finding is that PTEN deletion and phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) accumulation is insufficient to initiate leucine uptake, mTORC1 activity, HIF1a or c-Myc expression in T cells and hence cannot drive T-ALL metabolic reprogramming. Instead, a key regulator for leucine transport in T-ALL is identified as NOTCH. Mass spectrometry based proteomics identifies SLC7A5 as the dominant System L-amino acid transporter in primary PTEN-/- T-ALL cells. Importantly, expression of SLC7A5 is critical for the malignant transformation induced by PTEN deletion. These data highlight the importance of regulated amino acid transport for T cell malignancies and how a single amino acid transporter can play a key role.