Transcriptional control of autophagy-lysosome function drives pancreatic cancer metabolism.

Activation of cellular stress response pathways to maintain metabolic homeostasis is emerging as a critical growth and survival mechanism in many cancers. The pathogenesis of pancreatic ductal adenocarcinoma (PDA) requires high levels of autophagy, a conserved self-degradative process. However, the regulatory circuits that activate autophagy and reprogram PDA cell metabolism are unknown. Here we show that autophagy induction in PDA occurs as part of a broader transcriptional program that coordinates activation of lysosome biogenesis and function, and nutrient scavenging, mediated by the MiT/TFE family of transcription factors. In human PDA cells, the MiT/TFE proteins--MITF, TFE3 and TFEB--are decoupled from regulatory mechanisms that control their cytoplasmic retention. Increased nuclear import in turn drives the expression of a coherent network of genes that induce high levels of lysosomal catabolic function essential for PDA growth. Unbiased global metabolite profiling reveals that MiT/TFE-dependent autophagy-lysosome activation is specifically required to maintain intracellular amino acid pools. These results identify the MiT/TFE proteins as master regulators of metabolic reprogramming in pancreatic cancer and demonstrate that transcriptional activation of clearance pathways converging on the lysosome is a novel hallmark of aggressive malignancy.

(S)-N-[(4-{(S)-1-[2-(4-Meth-oxy-benz-amido)-2-methyl-propano-yl]pyrrolidine-2-carboxamido}-3,4,5,6-tetra-hydro-2H-pyran-4-yl)carbon-yl]proline dimethyl sulfoxide monosolvate (4-MeBz-Aib-Pro-Thp-Pro-OH).

The asymmetric unit of the title compound, C28H38N4O8·C2H6OS, contains one tetra-peptide and one disordered dimethyl sulfoxide (DMSO) mol-ecule. The central five-membered ring (Pro(2)) of the peptide mol-ecule has a disordered envelope conformation [occupancy ratio 0.879 (2):0.121 (2)] with the envelope flap atom, the central C atom of the three ring methylene groups, lying on alternate sides of the mean ring plane. The terminal five-membered ring (Pro(4)) also adopts an envelope conformation with the C atom of the methylene group closest to the carboxylic acid function as the envelope flap, and the six-membered tetra-hydro-pyrane ring shows a chair conformation. The tetra-peptide exists in a helical conformation, stabilized by an intra-molecular hydrogen bond between the amide N-H group of the heterocyclic α-amino acid Thp and the amide O atom of the 4-meth-oxy-benzoyl group. This inter-action has a graph set motif of S(10) and serves to maintain a fairly rigid ß-turn structure. In the crystal, the terminal hy-droxy group forms a hydrogen bond with the amide O atom of Thp of a neighbouring mol-ecule, and the amide N-H group at the opposite end of the mol-ecule forms a hydrogen bond with the amide O atom of Thp of another neighbouring mol-ecule. The combination of both inter-molecular inter-actions links the mol-ecules into an extended three-dimensional framework.

Lysine-specific demethylase 2B (KDM2B)-let-7-enhancer of zester homolog 2 (EZH2) pathway regulates cell cycle progression and senescence in primary cells.

Sustained expression of the histone demethylase, KDM2B (Ndy1/FBXL10/JHDM1B), bypasses cellular senescence in primary mouse embryonic fibroblasts (MEFs). Here, we show that KDM2B is a conserved regulator of lifespan in multiple primary cell types and defines a program in which this chromatin-modifying enzyme counteracts the senescence-associated down-regulation of the EZH2 histone methyltransferase. Senescence in MEFs epigenetically silences KDM2B and induces the tumor suppressor miRNAs let-7b and miR-101, which target EZH2. Forced expression of KDM2B promotes immortalization by silencing these miRNAs through locus-specific histone H3 K36me2 demethylation, leading to EZH2 up-regulation. Overexpression of let-7b down-regulates EZH2, induces premature senescence, and counteracts immortalization of MEFs driven by KDM2B. The KDM2B-let-7-EZH2 pathway also contributes to the proliferation of immortal Ink4a/Arf null fibroblasts suggesting that, beyond its anti-senescence role in primary cells, this histone-modifying enzyme functions more broadly in the regulation of cellular proliferation.

KDM2B promotes pancreatic cancer via Polycomb-dependent and -independent transcriptional programs.

Epigenetic mechanisms mediate heritable control of cell identity in normal cells and cancer. We sought to identify epigenetic regulators driving the pathogenesis of pancreatic ductal adenocarcinoma (PDAC), one of the most lethal human cancers. We found that KDM2B (also known as Ndy1, FBXL10, and JHDM1B), an H3K36 histone demethylase implicated in bypass of cellular senescence and somatic cell reprogramming, is markedly overexpressed in human PDAC, with levels increasing with disease grade and stage, and highest expression in metastases. KDM2B silencing abrogated tumorigenicity of PDAC cell lines exhibiting loss of epithelial differentiation, whereas KDM2B overexpression cooperated with KrasG12D to promote PDAC formation in mouse models. Gain- and loss-of-function experiments coupled to genome-wide gene expression and ChIP studies revealed that KDM2B drives tumorigenicity through 2 different transcriptional mechanisms. KDM2B repressed developmental genes through cobinding with Polycomb group (PcG) proteins at transcriptional start sites, whereas it activated a module of metabolic genes, including mediators of protein synthesis and mitochondrial function, cobound by the MYC oncogene and the histone demethylase KDM5A. These results defined epigenetic programs through which KDM2B subverts cellular differentiation and drives the pathogenesis of an aggressive subset of PDAC.

The WTX tumor suppressor regulates mesenchymal progenitor cell fate specification.

WTX is an X-linked tumor suppressor targeted by somatic mutations in Wilms tumor, a pediatric kidney cancer, and by germline inactivation in osteopathia striata with cranial sclerosis, a bone overgrowth syndrome. Here, we show that Wtx deletion in mice causes neonatal lethality, somatic overgrowth, and malformation of multiple mesenchyme-derived tissues, including bone, fat, kidney, heart, and spleen. Inactivation of Wtx at different developmental stages and in primary mesenchymal progenitor cells (MPCs) reveals that bone mass increase and adipose tissue deficiency are due to altered lineage fate decisions coupled with delayed terminal differentiation. Specification defects in MPCs result from aberrant ß-catenin activation, whereas alternative pathways contribute to the subsequently delayed differentiation of lineage-restricted cells. Thus, Wtx is a regulator of MPC commitment and differentiation with stage-specific functions in inhibiting canonical Wnt signaling. Furthermore, the constellation of anomalies in Wtx null mice suggests that this tumor suppressor broadly regulates MPCs in multiple tissues.