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The Warburg effect is a tumorigenic metabolic adaptation process characterized by augmented aerobic glycolysis, which enhances cellular bioenergetics. In normal cells, energy homeostasis is controlled by AMPK; however, its role in cancer is not understood, as both AMPK-dependent tumor-promoting and -inhibiting functions were reported. Upon stress, energy levels are maintained by increased mitochondrial biogenesis and glycolysis, controlled by transcriptional coactivator PGC-1α and HIF, respectively. In normoxia, AMPK induces PGC-1α, but how HIF is activated is unclear. Germline mutations in the gene encoding the tumor suppressor folliculin (FLCN) lead to Birt-Hogg-Dube (BHD) syndrome, which is associated with an increased cancer risk. FLCN was identified as an AMPK binding partner, and we evaluated its role with respect to AMPK-dependent energy functions. We revealed that loss of FLCN constitutively activates AMPK, resulting in PGC-1α-mediated mitochondrial biogenesis and increased ROS production. ROS induced HIF transcriptional activity and drove Warburg metabolic reprogramming, coupling AMPK-dependent mitochondrial biogenesis to HIF-dependent metabolic changes. This reprogramming stimulated cellular bioenergetics and conferred a HIF-dependent tumorigenic advantage in FLCN-negative cancer cells. Moreover, this pathway is conserved in a BHD-derived tumor. These results indicate that FLCN inhibits tumorigenesis by preventing AMPK-dependent HIF activation and the subsequent Warburg metabolic transformation., Introduction Kidney cancer is a metabolic disease, because renal cancer genes, including VHL, MET, TSC1, TSC2, FH, and SDH, are involved in metabolic sensing and adaptation to fluctuations in oxygen, [...]

Author(s): Aldo Scarpa; David K. Chang; Katia Nones; Vincenzo Corbo; Ann-Marie Patch; Peter Bailey; Rita T. Lawlor; Amber L. Johns; David K. Miller; Andrea Mafficini; Borislav Rusev; Maria Scardoni; Davide [...]

The diagnosis of pancreatic neuroendocrine tumours (PanNETs) is increasing owing to more sensitive detection methods, and this increase is creating challenges for clinical management. We performed whole-genome sequencing of 102 primary PanNETs and defined the genomic events that characterize their pathogenesis. Here we describe the mutational signatures they harbour, including a deficiency in G:C [greater than] T:A base excision repair due to inactivation of MUTYH, which encodes a DNA glycosylase. Clinically sporadic PanNETs contain a larger-than-expected proportion of germline mutations, including previously unreported mutations in the DNA repair genes MUTYH, CHEK2 and BRCA2. Together with mutations in MEN1 and VHL, these mutations occur in 17% of patients. Somatic mutations, including point mutations and gene fusions, were commonly found in genes involved in four main pathways: chromatin remodelling, DNA damage repair, activation of mTOR signalling (including previously undescribed EWSR1 gene fusions), and telomere maintenance. In addition, our gene expression analyses identified a subgroup of tumours associated with hypoxia and HIF signalling., Author(s): Aldo Scarpa (corresponding author) [1, 2]; David K. Chang [3, 4, 5, 6, 7]; Katia Nones [8, 9]; Vincenzo Corbo [1, 2]; Ann-Marie Patch [8, 9]; Peter Bailey [3, [...]

In transformed cells, induction of apoptosis by adenovirus type 2 (Ad2) early region 40RF 4 (E4orf4) correlates with, accumulation of E4orf4 in the cell membrane--cytoskeleton fraction. However, E4orf4 is largely expressed in nuclear regions before the onset of apoptosis. To determine the relative contribution of nuclear E4orf4 versus membrane-associated E4orf4 to cell death signaling, we engineered green fluorescent fusion proteins to target E4orf4 to specific cell compartments. The targeting of Ad2 E4orf4 to cell membranes through a CAAX-box or a myristylation consensus signal sufficed to mimic the fast Src-dependent apoptotic program induced by wild-type E4orf4. In marked contrast, the nuclear targeting of E4orf4 abolished the early induction of extranuclear apoptosis. However, nuclear E4orf4 still induced a delayed cell death response independent of Src-like activity and of E4orf4 tyrosine phosphorylation. The zVAD.fmk-inhibitable caspases were dispensable for execution of both cell death programs. Nevertheless, both pathways led to caspase activation in some cell types through the mitochondrial pathway. Finally, our data support a critical role for calpains upstream in the death effector pathway triggered by the Src-mediated cytoplasmic death signal. We conclude that Ad2 E4orf4 induces two distinct cell death responses, whose relative contributions to cell killing may be determined by the genetic background.

Integrated genomic analysis of 456 pancreatic ductal adenocarcinomas identified 32 recurrently mutated genes that aggregate into 10 pathways: KRAS, TGF-, WNT, NOTCH, ROBO/SLIT signalling, G1/S transition, SWI-SNF, chromatin modification, DNA repair and RNA processing. Expression analysis defined 4 subtypes: (1) squamous; (2) pancreatic progenitor; (3) immunogenic; and (4) aberrantly differentiated endocrine exocrine (ADEX) that correlate with histopathological characteristics. Squamous tumours are enriched for TP53 and KDM6A mutations, upregulation of the TP63[DELTA]N transcriptional network, hypermethylation of pancreatic endodermal cell-fate determining genes and have a poor prognosis. Pancreatic progenitor tumours preferentially express genes involved in early pancreatic development (FOXA2/3, PDX1 and MNX1). ADEX tumours displayed upregulation of genes that regulate networks involved in KRAS activation, exocrine (NR5A2 and RBPJL), and endocrine differentiation (NEUROD1 and NKX2-2). Immunogenic tumours contained upregulated immune networks including pathways involved in acquired immune suppression. These data infer differences in the molecular evolution of pancreatic cancer subtypes and identify opportunities for therapeutic development., Author(s): Peter Bailey [1, 2]; David K. Chang [2, 3, 4, 5]; Katia Nones [1, 6]; Amber L. Johns [3]; Ann-Marie Patch [1, 6]; Marie-Claude Gingras [7, 8, 9]; David [...]

The adenoviral early region 4 open reading frame 4 (E4orf4) death factor induces p53-independent apoptosis in many cell types and appears to kill selectively transformed cells. Here we show that expression of E4orf4 in transformed epithelial cells results in early caspase-independent membrane blebbing, associated with changes in the organization of focal adhesions and actin cytoskeleton. Evidence that E4orf4 can associate with and modulate Src family kinase activity, inhibiting Src-dependent phosphorylation of focal adhesion kinase (FAK) and paxillin while increasing phosphorylation of cortactin and some other cellular proteins, is presented. Furthermore, E4orf4 dramatically inhibited the ability of FAK and c-src to cooperate in induction of tyrosine phosphorylation of cellular substrates, suggesting that E4orf4 can interfere with the formation of a signaling complex at focal adhesion sites. Consistent with a functional role for E4orf4--Src interaction, overexpression of activated c-src dramatically potentiated E4orf4-induced membrane blebbing and apoptosis, whereas kinase dead c-src constructs inhibited E4orf4 effects on cell morphology and death. Moreover treatment of E4orf4-expressing cells with PP2, a selective Src kinase inhibitor, led to inhibition of E4orf4-dependent membrane blebbing and later to a marked decrease in E4orf4-induced nuclear condensation. Taken together, these observations indicate that expression of adenovirus 2 E4orf4 can initiate caspase-independent extranuclear manifestations of apoptosis through a modulation of Src family kinases and that these are involved in signaling E4orf4-dependent apoptosis. This study also suggests that Src family kinases are likely to play a role in the cytoplasmic execution of apoptotic programs. Key words: actin * blebbing * Src family kinase * focal adhesion kinase * cortactin