Mediator Of Cellular Homeostasis Research Articles

The discrete roles of individual FOXO transcription factor family members in B-cell malignancies.

Forkhead box (FOX) class O (FOXO) proteins are a dynamic family of transcription factors composed of four family members: FOXO1, FOXO3, FOXO4 and FOXO6. As context-dependent transcriptional activators and repressors, the FOXO family regulates diverse cellular processes including cell cycle arrest, apoptosis, metabolism, longevity and cell fate determination. A central pathway responsible for negative regulation of FOXO activity is the phosphatidylinositol-3-kinase (PI3K)-AKT signalling pathway, enabling cell survival and proliferation. FOXO family members can be further regulated by distinct kinases, both positively (e.g., JNK, AMPK) and negatively (e.g., ERK-MAPK, CDK2), with additional post-translational modifications further impacting on FOXO activity. Evidence has suggested that FOXOs behave as 'bona fide' tumour suppressors, through transcriptional programmes regulating several cellular behaviours including cell cycle arrest and apoptosis. However, an alternative paradigm has emerged which indicates that FOXOs operate as mediators of cellular homeostasis and/or resistance in both 'normal' and pathophysiological scenarios. Distinct FOXO family members fulfil discrete roles during normal B cell maturation and function, and it is now clear that FOXOs are aberrantly expressed and mutated in discrete B-cell malignancies. While active FOXO function is generally associated with disease suppression in chronic lymphocytic leukemia for example, FOXO expression is associated with disease progression in diffuse large B cell lymphoma, an observation also seen in other cancers. The opposing functions of the FOXO family drives the debate about the circumstances in which FOXOs favour or hinder disease progression, and whether targeting FOXO-mediated processes would be effective in the treatment of B-cell malignancies. Here, we discuss the disparate roles of FOXO family members in B lineage cells, the regulatory events that influence FOXO function focusing mainly on post-translational modifications, and consider the potential for future development of therapies that target FOXO activity.

Directional divergence of Ep300 duplicates in teleosts and its implications

BackgroundEP300 is a conserved protein in vertebrates, which serves as a key mediator of cellular homeostasis. Mutations and dysregulation of EP300 give rise to severe human developmental disorders and malignancy. Danio rerio is a promising model organism to study EP300 related diseases and drugs; however, the effect of EP300 duplicates derived from teleost-specific whole genome duplication should not just be neglected.ResultsIn this study, we obtained EP300 protein sequences of representative teleosts, mammals and sauropsids, with which we inferred a highly supported maximum likelihood tree. We observed that Ep300 duplicates (Ep300a and Ep300b) were widely retained in teleosts and universally expressed in a variety of tissues. Consensus sequences of Ep300a and Ep300b had exactly the same distribution of conserved domains, suggesting that their functions should still be largely overlapped. We analyzed the molecular evolution of Ep300 duplicates in teleosts, using branch-site models, clade models and site models. The results showed that both duplicates were subject to strong positive selection; however, for an extant species, generally at most one copy was under positive selection. At the clade level, there were evident positive correlations between evolutionary rates, the number of positively selected sites and gene expression levels. In Ostariophysi, Ep300a were under stronger positive selection than Ep300b; in Neoteleostei, another species-rich teleost clade, the contrary was the case. We also modeled 3D structures of zf-TAZ domain and its flanking regions of Ep300a and Ep300b of D. rerio and Oryzias latipes and found that in either species the faster evolving copy had more short helixes.ConclusionsCollectively, the two copies of Ep300 have undoubtedly experienced directional divergence in main teleost clades. The divergence of EP300 between teleosts and mammals should be greater than the divergence between different teleost clades. Further studies are needed to clarify to what extent the EP300 involved regulatory network has diverged between teleosts and mammals, which would also help explain the huge success of teleosts.

Abstract A038: uPA/uPAR/MMP9 signaling hindered by heme oxygenase-1 in prostate cancer: Impact on cell invasiveness

Abstract Cell motility plays a crucial role in cancer metastasis. The actin cytoskeleton behaves as the cellular engine behind this process and is governed by complex signaling transduction cascades. Cancer cells have shown a variety of alterations both in the expression and localization of cytoskeleton-regulating proteins, which increase their capacity to migrate and invade homing organs. Heme oxygenase 1 (HO-1) is a stress response protein and a critical mediator of cellular homeostasis. Although HO-1’s role in cancer has been controversial, we have previously shown that its pharmacologic or genetic upregulation is associated with a less aggressive phenotype in PCa. HO-1 inhibits cell proliferation, migration, and invasion; impairs tumor growth and angiogenesis in vivo; and downregulates the expression of target genes associated with inflammation. We have also demonstrated that HO-1 is implicated in prostate cancer (PCa) cell adhesiveness and zippering (an increment in the number of filopodia between cells as well as a decrease in the levels of MMP9 (RTqPCR, Zimography, and Microarray analysis) favoring a more adhesive phenotype. However, the molecular mechanism behind this modulation was not yet deciphered. In this work we first assessed the presence of MMP9 in filopodia-like protrusions between neighboring cells to rule out that these increased protrusions were invadopodia structures. HO-1 was induced pharmacologically (hemin 80 uM, 24 h), fixed with PFA and stained with anti-HO-1 and anti-MMP9 antibodies. PCa cells were imaged by confocal microscopy. We observed that MMP9 did not colocalize with HO-1 and was absent at the leading edge of PCa cells. It is broadly known that MMP9 and the plasminogen activator urokinase (uPA) are important factors for cancer invasion and metastasis, both of them responsible for degrading the extracellular matrix (ECM). To assess whether the forced expression of HO-1 modulated the MMP9/uPA pathway, we studied the expression of several inhibitors and activators of this cascade through a transcriptomics approach. The RNAseq profiling for both PCa cells overexpressing HO-1 pharmacologically or genetically showed a direct regulation of the critical factors in the uPA/uPAR cascade, such as the downregulation of the axis activators uPA/uPAR (PLAU/PLAUR) and tPA (PLAT), and the upregulation of the axis inhibitors CPB2 (thrombin activator of fibrinolysis inhibitor), SERPINF2 (alpha 2 anti- plasmin), and F12 (factor XIIA). Our findings were further validated by an uPA ELISA revealing that under the same experimental conditions, the levels of this urokinase secreted to the conditioned media were significantly reduced. Altogether, our work delineates a molecular axis by which HO-1 potentially shuts down the acquisition of an invasive tumor cell phenotype, crucial for PCa cancer metastasis. Citation Format: Alejandra V. Paez, Javier H. Cotignola, Elba S. Vazquez, Geraldine Gueron. uPA/uPAR/MMP9 signaling hindered by heme oxygenase-1 in prostate cancer: Impact on cell invasiveness [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A038.