scholarly journals p53-PHLDA3-Akt Network: The Key Regulators of Neuroendocrine Tumorigenesis

2020 ◽  
Vol 21 (11) ◽  
pp. 4098
Author(s):  
Yu Chen ◽  
Rieko Ohki
Keyword(s):  
Tumor Suppressor ◽  
Neuroendocrine Tumors ◽  
Target Genes ◽  
Islet Cells ◽  
Suppressor Gene ◽  
Protein Product ◽  
P53 Target Gene ◽  
The Relationship ◽  
Deficient Mice

p53 is a well-known tumor suppressor gene and one of the most extensively studied genes in cancer research. p53 functions largely as a transcription factor and can trigger a variety of antiproliferative programs via induction of its target genes. We identified PHLDA3 as a p53 target gene and found that its protein product is a suppressor of pancreatic neuroendocrine tumors (PanNETs) and a repressor of Akt function. PHLDA3 is frequently inactivated by loss of heterozygosity (LOH) and methylation in human PanNETs, and LOH at the PHLDA3 gene locus correlates with PanNET progression and poor prognosis. In addition, in PHLDA3-deficient mice, pancreatic islet cells proliferate abnormally and acquire resistance to apoptosis. In this article, we briefly review the roles of p53 and Akt in human neuroendocrine tumors (NETs) and describe the relationship between the p53-PHLDA3 and Akt pathways. We also discuss the role of PHLDA3 as a tumor suppressor in various NETs and speculate on the possibility that loss of PHLDA3 function may be a useful prognostic marker for NET patients indicating particular drug therapies. These results suggest that targeting the downstream PHLDA3-Akt pathway might provide new therapies to treat NETs.

scholarly journals Persistent human papillomavirus infection in the etiology of cervical carcinoma: The role of immunological, genetic, viral and cellular factors

2014 ◽  
Vol 142 (5-6) ◽  
pp. 378-383 ◽  
Author(s):  
Radomir Zivadinovic ◽  
Aleksandra Petric ◽  
Goran Lilic ◽  
Vekoslav Lilic ◽  
Biljana Djordjevic
Keyword(s):  
Cell Cycle ◽  
Human Papillomavirus ◽  
Tumor Suppressor ◽  
Tumor Suppressor Gene ◽  
P53 Protein ◽  
Suppressor Gene ◽  
Protein Product ◽  
Cervical Carcinogenesis ◽  
Hpv E7

The aim of this paper was to present the role of human papillomavirus (HPV) in cervical carcinogenesis from several aspects. By explaining the HPV virus lifecycle and structure, its effect on cervical cell cycle and subversion of immune response can be better understood. Early E region of the viral genome encodes proteins that are directly involved in carcinogenesis. The E6 protein binds to p53 protein (product of tumor-suppressor gene) blocking and degrading it, which in turn prevents cell cycle arrest and apoptosis induction. E6 is also capable of telomerase activation, which leads to cell immortalization; it also reacts with host proto-oncogene c-jun, responsible for transcription, shortens G1 phase and speeds up the transition from G1 to S phase of the cells infected by HPV. E7 forms bonds with retinoblastoma protein (product of tumor-suppressor gene) and inactivates it. It can inactivate cyclin inhibitors p21, p27, and abrogate the mitotic spindle checkpoint with the loss of protective effect of pRB and p53. The immune system cannot initiate early immunological reaction since the virus is non-lytic, while the concentration of viral proteins - antigens is low and has a basal intracellular position. Presentation through Langerhans cells (LC) is weak, because the number of these cells is low due to the effect of HPV. E7 HPV reduces the expression of E-cadherin, which is responsible for LC adhesion to HPVtransformed keratinocytes. Based on these considerations, it may be concluded that the process of cervical carcinogenesis includes viral, genetic, cellular, molecular-biological, endocrine, exocrine and immunological factors.

Neurofibromin can inhibit Ras-dependent growth by a mechanism independent of its GTPase-accelerating function

1994 ◽  
Vol 14 (1) ◽  
pp. 641-645
Author(s):  
M R Johnson ◽  
J E DeClue ◽  
S Felzmann ◽  
W C Vass ◽  
G Xu ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Tumor Suppressor Gene ◽  
Suppressor Gene ◽  
Protein Product ◽  
Growth Inhibitory ◽  
Nf1 Gene ◽  
A Cell ◽  
Dependent Growth ◽  
Nih 3T3

The NF1 gene, which is altered in patients with type 1 neurofibromatosis, has been postulated to function as a tumor suppressor gene. The NF1 protein product neurofibromin stimulates the intrinsic GTPase activity of active GTP-bound Ras, thereby inactivating it. Consistent with a tumor suppressor function, we have found that the introduction of NF1 in melanoma cell lines that are deficient in neurofibromin inhibited their growth and induced their differentiation. In addition, overexpression of neurofibromin in NIH 3T3 cells was growth inhibitory but did not alter the level of GTP.Ras in the cells. Transformation by v-ras, whose protein product is resistant to GTPase stimulation by neurofibromin, was inhibited in a cell line overexpressing neurofibromin, while transformation by v-raf was not altered. The results demonstrate that NF1 is a tumor suppressor gene that can inhibit Ras-dependent growth by a regulatory mechanism that is independent of neurofibromin's ability to stimulate Ras GTPase.

scholarly journals MEN4 and CDKN1B mutations: the latest of the MEN syndromes

2017 ◽  
Vol 24 (10) ◽  
pp. T195-T208 ◽  
Author(s):  
Rami Alrezk ◽  
Fady Hannah-Shmouni ◽  
Constantine A Stratakis
Keyword(s):  
Tumor Suppressor ◽  
Neuroendocrine Tumors ◽  
Pituitary Adenomas ◽  
Wide Spectrum ◽  
Susceptibility Gene ◽  
Germline Mutations ◽  
Suppressor Gene ◽  
Loss Of Function ◽  
Putative Tumor Suppressor

Multiple endocrine neoplasia (MEN) refers to a group of autosomal dominant disorders with generally high penetrance that lead to the development of a wide spectrum of endocrine and non-endocrine manifestations. The most frequent among these conditions is MEN type 1 (MEN1), which is caused by germline heterozygous loss-of-function mutations in the tumor suppressor geneMEN1. MEN1 is characterized by primary hyperparathyroidism (PHPT) and functional or nonfunctional pancreatic neuroendocrine tumors and pituitary adenomas. Approximately 10% of patients with familial or sporadic MEN1-like phenotype do not haveMEN1mutations or deletions. A novel MEN syndrome was discovered, initially in rats (MENX), and later in humans (MEN4), which is caused by germline mutations in the putative tumor suppressorCDKN1B. The most common phenotype of the 19 established cases of MEN4 that have been described to date is PHPT followed by pituitary adenomas. Recently, somatic or germline mutations inCDKN1Bwere also identified in patients with sporadic PHPT, small intestinal neuroendocrine tumors, lymphoma and breast cancer, demonstrating a novel role forCDKN1Bas a tumor susceptibility gene for other neoplasms. In this review, we report on the genetic characterization and clinical features of MEN4.

scholarly journals KLF2 Inhibits the Migration and Invasion of Prostate Cancer Cells by Downregulating MMP2

2018 ◽  
Vol 13 (1) ◽  
pp. 155798831881690 ◽  
Author(s):  
Binshuai Wang ◽  
Mingyuan Liu ◽  
Yimeng Song ◽  
Changying Li ◽  
Shudong Zhang ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Tumor Suppressor ◽  
Cell Function ◽  
Malignant Tumors ◽  
Suppressor Gene ◽  
Migration And Invasion ◽  
Tissue Samples ◽  
Tumor Tissues ◽  
Luciferase Activity Assay

KLF2, a member of the Kruppel-like factor (KLF) family, is thought to be a tumor suppressor in many kinds of malignant tumors. Its functions in prostate cancer (PCa) are unknown. This study aimed to explore the role of KLF2 in the migration and invasion of PCa cells. The expression of KLF2 was measured by immunohistochemistry in PCa tissues and in paired non-tumor tissues. KLF2 and MMP2 expression in cells was measured by Western blot and RT-qPCR. Adenoviruses and siRNAs were used in cell function tests to investigate the role of KLF2 in regulating MMP2. Interactions between KLF2 and MMP2 were analyzed by a luciferase activity assay. The present study, for the first time, identified that KLF2 was downregulated both in PCa clinical tissue samples and in cancer cell lines. The overexpression of KLF2 inhibited the migration and invasion of PCa cells via the suppression of MMP2.This study demonstrates that KLF2 might act as a tumor suppressor gene in PCa and that the pharmaceutical upregulation of KLF2 may be a potential approach for treatment.

scholarly journals Transcriptional role of p53 in interferon-mediated antiviral immunity

2008 ◽  
Vol 205 (8) ◽  
pp. 1929-1938 ◽  
Author(s):  
César Muñoz-Fontela ◽  
Salvador Macip ◽  
Luis Martínez-Sobrido ◽  
Lauren Brown ◽  
Joseph Ashour ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Viral Replication ◽  
Viral Infections ◽  
Suppressor Gene ◽  
Central Component ◽  
Type I ◽  
Infected Cells

Tumor suppressor p53 is activated by several stimuli, including DNA damage and oncogenic stress. Previous studies (Takaoka, A., S. Hayakawa, H. Yanai, D. Stoiber, H. Negishi, H. Kikuchi, S. Sasaki, K. Imai, T. Shibue, K. Honda, and T. Taniguchi. 2003. Nature. 424:516–523) have shown that p53 is also induced in response to viral infections as a downstream transcriptional target of type I interferon (IFN) signaling. Moreover, many viruses, including SV40, human papillomavirus, Kaposi's sarcoma herpesvirus, adenoviruses, and even RNA viruses such as polioviruses, have evolved mechanisms designated to abrogate p53 responses. We describe a novel p53 function in the activation of the IFN pathway. We observed that infected mouse and human cells with functional p53 exhibited markedly decreased viral replication early after infection. This early inhibition of viral replication was mediated both in vitro and in vivo by a p53-dependent enhancement of IFN signaling, specifically the induction of genes containing IFN-stimulated response elements. Of note, p53 also contributed to an increase in IFN release from infected cells. We established that this p53-dependent enhancement of IFN signaling is dependent to a great extent on the ability of p53 to activate the transcription of IFN regulatory factor 9, a central component of the IFN-stimulated gene factor 3 complex. Our results demonstrate that p53 contributes to innate immunity by enhancing IFN-dependent antiviral activity independent of its functions as a proapoptotic and tumor suppressor gene.

scholarly journals Transcriptional Regulation of Genes by Ikaros Tumor Suppressor in Acute Lymphoblastic Leukemia

2020 ◽  
Vol 21 (4) ◽  
pp. 1377
Author(s):  
Pavan Kumar Dhanyamraju ◽  
Soumya Iyer ◽  
Gayle Smink ◽  
Yevgeniya Bamme ◽  
Preeti Bhadauria ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Tumor Suppressor ◽  
Chromatin Remodeling ◽  
Target Genes ◽  
Cellular Proliferation ◽  
Lymphoblastic Leukemia ◽  
Regulatory Elements ◽  
Binding Motif ◽  
Functional Inactivation

Regulation of oncogenic gene expression by transcription factors that function as tumor suppressors is one of the major mechanisms that regulate leukemogenesis. Understanding this complex process is essential for explaining the pathogenesis of leukemia as well as developing targeted therapies. Here, we provide an overview of the role of Ikaros tumor suppressor and its role in regulation of gene transcription in acute leukemia. Ikaros (IKZF1) is a DNA-binding protein that functions as a master regulator of hematopoiesis and the immune system, as well as a tumor suppressor in acute lymphoblastic leukemia (ALL). Genetic alteration or functional inactivation of Ikaros results in the development of high-risk leukemia. Ikaros binds to the specific consensus binding motif at upstream regulatory elements of its target genes, recruits chromatin-remodeling complexes and activates or represses transcription via chromatin remodeling. Over the last twenty years, a large number of Ikaros target genes have been identified, and the role of Ikaros in the regulation of their expression provided insight into the mechanisms of Ikaros tumor suppressor function in leukemia. Here we summarize the role of Ikaros in the regulation of the expression of the genes whose function is critical for cellular proliferation, development, and progression of acute lymphoblastic leukemia.

scholarly journals miR-509-5p Inhibits the Proliferation and Invasion of Osteosarcoma by Targeting TRIB2

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Jiekun Guo ◽  
Qiang Wu ◽  
Xiaoming Peng ◽  
Bin Yu
Keyword(s):  
Tumor Suppressor ◽  
Cell Lines ◽  
Transcriptional Activity ◽  
Preventive Intervention ◽  
Suppressor Gene ◽  
Rt Pcr ◽  
Malignant Bone Tumors ◽  
Direct Target ◽  
Proliferation And Invasion

Osteosarcoma (OS) is one of the most common malignant bone tumors in adolescents with a poor prognosis. Though miR-509-5p has been reported as a tumor suppressor in several human cancers, the role of miR-509-5p in OS remains unclear. In this study, our result of real-time PCR (RT-PCR) showed that the expression of miR-509-5p was significantly decreased in OS tissues and cell lines. Overexpression of miR-509-5p significantly suppressed cell proliferation and invasion in OS cell lines. Moreover, we identified tribbles homolog 2 (TRIB2) as the direct target of miR-509-5p. Knockdown of TRIB2 could inhibit the malignant capacity of OS cells. At last, we reported that TRIB2 could inhibit the bioactivity of the tumor suppressor gene p21 via blocking its transcriptional activity. Collectively, our study revealed that miR-509-5p functions as a tumor suppressor by targeting TRIB2 in OS and thus could affect the activity of p21, suggesting that miR-509-5p is a novel preventive intervention for OS patients.

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