Cancer

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c-Sis

Human c-sis/PDGF-β proto-oncogene is overexpressed in a large percentage of human tumor cells involving a growth-promoting, autocrine growth circuit. The c-sis/PDGF-β promoter contains a unique homopurine/homopyrimidine sequence (SIS proximal element, SPE), which is crucial for transciption stimulating nuclear-binding factors.[1] The human sis gene is located at 22q12.3-13.1 on the long arm of chromosome 22.

: malignant pathology : non-malignant pathology : PDGF, platelet derived growth factor : v-sis :

The v-sis oncogene of the simian sarcoma virus is a retroviral homolog of the cellular gene encoding the β chain of PDGF (9,10) The hypothesis that unscheduled production of PDGF may contribute to the growth of spontaneous tumors is supported by the finding that PDGF is frequently produced by cell lines from human tumors such as glioblastoma and fibrosarcoma (11), melanoma (12), breast carcinoma (13), lung carcinoma (14), glioma (15), esophageal carcinoma (16) and Kaposi’s sarcoma (17). Gene transfer experiments have shown that overexpression of the normal human PDGF-β gene (c-sis, proto-oncogene) can cause the generation of fibrosarcoma (18), vascular connective tissue stroma with no necrosis (19) and tumorigenic and metastatic effects (2022). [3]

Regulation of expression of platelet derived growth factor polypeptide B encoded by the c-sis proto-oncogene is important in a number of physiological and pathological conditions.[2] Sequences upstream of the c-sis RNA CAP site respond to the HTLV-I transactivator protein to increase RNA synthesis from either the c-sis or HTLV I promoter. [2]

Platelet-derived growth factor (PDGF) is a ubiquitous, potent mitogen and chemotactic factor for many connective tissue cells. PDGF occurs as a three-disulfide-linked dimer composed of two homologous chains, α and β (1,2). The biological function of PDGF is mediated through binding to two cell surface proteins, PDGF receptors α and ß (35). Binding of PDGF to the extracellular part of either receptor type leads to dimerization of receptor molecules, followed by activation of the receptor protein-tyrosine kinase (6) and generation of phosphorylation-mediated signals that initiate the biological response (7,8).

PDGF has been implicated in the pathogenesis of several non-malignant proliferative diseases including atherosclerosis (2324), fibrosis (25), restenosis following vascular angioplasty (26), giant cell arteritis (27), aseptic loosening (28) and bronchiolitis obliterans syndrome (29). [3]

: malignant pathology : non-malignant pathology : PDGF, platelet derived growth factor : v-sis :
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oncogenes

Alteration of a gene that normally controls cell growth can promote the uncontrolled growth characteristic of cancer. The normal form of the gene is termed a proto-oncogene, and the malignantly transformed gene is termed an oncogene.

Oncogenes: c-Fos : c-Jun : c-Myc : c-Sis : Ras : Rb :
Tumor Suppressor Genes: TP53

Damaged genes are passed down through the cancer cell line, and may be dominant or recessive genes:

Recessive: tumor suppressors, growth suppressors, recessive oncogenes or anti-oncogenes. Malignant transformation can result from genetic damage to genes coding for growth factors, growth factor receptors and/or proteins for signal transduction cascades.

Dominant: Proto-oncogenes participate in a variety of normal cellular functions, but have the potential to tranform into cellular oncogenes when damaged. Proto-oncogenes normally function in the various signal transduction cascades that regulate cell growth, proliferation and differentiation. Cellular proto-oncogenes resident in transforming retroviruses are designated as c- (cellular origin) as opposed to v- (retroviral origin). Oncogenes are malignantly transformed proto-oncogenes - table  Oncogenes Proto-oncogenes

14-3-3 proteins are a family of highly conserved cellular proteins that play key roles in the regulation of central physiological pathways. More than 200 14-3-3 target proteins have been identified, including proteins involved in mitogenic and cell survival signaling, cell cycle control and apoptosic cell death. Importantly, the involvement of 14-3-3 proteins in the regulation of various oncogenes and tumor suppressor genes points to a potential role in human cancer. Tzivion G, Gupta VS, Kaplun L, Balan V. 14-3-3 proteins as potential oncogenes. Semin Cancer Biol. 2006 Jun;16(3):203-13. Epub 2006 Apr 1.

Oncogenes: c-Fos : c-Jun : c-Myc : c-Sis : Ras : Rb :
Tumor Suppressor Genes: TP53
Proto-oncogene/oncogene families ● growth factor genesreceptor tyrosine kinases ( RTKs) ● membrane ssociated non-receptor tyrosine kinases (PTKs) ● G-protein coupled receptors (GPCRs) ● Serine/Threonine Kinases ● nuclear DNA-binding/transcription factors

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