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T-cell protein tyrosine phosphatase (TC-PTP, encoded by PTPN2) is a nonreceptor PTP that is most highly expressed in hematopoietic tissues. TC-PTP modulates a variety of physiological functions including cell cycle progression, cell survival and proliferation, and hematopoiesis through tyrosine
Dual-specificity phosphatase 5 (DUSP5), which regulates the duration and magnitude of ERK1/2 phosphoactivation within the mitogen-activated protein kinase (MAPK) cascade, has recently been proposed to be a tumor suppressor. However, the epigenetic regulation of DUSP5 and its critical roles in
Nodularin and microcystin-LR are cyanobacterial toxins and environmental hazards. Nodularin inhibits protein phosphatases 1 and 2A with the same potency as does microcystin-LR, which has recently been identified as a potent tumor promoter in rat liver. Our results suggested that nodularin is also a
Oval cells isolated from livers of carcinogen-treated rats have morphologic and biochemical features of immature hepatocytes but seem to lack glucose-6-phosphatase (G6Pase) activity. The authors reinvestigated this question using histochemical methods for visualization of G6Pase activity by light
We previously reported that deficiency in the gene encoding the catalytic subunit of protein phosphatase 6 (Ppp6c) predisposes mouse skin tissue to papilloma formation initiated by DMBA. Here, we demonstrate that Ppp6c loss acts as a tumor promoter in UVB-induced squamous cell carcinogenesis.
The effects of the hepatocarcinogenic peroxisome proliferating hypolipidemic agents clofibrate (CF) and nafenopin (NF) on rat liver carcinogenesis initiated by N-2-fluorenylacetamide (FAA) were studied and compared with that of the neoplasm promoter phenobarbital (PB). Male F344 rats were fed 0.02%
The model carcinogen 4-nitroquinoline 1-oxide (4-NQO) has historically been characterized as "UV-mimetic" with respect to its genotoxic properties. However, recent evidence indicates that 4-NQO, unlike 254-nm UV light, may exert significant cytotoxic and/or mutagenic potential via the generation of
Protein phosphatase 2A (PP2A) is a serine-threonine phosphatase that regulates cell signaling pathways. Its inactivation is correlated with tumor malignancy, possibly due to the effects on cell differentiation and malignant cell transformation. Therefore, it has been noted that PP2A could be a
Both benign and malignant thyroid disease are well-established components of Cowden syndrome (CS), an autosomal dominant disorder characterized by multiple hamartomas and breast cancer that may be considered a phakomatosis. The susceptibility gene for CS is PTEN, a tumor suppressor gene on 10q23.3
Increased phosphorylation in cancers can stimulate growth and up-regulate certain receptors. To test whether the functional response of phosphatase receptors is up-regulated during carcinogenesis, we examined the effects of ligands on net phosphorylation in isolated membranes derived from hamster
Squamous cell carcinomas were induced in the hamster cheek pouch with 9,10-dimethyl-1,2-benzanthracene. The process of carcinogenesis was inhibited by phenylphosphate, an inducer of alkaline phosphatase. Orthophosphate and l-phenylalanine, which inhibit alkaline phosphatase, had a promoting effect
Alkaline phosphatase (AP) activity was not detectable by histochemical staining in the glandular stomachs of normal rats. However, AP activity was present at high levels in the brush borders of the intestine and persisted after fixation of the tissues in Formalin at room temperature. Foci of AP
Many mitogens and human oncogenes activate extracellular regulated kinases (ERKs), which in turn convey proliferation signals. ERKs or mitogen-activated protein (MAP) kinases are inactivated in vitro by MAP kinase phosphatases (MKPs). The gene encoding one of these MKPs, MKP-1, is a serum-inducible
We recently isolated the r-PTPeta gene, which encodes a receptor-type tyrosine phosphatase protein that suppresses the neoplastic phenotype of retrovirally transformed rat thyroid cells. The human homologue gene PTPRJ/DEP-1 is deleted in various tumors. Moreover, the Gln276Pro polymorphism, located
The expression of phosphatase and tensin homolog (PTEN), a tumor suppressor gene, is frequently down-regulated in gastric carcinomas due to mutation, loss of heterozygosity, and promoter hypermethylation. However, it is unknown if additional mechanisms may account for the down-regulation of PTEN