We further found that

estrogen receptor alpha (ERα) could up-regulate PTPRO expression as a transcription factor. Moreover, an in vitro study showed that cell proliferation was inhibited and apoptosis was promoted in PTPRO-transduced HCC cell lines, whereas an in vivo study represented that tumor number and size was increased in ptpro−/− mice. As a result of its tumor-suppressive position, PTPRO was proved to down-regulate signal transducers and activators of transcription (STAT3) activity dependent on Janus kinase 2 (JAK2) and phosphoinositide 3-kinase (PI3K) dephosphorylation. Conclusions: PTPRO expression results in pathological deficiency and gender bias in HCC, which could be attributed to ERα regulation. The suppressive role of PTPRO in HCC could be ascribed Ixazomib clinical trial to STAT3 inactivation. (HEPATOLOGY 2013)

Protein tyrosine phosphatase receptor type O (PTPRO), one of the receptor types of phosphotyrosine phosphatases (PTP), was initially discovered in human renal glomerulus.1 It contains six isoforms; the full-length type is expressed in kidney, brain, lung, liver, and breast, whereas the truncated types are expressed in macrophages and B lymphocytes.2 PTPRO is a transmembrane protein; its intracellular region contains a PTP domain that catalyzes the dephosphorylation of tyrosine peptides. This critical function of PTPs is involved in numerous intracellular signaling events that Y-27632 serve various biological behaviors, such as cell proliferation, differentiation, apoptosis, and so forth.3, 4 Recently, an accumulation of evidence has enriched the understanding of cancer biology, and it has been observed that PTPRO exhibits important

aspects concerning tumor suppression. Initially, it was discovered that overexpression of PTPRO enhances apoptosis of the terminally differentiated leukemic cell line, U937, in the presence of 12-O-tetradecanoylphorbol-13-acetate.5 Subsequently, the PTPRO level was shown to be statistically weakened; the promoter region of the gene, ptpro, is frequently methylated in human chronic leukemia, lung cancer, breast cancer, hepatocellular carcinoma (HCC), and so forth.6-10 In support of the role of PTPRO as a tumor suppressor, it was this website demonstrated that PTPRO could inhibit cell proliferation in lung cancer cell line A549.8 Additionally, it has been revealed that PTPRO expression can be suppressed by estrogen receptor β (ERβ) in breast cancer. Using an in vitro study, it was demonstrated that ERβ, conjugated with 17β-estradiol (E2), functions at the AP-1 (activator protein 1) site located in the promoter region of ptpro, giving rise to the separation of c-jun and c-fos from AP-1 and leading to the inhibition of ptpro transcription.9 Human HCC, one of the most malignant cancers in the world, is closely associated with a history of chronic hepatitis caused by hepatitis B or C virus (HBV or HCV).11, 12 The global incidence of clinical HCC exhibits a striking gender disparity and occurs much more frequently in male patients.