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Many patients with chronic hepatitis caused by hepatitis C virus (HCV) infection develop liver fibrosis with high risk for hepatocellular carcinoma (HCC), but the mechanism underling this process is unclear. Conversely, transforming growth factor beta (TGF-␤) activates not only TGF-␤ type I receptor (T␤RI) but also c-Jun N-terminal kinase (JNK), which convert the mediator Smad3 into two distinctive phosphoisoforms: C-terminally phosphorylated Smad3 (pSmad3C) and linker-phosphorylated Smad3 (pSmad3L). Whereas the T␤RI/pSmad3C pathway suppresses epithelial cell growth by upregulating p21 WAF1 transcription, JNK/pSmad3L-mediated signaling promotes extracellular matrix deposition, partly, by upregulating plasminogen activator inhibitor 1 (PAI-1). We studied the domain-specific Smad3 phosphorylation in biopsy specimens representing chronic hepatitis, cirrhosis, or HCC from 100 patients chronically infected with HCV, and correlated Smad3 phosphorylation with clinical course. As HCV-infected livers progressed from chronic hepatitis through cirrhosis to HCC, hepatocytic pSmad3L/PAI-1 increased with fibrotic stage and necroinflammatory grade, and pSmad3C/p21 WAF1 decreased.

A direct borylation of aryl halides or triflates with dialkoxyborane was investigated. The coupling reaction of pinacolborane with aryl halides or triflates in the presence of a catalytic amount of PdCl(2)(dppf) together with a base provided arylboronates in high yields. The product distributions were strongly dependent on the base employed, and the tertiary amine, especially Et(3)N, was effective for the selective formation of the boron-carbon bond. The reaction conditions were so mild that arylboronates having a variety of functional groups such as carbonyl, cyano, and nitro groups were readily prepared.

Tetrakis(methoxo)- or bis(pinacolato)diboron [(RO)2BB(OR)2; (RO)2 = (MeO)2 (4a) and Me4C2O2 (1)] added to both terminal and internal alkynes in the presence of a catalytic amount of Pt(PPh3)4 to provide stereodefined cis-bis(boryl)alkenes (3) in excellent yields. Because reagents and reaction conditions were sufficiently mild, the procedure was readily extended to various functionalized alkynes. Mechanistic study revealed that the oxidative addition of bis(pinacolato)diboron (1) to Pt(PPh3)4 generates cis-Pt(BO2C2Me4)2(PPh3)2 (5), whose structure was fully characterized by multinuclear NMR spectroscopies as well as single-crystal X-ray diffraction analysis. Complex 5 exhibited high reactivity for insertion to the alkyne giving 3 in high yields, thus implying that the oxidative addition of the B−B bond to a Pt(0) complex is an initial step in the platinum(0)-catalyzed diboration of alkynes.

Transforming growth factor

H epatocellular carcinoma (HCC) is the fifth most common cancer worldwide and one of the most deadly, causing approximately 600,000 deaths yearly. 1 The overall incidence of HCC continues to rise, especially in western Europe and the United States. 2 During the past 20 years, striking advances have enhanced our understanding of HCC. More than 85% of HCC cases are related to known hepatitis B virus (HBV) and hepatitis C virus (HCV).

Cancer cells often gain advantage by reducing the tumorsuppressive activity of transforming growth factor-B (TGF-B) together with stimulation of its oncogenic activity as in Ras-transformed cells; however, molecular mechanisms remain largely unknown. TGF-B activates both its type I receptor (TBRI) and c-Jun NH 2 -terminal kinase (JNK), which phosphorylate Smad2 and Smad3 at the COOH-terminal (pSmad2/3C) and linker regions (pSmad2/3L). Here, we report that Ras transformation suppresses TBRI-mediated pSmad3C signaling, which involves growth inhibition by down-regulating c-Myc. Instead, hyperactive Ras constitutively stimulates JNK-mediated pSmad2/3L signaling, which fosters tumor invasion by up-regulating plasminogen activator inhibitor-1 and matrix metalloproteinase-1 (MMP-1), MMP-2, and MMP-9. Conversely, selective blockade of linker phosphorylation by a mutant Smad3 lacking JNK-dependent phosphorylation sites results in preserved tumor-suppressive function via pSmad3C in Ras-transformed cells while eliminating pSmad2/ 3L-mediated invasive capacity. Thus, specific inhibition of the JNK/pSmad2/3L pathway should suppress cancer progression by shifting Smad-dependent signaling from oncogenesis to tumor suppression. [Cancer Res 2007;67(11):5090-6]

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