Betacellulin, a member of the epidermal growth factor family, has been identified in the conditioned medium of cell lines derived from mouse pancreatic beta cell tumors. Betacellulin is a 32-kilodalton glycoprotein that appears to be processed from a larger transmembrane precursor by proteolytic cleavage. The carboxyl-terminal domain of betacellulin has 50 percent sequence similarity with that of rat transforming growth factor alpha. Betacellulin is a potent mitogen for retinal pigment epithelial cells and vascular smooth muscle cells.

Increasing evidence has indicated that perturbation of cyclins is one of the major factors leading to cancer. The aim of this study was not only to investigate various cell cycle-related kinase activities in hepatocellular carcinoma (HCC), but also to analyze the difference of cell cycle-related kinase activity levels between hepatitis C virus (HCV)-induced HCC and HCVinduced cirrhosis. The protein levels of cyclins D1, E, A, and H, and of cyclin dependent kinase 1 (Cdk1), Cdk2, Cdk4, Cdk6, and Cdk7 in HCC and in surrounding nontumorous cirrhosis were determined by Western blot. The enzymatic activities of cyclins D1, E, A, Cdk1, Cdk4, Cdk6, Cdk7, and Wee1 were measured using in vitro kinase assays. Protein levels and kinase activities of cyclin D1, Cdk4, cyclin E, cyclin A, and Wee1 were significantly elevated in HCC compared with surrounding cirrhotic tissues. The enhanced cyclin D1-related kinase activity in HCC was accompanied by the up-regulation of Cdk4 activity, but not Cdk6 activity. The kinase activities of Cdk6, Cdk7, and Cdk1 did not differ between HCC and surrounding cirrhotic tissues. In addition, the protein levels and kinase activities of cyclin D1, Cdk4, and cyclin E were higher in poorly differentiated HCC and advanced HCC. In conclusion, the increases of cyclin D1, Cdk4, cyclin E, cyclin A, and Wee1 play an important role in the development of HCC from cirrhosis. Cyclin D1, Cdk4, and cyclin E activation may be closely related to the histopathologic grade and progression of HCC. R ecent studies, including our research, have revealed that the deranged expression of cell cyclerelated proteins is one of the major factors contributing to hepatocellular carcinoma (HCC) development. 1-6 Here we investigated biochemical differences of various cell cycle-related kinase activities and protein levels in cirrhosis and HCC.Specific cyclin/cyclin-dependent kinase (Cdk) complexes are activated at different intervals during the cell cycle. 7-15 Cyclin D1/Cdk4 and cyclin D1/Cdk6 are activated in mid-G1 (Fig. 1, phase 1), whereas cyclin E/Cdk2 complexes are required for the G1/S transition (Fig. 1, phase 2), cyclin A/Cdk2 for the progression of DNA synthesis (Fig. 1, phase 3), and cyclin A-B/Cdk1 for the G2/M transition (Fig. 1, phase 4) of mitosis. The activation of cyclin D1/Cdk4 and cyclin D1/Cdk6 complexes at mid-G1 is responsible for the phosphorylation of retinoblastoma protein (pRb), and 2 Rb related proteins, p107, and p130. Members of the pRb family form complexes with transcription factors of the E2F family. 16 This interaction with pRb family members blocks the transcriptional activity of E2Fs; the complexes formed also function as active transcriptional repressor complexes at the promoters of some cell cycle genes. Phosphorylation of the pRb family inhibits the interaction with E2F family transcription factor and permits the expression of genes necessary for S-phase entry (cyclin A, proliferating cell nuclear antigen, and so on). 17 The expression of cyclins E and A at mid-to late-G1 permits the form...

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Amplification found in a number of cyclin genes, especially in cyclin D and E, is an important event process that takes place in cancers, including hepatocellular carcinoma (HCC). The activities of a wide range of cell cycle-related kinases remain obscure in HCC. The purpose of the present study is to determine the cyclins and kinase activities of HCC in Long-Evans Cinnamon (LEC) rats. Cyclin D1, E, A, H, Cdk1(cyclin-dependent kinase; Cdc2), Cdk4, and Cdk6 protein levels were determined by Western blot analysis at different pathologic stages of liver tissues exhibiting HCC. Enzymatic activities of cyclin D1, E, A, Cdk4, Cdk6, Cdc2, Cdk7, and Wee1 kinase were measured by in-gel kinase assay. Protein levels and kinase activities of cyclin D1, E, Cdk4, cyclin A, and Wee1 increased proportionally with the development of HCC, especially in the transition process from chronic hepatitis to HCC. Although Cdc2 kinase activity was found to increase slightly from normal liver to chronic hepatitis, its activity remained unchanged in the process from chronic hepatitis to HCC. Cdk6 and Cdk7 activities remained unchanged in the process from normal liver to HCC. These data suggest that the increase in Cdc2 kinase may play a role in the process from normal liver to chronic hepatitis, whereas the predominant increase in cyclin D1, Cdk4, cyclin E, cyclin A, and Wee1 suggests involvement not only in the process from normal liver to chronic hepatitis, but also during transition into HCC. (HEPATOLOGY 2000;32:711-720.)The inbred strain of Long-Evans Cinnamon (LEC) rats was established from the closed colony of Long Evans rats. 1 These rats exhibit severe acute liver damage with jaundice spontaneously at the age of 4 to 5 months, leading to fulminant hepatic failure in more than 50%. The rats usually survive chronic hepatitis and within a year develop cholangiofibrosis and hepatocellular carcinoma (HCC). [2][3][4][5] Because the natural history of liver disease in LEC rats resembles that of human liver disease in which HCC follows persistent chronic liver disease, LEC rats are regarded as one of the most useful animal models of HCC. 3 Hitherto, little is known about the mechanism that leads to the progression of HCC. Recently, it has been known that changes do occur that alter the cell cycle of related proteins during the malignant transformation process. [6][7][8][9] Because cyclins are prime cell regulating events leading to proliferation in animal cells, the deranged expression of different cyclins may also be the key to carcinogenesis in LEC rats.We have previously reported on the importance of protein phosphorylation in signal transduction in relation to proliferation, differentiation, and carcinogenesis of hepatocytes. [10][11][12][13] Most cell cycle-related proteins show phosphorylation enzymatic activity contributing to cell cycle transition. 6,14-16 Cyclins and their catalytic subunit, the cell-dependent kinases, play key roles in the regulation of animal cell cycle events. 14 Progress of cells through the cycle is governed b...

Protein drugs have great potential as targeted therapies, yet their application suffers from several drawbacks, such as instability, short half‐life, and adverse immune responses. Thus, protein delivery approaches based on stimuli‐responsive nanocarriers can provide effective strategies for selectively enhancing the availability and activation of proteins in targeted tissues. Herein, polymeric micelles with the ability of encapsulating proteins are developed via concurrent ion complexation and pH‐cleavable covalent bonding between proteins and block copolymers directed to pH‐triggered release of the protein payload. Carboxydimethylmaleic anhydride (CDM) is selected as the pH‐sensitive moiety, since the CDMamide bond is stable at physiological pH (pH 7.4), while it cleaves at pH 6.5, that is, the pathophysiological pH of tumors and inflammatory tissues. By using poly(ethylene glycol)‐poly(l‐lysine) block copolymers having 45% CDM addition, different proteins with various sizes and isoelectric points are loaded successfully. By using myoglobin‐loaded micelles (myo/m) as a model, the stability of the micelles in physiological conditions and the dissociation and release of functional myoglobin at pH 6.5 are successfully confirmed. Moreover, myo/m shows extended half‐life in blood compared to free myoglobin and micelles assembled solely by polyion complex, indicating the potential of this system for in vivo delivery of proteins.