Effect of simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on alpha-fetoprotein gene expression through interaction with the ras-mediated pathway

Cardiac-specific deletion of FDPS induces cardiac remodeling and dysfunction by enhancing the activity of small GTP-binding proteins

The mevalonate pathway is essential for cholesterol biosynthesis. Previous studies have suggested that the key enzyme in this pathway, farnesyl diphosphate synthase (FDPS), regulates the cardiovascular system. We used human samples and mice that were deficient in cardiac FDPS (c-Fdps^-/- mice) to investigate the role of FDPS in cardiac homeostasis. Cardiac function was assessed using echocardiography. Left ventricles were examined and tested for histological and molecular markers of cardiac remodeling. Our results showed that FDPS levels were downregulated in samples from patients with cardiomyopathy. Furthermore, c-Fdps^-/- mice exhibited cardiac remodeling and dysfunction. This dysfunction was associated with abnormal activation of Ras and Rheb, which may be due to the accumulation of geranyl pyrophosphate. Activation of Ras and Rheb stimulated downstream mTOR and ERK pathways. Moreover, administration of farnesyltransferase inhibitors attenuated cardiac remodeling and dysfunction in c-Fdps^-/- mice. These results indicate that FDPS plays an important role in cardiac homeostasis. Deletion of FDPS stimulates the downstream mTOR and ERK signaling pathways, resulting in cardiac remodeling and dysfunction. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Molecular structure and biological function of alpha-fetoprotein

Mammalian alpha-fetoprotein (AFP) as a fetal specific alpha-globulin has long been used as a serum fetal defect/tumor marker for diagnosis and prediction of liver diseases. In the last decade, clinical and basic research data indicated that AFP acts not only as a biomarker but also as an intracellular signal molecule to play multifarious role in the development of hepatocellular carcinoma.

The promoting molecular mechanism of alpha-fetoprotein on the growth of human hepatoma Bel7402 cell line

AIM: The goal of this study was to characterize the AFP receptor, its possible signal transduction pathway and its proliferative functions in human hepatoma cell line Bel 7402.

METHODS: Cell proliferation enhanced by AFP was detected by MTT assay, ³H-thymidine incorporation and S-stage percentage of cell cycle analysis. With radioactive labeled ¹²⁵I-AFP for receptor binding assay; cAMP accumulation, protein kinase A activity were detected by radioactive immunosorbent assay and the change of intracellular free calcium ([Ca²⁺]_i) was monitored by scanning fluorescence intensity under TCS-NT confocal microscope. The expression of oncogenes N-ras, p53, and p21^ras in the cultured cells in vitro were detected by Northern blotting and Western blotting respectively.

RESULTS: It was demonstrated that AFP enhanced the proliferation of human hepatoma Bel 7402 cell in a dose dependent fashion as shown in MTT assay, ³H-thymidine incorporation and S-phase percentage up to 2-fold. Two subtypes of AFP receptors were identified in the cells with Kds of 1.3 × 10^-9 mol·L^-1 and 9.9 × 10^-8 mol·L^-1 respectively. Pretreatment of cells with AFP resulted in a significant increase (625%) in cAMP accumulation. The activity of protein kinase A activity were increased up to 37.5, 122.6, 73.7 and 61.2% at treatment time point 2, 6, 12 and 24 hours. The level of intracellular calcium were elevated after the treatment of alpha-fetoprotein and achieved to 204% at 4 min. The results also showed that AFP (20 mg·L^-1) could upregulate the expression of N-ras oncogenes and p53 and p21^ras in Bel 7402 cells. In the later case, the alteration were 81.1% (12 h) and 97.3% (12 h) respectively compared with control.

CONCLUSION: These results demonstrate that AFP is a potential growth factor to promote the proliferation of human hepatoma Bel 7402 cells. Its growth-regulatory effects are mediated by its specific plasma membrane receptors coupled with its transmembrane signaling transduction through the pathway of cAMP-PKA and intracellular calcium to regulate the expression of oncogenes.