Search

Hepatocellular carcinoma (HCC) is the most prevalent primary liver malignancy and is a major cause of cancer-related mortality in the world. This study aimed to characterize glutamine amino acid transporter expression profiles in HCC compared to those of normal liver cells. In vitro and in vivo models of HCC were studied using qPCR, whereas the prognostic significance of glutamine transporter expression levels within patient tumors was analyzed through RNAseq. Solute carrier (SLC) 1A5 and SLC38A2 were targeted through siRNA or gamma-p-nitroanilide (GPNA). HCC cells depended on exogenous glutamine for optimal survival and growth. Murine HCC cells showed superior glutamine uptake rate than normal hepatocytes (p < 0.0001). HCC manifested a global reprogramming of glutamine transporters compared to normal liver: SLC38A3 levels decreased, whereas SLC38A1, SLC7A6, and SLC1A5 levels increased. Also, decreased SLC6A14 and SLC38A3 levels or increased SLC38A1, SLC7A6, and SLC1A5 levels predicted worse survival outcomes (all p < 0.05). Knockdown of SLC1A5 and/or SLC38A2 expression in human Huh7 and Hep3B HCC cells, as well as GPNA-mediated inhibition, significantly decreased the uptake of glutamine; combined SLC1A5 and SLC38A2 targeting had the most considerable impact (all p < 0.05). This study revealed glutamine transporter reprogramming as a novel hallmark of HCC and that such expression profiles are clinically significant. [ABSTRACT FROM AUTHOR]

The epidermal growth factor receptor (EGFR) was recently identified as a signal transducer of G protein-coupled receptors (GPCRs). In this study, we have examined the contribution of EGFR transactivation to the growth-promoting effect of GPCRs on vascular smooth muscle cells. Activation of the [G.sub.q]-coupled ANG II receptor or [G.sub.i]-coupled lysophosphatidic acid receptor resulted in increased tyrosine phosphorylation and activation of EGFR. Specific inhibition of EGFR kinase activity by tyrphostin AG-1478 or expression of a dominant-negative EGFR mutant abolished this response. Importantly, inhibition of EGFR function strongly attenuated the global stimulation of protein synthesis by GPCR agonists in vitro in cultured aortic smooth muscle cells and in vivo in the rat aorta and in small resistance arteries. The growth inhibition was associated with a marked reduction of extracellular signal-regulated kinase and phosphoinositide 3-kinase pathway activity and the resulting suppression of eukaryotic translation initiation factor 4E and 4E binding protein 1 phosphorylation. Our results demonstrate that EGFR transactivation is a physiologically relevant action of GPCRs linked to translational control and protein synthesis. smooth muscle cell; translation; signal transduction; epidermal growth factor

A study was conducted to examine the regulation of the acute phase response in vivo by analyzing the influence of pentoxifylline (PX) treatment in rats after an intravenous injection of Escherichia coli. Total RNA was determined from the liver single radial diffusion was carried out to determine albumin plasma levels. Results indicated that PX increased animal survival in lethal frameworks of infection and effective blocks LPS fever.

The role of insulin or insulin-like growth factor 1 (IGF-1) in the regulation of protein synthesis and degradation in the epitrochlearis was compared and contrasted after the administration of live Escherichia coli in the blood. The effects of the insulin and IGF-1 on skeletal muscle protein metabolism during the anorexic, hypermetabolic and recovery phases of the immunological response to bacteremia were analyzed. The findings suggest that defective protein synthesis and degradation were caused by an infectious attack independent of the nutritional state of the epitrochlearis.

Protein synthesis is known to decrease during sepsis as a result of altered translational control and a defect in peptide-chain initiation. Interleukin-1 (IL-1) has been suggested to mediate the effects of sepsis on protein metabolism by causing a reduction in skeletal muscle protein synthesis. In a study of septic rats, injection of an IL-1 antagonist (IL-1a) blocked sepsis-induced inhibition of protein synthesis in the gastrocnemius. Ribosome analysis revealed that IL-1a prevented increases in 40s and 60S ribosomal subunits but had no effect on the epsilon-subunit of eukaryotic initiation factor 2B (eIF-2Bepsilon) protein, suggesting the correlation of the inhibition of protein synthesis with eIF-2Bepsilon expression.

Expression of the beta and epsilon subunits of eukaryotic initiation factor 2B (eIF-2B) in the gastrocnemius decreases during sepsis in rats. The lowered expression of eIF-2B is responsible for a decrease in protein synthesis in skeletal muscles with fast-twitch fibers. Decrease in the expression of the epsilon subunit correlates to a decrease in its mRNA level. Expression of eIF-2B-epsilon in the heart is, however, unaffected. Compounds such as amrinone that prevent the sepsis-induced suppression of protein synthesis in gastrocnemius maintain normal expression of eIF-2B.

Abstract Background The Ras-dependent ERK1/2 MAP kinase signaling pathway plays a central role in cell proliferation control and is frequently activated in human colorectal cancer. Small-molecule inhibitors of MEK1/MEK2 are therefore viewed as attractive drug candidates for the targeted therapy of this malignancy. However, the exact contribution of MEK1 and MEK2 to the pathogenesis of colorectal cancer remains to be established. Methods Wild type and constitutively active forms of MEK1 and MEK2 were ectopically expressed by retroviral gene transfer in the normal intestinal epithelial cell line IEC-6. We studied the impact of MEK1 and MEK2 activation on cellular morphology, cell proliferation, survival, migration, invasiveness, and tumorigenesis in mice. RNA interference was used to test the requirement for MEK1 and MEK2 function in maintaining the proliferation of human colorectal cancer cells. Results We found that expression of activated MEK1 or MEK2 is sufficient to morphologically transform intestinal epithelial cells, dysregulate cell proliferation and induce the formation of high-grade adenocarcinomas after orthotopic transplantation in mice. A large proportion of these intestinal tumors metastasize to the liver and lung. Mechanistically, activation of MEK1 or MEK2 up-regulates the expression of matrix metalloproteinases, promotes invasiveness and protects cells from undergoing anoikis. Importantly, we show that silencing of MEK2 expression completely suppresses the proliferation of human colon carcinoma cell lines, whereas inactivation of MEK1 has a much weaker effect. Conclusion MEK1 and MEK2 isoforms have similar transforming properties and are able to induce the formation of metastatic intestinal tumors in mice. Our results suggest that MEK2 plays a more important role than MEK1 in sustaining the proliferation of human colorectal cancer cells.