No abstract

SUMMARY The human gene PTPN11, which encodes the tyrosine phosphatase Shp2, may act as a proto-oncogene, as dominantly activating mutations have been detected in several types of leukemia. Herein we report a tumor suppressor function of Shp2. Hepatocyte-specific deletion of Shp2 promotes inflammatory signaling through the Stat3 pathway and hepatic inflammation/necrosis, resulting in regenerative hyperplasia and development of tumors in aged mice. Furthermore, Shp2 ablation dramatically enhanced diethylenenitrite (DEN)-induced hepatocellular carcinoma (HCC) development, which was abolished by concurrent deletion of Shp2 and Stat3 in hepatocytes. Decreased Shp2 expression was detected in a sub-fraction of human HCC specimens. Thus, in contrast to the leukemogenic effect of dominant active mutants, PTPN11/Shp2 has a tumor suppressor function in liver.

DNA arrays of the entire set of Escherichia coli genes were used to measure the genomic expression patterns of cells growing in late logarithmic phase on minimal glucose medium and on Luria broth containing glucose. Ratios of the transcript levels for all 4,290E. coli protein-encoding genes (cds) were obtained, and analysis of the expression ratio data indicated that the physiological state of the cells under the two growth conditions could be ascertained. The cells in the rich medium grew faster, and expression of the majority of the translation apparatus genes was significantly elevated under this growth condition, consistent with known patterns of growth rate-dependent regulation and increased rate of protein synthesis in rapidly growing cells. The cells grown on minimal medium showed significantly elevated expression of many genes involved in biosynthesis of building blocks, most notably the amino acid biosynthetic pathways. Nearly half of the known RpoS-dependent genes were expressed at significantly higher levels in minimal medium than in rich medium, and rpoS expression was similarly elevated. The role of RpoS regulation in these logarithmic phase cells was suggested by the functions of the RpoS dependent genes that were induced. The hallmark features of E. coli cells growing on glucose minimal medium appeared to be the formation and excretion of acetate, metabolism of the acetate, and protection of the cells from acid stress. A hypothesis invoking RpoS and UspA (universal stress protein, also significantly elevated in minimal glucose medium) as playing a role in coordinating these various aspects and consequences of glucose and acetate metabolism was generated. This experiment demonstrates that genomic expression assays can be applied in a meaningful way to the study of whole-bacterial-cell physiology for the generation of hypotheses and as a guide for more detailed studies of particular genes of interest.

In contrast to the tumor suppressor effect of SULF1, SULF2 has an oncogenic effect in HCC mediated in part through up-regulation of FGF signaling and GPC3 expression.

Liver cirrhosis is a predominant risk factor for hepatocellular carcinoma (HCC). However, the mechanism underlying the progression from cirrhosis to HCC remains unclear. Herein we report the concurrent increase of liver progenitor cells (LPCs) and transforming growth factor‐β (TGF‐β) in diethylnitrosamine (DEN)‐induced rat hepatocarcinogenesis and cirrhotic livers of HCC patients. Using several experimental approaches, including 2‐acetylaminofluorene/partial hepatectomy (2‐AAF/PHx) and 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine (DDC)‐elicited murine liver regeneration, we found that activation of LPCs in the absence of TGF‐β induction was insufficient to trigger hepatocarcinogenesis. Moreover, a small fraction of LPCs was detected to coexpress tumor initiating cell (T‐IC) markers during rat hepatocarcinogenesis and in human HCCs, and TGF‐β levels were positively correlated with T‐IC marker expression, which indicates a role of TGF‐β in T‐IC generation. Rat pluripotent LPC‐like WB‐F344 cells were exposed to low doses of TGF‐β for 18 weeks imitating the enhanced TGF‐β expression in cirrhotic liver. Interestingly, long‐term treatment of TGF‐β on WB‐F344 cells impaired their LPC potential but granted them T‐IC properties including expression of T‐IC markers, increased self‐renewal capacity, stronger chemoresistance, and tumorigenicity in NOD‐SCID mice. Hyperactivation of Akt but not Notch, signal transducer and activator of transcription 3 (STAT3), or mammalian target of rapamycin (mTOR) was detected in TGF‐β‐treated WB‐F344 cells. Introduction of the dominant‐negative mutant of Akt significantly attenuated T‐IC properties of those transformed WB‐F344 cells, indicating Akt was required in TGF‐β‐mediated‐generation of hepatic T‐ICs. We further demonstrate that TGF‐β‐induced Akt activation and LPC transformation was mediated by microRNA‐216a‐modulated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) suppression. Conclusion: Hepatoma‐initiating cells may derive from hepatic progenitor cells exposed to chronic and constant TGF‐β stimulation in cirrhotic liver, and pharmaceutical inhibition of microRNA‐216a/PTEN/Akt signaling could be a novel strategy for HCC prevention and therapy targeting hepatic T‐ICs. (HEPATOLOGY 2012;56:2255–2267)

Escherichia coli KO11 (parent) and LY01 (mutant) have been engineered for the production of ethanol. Gene arrays were used to identify expression changes that occurred in the mutant, LY01, during directed evolution to improve ethanol tolerance (defined as extent of growth in the presence of added ethanol). Expression levels for 205 (5%) of the ORFs were found to differ significantly (p < 0.10) between KO11 and LY01 under each of six different growth conditions (p < 0.000001). Statistical evaluation of differentially expressed genes according to various classification schemes identified physiological areas of importance. A large fraction of differentially expressed ORFs were globally regulated, leading to the discovery of a nonfunctional fnr gene in strain LY01. In agreement with a putative role for FNR in alcohol tolerance, increasing the copy number of fnr(+) in KO11(pGS196) decreased ethanol tolerance but had no effect on growth in the absence of ethanol. Other differences in gene expression provided additional clues that permitted experimentation. Tolerance appears to involve increased metabolism of glycine (higher expression of gcv genes) and increased production of betaine (higher expression of betIBA and betT encoding betaine synthesis from choline and choline uptake, respectively). Addition of glycine (10 mM) increased ethanol tolerance in KO11 but had no effect in the absence of ethanol. Addition of betaine (10 mM) increased ethanol tolerance by over 2-fold in both LY01 and KO11 but had no effect on growth in the absence of ethanol. Both glycine and betaine can serve as protective osmolytes, and this may be the basis of their beneficial action. In addition, the marAB genes encoding multiple antibiotic resistance proteins were expressed at higher levels in LY01 as compared to KO11. Interestingly, overexpression of marAB in KO11 made this strain more ethanol-sensitive. Overexpression of marAB in LY01 had no effect on ethanol tolerance. Increased expression of genes encoding serine uptake (sdaC) and serine deamination (sdaB) also appear beneficial for LY01. Addition of serine increased the growth of LY01 in the presence and absence of ethanol but had no effect on KO11. Changes in the expression of several genes concerned with the synthesis of the cell envelope components were also noted, which may contribute to increased ethanol tolerance.

No abstract

Cyclin G1 deficiency is associated with reduced incidence of carcinogen-induced hepatocellular carcinoma (HCC), but its function in HCC progression remains obscure. We report a critical role of cyclin G1 in HCC metastasis. Elevated expression of cyclin G1 was detected in HCCs (60.6%), and its expression levels were even higher in portal vein tumor thrombus. Clinicopathological analysis revealed a close correlation of cyclin G1 expression with distant metastasis and poor prognosis of HCC. Forced expression of cyclin G1 promoted epithelial-mesenchymal transition (EMT) and metastasis of HCC cells in vitro and in vivo. Cyclin G1 overexpression enhanced Akt activation through interaction with p85 (regulatory subunit of phosphoinositide 3-kinase [PI3K]), which led to subsequent phosphorylation of glycogen synthase kinase-3b (GSK-3b) and stabilization of Snail, a critical EMT mediator. These results suggest that elevated cyclin G1 facilitates HCC metastasis by promoting EMT via PI3K/Akt/GSK-3b/Snail-dependent pathway. Consistently, we have observed a significant correlation between cyclin G1 expression and p-Akt levels in a cohort of HCC patients, and found that combination of these two parameters is a more powerful predictor of poor prognosis. Conclusions: Cyclin G1 plays a pivotal role in HCC metastasis and may serve as a novel prognostic biomarker and therapeutic target.