The farnesyltransferase inhibitor FTI-277 suppresses the 24-kDa FGF2-induced radioresistance in HeLa cells expressing wild-type RAS.

In this paper, we describe the effect of the inhibitor of farnesyltransferase (FTI-277) on radioresistance induced by the 24-kDa isoform of FGF2 in human cells expressing wild-type RAS. Treatment with FTI-277 (20 microM) for 48 h prior to irradiation led to a significant decrease in survival of radioresistant cells expressing the 24-kDa isoform (HeLa 3A) but had no effect on the survival of control cells (HeLa PINA). The radiosensitizing effect of FTI-277 is accompanied by a stimulation of postmitotic cell death in HeLa 3A cells and by a reduction in G(2)/M-phase arrest in both cell types. These results clearly demonstrate that at least one farnesylated protein is involved in the regulation of the radioresistance induced by the 24-kDa isoform of FGF2. Furthermore, the radiation-induced G(2)/M-phase arrest is also under the control of farnesylated protein. This work also demonstrates that FTase inhibitors may be effective radiosensitizers of certain human tumors with wild-type RAS.     

Combination of the novel farnesyltransferase inhibitor RPR130401 and the geranylgeranyltransferase-1 inhibitor GGTI-298 disrupts MAP kinase activation and G(1)-S transition in Ki-Ras-overexpressing transformed adrenocortical cells.

To test the Kirsten-Ras (Ki-Ras) alternative prenylation hypothesis in malignant transformation, we used a novel farnesyltransferase inhibitor competitive to farnesyl-pyrophosphate, RPR130401, and a CaaX peptidomimetic geranylgeranyltransferase-1 inhibitor GGTI-298. In Ki-Ras-overexpressing transformed adrenocortical cells, RPR130401 at 1-10 microM inhibited very efficiently the [(3)H]farnesyl but not [(3)H]geranylgeranyl transfer to Ras. However, proliferation of these cells was only slightly sensitive to RPR130401 (IC(50)=30 microM). GGTI-298 inhibited the growth of these cells with an IC(50) of 11 microM but cell lysis was observed at 15 microM. The combination of 10 microM RPR130401 and 10 microM GGTI-298 inhibited efficiently (80%) cell proliferation. These combined inhibitors but not each inhibitor alone blocked the cell cycle in G(0)/G(1) and disrupted MAP kinase activation. Thus, combination of two inhibitors, at non-cytotoxic concentrations, acting on the farnesyl-pyrophosphate binding site of the farnesyltransferase and the CaaX binding site of the geranylgeranyltransferase-1 respectively is an efficient strategy for disrupting Ki-Ras tumorigenic cell proliferation.     

A Penalized Multinomial Approach to Smoothed Estimation of Disease Incidence

Raw estimates of disease rates over a geographical region are frequently quite variable, even though one may reasonably expect adjacent communities to have similar true rates. Smoother estimates are obtained by incorporating a penalty into a multinomial likelihood estimation procedure. For each pair of locations, this penalty increases with the difference between the rates and decreases with the distance between the two sites. The resulting estimates have smaller mean squared error than the raw estimates. Expansions are developed which demonstrate the contributions of the smoothing constant, spatial configuration, risk population and raw estimates to the amount of smoothing. Simulations and an example involving gastric cancer data illustrate the proposed method.     

Developmentally specific effects of the DNA cross-linking agent mitomycin C on phosphoenolpyruvate carboxykinase gene expression in vivo: Correlation with changes in chromatin structure within the promoter region of the gene

Previous studies in our laboratory have demonstrated that genotoxic chemical carcinogens have strong preferential effects on expression of certain inducible genes at nonovertly toxic doses in vivo. The effects of the DNA cross-linking agent and chemotherapy drug, mitomycin C (MMC), on expression of the developmental and hormone-regulated gene, phosphoenolpyruvate carboxykinase (PEPCK), were examined in chick embryo liver in vivo as a function of development and were compared with changes in the chromatin structure of the PEPCK gene promoter. The liver PEPCK gene was fully hormone inducible as early as 8 days of embryonic development but was refractory to MMC until after day 10. This onset of responsiveness to MMC was correlated with qualitative changes in the pattern of DNase I hypersensitive sites (DHS) within the PEPCK promoter. There was also a gradual decrease and then a complete loss of both hormone inducibility and MMC responsiveness between 14 and 17 days of development that was correlated with a quantitative change in the overall DNase sensitivity of the liver PEPCK gene promoter over this period. These results suggest that carcinogen sensitivity of the PEPCK gene is related to its ability to respond to its normal induction signals and that chromatin structure may play a central role in these effects. © 1998 John Wiley & Sons, Inc. J Biochem Mol Toxicol 12: 325–337, 1998     

Phytoplankton community metrics based on absolute and relative abundance and biomass: implications for multivariate analyses

Phytoplankton and water samples were collected at 12 locations along the temperate lowland Rideau River, Ontario, Canada. The stations were visited twice a month from May to September 1998, 1999, and 2000. Phytoplankton communities were quantified based on cell abundance, entity abundance (colonies, filaments or free-living cells) and biomass (converted from biovolume estimates based on cell shape and biometry), and were expressed as absolute and relative values. The resulting phytoplankton dataset was composed of six different metrics. The general objective was to assess which metric best explained the spatial and temporal variability in the phytoplankton communities of the Rideau River in response to fluctuating environmental variables. Relationships between phytoplankton metrics and water quality variables were assessed using canonical correspondence analyses. The absolute cell abundance metric showed the best relationship with water quality, followed by the cell entity metric. The biomass metric showed the poorest relationship with water quality variables, indicating that accounting for cell size does not provide additional information. The data expressed as absolute values were consistently better predictors of water quality compared to relative values.     

Detection of QTL affecting harvest traits in a commercial Atlantic salmon population

Genetic variation in performance and quality traits measured at harvest has previously been demonstrated in Atlantic salmon aquaculture populations. To map major loci underlying this variation, we utilized data from 10 families from a commercial breeding programme. Significant QTL were detected affecting harvest weight and length traits on linkage group 1, and affecting waste weight on linkage group 5. In total, 11 of the 29 linkage groups examined showed at least suggestive evidence for a QTL. These data suggest that major loci affecting economically important harvest characteristics are segregating in commercial salmon populations.     

Ligands for FKBP12 Increase Ca2+ Influx and Protein Synthesis to Improve Skeletal Muscle Function

Rapamycin at high doses (2–10 mg/kg body weight) inhibits mammalian target of rapamycin complex 1 (mTORC1) and protein synthesis in mice. In contrast, low doses of rapamycin (10 μg/kg) increase mTORC1 activity and protein synthesis in skeletal muscle. Similar changes are found with SLF (synthetic ligand for FKBP12, which does not inhibit mTORC1) and in mice with a skeletal muscle-specific FKBP12 deficiency. These interventions also increase Ca²⁺ influx to enhance refilling of sarcoplasmic reticulum Ca²⁺ stores, slow muscle fatigue, and increase running endurance without negatively impacting cardiac function. FKBP12 deficiency or longer treatments with low dose rapamycin or SLF increase the percentage of type I fibers, further adding to fatigue resistance. We demonstrate that FKBP12 and its ligands impact multiple aspects of muscle function.