Overexpression of the heat-shock protein 70 is associated to imatinib resistance in chronic myeloid leukemia.

Imatinib is an effective therapy for chronic myeloid leukemia (CML), a myeloproliferative disorder characterized by the expression of the recombinant oncoprotein Bcr-Abl. In this investigation, we studied an imatinib-resistant cell line (K562-r) generated from the K562 cell line in which none of the previously described mechanisms of resistance had been detected. A threefold increase in the expression of the heat-shock protein 70 (Hsp70) was detected in these cells. This increase was not associated to heat-shock transcription factor-1 (HSF-1) overexpression or activation. RNA silencing of Hsp70 decreased dramatically its expression (90%), and was accompanied by a 34% reduction in cell viability. Overexpression of Hsp70 in the imatinib-sensitive K562 line induced resistance to imatinib as detected by a large reduction in cell death in the presence of 1 muM of imatinib. Hsp70 level was also increased in blast cells of CML patients resistant to imatinib, whereas the level remained low in responding patients. Taken together, the results demonstrate that overexpression of Hsp70 can lead to both in vitro and in vivo resistance to imatinib in CML cells. Moreover, the overexpression of Hsp70 detected in imatinib-resistant CML patients supports this mechanism and identifies potentially a marker and a therapeutic target of CML evolution.

Cellular localization of isoprenoid biosynthetic enzymes in Marchantia polymorpha. Uncovering a new role of oil bodies.

Like seed plants, liverworts synthesize and accumulate a myriad of isoprenoid compounds. Using antibodies raised against several isoprenoid biosynthetic enzymes, we investigated their intracellular compartmentation by in situ immunolocalization from Marchantia polymorpha. The enzymes examined were deoxy-xylulose phosphate synthase, geranyl diphosphate synthase, farnesyl diphosphate synthase, geranylgeranyl diphosphate synthase, monoterpene synthase, geranylgeranyl diphosphate reductase, phytoene synthase, and phytoene desaturase. Our results show that liverwort oil bodies, which are organelles bound by a single unit membrane, possess isoprenoid biosynthetic enzymes similar to those found in plastids and the cytosol. We postulate that oil bodies play a dynamic role in cell metabolism in addition to their role as sites of essential oil accumulation and sequestration. The occurrence of such enzymes in different cellular compartments might be due to multiple targeting of gene products to various organelles.

Imaging fluorescence resonance energy transfer between two green fluorescent proteins in living yeast.

We show that fluorescence resonance energy transfer between two mutants of the green fluorescent protein (GFP) can be monitored by imaging microscopy in living yeast. This work is based on the constitutive expression of a GFP-containing fusion protein and the inducible expression of the tobacco etch virus (TEV) protease. In the fusion protein, the P4.3 GFP mutant is linked to the YS65T GFP mutant by a spacer bearing the TEV protease-specific cleavage site.

[Risk factors of vertebral osteoporosis. Results of a study of 2279 women referred to a menopause clinic]. / Facteurs de risque de l'ostéoporose vertébrale. Résultats d'une étude de 2,279 femmes adressées à une consultation de ménopause.

The principal clinical risk factors of osteoporosis were correlated with vertebral bone density measured by biphoton absorptiometry in 2,279 women referred to a menopause clinic. Age, age at puberty, the menopause and how long ago it had occurred, smoking and past history of osteoporosis were negatively and independently correlated with bone density. Early onset of the menopause significantly increased the risk of a low bone density as compared with a natural or surgical menopause occurring after the age of 45. In contrast, estrogen replacement therapy and excess weight decreased this risk after the menopause. Osteoarthrosis and 25 (OH) vit. D3 levels were positively correlated with bone density. These variables taken together in a multiple linear regression model were able to explain only 25 per cent of the variations in bone density between individuals, suggesting the predominant role of other factors not taken into account in our study, notably of a genetic and environmental nature. Before the menopause, none of the factors studied enabled prediction of the risk defined by a low bone density. Among women with one or more clinical risk factors correlated with bone density, 29 per cent in fact had low bone density, as compared with 20 per cent in the absence of such factors. In contrast, 54 per cent of women with a low bone density had no risk factor. The results of this study show that the exception of secondary causes of osteoporosis, the majority of so-called "risk" factors which can be assessed by history have only a minimal influence on bone density.(ABSTRACT TRUNCATED AT 250 WORDS)

Obesity and postmenopausal bone loss: the influence of obesity on vertebral density and bone turnover in postmenopausal women.

This study was undertaken to evaluate the effect of obesity on the postmenopausal bone mass. Bone mineral density, measured by dual photon absorptiometry of the lumbar spine, serum osteocalcin (OC), fasting urinary calcium to creatinine (Ca:Cr), serum estradiol (E2) dehydroepiandrosterone (DHA) and testosterone (T) were measured in 176 women aged 45-71 years. Women were divided into four groups according to their menopausal status and their weight: 49 perimenopausal, 28 obese perimenopausal, 49 obese postmenopausal. Within each population (perimenopausal and postmenopausal), mean age was the same, only weight was significantly different (p less than 0.0001). For the two groups of postmenopausal women mean interval since menopause (YSM) was the same (5.8 +/- 3 and 5.4 +/- 5 yr). Comparison between groups revealed a significant effect of menopausal status and obesity on BMD and bone turnover. As compared to perimenopausal women, BMD was lower, OC and Ca: Cr higher only in nonobese-postmenopausal women. E2, T, DHA did not differ between the two groups of postmenopausal women. The results of this study suggest that even moderate obesity can play a protective role on postmenopausal bone loss.

A New Method for the Screening of Mutations Related to Protoplasmic Incompatibility, Differentiation and Plasma Membrane in the Fungus PODOSPORA ANSERINA.

In Podospora anserina previous investigations showed that mutations in genes involved in the control of protoplasmic incompatibility cause defects at various stages of differentiation during the life cycle and also modify properties of the plasma membrane. To establish these relationships in another way, a new method for screening mutations has been developed as a first step. Eighty-five new mutants were selected for resistance to toxic products (sorbose or thiourea); in a second step these mutants were tested for modifications of protoplasmic incompatibility and cellular differentiation. Seven of the sorbose or thiourea resistant-mutants (i.e., 8%) exhibited new patterns of protoplasmic incompatibility. Genetic analyses were carried out with three mutants. Mutation X25 suppresses protoplasmic incompatibility resulting from all allelic interactions and restores the fertility of the crosses female symbol Vx male symbol V1 and female symbol Z1 x male symbol Z2. Mutation V41 is an allele of the v locus with new properties. Mutation X61 totally suppresses the V/V'1 interaction and weakens all of the other allelic incompatibility systems; X61 strains are defective in protoperithecia differentiation. Electrophoresis of plasma membrane proteins showed that X61 strains lack two polypeptides whose apparent molecular weights are 41,000 and 44,000. This new screening method is especially efficient for obtaining new mutants and identifying additional genes involved in incompatibility. These results provide further support demonstrating the relationships between protoplasmic incompatibility, cellular differentiation and plasma membrane.