Counter-regulatory responses to postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia vs surgical and non-surgical control individuals

AIMS/HYPOTHESIS

Post-bariatric hypoglycaemia is an increasingly recognised complication of bariatric surgery, manifesting particularly after Roux-en-Y gastric bypass. While hyperinsulinaemia is an established pathophysiological feature, the role of counter-regulation remains unclear. We aimed to assess counter-regulatory hormones and glucose fluxes during insulin-induced postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia after Roux-en-Y gastric bypass vs surgical and non-surgical control individuals.

METHODS

In this case-control study, 32 adults belonging to four groups with comparable age, sex and BMI (patients with post-bariatric hypoglycaemia, Roux-en-Y gastric bypass, sleeve gastrectomy and non-surgical control individuals) underwent a postprandial hypoglycaemic clamp in our clinical research unit to reach the glycaemic target of 2.5 mmol/l 150-170 min after ingesting 15 g of glucose. Glucose fluxes were assessed during the postprandial and hypoglycaemic period using a dual-tracer approach. The primary outcome was the incremental AUC of glucagon during hypoglycaemia. Catecholamines, cortisol, growth hormone, pancreatic polypeptide and endogenous glucose production were also analysed during hypoglycaemia.

RESULTS

The rate of glucose appearance after oral administration, as well as the rates of total glucose appearance and glucose disappearance, were higher in both Roux-en-Y gastric bypass groups vs the non-surgical control group in the early postprandial period (all p<0.05). During hypoglycaemia, glucagon exposure was significantly lower in all surgical groups vs the non-surgical control group (all p<0.01). Pancreatic polypeptide levels were significantly lower in patients with post-bariatric hypoglycaemia vs the non-surgical control group (median [IQR]: 24.7 [10.9, 38.7] pmol/l vs 238.7 [186.3, 288.9] pmol/l) (p=0.005). Other hormonal responses to hypoglycaemia and endogenous glucose production did not significantly differ between the groups.

CONCLUSIONS/INTERPRETATION

The glucagon response to insulin-induced postprandial hypoglycaemia is lower in post-bariatric surgery individuals compared with non-surgical control individuals, irrespective of the surgical modality. No significant differences were found between patients with post-bariatric hypoglycaemia and surgical control individuals, suggesting that impaired counter-regulation is not a root cause of post-bariatric hypoglycaemia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04334161.

Effects of Aerobic Exercise on Systemic Insulin Degludec Concentrations in People with Type 1 Diabetes

BACKGROUND

There is conflicting evidence on the effect of exercise on systemic insulin concentrations in adults with type 1 diabetes.

METHODS

This prospective single-arm study examined the effect of exercise on systemic insulin degludec (IDeg) concentrations. The study involved 15 male adults with type 1 diabetes (age 30.7 ± 8.0 years, HbA1c 6.9 ± 0.7%) on stable IDeg regimen. Blood samples were collected every 15 minutes at rest, during 60 minutes of cycling (66% VO₂max) and until 90 minutes after exercise termination. IDeg concentrations were quantified using high-resolution mass-spectrometry and analyzed applying generalized estimation equations.

RESULTS

Compared to baseline, systemic IDeg increased during exercise over time (P < .001), with the highest concentrations observed toward the end of the 60-minute exercise (17.9% and 17.6% above baseline after 45 minutes and 60 minutes, respectively). IDeg levels remained elevated until the end of the experiment (14% above baseline at 90 minutes after exercise termination, P < .001).

CONCLUSIONS

A single bout of aerobic exercise increases systemic IDeg exposure in adults on a stable basal IDeg regimen. This finding may have important implications for future hypoglycemia mitigation strategies around physical exercise in IDeg-treated patients.

Multiplexed Assay to Quantify the PP-Fold Family of Peptides in Human Plasma Using Microflow Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Peptide Tyr-Tyr (PYY1-36), pancreatic polypeptide (PP1-36) and neuropeptide Y (NPY1-36) constitute the PP-fold family of peptides that is involved in metabolic regulation. Very low plasma concentrations and cleavage into active 3-36 fragments challenge bioanalytical assays used for the quantification of these peptides.

METHODS

We developed a multiplexed isotopic dilution assay to quantify PYY1-36, PP1-36, and NPY1-36 and their dipeptidyl peptidase-4 (DPP4)-derived metabolites PYY3-36, PP3-36 and NPY3-36. All peptides were immunocaptured from plasma using a monoclonal antibody and quantified by micro-ultra-HPLC-MS/MS. Blood samples from healthy volunteers were collected fasting and 30 min after nutrient stimulation. Method comparison was performed with commercial immunoassays.

RESULTS

Linearity was shown in the measured intervals (r2 > 0.99). The lower limit of quantification (LLOQ) with a CV at 20% was 1.5 pM for PYY1-36 and PYY3-36, 3.0 pM for PP1-36 and PP3-36, 0.8 pM for NPY1-36 and 0.5 pM for NPY3-36. In all cases, intra- and inter-assay bias and imprecision were <21%. Pre-analytical stability required addition of a protease inhibitor cocktail. Physiological concentrations of PYY3-36, NPY3-36, PP1-36 and PP3-36 were above the LLOQ in 43% to 100% of the samples. PYY1-36 and NPY1-36 were above the LLOQ in 9% and 0% of the samples, respectively. Immunoassays showed higher concentrations of measurands and poor agreement when compared with micro-UHPLC-MS/MS.

CONCLUSIONS

The assay allowed for specific multiplexed analysis of the PP-fold family of peptides and their DPP4-cleaved fragments in a single sample, thereby offering new perspectives to study the role and therapeutic potential of these essential peptide hormones in health and metabolic disease.

On the road of dried blood spot sampling for antidoping tests: Detection of GHRP-2 abuse

Dried blood spots (DBSs) sampling is gaining support by the antidoping community because of simplicity and cost-effective characteristics, especially in collection, transport, and storage. Nevertheless, DBS applicability demands specific studies for each of the analytes proposed for testing. Here, GHRP-2 has been selected as a representing member of the growth hormone-releasing peptides (GHRPs) family to provide further evidence of DBS suitability for GHRPs abuse detection in sport testing. An analytical procedure to extract GHRP-2 and its main metabolite (AA-3) from DBS and to detect them by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. The method has been validated for the detection of GHRP-2. Specificity and identification capabilities have been assessed in agreement with antidoping guidelines. The low AA-3 levels found in DBS samples prevented its effective application for the determination of this metabolite. The limit of detection (LoD) for GHRP-2 has been established at 50 pg/ml. Long-term stability (>2 years) has been confirmed. The procedure has been successfully applied to actual DBS samples from an administration study with a single intravenous dose of GHRP-2 (100 μg) being detected up to 4 h after drug injection. GHRP-2 concentrations have been higher in venous blood DBS than in capillary blood DBS. Despite the observed differences, a similar detection window has been achieved independently of the type of blood used. In summary, this study provides specific evidence supporting DBS usefulness to detect GHRP-2, and potentially other GHRPs family members, for antidoping tests.

Rapid quantification of insulin degludec by immunopurification combined with liquid chromatography high-resolution mass spectrometry

Insulin degludec is an ultra-long-acting insulin analogue that is increasingly being used in diabetes due to its favourable efficacy and safety profile. Thus, there is an increasing demand for a reliable and specific analytical method to quantify insulin degludec for research, pharmaceutical industry and clinical applications. We developed and validated an automated, high-throughput method for quantification of insulin degludec in human blood samples across the expected clinical range combining immunopurification with high-resolution mass spectrometry. Validation was performed according to the requirements of the US Food and Drug Administration. The method satisfyingly met the following parameters: lower limit of quantification (120 pM), linearity, accuracy (error < 5%), precision (CV < 7.7%), selectivity, carry-over, recovery (89.7–97.2%), stability and performance in the presence of other insulin analogues. The method was successfully applied to clinical samples of patients treated with insulin degludec showing a good correlation with the administered dose (r² = 0.78). High usability of the method is supported by the small specimen volume, automated sample processing and short analysis time. In conclusion, this reliable, easy-to-use and specific mass spectrometric insulin degludec assay offers great promise to address the current unmet need for standardized insulin analytics in academic and industrial research.

Detection of Stimulated Erythropoiesis by the RNA-Based 5'-Aminolevulinate Synthase 2 Biomarker in Dried Blood Spot Samples

BACKGROUND

Despite implementation of the Athlete Biological Passport 10 years ago, blood doping remains difficult to detect. Thus, there is a need for new biomarkers to increase the sensitivity of the adaptive model. Transcriptomic biomarkers originating from immature reticulocytes may be reliable indicators of blood manipulations. Furthermore, the use of dried blood spots (DBSs) for antidoping purposes constitutes a complementary approach to venous blood collection. Here, we developed a method of quantifying the RNA-based 5′-aminolevulinate synthase 2 (ALAS2) biomarker in DBS.

MATERIALS

The technical, interindividual, and intraindividual variabilities of the method, and the effects of storage conditions on the production levels of ALAS2 RNA were assessed. The method was used to monitor erythropoiesis stimulated endogenously (blood withdrawal) or exogenously (injection of recombinant human erythropoietin).

RESULTS

When measured over a 7-week period, the intra- and interindividual variabilities of ALAS2 expression in DBS were 12.5%–42.4% and 49%, respectively. Following withdrawal of 1 unit of blood, the ALAS2 RNA in DBS increased significantly for up to 15 days. Variations in the expression level of this biomarker in DBS samples were more marked than those of the conventional hematological parameters, reticulocyte percentage and immature reticulocyte fraction. After exogenous stimulation of erythropoiesis via recombinant human erythropoietin injection, ALAS2 expression in DBS increased by a mean 8-fold.

CONCLUSIONS

Monitoring of transcriptomic biomarkers in DBS could complement the measurement of hematological parameters in the Athlete Biological Passport and aid the detection of blood manipulations.

Determination of Recent Growth Hormone Abuse Using a Single Dried Blood Spot

BACKGROUND

Although it is being increasingly applied, blood collection for drug testing in sport presents some logistic issues that complicate full applicability on a large scale. The use of dried blood spots (DBS) could benefit compliant blood testing considerably owing to its simplicity, minimal invasiveness, analyte stability, and reduced costs. The aim of this study was to evaluate the applicability of DBS to the methodology approved by the World Anti-Doping Agency (WADA) for detection of doping by recombinant human growth hormone (rhGH) in serum.

METHODS

A protocol for a single DBS analysis using the hGH isoforms differential immunoassays (kit 1 and kit 2) was developed and validated. A clinical study with healthy volunteers injected for 3 consecutive days with a low subcutaneous dose (0.027 mg · kg−1 · day−1 · person−1) of rhGH was conducted. Finger prick DBS and paired-time serum samples from arm venipuncture were compared.

RESULTS

The analysis of the DBS-based protocol indicated that with only a single blood spot it was possible to detect positivity for growth hormone abuse. In spite of the low rhGH dose administered and independently of the kit used, the window of detection for DBS was confirmed in all analyzed samples up to 8 h after rhGH administration and extended up to 12 h in 50% of the cases. Serum positivity was detected in all studied samples for 12 h after administration.

CONCLUSIONS

These results support the usefulness of DBS as a biological matrix for testing recent growth hormone abuse.

Reversible glutathionylation of Sir2 by monothiol glutaredoxins Grx3/4 regulates stress resistance

The regulatory mechanisms of yeast Sir2, the founding member of the sirtuin family involved in oxidative stress and aging, are unknown. Redox signaling controls many cellular functions, especially under stress situations, with dithiol glutaredoxins (Grxs) playing an important role. However, monothiol Grxs are not considered to have major oxidoreductase activity. The present study investigated the redox regulation of yeast Sir2, together with the role and physiological impact of monothiol Grx3/4 as Sir2 thiol-reductases upon stress. S-glutathionylation of Sir2 upon disulfide stress was demonstrated both in vitro and in vivo, and decreased Sir2 deacetylase activity. Physiological levels of nuclear Grx3/4 can reverse the observed post-translational modification. Grx3/4 interacted with Sir2 and reduced it after stress, thereby restoring telomeric silencing activity. Using site-directed mutagenesis, key cysteine residues at the catalytic domain of Sir2 were identified as a target of S-glutathionylation. Mutation of these residues resulted in cells with increased resistance to disulfide stress. We provide new mechanistic insights into Grx3/4 regulation of Sir2 by S-deglutathionylation to increase cell resistance to stress. This finding offers news perspectives on monothiol Grxs in redox signaling, describing Sir2 as a physiological substrate regulated by S-glutathionylation. These results might have a relevant role in understanding aging and age-related diseases.

Characterization of secretomes from a human blood brain barrier endothelial cells in-vitro model after ischemia by stable isotope labeling with aminoacids in cell culture (SILAC)

The human immortalized brain endothelial cell line hCMEC/D3 is considered a simple in-vitro model of the blood-brain-barrier. Our aim was to characterize changes in the secretome of hCMEC/D3 subjected to oxygen and glucose deprivation (OGD) to identify new proteins altered after ischemia and that might trigger blood-brain-barrier disruption and test their potential as blood biomarkers for ischemic stroke. Using a quantitative proteomic approach based on SILAC, 19 proteins were found differentially secreted between OGD and normoxia/normoglycemia conditions. Among the OGD-secreted proteins, protein folding was the main molecular function identified and for the main canonical pathways there was an enrichment in epithelial adherens junctions and aldosterone signaling. Western blot was used to verify the MS results in a set of 9 differentially secreted proteins and 5 of these were analyzed in serum samples of 38 ischemic stroke patients, 18 stroke-mimicking conditions and 18 healthy controls.

SIGNIFICANCE

"We characterized changes in the secretome of hCMEC/D3 cells after an ischemic insult by SILAC and identified proteins associated with ischemia that might be involved in the disruption of the blood-brain barrier. Besides we analyzed the putative potential of the candidate proteins to become biomarkers for the diagnosis of ischemic stroke.

Sir2 is induced by oxidative stress in a yeast model of Huntington disease and its activation reduces protein aggregation

Huntington disease (HD) is a neurodegenerative disorder caused by expansion of CAG trinucleotide repeats, leading to an elongated polyglutamine sequence (polyQ) in the huntingtin protein. Misfolding of mutant polyQ proteins with expanded tracts results in aggregation, causing cytotoxicity. Oxidative stress in HD has been documented in humans as important to disease progression. Using yeast cells as a model of HD, we report that when grown at high glucose concentration, cells expressing mutant polyQ do not show apparent oxidative stress. At higher cell densities, when glucose becomes limiting and cells are metabolically shifting from fermentation to respiration, protein oxidation and catalase activity increases in relation to the length of the polyQ tract. Oxidative stress, either endogenous as a result of mutant polyQ expression or exogenously generated, increases Sir2 levels. Δ sir2 cells expressing expanded polyQ lengths show signs of oxidative stress even at the early exponential phase. In a wild-type background, isonicotinamide, a Sir2 activator, decreases mutant polyQ aggregation and the stress generated by expanded polyQ. Taken together, these results describe mutant polyQ proteins as being more toxic in respiring cells, causing oxidative stress and an increase in Sir2 levels. Activation of Sir2 would play a protective role against this toxicity.

The forkhead transcription factor Hcm1 promotes mitochondrial biogenesis and stress resistance in yeast

In Saccharomyces cerevisiae, the forkhead transcription factor Hcm1 is involved in chromosome segregation, spindle pole dynamics, and budding. We found that Hcm1 interacts with the histone deacetylase Sir2 and shifts from cytoplasm to the nucleus in the G(1)/S phase or in response to oxidative stress stimuli. The nuclear localization of Hcm1 depends on the activity of Sir2 as revealed by activators and inhibitors of the sirtuins and the Δsir2 mutant. Hcm1-overexpressing cells display more mitochondria that can be attributed to increased amounts of Abf2, a protein involved in mitochondrial biogenesis. These cells also show higher rates of oxygen consumption and improved resistance to oxidative stress that would be explained by increased catalase and Sod2 activities and molecular chaperones such as Hsp26, Hsp30, and members of Hsp70 family. Microarray analyses also reveal increased expression of genes involved in mitochondrial energy pathways and those allowing the transition from the exponential to the stationary phase. Taken together, these results describe a new and relevant role of Hcm1 for mitochondrial functions, suggesting that this transcription factor would participate in the adaptation of cells from fermentative to respiratory metabolism.

Proteomic and oxidative stress analysis in human brain samples of Huntington disease

Huntington disease (HD) is a neurodegenerative disorder caused by expansion of CAG repeats in exon 1 of the huntingtin gene, affecting initially the striatum and progressively the cortex. This work reports a proteomic analysis of human brain postmortem samples obtained from striatum and cortex of patients with HD compared to samples of age- and sex-matched controls. Antioxidant defense proteins that were strongly induced in striatum, but also detectable in cortex, were identified as peroxiredoxins 1, 2, and 6, as well as glutathione peroxidases 1 and 6. The activities of other antioxidant enzymes such as mitochondrial superoxide dismutase and catalase were also increased in HD. Aconitase, a protein involved in energy metabolism, showed decreased activities in striatum of HD patients. Protein carbonyls, used as markers of oxidative stress, were increased in HD, and glial fibrillary acidic protein, aconitase, gamma-enolase, and creatine kinase B were identified as the main targets. Taken together, these results indicate that oxidative stress and damage to specific macromolecules would participate in the disease progression. Also, these data support the rationale for therapeutic strategies that either potentiate antioxidant defenses or avoid oxidative stress generation to delay disease progression.

Manganese is the link between frataxin and iron-sulfur deficiency in the yeast model of Friedreich ataxia

Friedreich ataxia is a human neurodegenerative and myocardial disease caused by decreased expression of the mitochondrial protein frataxin. Proteomic analysis of the mutant yeast model of Friedreich ataxia presented in this paper reveals that these cells display increased amounts of proteins involved in antioxidant defenses, including manganese-superoxide dismutase. This enzyme shows, however, lower activity than that found in wild type cells. Our results indicate that this lack of activity is a consequence of cellular manganese deficiency, because in manganese-supplemented cultures, cell manganese content, and manganese-superoxide dismutase activity were restored. One of the hallmarks of Friedreich ataxia is the decreased activity of iron/sulfur-containing enzymes. The activities of four enzymes of this group (aconitase, glutamate synthase, succinate dehydrogenase, and isopropylmalate dehydratase) have been analyzed for the effects of manganese supplementation. Enzyme activities were recovered by manganese treatment, except for aconitase, for which, a specific interaction with frataxin has been demonstrated previously. Similar results were obtained when cells were grown in iron-limited media suggesting that manganese-superoxide dismutase deficiency is a consequence of iron overload. In conclusion, these data indicate that generalized deficiency of iron-sulfur protein activity could be a consequence of manganese-superoxide dismutase deficiency, and consequently, it opens new strategies for Friedreich ataxia treatment.

Tumor-infiltrating cells as a prognostic factor in Hodgkin's lymphoma: a quantitative tissue microarray study in a large retrospective cohort of 267 patients

The present study aimed to describe the general tissular composition of the immune infiltrate observed in Hodgkin's lymphoma (HL) and its possible relationship with clinical and survival prognostic factors. In this retrospective study of 267 HL patients, the relative proportions of infiltrating T lymphocytes (CD4+, CD8+), natural killer cells (CD 56+, CD 57+), cytotoxic cells (Granzyme B+, TIA-1+) and dendritic cells (CD 21+, S-100+) were quantified immunohistochemically with tissue microarray technology. Our results confirm the predominance of CD4 + T lymphocytes in the background of tumoral cells, in addition to a high number of cytotoxic lymphocytes (CD8, CD 57 and TIA-1). Patients with low numbers of infiltrating CD8, CD 56, CD 57+cells and high numbers of Granzyme B and TIA-1+cells presented a significantly unfavourable clinical course (presence of leukocytosis, B symptoms, advanced clinical stage (III/IV), non-responding patients). A reduced infiltration of CD4+T lymphocytes was related with the presence of Epstein - Barr virus. Significantly longer survival times were observed in patients with a high level of infiltrating CD 57, as well as a low level of Granzyme B and TIA-1+cells (log-rank test). When evaluated in a multivariate model, high levels of infiltrating TIA-1 and Granzyme B+cells were shown to be independent prognostic factors that negatively influenced overall survival. The presence of TIA-1+cells was found to be the only unfavorable prognostic factor of event-free survival and disease-free survival. The overall detection of tumor-infiltrating cells in HL confirms the importance of cytotoxic T lymphocyte infiltration (Granzyme B and TIA-1+cells) in these patients. Independently of the classical clinical and pathological features, these cells appear to be an unfavourable prognostic factor in HL and, more particularly, the presence of cytotoxic TIA-1+cells.

Oxidative damage to specific proteins in replicative and chronological-aged Saccharomyces cerevisiae: common targets and prevention by calorie restriction

Oxidative modifications of cellular components have been described as one of the main contributions to aged phenotype. In Saccharomyces cerevisiae, two distinct life spans can be considered, replicative and chronological. The relationship between both aging models is still not clear despite suggestions that these phenomena may be related. In this work, we show that replicative and chronological-aged yeast cells are affected by an oxidative stress situation demonstrated by increased protein carbonylation when compared with young cells. The data on the identification of these oxidatively modified proteins gives clues to better understand cellular dysfunction that occurs during aging. Strikingly, although in both aging models metabolic differences are important, major targets are almost the same. Common targets include stress resistance proteins (Hsp60 and Hsp70) and enzymes involved in glucose metabolism such as enolase, glyceraldehydes-3-P dehydrogenase, fructose-1,6-biphosphate aldolase, pyruvate decarboxylase, and alcohol dehydrogenase. In both aging models, calorie restriction results in decreased damage to these proteins. In addition, chronological-aged cells grown under glucose restriction displayed lowered levels of lipid peroxidation product lipofuscin. Intracellular iron concentration is kept almost unchanged, whereas in non-restricted cells, the values increase up 4-5 times. The pro-oxidant effects of such increased iron concentration would account for the damage observed. Also, calorie-restricted cells show undamaged catalase, which clearly appears carbonylated in cells grown at a high glucose concentration. These results may explain lengthening of the viability of chronological-aged cells and could have an important role in replicative life span extension by calorie restriction.

Analysis of dihydrofolate reductase and reduced folate carrier gene status in relation to methotrexate resistance in osteosarcoma cells

BACKGROUND

To evaluate the impact of dihydrofolate reductase (DHFR) and reduced folate carrier (RFC) genes on methotrexate (MTX) resistance in osteosarcoma cells in relation to retinoblastoma (RB1) gene status.

MATERIALS AND METHODS

A series of human osteosarcoma cell lines-either sensitive or resistant to MTX-and 16 osteosarcoma tumour samples were used in this study.

RESULTS

In U-2OS MTX-resistant variants, and in other RB1-positive cell lines, MTX resistance was associated with increased levels of DHFR and with a slight decrease of RFC gene expression. In Saos-2 MTX-resistant variants, and in another RB1-negative cell line, development of MTX resistance was associated with a decrease in expression of RFC, without any significant involvement of DHFR. In osteosarcoma clinical samples, amplification of the DHFR gene at clinical onset appeared to be more frequent in RB1-positive compared with RB1-negative tumours.

CONCLUSIONS

Amplification of the DHFR gene may occur more frequently in the presence of RB1-mediated negative regulation of its activity and can be present at clinical onset in osteosarcoma patients. Simultaneous evaluation of RFC, DHFR and RB1 gene status at the time of diagnosis may become the basis for the identification of potentially MTX-unresponsive osteosarcoma patients, who could benefit from treatment protocols with alternative antifolate drugs.

Genomic imbalances associated with methotrexate resistance in human osteosarcoma cell lines detected by comparative genomic hybridization-based techniques

Methotrexate (MTX) is one of the most important drugs for osteosarcoma (OS) treatment. To identify genetic aberrations associated with the development of MTX resistance in OS cells, in addition to the previously reported expression changes of dihydrofolate reductase (DHFR) and reduced folate carrier (RFC) genes, comparative genomic hybridization (CGH)-based techniques were used. The direct comparison between MTX-resistant variants of U-2OS or Saos-2 human OS cell lines with their respective parental cell lines by CGH on chromosomes revealed that development of MTX resistance was associated with gain of the chromosomal regions 5q12-q15 and 11q14-qter in U-2OS variants, and with gain of 8q22-qter in Saos-2 variants. Further analyses by CGH on microarrays demonstrated a progressively increasing gain of mixed lineage leukemia (MLL) gene (11q23) in U-2OS MTX-resistant variants, which was also confirmed by fluorescence in situ hybridization (FISH), in addition to gain of FGR (1p36), amplification/overexpression of DHFR, and slight decrease of RFC expression. In Saos-2 MTX-resistant variants, gain of MYC (8q24.12-q24.13) was detected, together with a remarkable decrease of RFC expression. Further analyses of DHFR, MLL, MYC, and RFC gene status in four additional human OS cell lines revealed that only gain of DHFR and MLL were associated with an inherent lower sensitivity to MTX. These data demonstrate that genetic analyses with complementary techniques are helpful for the identification of new candidate genes, which might be considered for an early identification of MTX unresponsive tumors.

Value of P-glycoprotein and clinicopathologic factors as the basis for new treatment strategies in high-grade osteosarcoma of the extremities

PURPOSE

To evaluate the prognostic value of P-glycoprotein and clinicopathologic parameters in a large series of high-grade osteosarcoma (OS) patients treated at the Rizzoli Institute.

PATIENTS AND METHODS

With the use of immunohistochemistry, P-glycoprotein was assessed in 149 patients with primary, nonmetastatic, high-grade OS who were homogeneously treated with chemotherapy protocols based on doxorubicin, high-dose methotrexate, and cisplatin and the addition of ifosfamide in the postoperative phase.

RESULTS

P-glycoprotein positivity was found in 47 of 149 cases (32%) and was significantly associated with a higher incidence of relapse and a worse outcome, as was age younger than 12 years and tumor volume greater then 150 mL at diagnosis. Multivariate analysis further confirmed the prognostic value of these parameters, which all were independent adverse prognostic factors. Event-free survival and proportional hazards regression analyses confirmed that overexpression of P-glycoprotein at clinical onset is the most important adverse prognostic factor for high-grade OS patients treated with these chemotherapy protocols.

CONCLUSION

Increased P-glycoprotein levels, together with tumor volume and age, should be taken into consideration to identify, at time of diagnosis, subgroups of OS patients with a higher risk of recurrence. This subgroup identification will constitute the basis for drawing individualized treatment protocols on the basis of risk evaluation, with the aim of using more aggressive chemotherapy, or combination chemotherapy with other adjuvants, only in those patients for which more aggressive regimens are strictly necessary and warranted.

Effectiveness of Ecteinascidin-743 against drug-sensitive and -resistant bone tumor cells

PURPOSE

The identification of new drugs is strongly needed for bone tumors.Ecteinascidin-743 (ET-743), a highly promising antitumor agent isolated from the marine tunicate Ecteinascidia turbinata, is currently under Phase II clinical investigation in Europe and the United States for treatment of soft tissue sarcoma. In this study, we analyzed the preclinical effectiveness of this drug in osteosarcoma and Ewing's sarcoma.

EXPERIMENTAL DESIGN

The effects of ET-743 were evaluated against a panel of human osteosarcoma and Ewing's sarcoma cell lines characterized by different drug responsiveness and compared with the effects of standard anticancer agents. In addition, combination treatments with ET-743 and the other standard chemotherapy agents for sarcoma were analyzed to highlight the best drug-to-drug interaction

RESULTS

A potent activity of ET-743 was clearly observed against both drug-sensitive and drug-resistant (multidrug-resistant, methotrexate- and cisplatin-resistant) bone tumor cells at concentrations that are easily achievable in patients (pM to nM range). Ewing's sarcoma cells appeared to be particularly sensitive to the effects of this drug. The analysis of the effects of ET-743 on cell cycle, apoptosis, and differentiation indicated that both osteosarcoma and Ewing's sarcoma cells had a slower progression through the different phases of the cell cycle after treatment with ET-743. However, the drug was able to induce a massive apoptosis in Ewing's sarcoma but not in osteosarcoma cells. In the latter neoplasm, ET-743 showed a differential effect, as indicated by the significant increase in the expression and activity of alkaline phosphatase, a marker of osteoblastic differentiation. Concurrent exposure of cells to ET-743 and other chemotherapeutic agents resulted in greater than additive interactions when doxorubicin and cisplatin were used, whereas subadditive effects were observed with methotrexate, vincristine, and actinomycin D.

CONCLUSIONS

Overall, these results encourage the inclusion of this drug in the treatment of patients with bone tumors, although a careful design of new regimens is required to identify the best therapeutic conditions.