P–587 Highly purified human menopausal gonadotrophin (HP-hMG, Menopur) as a ready-to-use solution for injection in pre-filled pen is bioequivalent to HP-hMG powder for reconstitution

Study question

Are serum FSH levels after single subcutaneous dosing of HP-hMG in a liquid formulation and a powder formulation bioequivalent?

Summary answer

The 90% CIs for the geometric mean ratios of serum FSH AUCt and Cmax were both within 0.8000–1.2500, thus the two formulations are bioequivalent.

What is known already

For several decades, HP-hMG (Menopur) has been used for the treatment of infertility; its efficacy and safety compared to other gonadotropins have been consistently demonstrated in several prospective, randomised controlled trials and meta-analyses (Deeks et al 2018; Bordewijk et al 2019). Menopur powder for reconstitution is available in multidose and single dose formulations. Up to 3 single dose vials (each containing 75 IU) may be dissolved into 1 mL solvent for administration. Recently, and for the first time, Menopur has been successfully formulated in a stable, ready-to-use solution for injection, which may be administered by a pre-filled pen.

Study design, size, duration

This was a randomised, two-way crossover, single dose, bioequivalence trial comparing Menopur liquid injected by pre-filled pen, with Menopur powder injected by conventional syringe and needle. The primary endpoints were AUCt and Cmax of baseline-adjusted FSH. Pituitary-suppressed, healthy women were randomised to receive one treatment sequence including a single subcutaneous injection of 450 IU Menopur liquid (600 IU/0.96 mL) and of 450 IU Menopur powder by two subcutaneous injections of 225 IU in 1 mL.

Participants/materials, setting, methods

Blood samples were collected pre- and post-dose, until 9 days after each injection. The PK parameters of FSH and hCG were assessed by noncompartmental methods with adjustment for endogenous pre-dose levels. Highly sensitive and specific electrochemiluminescence immunoassays were used for quantification and the LLOQ of the FSH and hCG assays were 1.47 mIU/mL and 0.5 mIU/mL, respectively, and the total validated CV was within 5% for both assays.

Main results and the role of chance

In total, 76 women were randomised and 56 completed the trial. The main reason for discontinuation was insufficient pituitary suppression prior to the second administration of HP-hMG. The mean FSH and hCG serum concentration-time profiles were comparable between the two HP-hMG formulations. The geometric mean ratios and 90% confidence intervals of FSH for HP-hMG liquid versus HP-hMG powder were 1.12 [1.0562; 1.1889] for AUCt and 1.17 [1.0946; 1.2490] for Cmax, showing that the two formulations were bioequivalent. Maximal serum FSH concentrations were reached at 18.19 h for HP-HMG liquid and 15.55 h for HP-hMG powder. In addition to FSH, the PK parameters for hCG were compared between the two HP-hMG formulations. The geometric mean ratios and 90% confidence intervals for HP-hMG liquid versus HP-hMG powder were 0.93 [0.86; 1.01] for AUCt and 0.94 [0.86; 1.02] for Cmax. There was no difference between the two groups in the incidence or severity of adverse events, and both preparations were well tolerated. Mild injection site reactions were less common after administration of HP-hMG liquid by a single injection compared to HP-hMG powder by two injections and were mostly related to pain and erythema after drug administration.

Limitations, reasons for caution

This bioequivalence study is based on the comparison of single dose administrations in healthy female volunteers of reproductive age.

Wider implications of the findings: The new HP-hMG solution for injection in a pre-filled pen will deliver the efficacy and safety of Menopur in a convenient delivery device.

Trial registration number

NA

Evaluation of applying IHC4 as a prognostic model in the translational study of Intergroup Exemestane Study (IES): PathIES

BACKGROUND

Intergroup Exemestane Study (IES) was a randomised study that showed a survival benefit of switching adjuvant endocrine therapy after 2-3 years from tamoxifen to exemestane. This PathIES aimed to assess the role of immunohistochemical (IHC)4 score in determining the relative sensitivity to either tamoxifen or sequential treatment with tamoxifen and exemestane.

PATIENTS AND METHODS

Primary tumour samples were available for 1274 patients (27% of IES population). Only patients for whom the IHC4 score could be calculated (based on oestrogen receptor, progesterone receptor, HER2 and Ki67) were included in this analysis (N = 430 patients). The clinical score (C) was based on age, grade, tumour size and nodal status. The association of clinicopathological parameters, IHC4(+C) scores and treatment effect with time to distant recurrence-free survival (TTDR) was assessed in univariable and multivariable Cox regression analyses. A modified clinical score (PathIEscore) (N = 350) was also estimated.

RESULTS

Our results confirm the prognostic importance of the original IHC4, alone and in conjunction with clinical scores, but no significant difference with treatment effects was observed. The combined IHC4 + Clinical PathIES score was prognostic for TTDR (P < 0.001) with a hazard ratio (HR) of 5.54 (95% CI 1.29-23.70) for a change from 1st quartile (Q1) to Q1-Q3 and HR of 15.54 (95% CI 3.70-65.24) for a change from Q1 to Q4.

CONCLUSION

In the PathIES population, the IHC4 score is useful in predicting long-term relapse in patients who remain disease-free after 2-3 years. This is a first trial to suggest the extending use of IHC4+C score for prognostic indication for patients who have switched endocrine therapies at 2-3 years and who remain disease-free after 2-3 years.

Prognostic and predictive value of ERβ1 and ERβ2 in the Intergroup Exemestane Study (IES)-first results from PathIES†

BACKGROUND

Intergroup Exemestane Study (IES) was a randomised study that showed a survival benefit of switching adjuvant endocrine therapy after 2-3 years from tamoxifen to exemestane. PathIES aimed to assess the potential prognostic and predictive value of ERβ1 and ERβ2 expression in primary tumours in order to determine benefit in the two treatment arms.

PATIENTS AND METHODS

Primary tumour samples were available for 1256 patients (27% IES population). ERβ1 and ERβ2 expression was dichotomised at the median IHC score (high if ERβ1 ≥ 191, ERβ2 ≥ 164). Hazard ratios (HRs) were estimated by multivariable Cox proportional hazards models adjusting for clinicopathological factors. Treatment effects with biomarker expressions were determined by interaction tests. Analysis explored effects of markers both as a continuous variable and with dichotomised cut-offs.

RESULTS

Neither ERβ1 nor ERβ2 were associated with disease-free survival (DFS) or overall survival (OS) in the whole cohort. In patients treated with continued tamoxifen, high ERβ1 expression compared with low was associated with better DFS [HR = 0.38:95% confidence interval (CI) 0.21-0.68, P = 0.001]. DFS benefit of exemestane over tamoxifen (HR = 0.40:95% CI 0.22-0.70) was found in the low ERβ1 subgroup (interaction P = 0.01). No significant difference with treatment was observed for ERβ2 expression in either DFS or OS.

CONCLUSION

In the PathIES population, exemestane appeared to be superior to tamoxifen among patients with low ERβ1 expression but not in those with high ERβ1 expression. This is the first trial of its kind to report a parameter potentially predicting benefit of an aromatase inhibitor when compared with tamoxifen and an independent validation is warranted.

Soy-dairy protein blend and whey protein ingestion after resistance exercise increases amino acid transport and transporter expression in human skeletal muscle

Increasing amino acid availability (via infusion or ingestion) at rest or postexercise enhances amino acid transport into human skeletal muscle. It is unknown whether alterations in amino acid availability, from ingesting different dietary proteins, can enhance amino acid transport rates and amino acid transporter (AAT) mRNA expression. We hypothesized that the prolonged hyperaminoacidemia from ingesting a blend of proteins with different digestion rates postexercise would enhance amino acid transport into muscle and AAT expression compared with the ingestion of a rapidly digested protein. In a double-blind, randomized clinical trial, we studied 16 young adults at rest and after acute resistance exercise coupled with postexercise (1 h) ingestion of either a (soy-dairy) protein blend or whey protein. Phenylalanine net balance and transport rate into skeletal muscle were measured using stable isotopic methods in combination with femoral arteriovenous blood sampling and muscle biopsies obtained at rest and 3 and 5 h postexercise. Phenylalanine transport into muscle and mRNA expression of select AATs [system L amino acid transporter 1/solute-linked carrier (SLC) 7A5, CD98/SLC3A2, system A amino acid transporter 2/SLC38A2, proton-assisted amino acid transporter 1/SLC36A1, cationic amino acid transporter 1/SLC7A1] increased to a similar extent in both groups (P < 0.05). However, the ingestion of the protein blend resulted in a prolonged and positive net phenylalanine balance during postexercise recovery compared with whey protein (P < 0.05). Postexercise myofibrillar protein synthesis increased similarly between groups. We conclude that, while both protein sources enhanced postexercise AAT expression, transport into muscle, and myofibrillar protein synthesis, postexercise ingestion of a protein blend results in a slightly prolonged net amino acid balance across the leg compared with whey protein.

Comparison of two direct neutralizing assay formats using recombinant follicle-stimulating hormone as agonist

Characterizing anti-drug antibodies for neutralizing activity is commonly part of the immunogenicity testing package for most therapeutic proteins. Cell-based neutralization assays can generally be categorized as direct- or indirect assays depending on whether they are associated with therapeutics with agonistic- or antagonistic properties. This paper's aim is a comparison of the two direct neutralization assay formats; the variable- and fixed concentration assay format, using recombinant follicle-stimulating hormone as drug agonist. Essential validation- and performance parameters, such as sample through-put, cut-point, precision, sensitivity and drug tolerance, were compared. The fixed concentration assay format offers superior sample through-put (40 versus 6 samples), precision (coefficient of variation of ≤14% versus 34%) and almost 6 times better sensitivity and is generally recommended as the better option particularly for quasi-quantitative assessments of neutralizing antibodies.

A soy, whey and caseinate blend extends postprandial skeletal muscle protein synthesis in rats

BACKGROUND & AIMS

Blends of dairy and soy protein are used in commercial sports nutrition products; however, no studies have systematically compared blends to isolated protein sources and their effects on muscle protein synthesis (MPS). Dairy whey protein (WP), soy protein isolate (SP), and two blends (Blend 1 and Blend 2) consisting of ratios of 50:25:25 and 25:50:25 for whey:caseinate:soy, respectively, were evaluated for their ability to affect MPS.

METHODS

Male Sprague-Dawley rats were trained to eat 3 meals/day: a 4 g meal at 0700-0720 hours followed by ad lib feeding at 1300-1400 hours and 1800-1900 hours. After ~5 days of training, fasted rats were administered their respective 4 g meal at 0700-0720 hours and an intravenous flooding dose of (2)H5-phenylalanine 10 min prior to euthanasia. Individual rats were euthanized at designated postprandial time points. Blood and gastrocnemius samples were collected and the latter was used to measure mixed muscle protein fractional synthetic rates (FSR).

RESULTS

Plasma leucine concentrations peaked in all groups at 90 min and were still above baseline at 300 min post-meal. FSR tended to increase in all groups post-meal but initial peaks of FSR were different times (45, 90 and 135 min for WP or SP, Blend 1 and Blend 2, respectively). Blend 2 had a significantly higher FSR compared to WP alone at 135 min (P < 0.05).

CONCLUSIONS

Single source proteins and protein blends all enhance skeletal MPS after a meal, however, Blend 2 had a delayed FSR peak which was significantly higher than whey protein at 135 min.

Prognostic and predictive role of ESR1 status for postmenopausal patients with endocrine-responsive early breast cancer in the Danish cohort of the BIG 1-98 trial

BACKGROUND

Estrogen Receptor 1 (ESR1) aberrations may be associated with expression of estrogen receptor (ER) or progesterone receptor (PgR), human epidermal growth factor receptor-2 (HER2) or Ki-67 labeling index and prognosis.

PATIENTS AND METHODS

ESR1 was assessed in 1129 (81%) of 1396 postmenopausal Danish women with early breast cancer randomly assigned to receive 5 years of letrozole, tamoxifen or a sequence of these agents in the Breast International Group 1-98 trial and who had ER ≥ 1% after central review.

RESULTS

By FISH, 13.6% of patients had an ESR1-to-Centromere-6 (CEN-6) ratio ≥ 2 (amplified), and 4.2% had ESR1-to-CEN-6 ratio <0.8 (deleted). Deletion of ESR1 was associated with significantly lower levels of ER (P < 0.0001) and PgR (P = 0.02) and more frequent HER2 amplification. ESR1 deletion or amplification was associated with higher-Ki-67 than ESR1-normal tumors. Overall, there was no evidence of heterogeneity of disease-free survival (DFS) or in treatment effect according to ESR1 status. However, significant differences in DFS were observed for subsets based on a combination of ESR1 and HER2 status (P = 0.02).

CONCLUSIONS

ESR1 aberrations were associated with HER2 status, Ki-67 labeling index and ER and PgR levels. When combined with HER2, ESR1 may be prognostic but should not be used for endocrine treatment selection in postmenopausal women with endocrine-responsive early breast cancer.

Which patients benefit most from adjuvant aromatase inhibitors? Results using a composite measure of prognostic risk in the BIG 1-98 randomized trial

BACKGROUND

On average, aromatase inhibitors are better than tamoxifen when used as initial or sequential therapy for postmenopausal women with endocrine-responsive early breast cancer. Because there may be contraindications to their use based on side-effects or cost, we investigated subgroups in which aromatase inhibitors may be more or less important.

PATIENTS AND METHODS

Breast International Group 1-98 trial randomized 6182 women among four groups comparing letrozole and tamoxifen with sequences of each agent; 5177 (84%) had centrally confirmed estrogen receptor (ER) positivity. We assessed whether centrally determined ER, progesterone receptor (PgR), human epidermal growth factor receptor 2, and Ki-67 labeling index, alone or in combination with other prognostic features, predicted the magnitude of letrozole effectiveness compared with either sequence or tamoxifen monotherapy.

RESULTS

Individually, none of the markers significantly predicted differential treatment effects. Subpopulation treatment effect pattern plot analysis of a composite measure of prognostic risk revealed three patterns. Estimated 5-year disease-free survival for letrozole monotherapy, letrozole→tamoxifen, tamoxifen→letrozole, and tamoxifen monotherapy were 96%, 94%, 93%, and 94%, respectively, for patients at lowest risk; 90%, 91%, 93%, and 86%, respectively, for patients at intermediate risk; and 80%, 76%, 74%, and 69%, respectively, for patients at highest risk.

CONCLUSION

A composite measure of risk informs treatment selection better than individual biomarkers and supports the choice of 5 years of letrozole for patients at highest risk for recurrence.

Abstract P4-08-01: ESR1 Gene Aberrations Correlate with ER Protein Levels Measured by DCC and IHC

Background: The Estrogen receptor alfa (ER) is an established biomarker that has been studied in details on the protein and RNA level. Recently, the existence of amplifications and deletions of the ESR1 gene have been documented (1-3), although the frequency of the aberrations has been extensively debated. Here we hypothesize that a positive correlation exists between ESR1 gene copy number and ER protein content measured by both a biochemical ligand assay, dextran coated charcoal (DCC), and immunohistochemistry (IHC).

Material and Methods: From 289 primary high-risk breast cancer patients, randomized in the DBCG 77C trial between August 1977 and November 1982, ER data from DCC analyses was available. An ER positive tumor was defined as ≥10 fmol ER/mg protein (4). Archival tumor tissue was available from 257 patients. ESR1 copy number was analyzed with Dako

Histology FISH Accessory Kit (K5599, DAKO, Glostrup, Denmark) using a probe covering the ESR1 gene at 6q25 and a centromere 6 reference probe (3). IHC analysis for ER was applied on archival paraffin embedded tissue using the antibody ER1D5 (DAKO), 1:200 with a positive cut off value of 10% ER positive tumor cells.

Results: ESR1 FISH analysis was performed successfully in 215 (84%) patients. Amplification (ratio ESR1/CEN-6≥2) was observed in 47 of 215 patients (22%) and ESR1 deletion (ratio ESR1/CEN-6&lt;0.8) was observed in 69 (32%). A positive correlation of ER-DCC with both FISH ESR1 and ER-IHC was found (P&lt;0.0001). The ESR1 amplified tumors had higher average ER-DDC values compared to ESR1 normal tumors (ratio ESR1/ CEN6: 0,80-1,29) and tumors with ESR1 gain (ratio ESR1/CEN6: 1,30-1,99), while deleted tumors had lower ER-DCC values as illustrated in Figure 1.

A significant difference p=0.005 was found for the ESR1 deleted tumors compared to the ESR1 amplified tumors.

Fig. 1 Box plut showing the ER content according to ESR1/CEN-6 status

Discussion: Amplification of the ESR1 gene is associated with higher ER protein content by ER-DCC and more intense immunoreactivity by IHC while ESR1 deletions are associated with decreased content and immunoreactivity compared to tumors with normal ESR1 gene copy numbers. Major variations in ER content and immunoreactivity are however observed within tumors with a normal ESR1 copy number, and other mechanisms than gene aberrations seem to contribute. References:

1. Holst et al. (2007) Estrogen receptor alpha (ESR1) gene amplification is frequent in breast cancer Nat Genet 39: 655

2. Tomita et al. (2009) Estrogen receptor alpha gene ESR1 amplification may predict endocrine therapy responsiveness in breast cancer patients. Cancer Sci 100:1012

3. Nielsen et al. (2010) Amplification of ESR1 may predict resistance to adjuvant tamoxifen in postmenopausal patients with hormone receptor positive breast cancer. Breast cancer Res Treat, June 17 Epub

4. Thorpe et al. (1993) Short recurrence-free survival associated with high oestrogen receptor levels in the natural history of postmenopausal, primary breast cancer. Eur J Cancer 29A:971.

Resistance exercise increases leg muscle protein synthesis and mTOR signalling independent of sex

AIM

Sex differences are evident in human skeletal muscle as the cross-sectional area of individual muscle fibres is greater in men than in women. We have recently shown that resistance exercise stimulates mammalian target of rapamycin (mTOR) signalling and muscle protein synthesis in humans during early post-exercise recovery. Therefore, the aim of this study was to determine if sex influences the muscle protein synthesis response during recovery from resistance exercise.

METHODS

Seventeen subjects, nine male and eight female, were studied in the fasted state before, during and for 2 h following a bout of high-intensity leg resistance exercise. Mixed muscle protein fractional synthetic rate was measured using stable isotope techniques and mTOR signalling was assessed by immunoblotting from repeated vastus lateralis muscle biopsy samples.

RESULTS

Post-exercise muscle protein synthesis increased by 52% in the men and by 47% in the women (P < 0.05) and was not different between groups (P > 0.05). Akt phosphorylation increased in both groups at 1 h post-exercise (P < 0.05) and returned to baseline during 2 h post-exercise with no differences between groups (P > 0.05). Phosphorylation of mTOR and its downstream effector S6K1 increased significantly and similarly between groups during post-exercise recovery (P < 0.05). eEF2 phosphorylation decreased at 1- and 2 h post-exercise (P < 0.05) to a similar extent in both groups.

CONCLUSION

The contraction-induced increase in early post-exercise mTOR signalling and muscle protein synthesis is independent of sex and appears to not play a role in the sexual dimorphism of leg skeletal muscle in young men and women.

Prediction of responsiveness to adjuvant anthracyclines in high-risk breast cancer patients

597

Background: HER-2, TOP2A, and TIMP-1 have shown predictive properties regarding benefit from anthracyclines in patients with breast cancer. In the present study, TIMP-1 IHC was integrated with TOP2A FISH and HER-2 status in two separate profiles. Methods: The DBCG 89-D trial randomized 980 high-risk Danish breast cancer patients to nine series of CMF or CEF. CEF was superior to CMF in terms of DFS and OS (Ejlertsen et al, EJC 2007). HER-2 status and TOP2A copy number changes were determined as described previously (Knoop et al, J Clin Oncol. 2005). TMA s were constructed and analyzed centrally for TIMP-1 expression by IHC (± tumor cell immunoreactivity). TIMP-1 was combined with HER-2 into a joint HT marker (HT-non-responsive (HT-NR): HER-2 normal and TIMP-1 positive or HT-responsive (HT-R): HER-2 positive and/or TIMP-1 negative) and with TOP2A into a joint 2T marker (2T-NR: TOP2A normal and TIMP-1 positive or 2T-R: TOP2A abnormal and/or TIMP-1 negative). Relationships between IDFS, OS and the HT/2Tprofiles were analyzed using multivariate regression analysis. Results: Among patients with a HT-R profile CEF was superior to CMF in terms of both invasive disease-free survival (IDFS) (HR 0.62; 95% CI 0.45–0.86; p = 0.004) and overall survival (OS) (HR 0.63; 95% CI, 0.45–0.87; p = 0.005). In patients with a HT-NR profile, no significant differences between CEF and CMF were demonstrated for IDFS or OS. A significant HT profile (HT-R or HT-NR) versus treatment (CEF or CMF) interaction was detected by the Wald-test for both IDFS (p = 0.036) and OS (p = 0.047). An even more pronounced separation was observed regarding the 2T profile, and in patients with a 2T-R profile treatment with CEF was superior to CMF in terms of IDFS (HR 0.48; 95% CI 0.34–0.69; p < 0.001) and OS (HR 0.54; 95% CI, 0.38–0.77; p < 0.001). No significant difference was observed in patients with a 2T-NR profile. A highly significant 2T profile versus treatment interaction was detected for IDFS (p < 0.001) and OS (p = 0.004). Conclusions: Profiles created by joining TIMP-1 with either HER-2 status or TOP2A gene status seems advantageous compared to the use of a single marker.

[Table: see text]

Multifocality as a prognostic factor in breast cancer patients registered in Danish Breast Cancer Cooperative Group (DBCG) 1996-2001

The purpose of this study was to investigate the prognostic influence of multifocality in breast cancer patients. In a cohort of 7196 patients there were 945 patients with multifocality. We found no prognostic influence of multifocality on overall survival when controlling for known prognostic factors. We found a small but significant influence on disease-free survival (HR=1.16 [1.03-1.31]) and a strong correlation between multifocality and known prognostic factors. This was in accordance with an earlier study done on a smaller population and in a different period of time [Pedersen L, Gunnarsdottir KA, Rasmussen BB, Moeller S, Lanng C. The prognostic influence of multifocality in breast cancer patients. Breast 2004;13:188-193].

Central assessment of ER, PgR and HER2 in BIG 1–98 evaluating letrozole (L) compared to tamoxifen (T) as initial adjuvant endocrine therapy for postmenopausal women with hormone receptor-positive breast cancer

538

Background: The BIG 1–98 trial, a randomized double-blind Phase III trial, showed that L significantly improved disease-free survival (DFS) as compared with T. It is uncertain whether benefit of aromatase inhibitors vs. T differs according to PgR and/or HER2 status of the tumor. A central assessment of ER, PgR and HER2 was undertaken for BIG 1–98 to investigate this question. Methods: Paraffin-embedded primary tumor material was evaluable for 3650 (74%) of the 4922 patients (pts) randomized to the 2 monotherapy arms (L or T for 5 years; 51 months median follow-up). ER and PgR were measured by immunohistochemistry (IHC) and positivity was defined as =1% immunoreactive cells. HER2 expression was determined by IHC and positivity was confirmed by FISH. Cox modeling estimated hazard ratios (HR) comparing L vs. T on DFS and assessed treatment-by-covariate interactions. Results: By central assessment, 86% and 10% of tumors were classified as ER+/PgR+ and ER+/PgR-, respectively. Among these (n=3533), 7% were ER+/HER2+. DFS was superior in pts with ER+/PgR+ vs. ER+/PgR- tumors and in pts with ER+/HER2- vs. ER+/HER2+ tumors. The benefit of L vs. T did not differ by PgR (P=.48) or HER2 status (P=.55). Conclusion: In postmenopausal patients with ER+ tumors (=1% immunoreactive cells), of which 10% were PgR- and 7% HER2+, both PgR- and HER2+ status were associated with poorer DFS. The benefit of L over T was observed in all ER+ patients irrespective of PgR or HER2 status. In patients with ER+ tumors, PgR and HER2 status do not appear to be selection criteria for treatment with L vs. T.

[Table: see text]

No significant financial relationships to disclose.

Dysregulation of muscle fatty acid metabolism in type 2 diabetes is independent of malonyl-CoA

AIMS/HYPOTHESIS

An elevated lipid content within skeletal muscle cells is associated with the development of insulin resistance and type 2 diabetes mellitus. We hypothesised that in subjects with type 2 diabetes muscle malonyl-CoA (an inhibitor of fatty acid oxidation) would be elevated at baseline in comparison with control subjects and in particular during physiological hyperinsulinaemia with hyperglycaemia. Thus, fatty acids taken up by muscle would be shunted away from oxidation and towards storage (non-oxidative disposal).

MATERIALS AND METHODS

Six control subjects and six subjects with type 2 diabetes were studied after an overnight fast and during a hyperinsulinaemic (0.5 mU kg(-1) min(-1)), hyperglycaemic clamp (with concurrent intralipid and heparin infusions) designed to increase muscle malonyl-CoA and inhibit fat oxidation. We used stable isotope methods, femoral arterial and venous catheterisation, and performed muscle biopsies to measure palmitate kinetics across the leg and muscle malonyl-CoA.

RESULTS

Basal muscle malonyl-CoA concentrations were similar in control and type 2 diabetic subjects and increased (p<0.05) in both groups during the clamp (control, 0.14+/-0.05 to 0.24+/-0.05 pmol/mg; type 2 diabetes, 0.09+/-0.01 to 0.20+/-0.02 pmol/mg). Basal palmitate oxidation across the leg was not different between groups at baseline and decreased in both groups during the clamp (p<0.05). Palmitate uptake and non-oxidative disposal were significantly greater in the type 2 diabetic subjects at baseline and during the clamp (p<0.05).

CONCLUSIONS/INTERPRETATION

Contrary to our hypothesis, the dysregulation of muscle fatty acid metabolism in type 2 diabetes is independent of muscle malonyl-CoA. However, elevated fatty acid uptake in type 2 diabetes may be a key contributing factor to the increase in fatty acids being shunted towards storage within muscle.

TOP2A aberrations as predictive and prognostic marker in high-risk breast cancer patients. A randomized DBCG Trial (DBCG89D)

532

Background: The primary objective of the study was to evaluate TOP2A as predictive marker for adjuvant treatment with epirubicin in high-risk breast cancer patients. As a secondary objective the prognostic characteristics of TOP2A gene aberrations was investigated. The data presented on the predictive properties is a follow-up to the data previously published (Knoop et al, J Clin Oncol 2005; 23: 7483–90). Methods: 962 pre- and postmenopausal high-risk Danish patients were enrolled in the DBCG89D protocol. The patients were randomly allocated to either 9 × CMF (cyclophosphamide, methotrexate, 5-flurouracil) (n=495) or 9 × CEF (cyclophosphamide, epirubicin, 5-flurouracil) (n=467) every 3 weeks. Tumor-tissue was available from 806 patients (84%). The tumors were analyzed for TOP2A copy number changes with the TOP2A FISH pharmDx Kit (Dako, Glostrup). Recurrence-free survival (RFS) was used as primary end-point. Univariate and multivariate statistics were used to assess the predictive and prognostic properties of the TOP2A gene aberrations. Results: The TOP2A test was successful in 96% of the patients. Ninety-two (12.0%) patients were found to have TOP2A amplified tumors, and 86 (11.1%) to have TOP2A deleted tumors. For the primary study endpoint (RFS) a significant predictive value of TOP2A gene amplifications was found (HR=0.39; CI: 0.22–0.70; p=0.0017). A similar trend was seen with respect to TOP2A deletions (HR=0.61; CI: 0.35–1.07; p=0.082). TOP2A gene aberrations were significantly associated with several established prognostic factors and had independent prognostic value, associated with a significant worse prognosis both for RFS (p=0.036) and overall survival (p=0.012). Conclusions: The DBCG89D study has shown that TOP2A amplifications are associated with a favorable outcome of adjuvant treatment with epirubicin in primary breast cancer. Further, TOP2A aberrations demonstrated an independent prognostic value.

[Table: see text]

The prognostic influence of multifocality in breast cancer patients

The aim of this study was to investigate whether multifocality (MF) is a factor that has significant effect on overall survival when controlling for known prognostic factors. A cohort of 929 breast cancer patients operated between 1985 and 1990 was investigated. Of these, 158 (17%) patients had MF tumors and 771 had unifocal tumors. To investigate whether MF is an independent prognostic factor for overall survival in breast cancer, a Cox regression model was applied. Only tumor size, positive lymph nodes, histologic grade and receptor status had a significant effect on overall survival in the multivariate analysis. We found a positive correlation between tumor size and MF and between the number of positive lymph nodes and MF. In conclusion, MF had no significant effect on overall survival besides that which can be explained by other prognostic factors.

Oral and intravenously administered amino acids produce similar effects on muscle protein synthesis in the elderly

BACKGROUND

Muscle protein synthesis is stimulated in the elderly when amino acid availability is increased.

OBJECTIVE

To determine which mode of delivery of amino acids (intravenous vs. oral ingestion) is more effective in stimulating the rate of muscle protein synthesis in elderly subjects.

DESIGN

Fourteen elderly subjects were assigned to one of two groups. Following insertion of femoral arterial and venous catheters, subjects were infused with a primed, continuous infusion of L-[ring-2H5] phenylalanine. Blood samples and muscle biopsies were obtained to measure muscle protein fractional synthesis rate (FSR) with the precursor-product model, phenylalanine kinetics across the leg with the three-pool model, and whole body phenylalanine kinetics. Protein metabolism parameters were measured in the basal period, and during the administration of oral amino acids (n=8) or a similar amount of intravenous amino acids (n=6).

RESULTS

Enteral and parenteral amino acid administration increased amino acid arterial concentrations and delivery to the leg to a similar extent in both groups. Muscle protein synthesis as measured by both FSR, and the three-pool model, increased during amino acid administration (P < 0.05 vs. basal) in both groups with no differences between groups. Whole body proteolysis did not change with the oral amino acids whereas it increased slightly during parenteral amino acid administration.

CONCLUSIONS

Increased amino acid availability stimulates the rate of muscle protein synthesis independent of the route of administration (enteral vs. parenteral).

Basal muscle amino acid kinetics and protein synthesis in healthy young and older men

CONTEXT

Sarcopenia is associated with loss of strength and function, eventually leading to loss of independence. Some studies suggest that basal muscle protein turnover is reduced with aging, but other studies do not confirm this finding.

OBJECTIVE

To determine if aging per se affects basal muscle protein turnover in men.

DESIGN AND SETTING

Cross-sectional study conducted from June 1997 to July 2000 in a general US community.

PARTICIPANTS

Twenty-six young (mean [SE] age, 28 [2] years) and 22 older (mean [SE] age, 70 [1] years) men, who were healthy and independent based on activities of daily living, physical examinations, and screening tests. Subjects were excluded if they had cardiac, pulmonary, liver, or kidney disease; any impairment in activities of daily living; or steroid use.

MAIN OUTCOME MEASURES

We measured basal muscle protein and amino acid kinetics, based on stable isotope techniques with femoral arteriovenous catheterization and muscle biopsies. Three models (arteriovenous balance, three-pool, and fractional synthesis rate) were used to estimate the metabolic parameters.

RESULTS

Mean (SE) total leg volume was 9.60 (0.32) L in older men vs 10.83 (0.43) L in younger men, which suggests muscle loss in the older men. Net muscle protein balance was similar in both groups (older men, - 19 [2] nmol/min per 100 mL of leg volume vs younger men, - 21 [2] nmol/min per 100 mL of leg volume; P =.51). Small differences were found in mean (SE) muscle protein synthesis in comparisons of older vs younger men: arteriovenous balance, 48 (5) nmol/min per 100 mL of leg volume vs 32 (3) nmol/min per 100 mL of leg volume; P =.004; three-pool, 58 (5) nmol/min per 100 mL of leg volume vs 43 (4) nmol/min per 100 mL of leg volume; P =.04; and fractional synthesis rate, 0.0601 (0.0046) %/h vs 0.0578 (0.0047) %/h; P =.73. Small differences were also found in mean (SE) muscle protein breakdown: arteriovenous balance, 66 (5) nmol/min per 100 mL of leg volume in older vs 53 (4) nmol/min per 100 mL of leg volume in younger men, P =.045; and three-pool, 76 (6) nmol/min per 100 mL of leg volume vs 64 (5) nmol/min per 100 mL of leg volume, P =.14.

CONCLUSION

Differences in basal muscle protein turnover between older and younger men do not appear to explain muscle loss that occurs with age.

Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise

The present study was designed to determine whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). A primed, continuous infusion of L-[ring-(2)H(5)]phenylalanine, femoral arteriovenous catheterization, and muscle biopsies from the vastus lateralis were used to determine phenylalanine concentrations, enrichments, and net uptake across the leg. Blood and muscle phenylalanine concentrations were increased by approximately 130% after drink consumption in both trials. Amino acid delivery to the leg was increased during exercise and remained elevated for the 2 h after exercise in both trials. Delivery of amino acids (amino acid concentration times blood flow) was significantly greater in PRE than in POST during the exercise bout and in the 1st h after exercise (P < 0.05). Total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. These results indicate that the response of net muscle protein synthesis to consumption of an EAC solution immediately before resistance exercise is greater than that when the solution is consumed after exercise, primarily because of an increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.

Value of epidermal growth factor receptor, HER2, p53, and steroid receptors in predicting the efficacy of tamoxifen in high-risk postmenopausal breast cancer patients

PURPOSE

Few studies have examined the possible importance of biologic prognostic factors in breast cancer connected with differentiation and growth in predicting response to a specific adjuvant treatment. HER2, epidermal growth factor receptor (EGFR), and p53 have all been suggested as possible markers of tamoxifen resistance. The aim of this study was to investigate interactions between adjuvant treatment with tamoxifen and the content of EGFR, HER2, and p53 in steroid receptor-positive patients.

PATIENTS AND METHODS

A total of 1,716 high-risk postmenopausal breast cancer patients were randomly assigned to treatment with tamoxifen (868 women) or to observation (848 women) in a prospective trial (Danish Breast Cancer Cooperative Group's 77c protocol). The content of the steroid receptors and expression of p53, EGFR, and HER2 were determined by immunohistochemical analysis of paraffin-embedded tissue. The length of follow-up was 10 years. The end point for this analysis was disease-free survival.

RESULTS

Multivariate analysis demonstrated no increased risk of recurrence after treatment with tamoxifen for HER2-, EGFR-, and p53-positive, high-risk, steroid receptor-positive patients. Patients with steroid receptor-positive tumors and positive immunohistochemical staining for HER2, EGFR or p53 benefited from treatment with tamoxifen for 1 year, although the latter variable contained independent prognostic information by itself.

CONCLUSION

With the statistical power of the present randomized study, we did not find support for the hypothesis that HER2/EGFR or p53 status predicts benefit from tamoxifen treatment in estrogen receptor-positive patients with early-stage breast cancer. Thus, neither HER2, EGFR, nor p53 overexpression/accumulation should be used as a contraindication for giving tamoxifen.

The response of muscle protein anabolism to combined hyperaminoacidemia and glucose-induced hyperinsulinemia is impaired in the elderly

Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia. We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 +/- 3 yr) and elderly (72 +/- 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, -27 +/- 8 to 64 +/- 17; elderly, -16 +/- 4 to 29 +/- 7 nmol/(min.100 mL); P: < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P: = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 +/- 17 to 133 +/- 30 (P: = 0. 005); elderly, 62 +/- 9 to 70 +/- 14 nmol/(min.100 mL) (P: = NS)]. In both groups, protein breakdown decreased (P: = 0.012) and leg glucose uptake increased (P: = 0.0258) with the mixture. We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.

Is therapeutic drug monitoring a case for optimizing clinical outcome and avoiding interactions of the selective serotonin reuptake inhibitors?

The selective serotonin reuptake inhibitors (SSRIs) comprise citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline and they differ from each other in chemical structure, by pharmacokinetic properties and, most importantly, with respect to enzyme-specific metabolism and interactions. Citalopram is administered as a racemic mixture. The drug is oxidated to desmethylcitalopram in the liver, partially by CYP2C19 and partially by CYP3A4. Fluoxetine is administered as a racemate of R- and S-fluoxetine. Both R- and S-fluoxetine are metabolized by CYP2D6 to the active metabolites R- and S-norfluoxetine. Fluvoxamine is metabolized to inactive metabolites by CYP1A2 and CYP2D6. Paroxetine is metabolized to inactive metabolites partially by CYP2D6, and accordingly the metabolism of paroxetine is dependent on the genetic polymorphism of CYP2D6. Sertraline is metabolized to desmethylsertraline, probably by CYP3A4. Several analytical methods have been described for all SSRIs. Most assays are based on separation by high-performance liquid chromatography or gas chromatography. Stereoselective methods for the analysis of racemic citalopram and fluoxetine have been published. The SSRIs are generally well tolerated and their therapeutic indices are large. In several studies there has not been found a clear relationship between clinical efficacy and plasma concentration, nor any threshold that defines toxic concentrations. The available data do not suggest that any benefit be obtained from routine monitoring of SSRI plasma levels. Therefore therapeutic drug monitoring (TDM) of the SSRIs may be useful mainly in situations where poor compliance is suspected and when therapeutic failure or toxic events are experienced at clinically relevant dosages. Further, in special populations, such as in elderly patients, poor metabolizers of sparteine (CYP2D6) or mephenytoin (CYP2C19), and patients with liver impairment, the measurement of plasma concentrations may be useful.

An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise

This study was designed to determine the response of muscle protein to the bolus ingestion of a drink containing essential amino acids and carbohydrate after resistance exercise. Six subjects (3 men, 3 women) randomly consumed a treatment drink (6 g essential amino acids, 35 g sucrose) or a flavored placebo drink 1 h or 3 h after a bout of resistance exercise on two separate occasions. We used a three-compartment model for determination of leg muscle protein kinetics. The model involves the infusion of ring-(2)H(5)-phenylalanine, femoral arterial and venous blood sampling, and muscle biopsies. Phenylalanine net balance and muscle protein synthesis were significantly increased above the predrink and corresponding placebo value (P < 0.05) when the drink was taken 1 or 3 h after exercise but not when the placebo was ingested at 1 or 3 h. The response to the amino acid-carbohydrate drink produced similar anabolic responses at 1 and 3 h. Muscle protein breakdown did not change in response to the drink. We conclude that essential amino acids with carbohydrates stimulate muscle protein anabolism by increasing muscle protein synthesis when ingested 1 or 3 h after resistance exercise.

Androstenedione does not stimulate muscle protein anabolism in young healthy men

Androstenedione is the immediate precursor of testosterone. Androstenedione intake has been speculated to increase plasma testosterone levels and muscle anabolism. Thus, androstenedione supplements have become widely popular in the sport community to improve performance. This study was designed to determine whether 5 days of oral androstenedione (100 mg/day) supplementation increases skeletal muscle anabolism. Six healthy young men were studied before the treatment period and after 5 days of oral androstenedione supplementation. Muscle protein turnover parameters were compared to those of a control group studied twice as well and receiving no treatment. We measured muscle protein kinetics using a three-compartment model involving infusion of L-[ring-2H5]phenylalanine, blood sampling from femoral artery and vein, and muscle biopsies. Plasma testosterone, androstenedione, LH, and estradiol concentrations were determined by RIA. After ingestion of oral androstenedione, plasma testosterone and LH concentrations did not change from basal, whereas plasma androstenedione and estradiol concentrations were significantly increased (P<0.05). Compared to a control group, androstenedione did not affect muscle protein synthesis and breakdown, or phenylalanine net balance across the leg. We conclude that oral androstenedione does not increase plasma testosterone concentrations and has no anabolic effect on muscle protein metabolism in young eugonadal men.

Regulation of fatty acid oxidation in skeletal muscle

Researchers using animals are beginning to elucidate the control of fatty acid metabolism in muscle at the molecular and enzymatic level. This review examines the physiological data that has been collected from human subjects in the context of the proposed control mechanisms. A number of factors, including the availability of free fatty acids and the abundance of fatty acid transporters, may influence the rate of muscle fatty acid oxidation. However, the predominant point of control appears to be the rate at which fatty acyl-coenzyme A is transported into the mitochondria by the carnitine palmitoyl transferase system. In turn, evidence suggests that the intracellular concentration of malonyl-coenzyme A in muscle is an important regulator of carnitine palmitoyl transferase-I activity. Malonyl-coenzyme A is increased by glucose, which is likely the mechanism whereby glucose intake suppresses the transfer of fatty acids into the mitochondria for subsequent oxidation. In contrast, malonyl-coenzyme A levels decrease during exercise, which enables increased fatty acid oxidation. However, for any given carnitine palmitoyl transferase-I activity, there may be an effect of free fatty acid availability on fatty acid oxidation, particularly at low levels of free fatty acids. Nonetheless, the rate of glucose or glycogen metabolism is probably the primary regulator of the balance between glucose and fatty acid oxidation in muscle.

Postoperative radiotherapy in high-risk postmenopausal breast-cancer patients given adjuvant tamoxifen: Danish Breast Cancer Cooperative Group DBCG 82c randomised trial

BACKGROUND

Postmastectomy radiotherapy is associated with a lower locoregional recurrence rate and improved disease-free and overall survival when combined with chemotherapy in premenopausal high-risk breast-cancer patients. However, whether the same benefits apply also in postmenopausal women treated with adjuvant tamoxifen for similar high-risk cancer is unclear. In a randomised trial among postmenopausal women who had undergone mastectomy, we compared adjuvant tamoxifen alone with tamoxifen plus postoperative radiotherapy.

METHODS

Between 1982 and 1990, postmenopausal women with high-risk breast cancer (stage II or III) were randomly assigned adjuvant tamoxifen (30 mg daily for 1 year) alone (689) or with postoperative radiotherapy to the chest wall and regional lymph nodes (686). Median follow-up was 123 months. The endpoints were first site of recurrence (locoregional recurrence, distant metastases, or both), and disease-free and overall survival.

FINDINGS

Locoregional recurrence occurred in 52 (8%) of the radiotherapy plus tamoxifen group and 242 (35%) of the tamoxifen only group (p<0.001). In total there were 321 (47%) and 411 (60%) recurrences, respectively. Disease-free survival was 36% in the radiotherapy plus tamoxifen group and 24% in the tamoxifen alone group (p<0.001). Overall survival was also higher in the radiotherapy group (385 vs 434 deaths; survival 45 vs 36% at 10 years, p=0.03).

INTERPRETATION

Postoperative radiotherapy decreased the risk of locoregional recurrence and was associated with improved survival in high-risk postmenopausal breast-cancer patients after mastectomy and limited axillary dissection, with 1 year of adjuvant tamoxifen treatment. Improved survival in high-risk breast cancer can best be achieved by a strategy of both locoregional and systemic tumour control.

In vitro metabolism of quinidine: the (3S)-3-hydroxylation of quinidine is a specific marker reaction for cytochrome P-4503A4 activity in human liver microsomes

The aim of this study was to evaluate the (3S)-3-hydroxylation and the N-oxidation of quinidine as biomarkers for cytochrome P-450 (CYP)3A4 activity in human liver microsome preparations. An HPLC method was developed to assay the metabolites (3S)-3-hydroxyquinidine (3-OH-Q) and quinidine N-oxide (Q-N-OX) formed during incubation with microsomes from human liver and from Saccharomyces cerevisiae strains expressing 10 human CYPs. 3-OH-Q formation complied with Michaelis-Menten kinetics (mean values of Vmax and Km: 74.4 nmol/mg/h and 74.2 microM, respectively). Q-N-OX formation followed two-site kinetics with mean values of Vmax, Km and Vmax/Km for the low affinity isozyme of 15.9 nmol/mg/h, 76.1 microM and 0.03 ml/mg/h, respectively. 3-OH-Q and Q-N-OX formations were potently inhibited by ketoconazole, itraconazole, and triacetyloleandomycin. Isozyme specific inhibitors of CYP1A2, -2C9, -2C19, -2D6, and -2E1 did not inhibit 3-OH-Q or Q-N-OX formation, with Ki values comparable with previously reported values. Statistically significant correlations were observed between CYP3A4 content and formations of 3-OH-Q and Q-N-OX in 12 human liver microsome preparations. Studies with yeast-expressed isozymes revealed that only CYP3A4 actively catalyzed the (3S)-3-hydroxylation. CYP3A4 was the most active enzyme in Q-N-OX formation, but CYP2C9 and 2E1 also catalyzed minor proportions of the N-oxidation. In conclusion, our studies demonstrate that only CYP3A4 is actively involved in the formation of 3-OH-Q. Hence, the (3S)-3-hydroxylation of quinidine is a specific probe for CYP3A4 activity in human liver microsome preparations, whereas the N-oxidation of quinidine is a somewhat less specific marker reaction for CYP3A4 activity, because the presence of a low affinity enzyme is demonstrated by different approaches.

Fluvoxamine is a potent inhibitor of the metabolism of caffeine in vitro

The selective serotonin re-uptake inhibitor, fluvoxamine, is a very potent inhibitor of CYP1A2, and accordingly causes pharmacokinetic interactions with drugs metabolised by CYP1A2, such as caffeine, theophylline, imipramine, tacrine and clozapine. Interaction between caffeine and fluvoxamine has been described in vivo, leading to lowering of total clearance of caffeine by 80% during fluvoxamine intake. The main purpose of the present study was to evaluate this interaction in vitro in human liver microsomes. A high-performance liquid chromatography method was developed in order to assay 1,3-dimethylxanthine, 1,7-dimethylxanthine, 3,7-dimethylxanthine and 1,3,7-trimethyluric acid formed from caffeine by human liver microsomes. The limit of detection was 0.06 nmol.mg protein-1.hr-1. As expected, fluvoxamine was a very potent inhibitor of the formation of the N-demethylated caffeine metabolites, displaying Ki values of 0.08-0.28 microM. The formation of 1,7-dimethylxanthine was virtually abolished by 10 microM of fluvoxamine, indicating that the N3-demethylation of caffeine is almost exclusively catalysed by CYP1A2. The CYP3A4 inhibitors, ketoconazole and bromocriptine, inhibited 1,3,7-trimethyluric acid formation with Kis of 0.75 microM and 5 microM, respectively, thus further supporting the involvement of CYP3A4 in the 8-hydroxylation of caffeine. The study shows that fluvoxamine, as expected, is a potent inhibitor of the metabolism of caffeine in vitro.

Fluvoxamine inhibits the CYP2C19-catalysed metabolism of proguanil in vitro

OBJECTIVE

The potent CYP1A2 inhibitor fluvoxamine has recently been shown also to be an effective inhibitor of the CYP2C19-mediated metabolism of the antimalarial drug proguanil in vivo. The purpose of the present study was to confirm this interaction in vitro.

METHODS

A high-performance liquid chromatography (HPLC) method was developed to assay 4-chlorophenylbiguanide (4-CPBG) and cycloguanil formed from proguanil by microsomes prepared from human liver. The limit of detection was 0.08 nmol mg-'. h-I.

RESULTS

The formation of 4-CPBG and cycloguanil could be described by one-enzyme kinetics, indicating that the formation of the two metabolites is almost exclusively catalysed by a single enzyme, i.e. CYP2C19 within the concentration range used, or that the contribution of an alternative low-affinity enzyme, probably CYP3A4, is very low. This notion was confirmed by the lack of potent inhibition by four CYP3A4 inhibitors: ketoconazole, bromocriptine, midazolam and dihydroergotamine. Fluvoxamine was a very effective inhibitor of the oxidation of proguanil, displaying Ki values of 0.69 micromol x l(-1) for the inhibition of cycloguanil formation and 4.7 micromol x l(-1) for the inhibition of 4-CPBG formation. As expected, the CYP2C19 substrate omeprazole inhibited the formation of both metabolites with an IC50 of 10 micromol x l(-1). Norfluoxetine and sulfaphenazole inhibited proguanil oxidation with Ki values of 7.3-16 micromol x l(-1), suggesting that the two compounds are moderate inhibitors of CYP2C19.

CONCLUSIONS

Fluvoxamine is a fairly potent inhibitor of CYP2C19 and it has the potential for causing drug-drug interactions with substrates for CYP2C19 such as imipramine, clomipramine, amitriptyline and diazepam. The combination of fluvoxamine and proguanil can not be recommended.

Postexercise recovery of skeletal muscle malonyl-CoA, acetyl-CoA carboxylase, and AMP-activated protein kinase

Previous studies have demonstrated that oxygen consumption and fat oxidation remain elevated in the postexercise period. The purpose of this study was to determine whether malonyl-CoA, an inhibitor of fatty acid oxidation, remains depressed in muscle after exercise. Rats were sprinted for 5 min (40 m/min, 5% grade) or run for 30 min (21 m/min, 15% grade). Red quadriceps malonyl-CoA returned to resting values by 90 min postexercise in the sprinting rats and remained significantly lower at least 90 min postexercise in the 30-min exercise group. AMP-activated protein kinase activity remained significantly elevated (P < 0.05) for 10 min after exercise in both groups. The most rapid rate of glycogen repletion was in the first 30 min postexercise. The respiratory exchange ratio decreased from a nonexercise value of 0.87 +/- 0.01 to an average 0.82 +/- 0.01 during the 90-min period after 30 min of exercise. Thus muscle malonyl-CoA remains depressed and fat oxidation is elevated for relatively prolonged periods after a single bout of exercise. This may allow fat oxidation to contribute more to muscle energy requirements, thus leaving more glucose for replenishment of muscle glycogen.

Influence of malonyl-CoA and palmitate concentration on rate of palmitate oxidation in rat muscle

5-Aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR) is taken up by perfused skeletal muscle and phosphorylated to form 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuraosyl-5'-monopho sph ate (analog of 5'-AMP) with consequent activation of AMP-activated protein kinase, phosphorylation of acetyl-CoA carboxylase, decrease in malonyl-CoA, and increase in fatty acid oxidation. This study was designed to determine the effect of increasing levels of palmitate on the rate of fatty acid oxidation. Malonyl-CoA concentration was manipulated with AICAR at different palmitate concentrations. Rat hindlimbs were perfused with Krebs-Henseleit bicarbonate containing 4% bovine serum albumin, washed bovine red cells, 200 microU/ml insulin, 10 mM glucose, and different concentrations of palmitate (0. 1-1.0 mM) without or with AICAR (2.0 mM). Perfusion with medium containing AICAR was found to activate AMP-activated protein kinase in skeletal muscle, inactivate acetyl-CoA carboxylase, and decrease malonyl-CoA at all concentrations of palmitate. The rate of palmitate oxidation increased as a function of palmitate concentration in both the presence and absence of AICAR but was always higher in the presence of AICAR. These results provide additional evidence that malonyl-CoA is an important regulator of the rate of fatty acid oxidation at palmitate concentrations in the physiological range.

The oxidative metabolism of metoprolol in human liver microsomes: inhibition by the selective serotonin reuptake inhibitors

OBJECTIVE

Biotransformation of metoprolol to alpha-hydroxymetoprolol (HM) and O-demethylmetoprolol (ODM) is mediated by CYP2D6. The selective serotonin reuptake inhibitors (SSRIs) are known to inhibit CYP2D6. The aim was to study in vitro the potential inhibitory effect of SSRIs on metoprolol biotransformation.

METHODS

Using microsomes from two human livers, biotransformation of metoprolol to alpha-hydroxymetoprolol (HM) and O-demethylmetoprolol (ODM) as a function of the concentrations of the SSRIs and of some of their metabolites was studied.

RESULTS

The kinetics of the formation of both metabolites are best described by a biphasic enzyme model. The estimated values of Vmax and kM for the high affinity site are for the alpha-hydroxylation in human liver HL-1 32 pmol mg(-1) min(-1) and 75 micromol x l(-1) respectively, and in human liver HL-9 39 pmol mg(-1) x min(-1) and 70 micromol x l(-1) respectively; for the O-demethylation in HL-1 131 pmol mg(-1) min(-1) and 95 micromol x l(-1) respectively, and in HL-9 145 pmol mg(-1) min(-1) and 94 micromol x l(-1) respectively. Quinidine is for both pathways a potent inhibitor of the high-affinity site, with K(i) values ranging from 0.03 to 0.18 micromol x l(-1). Fluoxetine, norfluoxetine and paroxetine are likewise potent inhibitors, with Ki values ranging from 0.30 to 2.1 micromol x l(-1) fluvoxamine, sertraline, desmethylsertraline, citalopram and desmethylcitalopram are less potent inhibitors, with K(i) values above 10 micromol x l(-1).

CONCLUSION

The rank order of the SSRIs for inhibition of metoprolol metabolism is comparable to that reported in the literature for other CYP2D6 substrates, with fluoxetine, norfluoxetine and paroxetine being the most potent. These findings need further investigation to determine their clinical relevance.

Endurance training attenuates the decrease in skeletal muscle malonyl-CoA with exercise

Muscle malonyl-CoA has been postulated to regulate fatty acid metabolism by inhibiting carnitine palmitoyltransferase 1. In nontrained rats, malonyl-CoA decreases in working muscle during exercise. Endurance training is known to increase a muscle's reliance on fatty acids as a substrate. This study was designed to investigate whether the decline in malonyl-CoA with exercise would be greater in trained than in nontrained muscle, thereby allowing increased fatty acid oxidation. After 6-10 wk of endurance training (2 h/day) or treadmill habituation (5-10 min/day), rats were killed at rest or after running up a 15% grade at 21 m/min for 5, 20, or 60 min. Training attenuated the exercise-induced drop in malonyl-CoA and prevented the exercise-induced increase in the constant for citrate activation of acetyl-CoA carboxylase in the red quadriceps muscle of rats run for 20 and 60 min. Hence, contrary to expectations, the decrease in malonyl-CoA was less in trained than in nontrained muscle during a single bout of prolonged submaximal exercise.

Effect of exercise intensity on skeletal muscle malonyl-CoA and acetyl-CoA carboxylase

Malonyl-CoA is synthesized by acetyl-CoA carboxylase (ACC) and is an inhibitor of fatty acid oxidation. Exercise induces a decline in skeletal muscle malonyl-CoA, which is accompanied by inactivation of ACC and increased activity of AMP-activated protein kinase (AMPK). This study was designed to determine the effect of exercise intensity on the enzyme kinetics of ACC, malonyl-CoA levels, and AMPK activity in skeletal muscle. Male Sprague-Dawley rats were killed (pentobarbital sodium anesthesia) at rest or after 5 min of exercise (10, 20, 30, or 40 m/min at 5% grade). The fast-twitch red and white regions of the quadriceps muscle were excised and frozen in liquid nitrogen. A progressive decrease in red quadriceps ACC maximal velocity (from 28.6 +/- 1.5 to 14.3 +/- 0.7 nmol . g-1 . min-1, P < 0.05), an increase in activation constant for citrate, and a decrease in malonyl-CoA (from 1.9 +/- 0.2 to 0.9 +/- 0.1 nmol/g, P < 0.05) were seen with the increase in exercise intensity from rest to 40 m/min. AMPK activity increased more than twofold. White quadriceps ACC activity decreased only during intense exercise. We conclude that the extent of ACC inactivation during short-term exercise is dependent on exercise intensity.

Fluvoxamine inhibits the CYP2C19-catalyzed bioactivation of chloroguanide

OBJECTIVE

To investigate the interaction between fluvoxamine and chloroguanide (INN, proguanil) to confirm that fluvoxamine inhibits CYP2C19.

METHODS

The study was carried out with a randomized, in vivo, crossover design. Six volunteers were extensive metabolizers of the S-mephenytoin oxidation polymorphism, and six volunteers were poor metabolizers. In period A of the study, each subject took 200 mg chloroguanide orally. In period B, each subject took 100 mg/day fluvoxamine for 8 days and on day 6 ingested 200 mg chloroguanide. In both periods, blood and urine were sampled at regular intervals. Chloroguanide and its two metabolites cycloguanil and 4-chlorphenylbiguanide in plasma and in urine were assayed by means of HPLC.

RESULTS

During fluvoxamine use, the median of the total clearance of chloroguanide decreased in a statistically significant way from 1282 ml/min to 782 ml/min among the extensive metabolizers, whereas there was no change among the poor metabolizers. The partial clearance of chloroguanide by means of cydoguanil and 4-chlorphenylbiguanide formation among the extensive metabolizers decreased from 222 ml/min and 97 ml/min before to 33 ml/min and 11 ml/min during fluvoxamine intake, respectively. Among poor metabolizers the corresponding values were 35 ml/min and 7.6 ml/min before and 38 ml/min and 6.9 ml/min during fluvoxamine intake. For each metabolite clearance the change was statistically significant among the extensive metabolizers but not among the poor metabolizers. Both cycloguanil and 4-chlorphenylbiguanide formation clearances were statistically significantly higher among the extensive metabolizers than the poor metabolizers in period A but not in period B (phenocopy).

CONCLUSION

Fluvoxamine is an effective inhibitor of CYP2C19.

Theophylline has no advantages over caffeine as a putative model drug for assessing CYPIA2 activity in humans

AIMS

The cytochrome P4501A2 (CYP1A2) catalyses the metabolism of a number of clinically used drugs, and thus there is an interest in determining the activity of CYP1A2 in patients before treatment with CYP1A2 substrates. Caffeine is the most commonly used model drug to assess CYP1A2 function, but due to the complex metabolism of caffeine, there is a need for an alternative drug to use as an index of CYP1A2 activity. In this study the CYP1A2 substrate theophylline was tested as a possible alternative to caffeine as a model drug for CYP1A2.

METHODS

Twelve healthy volunteers ingested 200 mg of caffeine, and the caffeine metabolic ratios (CMR), CMRurine = (AFMU + 1MX + 1MU)/17DMU and CMRplasma = 17DMX/137TMX were determined 6 h after drug intake. After a period of about 2 months the volunteers ingested 257 mg theophylline and blood samples were drawn and urine was collected during the following 48 h. The oral and partial clearance of theophylline were calculated via N-demethylation and 8-hydroxylation. The theophylline metabolic ratios, 1MU/13DMX and 3MX/13DMX being evaluated as indices of CYP1A2 catalysed N-demethylation and 13DMU/13DMX as an index of partly CYP1A2 catalysed 8-hydroxylation, were estimated in 0-12 h, 0-24 h and 0-48 h urine samples, and in plasma and spot urine samples 6 h after the intake of theophylline.

RESULTS

The theophylline plasma ratios for the N-demethylation pathways correlated with the oral clearance of theophylline (rs = 0.881-0.934, P < 0.001) and with the respective formation clearances of the metabolites (rs = 0.712-0.925, P < 0.05). Furthermore, all of the theophylline plasma ratios correlated with the caffeine plasma ratio (rs = 0.645-0.663, P < 0.05). None of the caffeine metabolic ratios and none of the 6 h urinary theophylline ratios correlated with the oral or the partial clearances of theophylline (rs = 0.042-0.556, P < 0.05). The theophylline 0-12 h urine ratios correlated with the oral clearance of theophylline (rs = 0.677-0.757, P < 0.05) and with the respective formation clearances of the metabolites (rs = 0.705-0.750, P < 0.05). However, none of the theophylline urine ratios correlated with any of the caffeine metabolic ratios.

CONCLUSIONS

In summary the theophylline 6 h plasma and 0-12 h urine ratios 1MU/13DMX and 3MX/13DMX, both reflecting N-demethylation seem to be predictors of the CYP1A2 mediated metabolism of theophylline, whereas only the plasma ratio correlated with the caffeine plasma 17DMX/13TMX ratio. Thus, it would appear that the plasma theophylline N-demethylation ratios are superior to the urine ratios as indices of CYP1A2 activity. However, because in some individuals the concentrations of theophylline metabolites in plasma were close to the limit of detection, it is concluded that theophylline does not have marked advantages over caffeine as a model drug for assessing CYP1A2 activity.

Imipramine demethylation in vivo: impact of CYP1A2, CYP2C19, and CYP3A4

OBJECTIVE

To further substantiate the role of CYP1A2 and CYP3A4 for the N-demethylation in vivo. At least three different P450s appear to be responsible for the N-demethylation of imipramine to desipramine in vivo: CYP1A2, CYP2C19, and CYP3A4. The role of CYP2C19 in this regard is well documented, but for the two other P450s the evidence is either indirect or based on in vitro studies.

METHODS

Phenotypic tests for imipramine N-demethylation, CYP1A2 (caffeine testing), CYP2C19 (mephenytoin and chloroguanide [proguanil] testing), and CYP3A4 (hydrocortisone and quinidine testing) were carried out in 32 healthy young Danes; all were poor (n = 31) or extremely slow extensive metabolizers (n = 1) of sparteine.

RESULTS

By exclusion of the insignificant log-transformed variables, multiple regression analysis for In (desipramine/imipramine) showed that only in (mephenytoin S/R) correlated (p = 0.013; r2 = 0.19). For in (2-hydroxydesipramine/2-hydroxyimipramine) we found that in (mephenytoin S/R) and in (4-chlorophenylbiguanide/chloroguanide) correlated (p = 0.001; r2 = 0.41).

CONCLUSION

We did not find in vivo evidence of either CYP1A2 or CYP3A4 activity in the N-demethylation of imipramine. This could be due in part to inadequate CYP1A2 and CYP3A4 in vivo function tests.

Griseofulvin and fluvoxamine interactions with the metabolism of theophylline

Theophylline is predominantly metabolized by cytochrome P4501A2 (CYP1A2). A possible interaction between griseofulvin and theophylline was reported to our laboratory, which led us to form the hypothesis that griseofulvin induces the metabolism of theophylline. One purpose of this study was to investigate this hypothesis. The study was carried out as a randomized crossover study of 12 healthy volunteers. In period A of the study, each volunteer received a single dose of 300 mg theophylline ethylenediamine orally. In period B, the subjects took fluvoxamine, 50 mg for 1 day and 100 mg for 6 days, and on day 4, the subjects ingested 300 mg theophylline ethylenediamine. Fluvoxamine is a potent inhibitor of CYP1A2, and period B was included as a positive control. In period C, the subjects took 500 mg griseofulvin for 9 days; on day 8 the subjects again ingested 300 mg theophylline ethylenediamine. Theophylline and its metabolites (1-methyluric acid [IMU], 3-methylxanthine [3MX], and 1,3-dimethyluric acid [13DMU]) in plasma and urine were assayed by high-performance liquid chromatography. During fluvoxamine intake, the median of the total clearance of theophylline decreased from 80 ml/min to 24 ml/min, and the half-life increased from 6.6 to 22 h. The partial formation clearances of the metabolites decreased from 17 to 1.7 ml/min, from 8.9 to 0.9 ml/min, and from 21 to 6.8 ml/min for 1MU, 3MX, and 13DMU, respectively. The results confirm that assessment of theophylline metabolism indeed serves as a biomarker for CYP1A2. During griseofulvin ingestion, the median of the total and partial clearances of theophylline were 84 ml/min, 22 ml/min (1MU), 9.4 ml/min (3MX), and 25 ml/min (13DMU). The half-life decreased significantly from 6.6 to 5.7 h. The increase in partial formation clearances of 1MU and 13DMU, but not of 3MX, were statistically significant. The increase in the total clearance reached only borderline significance. In four subjects a marked induction was seen for all pharmacokinetic parameters, suggesting that the susceptibility to induction is more pronounced in some subjects. This susceptibility could theoretically be explained by a polymorphism in the inducibility of the gene coding for the CYP1A2 enzyme.

Phosphorylation of rat muscle acetyl-CoA carboxylase by AMP-activated protein kinase and protein kinase A

This study was designed to compare functional effects of phosphorylation of muscle acetyl-CoA carboxylase (ACC) by adenosine 3',5'-cyclic monophosphate-dependent protein kinase (PKA) and by AMP-activated protein kinase (AMPK). Muscle ACC (272 kDa) was phosphorylated and then subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography. Functional effects of phosphorylation were determined by measuring ACC activity at different concentrations of each of the substrates and of citrate, an activator of the enzyme. The maximal velocity (Vmax) and the Michaelis constants (Km) for ATP, acetyl-CoA, and bicarbonate were unaffected by phosphorylation by PKA. Phosphorylation by AMPK increased the Km for ATP and acetyl-CoA. Sequential phosphorylation by PKA and AMPK, first without label and second with label, appeared to reduce the extent of label incorporation, regardless of the order. The activation constant (Ka) for citrate activation was increased to the same extent by AMPK phosphorylation, regardless of previous or subsequent phosphorylation by PKA. Thus muscle ACC can be phosphorylated by PKA but with no apparent functional effects on the enzyme. AMPK appears to be the more important regulator of muscle ACC.

Comparison of two monoclonal antibodies for the detection of estrogen receptors in primary breast carcinomas

A new monoclonal antibody against estrogen receptor (ID5, Dako) has shown promising results when applied to formalin fixed, paraffin embedded tissue. In order to determine whether this antibody can compete in specificity and sensitivity with the ER-ICA antibody (Abbott Laboratories), a comparative, prospective study of the two antibodies was carried out on paraffin embedded and fresh frozen tissue in three laboratories. Two hundred and fifteen breast carcinomas were examined. Formalin fixed, paraffin embedded tissue was available from 215 tumors, and fresh frozen tissue from 189 of the tumors. Of these, 124 tumors were also investigated by the enzyme-linked immunosorbent assay. The results from each of the three laboratories correspond with those obtained for the whole material. The percentage of tumors positive for estrogen receptors within the different methods, was as follows: 71% by ID5 on paraffin sections, 50% by ER-ICA on paraffin sections, 65% ER-ICA on frozen sections and 88% by the EIA. When comparing the different immunohistochemical results and the EIA in 2 x 2 tables, agreement was reached in 69% to 91% of the cases. The best agreement (91%) was found between results obtained with the ID5 antibody used on formalin fixed, paraffin embedded tissue and the ER-ICA kit used on fresh frozen tissue. The advantages of using the ID5 antibody are associated with its applicability to formalin fixed, paraffin embedded tissue: improved morphology, reproducibility, retrospective studying and low costs. Finally, it is reproducible not only within the same laboratory but also among different laboratories.

Determination of urinary metabolites of caffeine for the assessment of cytochrome P4501A2, xanthine oxidase, and N-acetyltransferase activity in humans

Caffeine metabolism via the 3-demethylation pathway is sequentially catalyzed by cytochrome P4501A2 (CYP1A2), xanthine oxidase, and N-acetyltransferase. The activities of the three enzymes can be estimated from urinary metabolic ratios of four caffeine metabolites, 5-acetylamino-6-formylamino-3-methyluracil (AFMU), 1-methyluric acid (1MU), 1-methylxanthine (1MX), and 1,7-dimethyluric acid (17DMU), after the ingestion of caffeine. A method for quantitation of the four metabolites in human urine has been developed. The method is based on a one-step extraction with ethyl acetate/2-propanol followed by high-performance liquid chromatography with UV detection. The detection limit was 1 microM for AFMU, 1MU, and 1MX and 2 microM for 17DMU. The intraday and interday coefficients of variation were < 3% and < 7%, respectively, and the accuracy was within +/- 3%. The method was employed in a population study of 277 healthy volunteers, each of whom ingested 200 mg caffeine and provided a urine sample approximately 6 h later. The metabolite concentration ranges in the urines were 2.1-327 microM, 4.0-744 microM, 4.9-598 microM, and 6.4-260 microM for AFMU, 1MU, 1MX, and 17DMU, respectively. The CYP1A2 ratio (AFMU + 1MU + 1MX/17DMU) was significantly lower in women than in men, excluding smokers and oral contraceptive users. The CYP1A2 ratio was higher in smokers than in nonsmokers, confirming the induction of CYP1A2 by smoking. In women using oral contraceptives, the CYP1A2 ratio was, as expected, significantly lower than in women not using oral contraceptives. For the N-acetyltransferase ratio (AFMU/1MX) and the xanthine oxidase ratio (1MU/1MX), no differences were seen in terms of sex, smoking habits, or the use of oral contraceptives. All results are in agreement with previous reports on CYP1A2, N-acetyltransferase, and xanthine oxidase activities in humans. Thus, the method is both analytically and biologically reliable for the assessment of CYP1A2, N-acetyltransferase, and xanthine oxidase in humans.

Determination of theophylline and its metabolites in human urine and plasma by high-performance liquid chromatography

A method for the quantitation of theophylline (13DMX) and the three metabolites, 1-methyluric acid (1MU), 3-methylxanthine (3MX) and 1,3-dimethyluric acid (13DMU) in human plasma and urine has been developed. The method is based on a simple one-step liquid-liquid extraction with ethylacetate-2-propanol followed by isocratic, reversed-phase high-performance liquid chromatography with UV detection (detection wavelength: 273 nm). The overall mean recoveries ranged from 86 to 95% for the four compounds. The detection limit was 1 microM for 1MU, 3MX and 13DMU and 2 microM for 13DMX in urine, and 0.1 microM for 1MU, 3MX and 13DMU and 0.2 microM for 13DMX in plasma. The intra-day and inter-day coefficient of variation was < 6% and < 9%, respectively, and the accuracy was within +/- 10% in both urine and plasma. The simple but sensitive method is highly suitable for the development of theophylline as a probe drug for assessing CYP1A2 activity in man.

Selective serotonin reuptake inhibitors and theophylline metabolism in human liver microsomes: potent inhibition by fluvoxamine

1. Fluvoxamine and seven other selective serotonin reuptake inhibitors (SRRI) were tested for their ability to inhibit a number of human cytochrome P450 isoforms (CYPs). 2. None of the drugs showed potent inhibition of CYP2A6 (coumarin 7-hydroxylase) or CYP2E1 (chlorzoxazone 6-hydroxylase), while norfluoxetine was the only potent inhibitor of CYP3A having IC50 values of 11 microM and 19 microM for testosterone 6 beta-hydroxylase and cortisol 6 beta-hydroxylase, respectively. 3. Norfluoxetine, sertraline and fluvoxamine inhibited CYP1A1 (7-ethoxyresorufin O-deethylase) in microsomes from human placenta (IC50 values 29 microM, 35 microM and 80 microM, respectively). Fluvoxamine was a potent inhibitor of CYP1A2-mediated 7-ethoxyresorufin O-deethylase activity (IC50 = 0.3 microM) in human liver. 4. In microsomes from three human livers fluvoxamine potently inhibited all pathways of theophylline biotransformation, the apparent inhibitor constant, Ki, was 0.07-0.13 microM, 0.05-0.10 microM and 0.16-0.29 microM for inhibition of 1-methylxanthine, 3-methylxanthine and 1,3-dimethyluric acid formation, respectively. Seven other SSRIs showed either weak or no inhibition of theophylline metabolism. 5. Ethanol inhibited the formation of 1,3-dimethyluric acid with K(i) value of 300 microM, a value which is consistent with inhibition of CYP2E1. Ethanol and fluvoxamine both inhibited 8-hydroxylation by about 45% and, in combination, the compounds decreased the formation of 1,3-dimethyluric acid by 90%, indicating that CYP1A2 and CYP2E1 are equally important isoforms for the 8-hydroxylation of theophylline. 6. It is concluded that pharmacokinetic interaction between fluvoxamine and theophylline is due to potent inhibition of CYP1A2.

Determination of theophylline metabolites in human liver microsomes by high-performance liquid chromatography

A method for the quantitation of three metabolites of theophylline, 1-methylxanthine (1 MX), 3-methylxanthine (3MX), and 1,3-dimethyluric acid (13DMU) in human liver microsomes has been developed. The method is based on a simple one-step extraction followed by isocratic, reversed-phase high-performance liquid chromatography with uv detection (detection wavelength: 273 nm). The detection limit was 0.03 nmol.mg-1.h-1, which corresponds to 10 pmol per sample for all three metabolites. Linear standard curves were obtained for all three compounds within a concentration range of 0.6-6.0 nmol.mg-1.h-1 for 3MX and 1MX and 2.4-24.0 nmol.mg-1.h-1 for 13DMU. The absolute recoveries ranged from 61 to 80%, 68 to 74%, and 74 to 85% for 1MX, 3MX, and 13DMU, respectively, within the concentration range of the standard curve. The reproducibility and repeatability showed a coefficient of variation < 12% at five concentrations within the standard curve range. The accuracy for all three metabolites was within +/- 5% at three concentrations, except for 1MX in the lowest concentration (12%). The simple but sensitive method developed is highly suitable as a probe for cytochrome P4501A2 (CYP1A2) and probably also CYP2E1 function in human liver microsomes.

Estrogen- and progesterone receptors in normal cycling endometrium as studied by end-point titration

A thorough knowledge of the normal physiological fluctuations in estrogen- (ER) and progesterone receptors (PgR) is essential to characterize the changes in ER and PgR in the abnormal endometrium. We investigated the distribution of ER and PgR in frozen human cycling endometrial tissue using the commercially available ER- and PgR-ICA kits. Two-fold end-point titration (EPT) of ER and PgR antibodies was implemented to semi-quantitate more accurately ER and PgR. Semiquantitation of ER and PgR using EPT was significantly correlated to results obtained using either simple scoring or enzyme-immunoassay (EIA) methods. ER and PgR staining fluctuated in relation to the menstrual cycle. In most subphases PgR exceeded ER in both epithelial and stromal cells. Highest levels of ER and PgR were demonstrated in the glands of the functionalis in mid-to-late proliferative phases, whereas both receptors were almost undetectable by immunohistology in the glands of mid-to-late secretory phases. Endometrial stromal cells had high and nearly constant EPT values for PgR, but low values for ER throughout the menstrual cycle. EPT values for ER and PgR were generally higher in the basalis than in the functionalis but showed similar cyclic fluctuations. Our results further substantiate the view that the response to hormonal stimulation is cell-type specific, and suggest differences in steroid metabolism according to cell type and layer.

Flow cytometric DNA ploidy defines patients with poor prognosis in node-negative breast cancer

Flow cytometric DNA analysis was performed on fine-needle aspirates from frozen tumour biopsies from 421 node-negative, non-adjuvantly-treated breast-cancer patients with a median observation time of 6.75 years. Among premenopausal patients (n = 175), those having at least one DNA "hypoploid" subpopulation defined as DNA index (DI) < 0.96 or 1.44 < or = 1.92 (n = 81) were characterized by early recurrences (log-rank p = 0.05), Wilcoxon p = 0.007), poor overall survival (OS) (p < 0.001) and poor survival after recurrence (p < 0.001). In the postmenopausal group (n = 246), there were no significant difference among 7 different DI classes regarding either recurrence-free survival (RFS) or OS. S-phase fraction (SPF), divided into quartiles, predicted OS in premenopausal patients only (p = 0.02). Conventional multivariate Cox analysis of OS in the premenopausal group revealed hypoploidy to be the only independent prognostic factor involving a relative risk (RR) of 22.8. Age < or = 40 years was of marginal significance, whereas SPF, histological grade (WHO), oestrogen and progesterone receptor (PgR) content, tumour size and number of lymph nodes removed were excluded from the model. Application of the conventional Cox model to the premenopausal group regarding RFS was found inappropriate due to lack of proportionality of the hazards of hypoploidy due to lack of proportionately of the hazards of hypoploidy, SPF and histological grade. However, introduction of time-dependent co-variates using 2 years as cut-off level showed hypoploidy with a RR of 3.52 and age < or = 40 years with a RR of 3.28 to be independent prognostic factors. In the postmenopausal group, the conventional Cox model identified the number of lymph nodes removed to be the only independent prognostic factor regarding RFS as well as OS, whereas SPF < 9% (lowest quartile) was of marginal significance in RFS analysis. Hypoploidy was correlated to high SPF, low PgR content and low differentiation, indicating that hypoploid tumours proliferate rapidly and hormone-independently. These patients may therefore benefit from adjuvant chemotherapy administered while tumour burden and risk of drug resistance are still low.