Prognostic value of EndoPredict test in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative primary breast cancer screened for the randomized, double-blind, phase III UNIRAD trial.

BACKGROUND: The purpose of this study was to evaluate the prognostic value of the multigene EndoPredict test in prospectively collected data of patients screened for the randomized, double-blind, phase III UNIRAD trial, which evaluated the addition of everolimus to adjuvant endocrine therapy in high-risk, hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative early breast cancer. PATIENTS AND METHODS: Patients were classified into low or high risk according to the EPclin score, consisting of a 12-gene molecular score combined with tumor size and nodal status. Association of the EPclin score with disease-free survival (DFS) and distant metastasis-free survival (DMFS) was evaluated using Kaplan-Meier estimates. The independent prognostic added value of EPclin score was tested in a multivariate Cox model after adjusting on tumor characteristics. RESULTS: EndoPredict test results were available for 768 patients: 663 patients classified as EPclin high risk (EPCH) and 105 patients as EPclin low risk (EPCL). Median follow-up was 70 months (range 1-172 months). For the 429 EPCH randomized patients, there was no significant difference in DFS between treatment arms. The 60-month relapse rate for patients in the EPCL and EPCH groups was 0% and 7%, respectively. Hazard ratio (HR) supposing continuous EPclin score was 1.87 [95% confidence interval (CI) 1.4-2.5, P < 0.0001]. This prognostic effect remained significant when assessed in a Cox model adjusting on tumor size, number of positive nodes and tumor grade (HR 1.52, 95% CI 1.09-2.13, P = 0.0141). The 60-month DMFS for patients in the EPCL and EPCH groups was 100% and 94%, respectively (adjusted HR 8.10, 95% CI 1.1-59.1, P < 0.0001). CONCLUSIONS: The results confirm the value of EPclin score as an independent prognostic parameter in node-positive, hormone receptor-positive, HER2-negative early breast cancer patients receiving standard adjuvant treatment. EPclin score can be used to identify patients at higher risk of recurrence who may warrant additional systemic treatments.

Real-world EGFR testing practices for non-small-cell lung cancer by thoracic pathology laboratories across Europe.

BACKGROUND: Testing for epidermal growth factor receptor (EGFR) mutations is an essential recommendation in guidelines for metastatic non-squamous non-small-cell lung cancer, and is considered mandatory in European countries. However, in practice, challenges are often faced when carrying out routine biomarker testing, including access to testing, inadequate tissue samples and long turnaround times (TATs). MATERIALS AND METHODS: To evaluate the real-world EGFR testing practices of European pathology laboratories, an online survey was set up and validated by the Pulmonary Pathology Working Group of the European Society of Pathology and distributed to 64 expert testing laboratories. The retrospective survey focussed on laboratory organisation and daily EGFR testing practice of pathologists and molecular biologists between 2018 and 2021. RESULTS: TATs varied greatly both between and within countries. These discrepancies may be partly due to reflex testing practices, as 20.8% of laboratories carried out EGFR testing only at the request of the clinician. Many laboratories across Europe still favour single-test sequencing as a primary method of EGFR mutation identification; 32.7% indicated that they only used targeted techniques and 45.1% used single-gene testing followed by next-generation sequencing (NGS), depending on the case. Reported testing rates were consistent over time with no significant decrease in the number of EGFR tests carried out in 2020, despite the increased pressure faced by testing facilities during the COVID-19 pandemic. ISO 15189 accreditation was reported by 42.0% of molecular biology laboratories for single-test sequencing, and by 42.3% for NGS. 92.5% of laboratories indicated they regularly participate in an external quality assessment scheme. CONCLUSIONS: These results highlight the strong heterogeneity of EGFR testing that still occurs within thoracic pathology and molecular biology laboratories across Europe. Even among expert testing facilities there is variability in testing capabilities, TAT, reflex testing practice and laboratory accreditation, stressing the need to harmonise reimbursement technologies and decision-making algorithms in Europe.

Compliance to genomic test recommendations to guide adjuvant chemotherapy decision-making in the case of hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer, in real-life settings.

BACKGROUND: Genomic tests are a useful tool for adjuvant chemotherapy decision-making in the case of hormone receptor-positive (HR+), and human epidermal growth factor receptor 2-negative (HER2-) breast cancer with intermediate prognostic factors. Real-life data on the use of tests can help identify the target population for testing. METHODS: French multicentric study (8 centers) including patients, all candidates for adjuvant chemotherapy for HR-positive, HER2-negative early breast cancer. We describe the percentage of tests performed outside recommendations, according to the year of testing. We calculated a ratio defined as the number of tests required to avoid chemotherapy for one patient, and according to patient and cancer characteristics. We then performed a cost-saving analysis using medical cost data over a period of 1 year from diagnosis, calculated from a previous study. Finally, we calculated the threshold of the ratio (number of tests required to avoid chemotherapy for one patient) below which the use of genomic tests was cost-saving. RESULTS: A total of 2331 patients underwent a Prosigna test. The ratio (performed test/avoided chemotherapy) was 2.8 [95% CI: 2.7-2.9] in the whole population. In the group following recommendations for test indication, the ratio was 2.3 [95% CI: 2.2-2.4]. In the case of non-abidance by recommendations, the ratio was 3 [95% CI: 2.8-3.2]. Chemotherapy was avoided in 841 patients (36%) following the results of the Prosigna test. The direct medical costs saved over 1 year of care were 3,878,798€ and 1,718,472€ in the group of patients following test recommendations. We calculated that the ratio (performed test/avoided chemotherapy) needed to be under 6.9 for testing to prove cost-saving. CONCLUSION: The use of genomic testing proved cost-saving in this large multicentric real-life analysis, even in certain cases when the test was performed outside recommendations.

Multicentric neoadjuvant pilot Phase II study of cetuximab combined with docetaxel in operable triple negative breast cancer.

Systemic therapy for triple negative breast cancer (TNBC) is mostly based upon chemotherapy. Epithelial Growth Factor Receptor (EGFR) is overexpressed in around 50% of TNBC and may play a role in its pathogenesis. Consequently, we performed a multicentric pilot Phase II neoadjuvant trial of cetuximab (anti-EGFR antibody) combined with docetaxel for patients with operable, Stage II-III TNBC. Therapy consisted of weekly cetuximab (first infusion: 400 mg/m(2), then 250 mg/m(2)) combined with six cycles of docetaxel (T: 100 mg/m(2)) q.3 weeks. Subsequently, all patients underwent surgery. The primary endpoint was pathological complete response (pCR) while clinical response, toxicity and ancillary studies were secondary endpoints. Paraffin-embedded and frozen tumor samples were systematically collected in order to identify predictive biomarkers of efficacy and resistance. From a total of 35 accrued patients, 25 were assessable for pathologic response. The pCR rate was 24% [95% CI: 7.3-40.7]. Complete clinical response rate (cCR) was observed in 22% of cases. Conservative surgery was performed in 75% of patients. Toxicity, mostly cutaneous and hematologic, was manageable. The pre-therapy ratio between CD8+ and FOXP3+ tumor-infiltrating lymphocytes equal or higher than 2.75 was predictive of pCR: 43% versus 0%, p = 0.047. Cetuximab in combination with docetaxel displays a modest activity, but acceptable toxicity as neoadjuvant therapy of operable TNBC. Similarly to previous observations using panitumumab, another anti-EGFR antibody, the immune component of the tumor microenvironment may play an important role in predicting TNBC response to the neoadjuvant therapy.

Morphological and immunohistochemical study of ovarian and tubal dysplasia associated with tamoxifen.

Ovarian epithelial dysplasia was initially described in material from prophylactic oophorectomies for BReast CAncer gene (BRCA) mutation. Similar histopathological abnormalities have been revealed after ovulation stimulation. Given that tamoxifen (TAM) has a clomid-like effect and is sometimes used to induce ovulation, we studied the morphological features and immunohistochemical expression patterns of neoplasia-associated markers in adnexectomies previously exposed to TAM for breast cancer. We blindly reviewed 173 histopathological slides of adnexectomies according to three groups - oophorectomie sassociated with TAM exposure (n=42), oophorectomies associated with clomiphene exposure (n=15) and a spontaneously fertile non cancerous control group (n=116). Morphological features (with an ovarian and tubal dysplasia scoring system) and immunohistochemical expression patterns of Ki-67, p53 and Aldehyde dehydrogenase 1 (ALDH1 is an enzyme significantly associated with earlystage ovarian cancer) were evaluated and correlated. Mean tubal dysplasia score was significantly higher in the TAM group and clomiphene group than in controls (respectively 7.8 vs 3.5, P<0.007 and 6.8 vs 3.5, P=0.008). There is no statistical difference for the ovarian score in TAM group in comparison with the control group whereas we found a significant score for clomiphen group (6.5, P=0.009). Increased ALDH1 expression was observed in the two exposed group whereas expression patterns of Ki67 and p53 were moderate. Interestingly, ALDH1 expression was low in non-dysplastic epithelium, high in dysplasia, and constantly low in the two carcinoma. Furthermore, we confirm our previous results showing that ALDH1 may be a useful tissue biomarker in the subtle histopathological diagnosis of tubo-ovarian dysplasia.

Multicentric neoadjuvant phase II study of panitumumab combined with an anthracycline/taxane-based chemotherapy in operable triple-negative breast cancer: identification of biologically defined signatures predicting treatment impact.

BACKGROUND: Triple-negative breast cancer (TNBC) is a heterogeneous group of tumors for some of which the epithelial growth factor receptor (EGFR) pathway may play an important role. We investigated the efficacy and toxicity of an anti-EGFR antibody (panitumumab) combined with a standard neoadjuvant anthracycline-taxane-based chemotherapy in patients with operable, stage II-III, TNBC. PATIENTS AND METHODS: Treatment in this multicentric neoadjuvant pilot study consisted of panitumumab (9 mg/kg) for eight cycles q.3 weeks combined with four cycles of 5-fluorouracil, epidoxorubicin and cyclophosphamide (FEC100: 500/100/500 mg/m(2)) q.3 weeks, followed by four cycles of docetaxel (T: 100 mg/m(2)) q.3 weeks. Following therapy, all patients underwent surgical resection. Pathologic complete response (pCR) in assessable patients was the main end point while clinical response, toxicity and ancillary studies were secondary end points. Paraffin-embedded and frozen tumor samples were systematically collected with the aim to identify predictive biomarkers of efficacy and resistance in order to select biologically defined subpopulations for potential further clinical development of the anti-EGFR antibody. RESULTS: Sixty patients were included with 47 assessable for pathologic response. The pCR rates were 46.8% [95% confidence interval (CI): 32.5% to 61.1%] and 55.3% [95% CI: 41.1% to 69.5%] according, respectively, to Chevallier and Sataloff classifications. The complete clinical response (cCR) rate was 37.5%. Conservative surgery was carried out in 87% of cases. Toxicity was manageable. The association of high EGFR and low cytokeratin 8/18 expression in tumor cells on one hand and high density of CD8+ tumor-infiltrating lymphocytes on the other hand were significantly predictive of pCR. CONCLUSIONS: Panitumumab in combination with FEC100 followed by docetaxel appears efficacious, with acceptable toxicity, as neoadjuvant therapy of operable TNBC. Several biomarkers could help define large subsets of patients with a high probability of pCR, suggesting a potential interest to further develop this combination in biologically defined subgroups of patients with TNBC. CLINICAL TRIAL NUMBER: NCT00933517.

Rare EGFR exon 18 and exon 20 mutations in non-small-cell lung cancer on 10 117 patients: a multicentre observational study by the French ERMETIC-IFCT network.

BACKGROUND: There is scarce data available about epidermal growth factor receptor (EGFR) mutations other than common exon 19 deletions and exon 21 (L858R) mutations. PATIENTS AND METHODS: EGFR exon 18 and/or exon 20 mutations were collected from 10 117 non-small-cell lung cancer (NSCLC) samples analysed at 15 French National Cancer Institute (INCa)-platforms of the ERMETIC-IFCT network. RESULTS: Between 2008 and 2011, 1047 (10%) samples were EGFR-mutated, 102 (10%) with rare mutations: 41 (4%) in exon 18, 49 (5%) in exon 20, and 12 (1%) with other EGFR mutations. Exon 20 mutations were related to never-smoker status, when compared with exon 18 mutations (P < 0.001). Median overall survival (OS) of metastatic disease was 21 months [95% confidence interval (CI) 12-24], worse in smokers than in non-smoker patients with exon 20 mutations (12 versus 21 months; hazard ratio [HR] for death 0.27, 95% CI 0.08-0.87, P = 0.03). Under EGFR-tyrosine kinase inhibitors (TKIs), median OS was 14 months (95% CI 6-21); disease control rate was better for complex mutations (6 of 7, 86%) than for single mutations (16 of 40, 40%) (P = 0.03). CONCLUSIONS: Rare EGFR-mutated NSCLCs are heterogeneous, with resistance of distal exon 20 insertions and better sensitivity of exon 18 or complex mutations to EGFR-TKIs, probably requiring individual assessment.

Tu-be or not tu-be: that is the question about serous ovarian carcinogenesis.

Our understanding of the early natural history of epithelial ovarian carcinoma is limited by the access to early lesions as the disease is very often diagnosed at advanced stages. The incessant ovulation theory from the last century that indicated the ovary as the site for the initiation of high-grade serous cancers is contrary to the newly emerging idea that ovarian cancer could arise from the distal fallopian tube. In view of the recent pathological and molecular studies, we propose to discuss the genesis of high-grade serous ovarian cancer.

Panitumumab combined with irinotecan for patients with KRAS wild-type metastatic colorectal cancer refractory to standard chemotherapy: a GERCOR efficacy, tolerance, and translational molecular study.

BACKGROUND: The purpose of this study was to evaluate the combination of panitumumab and irinotecan in patients with KRAS wild-type metastatic colorectal cancer refractory to standard chemotherapy (oxaliplatin, fluoropyrimidines-irinotecan and bevacizumab). PATIENTS AND METHODS: KRAS status was first determined locally but subsequent validation of KRAS status and additional screenings (rare KRAS, NRAS, BRAF mutations and EGFR copy number) were centrally assessed. Patients received panitumumab (6 mg/kg) and irinotecan (180 mg/m²) every 2 weeks. RESULTS: Sixty-five eligible patients were analyzed. The objective response rate (ORR) was 29.2% [95% confidence interval (95% CI) 18.2-40.3]. Median progression-free and overall survivals were 5.5 and 9.7 months, respectively. Most frequent grade 3/4 toxic effects were skin 32.3%, diarrhea 15.4% and neutropenia 12.3%. Tissue samples were available for 60 patients. For the confirmed KRAS wild-type population codon 12 or 13 mutation (n = 54), ORR was 35.2% (95% CI 22.4.1-47.9). Thirteen patients had a NRAS, a BRAF or a rare KRAS mutation, and no tumor response was observed in this subgroup when compared with 46.3% (95% CI 31.1-61.6) ORR in the subgroup of 41 patients with no identified mutation. CONCLUSION: Panitumumab and irinotecan is an active third-line regimen in a well-defined population based on biomarkers. ClinicalTrials.gov Identifier NCT00655499.

[Early detection of ovarian cancer: tomorrow? A review]. / Vers un dépistage possible du cancer de l'ovaire?

Ovarian cancer is the most lethal of the gynaecological malignancies because this «silent killer¼ is almost always diagnosed at an advanced stage. Precursor lesions have at least been discovered. This review will describe in details specific features of tubal and ovarian preinvasive lesions and the old and novel techniques that could be used for early detection of ovarian cancer.

[Don't forget fallopian tubes! A morphologic and immunohistochemical study about Fallopian tubes with genetic risk (BRCA mutation)]. / N'oubliez pas les trompes ! Étude morphologique et immunohistochimique des trompes à risque génétique (mutation BRCA).

OBJECTIVES: The objective of this study was to describe morphologic and immunohistochemical features of precursor tubal lesions in prophylactically removed Fallopian tubes. PATIENTS AND METHODS: Hundred and forty-seven bilateral salpingectomies (genetic predisposition or group A: n=57; and control group or group B: n=90) were reviewed by two pathologists blinded to clinical data. Seven epithelial cytological and architectural features were studied to compare the degree of tubal epithelial abnormalities between the two groups. Immunohistochemical expression patterns of Ki67 and p53 were also evaluated. RESULTS: Serous tubal intraepithelial lesions (STIL) have been identified in group A with stronger expression for Ki67 and p53 (especially in BRCA 1 group) than in group B. DISCUSSION AND CONCLUSION: The current results show the importance of salpingo-oophrectomy in BRCA mutation carriers and the complete histopathological sampling of the Fallopian tubes.

Anti-melanoma efficacy of internal radionuclide therapy in relation to melanin target distribution.

Targeted internal radionuclide therapy (TRT) could be an efficient, specific way to treat disseminated melanoma. Based on a previous pharmacomodulation study, we selected a quinoxaline-derived molecule (ICF01012) for its melanin specificity and kinetic properties suitable for TRT. Here, we determined the efficacy of [(131)I]ICF01012 radiotherapy in vitro and in vivo in relation to melanogenesis using human melanoma models. [(125)I]ICF01012 uptake was first assessed in relation to melanin content. We found that melanin distribution in different models was representative of pathology seen in human tumours: melanin content was high in the extracellular space of SKMel3 tumours, and accumulated primarily in melanophages in M4Beu tumours. Targeted [(131)I]ICF01012 radiotherapy had a strong anti-tumoural efficacy in pigmented versus unpigmented tumours, regardless of target distribution and content. This study supports the use of melanin targeting with (131)I-labelled iodoquinoxaline for effective treatment of melanoma.

Correlation between molecular metastases in sentinel lymph nodes of breast cancer patients and St Gallen risk category.

AIMS: To evaluate the clinical significance of tumour metastases detected using real-time reverse transcription-PCR (RT-PCR) in sentinel lymph nodes (SLN) of breast cancer patients. METHODS: Sixty-seven patients with T1-T2 primary breast cancer were included in a prospective study. SLN were analysed for the presence of metastatic tumour cells using standard histopathology staining, immunochemistry (IHC) and multimarker real-time RT-PCR assay for mammaglobin (MMG), carcinoembryonic antigen (CEA) and cytokeratin-19 (CK19) mRNA expression. Correlations between molecular metastases and traditional clinicopathological prognostic factors, including St Gallen risk categories were studied. RESULTS: Of the 67 patients, 15 (22.3%) had one or more pathology-positive SLN. Five (9.6%) pathology-negative SLN were positive by IHC and 19 (36.5%) by RT-PCR. Of note, RT-PCR analysis was also positive in all cases with pathology- or IHC-positive SLN. MMG was the most informative tumour marker in the panel. Molecularly detected metastases were significantly associated with intermediate St Gallen risk category (p=0.023). CONCLUSION: Molecular staging of SLN using real-time RT-PCR for early breast cancer could serve as a useful complement to standard clinicopathological risk factors. Studies with long-term follow-up are necessary to define the impact of molecular metastases on disease free survival and overall survival.

Effects of MDR reversing agent combinations on the 3H-daunomycin accumulation in drug-sensitive and drug-resistant human cancer cells.

BACKGROUND: As multidrug resistant (MDR) tumour cells generally exhibit a drug accumulation deficit, the effects of three prototype modulators and their combinations were investigated by studying the modulation of 3H-dounomycin cellular accumulation. MATERIALS AND METHODS: Two cell lines derived from a rhino-pharingeal human carcinoma, either sensitive (KB-3-1) or selected as MDR (KB-A1) were used. Verapamil (10mumol.L-1), PSC 833 (lmumol.L-1) and S9788 (5mumol.L-1) were tested alone or in association two by two. The cells were characterized by reverse transcriptase polymerase chain reaction (RT-PCR) in terms of pleiotropic resistance gene expression. RESULTS: A strong mdr1 and a light LRP gene expression were found in KB-A1 resistant cells compared to KB-3-1, whereas MRP expression was found to a similar extent. Relative to the KB-3-1, cells, accumulation of 3H-daunomycin was reduced to 31 +/- 5% in the KB-A1 cells. In these KB-A1 cells, the three agents tested significantly increased the 3H-daunomycin intracellular concentration, S9788 being the most active (311 +/- 37%) and inducing a near complete reversion to the basal level of the sensitive cells. Verapamil and PSC 833 demonstrated an additive effect (252 +/- 69% compared to 188 +/- 33% and 126 +/- 27%, respectively). On KB-3-1 sensitive cells, S9788 had no effect, while verapamil or PSC 833 moderately increased the 3H-daunomycin accumulation, without additive effect. CONCLUSION: These results show a strong MDR reversing effect of S9788, which appears specific to P-glycoprotein (Pgp) and an additive effect between verapamil and PSC 833, suggesting a better therapeutic efficiency if used in well defined combinations.

Comparative 99mTc-sestamibi and 3H-daunomycin uptake in human carcinoma cells: relation to the MDR phenotype and effects of reversing agents.

UNLABELLED: Because 99mTc-sestamibi (MIBI) appears to be a potent candidate for multidrug resistance (MDR) evaluation in tumors, its cellular uptake should be similar to that of 3H-daunomycin in a variety of conditions of expression and inhibition of MDR activity. METHODS: We used a human rhinopharyngeal carcinoma cell line (KB-3-1) and its MDR variant (KB-A1). Cells were incubated 2 h with 99mTc-MIBI and 3H-daunomycin under control conditions or in the presence of a reversing agent such as verapamil (10 pmol/L), PSC833 (1 micromol/L) or S9788 (5 micromol/L). RESULTS: Relative to the KB-3-1-sensitive cells, accumulations of 99mTc-MIBI and 3H-daunomycin were reduced to 31% +/- 5% and 36% +/- 11% (P < 0.001 for both) in KB-A1-resistant cells. In sensitive cells, accumulation of both agents was increased by verapamil and PSC833 (range 115%-140%; P < 0.05) but not by S9788. In KB-A1 cells, only S9788 significantly increased the cellular uptake of 99mTc-MIBI (138% +/- 25%; P < 0.01), whereas the intracellular uptake of 3H-daunomycin was markedly increased with the three reversing agents (up to 311% +/- 37% with S9788; P < 0.001). With this last treatment, uptake of 3H-daunomycin in KB-A1 cells nearly returned to its basal level in sensitive cells. CONCLUSION: 99mTc-MIBI monitors the MDR phenotype of tumor cells effectively but responds to reversing agents differently than 3H-daunomycin.

Comparison between technetium-99m-sestamibi and hydrogen-3-daunomycin myocardial cellular retention in vitro.

UNLABELLED: This study was undertaken to verify whether 99mTc-sestamibi uptake parallels that of 3H-daunomycin in cells treated with multidrug resistance (MDR) reversing agents. Since we have detected in a previous work a moderate typical MDR phenotype in rat cardiac cells, a model of cultured myocardial cells was used. METHODS: Newborn-rat cultured myocardial cells were incubated 120 min with the MDR-reversing agent verapamil 50 microM, PSC833 1 microM or S9788 10 microM alone or in combination, and the cellular retention of 3H-daunomycin and 99mTc-sestamibi was counted. RESULTS: Hydrogen-3-daunomycin cellular accumulation was never modified by more than 15% when compared to control values, while 99mTc-sestamibi decreased to 75% +/- 32% (m +/- s.d.) of controls in the presence of S9788 and to 44% +/- 19% when S9788 was associated with verapamil. CONCLUSION: The variations of 99mTc-sestamibi and 3H-daunomycin cellular accumulation induced by MDR-reversing agents in cultured myocardial cells can be dramatically different. While some MDR-reversing agents can significantly increase the 3H-daunomycin retention in cardiac cells, they have unexpected effects on that of 99mTc-sestamibi.

In vitro detection of the MDR phenotype in rat myocardium: use of PCR, [3H]daunomycin and MDR reversing agents.

A decrease in the intracellular drug concentration in resistant cells as compared to sensitive cells is one of the characteristics of the MDR phenotype. P-glycoprotein (Pgp) is thought to be responsible for an active efflux of some lipophilic drugs such as anthracyclines. Anthracyclines such as daunomycin are highly effective anticancer agents but induce a well-described, while incompletely explained, cardiac toxicity. In this study, we investigated the MDR phenotype in rat myocardium in terms of gene expression, detection of Pgp and indirect evaluation of Pgp function. A clear mdr1a gene specific expression in rat cultured myocardial cells and cardiac tissue was detected by RT-PCR. The incorporation of [3H]daunomycin in myocardial cell cultures was studied with and without reversing agents. Daunomycin was found to have a high accumulation in cardiac cells illustrated by a Ci/Ce ratio of 2890. This high accumulation was moderately but significantly (p < 0.05) increased in the presence of a MDR reversing agent such as verapamil, PSC 833 or S9788. These results suggest that blockade of the Pgp in humans may result in an increased toxicity of several Pgp substrates in normal tissues like the myocardium.

Enzymatic activities of mitochondrial respiratory complexes from children muscular biopsies. Age-related evolutions.

Measurements were performed to determine maximum enzymatic activities of citrate synthetase and respiratory complexes I, III, and IV of mitochondria obtained from muscular biopsies in control children. The significant number of determinations carried out (43 different biopsies in controls aged 3.8 to 19.1 years) permits the formulation of a table of statistically validated reference values for these activities. These values are independent of sex of the controls, and of the studied muscles. Citrate synthetase activity, which remains stable in this age range, thus constitutes a good internal indicator of mitochondrial activity. Complexes I and III manifest activity which does not vary with age. On the other hand, cytochrome oxidase activity shows a highly significant decrease in this age group. This decrease may be correlated with qualitative changes (subunits VIa and VIIa) in composition of this complex.