La résistance des cellules cancéreuses à la chimiothérapie est une cause majeure de l’échec thérapeutique. Des études suggèrent qu’une adaptation du métabolisme énergétique pourrait jouer un rôle dans cette résistance. Ce travail de thèse montre que la résistance des cellules cancéreuses mammaires MCF-7dox à la doxorubicine est associée à une diminution de l’activité du complexe I de la chaîne respiratoire mitochondriale et à un métabolisme des cardiolipines (CL) particulier (diminution de la quantité de CL et augmentation de la quantité de MLCL, la forme immature des CL). Nos résultats montrent aussi que les mitochondries des cellules MCF-7dox expriment deux pompes d’efflux ATP-dépendantes (BCRP et MRP1) qui participent à limiter la quantité de doxorubicine accumulée dans ces mitochondries. De plus, l’activité de ces deux transporteurs dépend partiellement de l’ATP mitochondrial dont l’efficacité de synthèse est améliorée dans les cellules MCF-7dox. D’autre part, nous montrons que l’effet sensibilisant du DHA à la doxorubicine dans les cellules MCF-7dox implique un stress oxydant mitochondrial et s’accompagne d’une diminution de l’efficacité de la synthèse d’ATP. / Resistance of cancer cells to chemotherapy is a major cause of treatment failure. Studies have suggested that an adaptation of energy metabolism may play a role in the development of this resistance. The present work shows that resistance of the breast cancer cell line MCF-7dox to doxorubicin is associated with decreased activity of the mitochondrial respiratory chain complex I and particularly altered cardiolipin (CL) metabolism, (decreased CL levels and increased MLCL levels, the immature form of the CL). Our results also show that mitochondria from MCF-7dox cells express two ATP-dependent efflux pumps (BCRP and MRP1) limiting the accumulation of doxorubicin in these mitochondria. In addition, the activity of these two transporters is partially dependent on mitochondrial ATP synthesis which efficiency is improved in MCF-7dox cells. Moreover, we show that the sensitizing effect of DHA to doxorubicin in MCF-7dox cells is regulated by mitochondrial oxidative stress and is accompanied by a decrease in ATP synthesis efficiency.

Mitochondrial disorders, with incidence 1:5000 live births children, are one of the most common metabolic diseases. Clinically, it is heterogeneous group of disorders caused by mutations in more than 250 genes. Diagnostic of patients with suspected mitochondrial disorder relies on broad spectrum of biochemical analysis. One of them is a measurement of Mitochondrial Energy Generating Capacity (MEGC). The principle of MEGC analysis is measuring oxidations rate of 14 C - labeled substrates in 10 different incubations. These incubations contain [1-14 C]pyruvate, [U-14 C]malate or [1,4-14 C]succinate, donors and acceptors of Acetyl-CoA and inhibitors of TCA cycle. The results of MEGC analysis provide a variety of information about mitochondrial energy metabolism (MEM) of individual in particular tissue. In diagnostic of patients with suspected mitochondrial disorder is MEGC routinely determined in skeletal muscle. The aim of this study is to optimize MEGC analysis for its use in cultures skin fibroblasts. In sum, MEGC analysis was performed in 23 patients with primary deficiency of oxidative phosphorylation (OXPHOS), in 7 patients with secondary deficiency of OXPHOS and in 15 controls cell lines. The results of MEGC in cultured skin fibroblasts were then compared with results of spectrophotometric...