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RATIONALE Neurological dysfunction is common in primary coenzyme Q10 (2,3-dimethoxy, 5-methyl, 6-polyisoprene parabenzoquinone; CoQ10; ubiquinone) deficiencies, the most readily treatable subgroup of mitochondrial disorders. Therapeutic benefit from CoQ10 supplementation has also been noted in other neurodegenerative diseases. CoQ10 can be measured by high-performance liquid chromatography (HPLC) in plasma, muscle or leucocytes; however, there is no reliable method to quantify CoQ10 in cerebrospinal fluid (CSF). Additionally, many methods use CoQ9, an endogenous ubiquinone in humans, as an internal standard. METHODS Deuterated CoQ10 (d6-CoQ10) was synthesised by a novel, simple, method. Total CoQ10 was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using d6-CoQ10 as internal standard and 5 mM methylamine as an ion-pairing reagent. Chromatography was performed using a Hypsersil GOLD C4 column (150 × 3 mm, 3 µm). RESULTS CoQ10 levels were linear over a concentration range of 0–200 nM (R2 = 0.9995). The lower limit of detection was 2 nM. The inter-assay coefficient of variation (CV) was 3.6% (10 nM) and 4.3% (20 nM), and intra-assay CV 3.4% (10 nM) and 3.6% (20 nM). Reference ranges were established for CoQ10 in CSF (5.7–8.7 nM; n = 17), fibroblasts (57.0–121.6 pmol/mg; n = 50) and muscle (187.3–430.1 pmol/mg; n = 15). CONCLUSIONS Use of d6-CoQ10 internal standard has enabled the development of a sensitive LC/MS/MS method to accurately determine total CoQ10 levels. Clinical applications of CSF CoQ10 determination include identification of patients with cerebral CoQ10 deficiency, and monitoring CSF CoQ10 levels following supplementation. Copyright © 2013 John Wiley & Sons, Ltd.

Neurological dysfunction is common in primary coenzyme Q10 (2,3-dimethoxy, 5-methyl, 6-polyisoprene parabenzoquinone; CoQ10 ; ubiquinone) deficiencies, the most readily treatable subgroup of mitochondrial disorders. Therapeutic benefit from CoQ10 supplementation has also been noted in other neurodegenerative diseases. CoQ10 can be measured by high-performance liquid chromatography (HPLC) in plasma, muscle or leucocytes; however, there is no reliable method to quantify CoQ10 in cerebrospinal fluid (CSF). Additionally, many methods use CoQ9 , an endogenous ubiquinone in humans, as an internal standard.Deuterated CoQ10 (d6 -CoQ10 ) was synthesised by a novel, simple, method. Total CoQ10 was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using d6 -CoQ10 as internal standard and 5 mM methylamine as an ion-pairing reagent. Chromatography was performed using a Hypsersil GOLD C4 column (150 × 3 mm, 3 µm).CoQ10 levels were linear over a concentration range of 0-200 nM (R(2) = 0.9995). The lower limit of detection was 2 nM. The inter-assay coefficient of variation (CV) was 3.6% (10 nM) and 4.3% (20 nM), and intra-assay CV 3.4% (10 nM) and 3.6% (20 nM). Reference ranges were established for CoQ10 in CSF (5.7-8.7 nM; n = 17), fibroblasts (57.0-121.6 pmol/mg; n = 50) and muscle (187.3-430.1 pmol/mg; n = 15).Use of d6 -CoQ10 internal standard has enabled the development of a sensitive LC/MS/MS method to accurately determine total CoQ10 levels. Clinical applications of CSF CoQ10 determination include identification of patients with cerebral CoQ10 deficiency, and monitoring CSF CoQ10 levels following supplementation.

Neuroblastoma is a paediatric malignancy originating from the peripheric nervous system, with an incidence of ∼11 cases per million children in Europe. In spite of the relatively low number of patients diagnosed with neuroblastoma every year, this disease accounts for a large portion of cancer mortality in infants, indicating that it has a very significant clinical impact. Intelligently designed compounds, developed on the basis of a growing understanding of the molecular networks deregulated in common types of adult and paediatric cancers, are leading to a better outcome of neoplastic diseases. However, we still need to elucidate the key molecular networks activated or inactivated in neuroblastoma, in order to tailor clinical interventions that are more specific and less toxic to children. Despite aggressive, multi modal chemotherapeutic drug treatments, metastatic neuroblastoma is still largely incurable and survivors have to endure the long-term consequences of drug toxicity. One of the critical determinants of neuroblastoma aggressiveness is the MYCN protooncogene, which is amplified in ∼25% of neuroblastomas. MYCN is a transcription factor that binds to the regulatory region of target genes, inducing their activation or inactivation. In our laboratory, we have recently identified Clusterin, also known as CLU, ApoJ or Apolipoprotein J, as a significant MYCN target gene in neuroblastoma. In this chapter we will discuss the biology of Clusterin, its role as a neuroblastoma suppressor gene and the potential clinical implications.