Searching for early breast cancer biomarkers by serum protein profiling of pre-diagnostic serum; a nested case-control study

<p>Abstract</p> <p>Background</p> <p>Serum protein profiles have been investigated frequently to discover early biomarkers for breast cancer. So far, these studies used biological samples collected <it>at </it>or <it>after </it>diagnosis. This may limit these studies' value in the search for cancer biomarkers because of the often advanced tumor stage, and consequently risk of reverse causality. We present for the first time pre-diagnostic serum protein profiles in relation to breast cancer, using the Prospect-EPIC (European Prospective Investigation into Cancer and nutrition) cohort.</p> <p>Methods</p> <p>In a nested case-control design we compared 68 women diagnosed with breast cancer within three years after enrollment, with 68 matched controls for differences in serum protein profiles. All samples were analyzed with SELDI-TOF MS (surface enhanced laser desorption/ionization time-of-flight mass spectrometry). In a subset of 20 case-control pairs, the serum proteome was identified and relatively quantified using isobaric Tags for Relative and Absolute Quantification (iTRAQ) and online two-dimensional nano-liquid chromatography coupled with tandem MS (2D-nanoLC-MS/MS).</p> <p>Results</p> <p>Two SELDI-TOF MS peaks with m/z 3323 and 8939, which probably represent doubly charged apolipoprotein C-I and C3a des-arginine anaphylatoxin (C3a_desArg), were higher in pre-diagnostic breast cancer serum (p = 0.02 and p = 0.06, respectively). With 2D-nanoLC-MS/MS, afamin, apolipoprotein E and isoform 1 of inter-alpha trypsin inhibitor heavy chain H4 (ITIH4) were found to be higher in pre-diagnostic breast cancer (p < 0.05), while alpha-2-macroglobulin and ceruloplasmin were lower (p < 0.05). C3a_desArgand ITIH4 have previously been related to the presence of symptomatic and/or mammographically detectable breast cancer.</p> <p>Conclusions</p> <p>We show that serum protein profiles are already altered up to three years before breast cancer detection.</p

Standardization of method for determining glycosylated hemoglobin (Hb A1c) by cation exchange high performance liquid chromatography

Hemoblobin A1c is the most important parameter for the monitoring of metabolic control of patients with diabetes mellitus. The purpose of this study was to adapt the Mono S method to a conventional HPLC system, allowing highly selective HbA1c determination without the acquisition of kits or the use of dedicated systems The results obtained were compared to the Tinaquant® immune turbidimetric method and the Bio-Rad Variant® chromatographic method. The developed method presented intra-study precision (C.V. %) of 1.39-3.65 and inter-study precision (C.V. %) of 2.80-3.02%. The determination coefficients among methods were: HPLC Mono S x Tinaquant®: r²: 0.9856 (n=60) and HPLC Mono S x HPLC Bio-Rad Variant®: r²: 0.9806 (n=16). A conversion equation between HPLC Mono S and Bio-Rad Variant® was calculated allowing yielding comparable and interchangeable values. The HPLC Mono-S is a precise, low-cost method which yields similar values to the Bio-Rad Variant® method on conventional HPLC equipment.<br>A hemoglobina A1c é o parâmetro laboratorial mais importante no monitoramento do controle metabólico de pacientes portadores de diabetes melito. Dentre as metodologias existentes para a quantificação desta fração de hemoglobina, a cromatografia líquida de alta eficiência (CLAE) baseada em troca catiônica apresenta a melhor precisão, sendo o método de escolha. O objetivo deste trabalho foi adaptar o método Mono S a um sistema de CLAE convencional permitindo a disponibilidade da determinação altamente seletiva de Hb A1c sem a aquisição de kits e comparar os resultados obtidos com o método imunoturbidimétrico Tinaquant® (Roche®) e com o método de cromatografia líquida Bio-Rad Variant®. O método desenvolvido apresentou precisão intra-ensaio de 1,39-3,65% e inter-ensaio de 2,80-3,02%. Os coeficientes de determinação entre os métodos foram: CLAE Mono S x Tinaquant®: r² = 0,9856 (n=60) e CLAE Mono S x Bio-Rad Variant®: r² = 0,9806 (n=16). Não foram observadas diferenças entre CLAE Mono S e Bio-Rad Variant® através de gráfico de Bland-Altman e regressão de Passing-Bablok. Foi obtida uma equação de conversão entre os valores do método teste e os valores obtidos por métodos rastreáveis ao National Glycohemoglobin Standardization Program (NGSP), permitindo a obtenção de valores comparáveis e intercambiáveis entre as metodologias com o uso de instrumentos convencionais de CLAE e com custo reduzido