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Análise de elementos químicos em tecidos humanos com e sem patologia tumoral utilizando fluorescência de raios-X
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Resumo(s)
O cancro é uma das principais causas de morte a nível mundial, pelo que é essencial o
desenvolvimento de investigação que possa conduzir à descoberta de novos biomarcadores
tumorais. A técnica de Fluorescência de Raios-X tem-se revelado adequada para a análise dos
elementos químicos presentes em tecidos humanos, nomeadamente para comparação entre
tecidos normais e tumorais. No entanto, para uma correta determinação quantitativa destes
elementos é necessária a avaliação da matriz escura destas amostras, contendo os elementos
não detetados pela técnica utilizada.
Num estudo inicial, procedeu-se à determinação da matriz dos tecidos humanos para utilização
do método dos Parâmetros Fundamentais como método de quantificação. Foram analisados
4 Materiais de Referência Certificados e testadas diferentes composições de matriz com
o objetivo de alcançar o melhor resultado possível. A matriz obtida consiste em 10% H, 22% C,
3% N e 60% O e foi validada por comparação com outro método de exatidão já comprovada
(método comparativo com padrões), tendo-se demonstrado a sua aplicabilidade na quantificação
deste tipo de amostras.
Analisaram-se 39 pares de amostras de tecido humano incluídas em parafina por Micro-
Fluorescência de Raios-X, sendo cada par normal-tumor pertencente ao mesmo indivíduo.
Os tipos de tumor estudados foram os seguintes: adenocarcinomas do cólon e carcinomas da
mama do tipo não-especial. Para quantificação utilizou-se o método dos Parâmetros Fundamentais
pela aplicação da matriz determinada anteriormente. As áreas a quantificar em cada
amostra foram escolhidas com base numa rotina desenvolvida em ambiente R. A análise estatística
dos resultados foi feita com recurso ao software OriginPro®, tendo sido aplicados o teste
de normalidade Shapiro-Wilk e o teste não-paramétrico Kruskal-Wallis ANOVA.
Observou-se que no cólon, os elementos P, Fe e Cu apresentam concentrações significativamente
mais elevadas nos tecidos tumorais, enquanto na mama os elementos que têm concentrações
significativamente superiores em tecido tumoral são P, S, Ca, Fe, Cu e Zn. Concluiu-se
que o P e o Fe têm potencialidade como biomarcadores tumorais do cólon. Por outro lado, os
elementos P, S, Ca, Fe e Zn apresentam-se como possíveis biomarcadores tumorais da mama.
O Cu revelou ser um constituinte da parafina em que as amostras estão incluídas, pelo que não
deve ser avaliado em amostras com este material.
Cancer is one of the leading causes of death worldwide, so it is essential to develop research that can lead to the discovery of new tumour biomarkers. The X-Ray Fluorescence technique has proved to be adequate for the analysis of the chemical elements present in human tissues, namely for comparison between normal and tumour tissues. However, for a correct quantitative determination of these elements it is necessary to evaluate the dark matrix of these samples, which contains the elements that are not detected by the technique used for this purpose. In an initial study, the matrix of human tissues was determined for use with the Fundamental Parameters method as a quantification approach. Four Certified Reference Materials were analysed and different matrix compositions were tested in order to achieve the best possible result. The obtained matrix is composed of 10% H, 22% C, 3% N and 60% O and it has been validated by comparison with another method of proven accuracy (comparative method with standards). Its applicability in the quantification of this type of samples was demonstrated. 39 pairs of human tissue samples embedded in paraffin were analysed by Micro-X-Ray Fluorescence, each normal-tumour pair belonging to the same subject. The types of tumour studied were: adenocarcinomas of the colon and carcinomas of the breast of no special type. For quantification, the Fundamental Parameters method was used by the application of the matrix previously determined. The areas for quantification were chosen based on a routine developed in R environment. Statistical analysis of the results was performed using the OriginPro® software, the Shapiro-Wilk normality test and the Kruskal-Wallis ANOVA non-parametric test being applied. It was observed that in the colon, the elements P, Fe and Cu have significantly higher concentrations in tumour tissues, while in the breast the elements with significantly higher concentrations in tumour tissues are P, S, Ca, Fe, Cu and Zn. It was found that P and Fe have potential as tumour biomarkers for colon. On the other hand, the elements P, S, Ca, Fe and Zn are possible tumour biomarkers for breast. Cu has been shown to be a constituent of the paraffin in which the samples are embedded, so it should not be evaluated in samples embedded in this material.
Cancer is one of the leading causes of death worldwide, so it is essential to develop research that can lead to the discovery of new tumour biomarkers. The X-Ray Fluorescence technique has proved to be adequate for the analysis of the chemical elements present in human tissues, namely for comparison between normal and tumour tissues. However, for a correct quantitative determination of these elements it is necessary to evaluate the dark matrix of these samples, which contains the elements that are not detected by the technique used for this purpose. In an initial study, the matrix of human tissues was determined for use with the Fundamental Parameters method as a quantification approach. Four Certified Reference Materials were analysed and different matrix compositions were tested in order to achieve the best possible result. The obtained matrix is composed of 10% H, 22% C, 3% N and 60% O and it has been validated by comparison with another method of proven accuracy (comparative method with standards). Its applicability in the quantification of this type of samples was demonstrated. 39 pairs of human tissue samples embedded in paraffin were analysed by Micro-X-Ray Fluorescence, each normal-tumour pair belonging to the same subject. The types of tumour studied were: adenocarcinomas of the colon and carcinomas of the breast of no special type. For quantification, the Fundamental Parameters method was used by the application of the matrix previously determined. The areas for quantification were chosen based on a routine developed in R environment. Statistical analysis of the results was performed using the OriginPro® software, the Shapiro-Wilk normality test and the Kruskal-Wallis ANOVA non-parametric test being applied. It was observed that in the colon, the elements P, Fe and Cu have significantly higher concentrations in tumour tissues, while in the breast the elements with significantly higher concentrations in tumour tissues are P, S, Ca, Fe, Cu and Zn. It was found that P and Fe have potential as tumour biomarkers for colon. On the other hand, the elements P, S, Ca, Fe and Zn are possible tumour biomarkers for breast. Cu has been shown to be a constituent of the paraffin in which the samples are embedded, so it should not be evaluated in samples embedded in this material.
Descrição
Palavras-chave
μ-XRF Matriz Escura Parâmetros Fundamentais Cancro Cólon Mama