RESUMO
INTRODUCTION: Neoadjuvant chemoradiation therapy has been shown to improve the outcome in patients with rectal cancer and is generally accepted as standard care; however, only selected patients would benefit from this treatment. We aimed to identify predictors of response to neoadjuvant chemoradiation therapy in colorectal cancer using formalin-fixed paraffin-embedded (FFPE) tissues as source of genetic materials and microarray analysis as investigation tool. METHODS: After optimization of RNA extraction methods from FFPE, microarray analysis was carried out on total RNA extracted from 12 pre-treatment FFPE rectal tissues using Megaplex pool A. Microarray data were analysed using an artificial neural network algorithm. Statistical analysis and correlation with clinicopathological data was performed using SPSS software. RESULTS: A distinct miRNA expression signature predictive of response to neoadjuvant CRT in 12 FFPE pre-treatment rectal cancer tissue samples was identified. These signatures consisted of three miRNA transcripts (miR-16, miR-590-5p and miR-153) to predict complete vs. incomplete response and two miRNA transcript (miR-519c-3p and miR-561) to predict good vs. poor response with a median accuracy of 100 %. CONCLUSION: Using microarray analysis of pretreatment FFPE rectal cancer tissues, we identified for the first time a group of miRNA predictors of response to neoadjuvant CRT. This, indeed, can lead to a significant improvement in patient selection criteria and personalized rectal cancer management.
Assuntos
Quimiorradioterapia , Regulação Neoplásica da Expressão Gênica , MicroRNAs/genética , Terapia Neoadjuvante , Neoplasias Retais/genética , Neoplasias Retais/terapia , Secções Congeladas , Perfilação da Expressão Gênica , Humanos , MicroRNAs/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Inclusão em Parafina , Prognóstico , RNA Neoplásico/genética , RNA Neoplásico/isolamento & purificação , Neoplasias Retais/tratamento farmacológico , Neoplasias Retais/radioterapia , Reto/metabolismo , Reto/patologia , Fixação de Tecidos , Resultado do TratamentoRESUMO
INTRODUCTION: Alterations in at least six of the genes that encode proteins involved in the mismatch repair (MMR) system have been identified in either HNPCC or sporadic colon cancer. We aimed to analyse the proportion of patients with colorectal cancer with loss of immunostaining for MMR proteins in order to determine the feasibility of molecular screening for the loss of MMR proteins through the study of unselected patients with colorectal cancer. METHODS: A group of 33 patients with colorectal cancer was randomly selected from the department of surgery bio-bank to determine the expression of MMR proteins in their FFPE tumour tissues using immunohistochemistry techniques. Changes in protein expression following transfection of colorectal tissues were observed in stained cells using Olympus BX60 microscope and image analySIS software. RESULTS: Of the tissue specimens in which acceptable immunostaining was achieved, three samples showed loss of one or more of the MMR proteins. Both hMLH1 and hPMS2 proteins were not expressed in a 36 years old woman with cancer of the caecum. The expression of hMSH6 protein was undetermined in tumour tissues retrieved from a 61 years old man with cancer of the proximal colon. The third case was a 77 years old man with no documented family history of cancer, who had carcinoma of the rectum. He showed loss of hMLH1 expression in the tumour tissues. CONCLUSIONS: Our findings and the previous reports pointed out the importance of molecular screening of patients with colorectal cancer for MSI using immunohistochemistry. This strategy managed to identify mutations in patients otherwise would not have been detected.