A research group led by Sandrine Imbeaud from the CNRS and Pierre and Marie Curie University, Villejuif, France, used microarrays to analyse the gene-expression patterns of samples from colon tumours and liver metastases collected from 13 patients with colorectal cancer. The microarray analyses were carried out before the patients were treated with combined chemotherapy of folinic acid, 5-fluorouracil and irinotecan.
Imbeaud and colleagues identified 679 genes that were differently expressed in patients who subsequently responded well to chemotherapy compared with patients who were resistant to the therapy. The results were validated by RT-PCR analysis, which confirmed the differential expression of 22 genes selected from the list. The findings were also confirmed by RT-PCR analysis of colon and liver tumour samples collected from two additional patients.
The authors were able to integrate their findings into global and interconnected molecular networks that characterise resistance in patients with colorectal cancer before they are exposed to chemotherapy. They conclude that knowledge of these networks could potentially be used to improve diagnosis and treatment of patients with colorectal cancer.