Detection of circulating tumour cells in blood by quantitative real-time RT-PCR: effect of pre-analytical time.
BACKGROUND
We and others have recently explored the use of quantitative real-time RT-PCR analysis for the detection of circulating tumour cells in blood of patients with breast cancer (BC). One major problem in these experiments is the in vitro instability of the cellular RNA. The copy number of mRNA can change during storage and transport at room temperature and this may hamper accurate quantitative measurements of specific transcripts, especially when working with small numbers of target mRNAs.


METHODS
Peripheral blood samples were obtained from two healthy volunteers and 13 patients with BC. Blood was stored at room temperature for 0, 1, 2, 4, 6, 24, 48 and 72 h. The potential alteration of gene expression for six target genes was investigated by quantitative real-time RT-PCR.


RESULTS
For beta-actin, GAPDH, cytokeratin-19 (CK-19) and HER2, a significant decrease in expression level occurs after 4 h (CK-19 and HER2), 6 h (beta-actin) or 24 h (GAPDH). Mammaglobin expression was only measurable in two samples and seems to be stable for at least 6 h. For vascular endothelial growth factor (VEGF), a statistically significant increase in expression level is observed in samples processed 24 h after collection.


CONCLUSIONS
Most transcripts were reduced in samples that were stored overnight at room temperature compared with fresh samples, but upregulation of transcripts, probably as an active response to cellular stress, also occurs when blood is removed from its in vivo environment and stored ex vivo. Optimally, blood samples and RNA should be processed or stabilised within 3 h after collection to avoid interference of the in vivo gene expression signature by ex vivo stress responses.
Benoy
Ina H
IH
Translational Cancer Research Group Antwerp, Pathology Laboratory, University of Antwerp/University Hospital Antwerp, Edegem, and Oncology Centre, General Hospital St-Augustinus, Wilrijk, Belgium.
Elst
Hilde
H
Van Dam
Peter
P
Scharpé
Simon
S
Van Marck
Eric
E
Vermeulen
Peter B
PB
Dirix
Luc Y
LY
D014408:Biomarkers, Tumor / Q000097:blood*; D001943:Breast Neoplasms / Q000097:blood* / Q000235:genetics / Q000473:pathology*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011379:Prognosis; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D013312:Stress, Physiological / Q000097:blood / Q000473:pathology; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000097:blood
D014408:Biomarkers, Tumor; D042461:Vascular Endothelial Growth Factor A