title: Stability and heterogeneity of expression profiles in lung cancer specimens harvested following surgical resection.
abstract: One of the major concerns in microarray profiling studies of clinical samples is the effect of tissue sampling and RNA extraction on data. We analyzed gene expression in lung cancer specimens that were serially harvested from tumor mass and snap-frozen at several intervals up to 120 minutes after surgical resection. Global gene expression was profiled on cDNA microarrays, and selected stress and hypoxia-activated genes were evaluated using real-time reverse transcription polymerase chain reaction (RT-PCR). Remarkably, similar gene expression profiles were obtained for the majority of samples regardless of the time that had elapsed between resection and freezing. Real-time RT-PCR studies showed significant heterogeneity in the expression levels of stress and hypoxia-activated genes in samples obtained from different areas of a tumor specimen at one time point after resection. The variations between multiple samplings were significantly greater than those of elapsed time between sampling/freezing. Overall samples snap-frozen within 30 to 60 minutes of surgical resection are acceptable for gene expression studies, thus making sampling and snap-freezing of tumor samples in a routine surgical pathology laboratory setting feasible. However, sampling and pooling from multiple sites of each tumor may be necessary for expression profiling studies to overcome the molecular heterogeneity present in tumor specimens.
authors.affiliation: University Health Network, Ontario Cancer Institute/Princess Margaret Hospital, Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada M5G 2M9.
authors.forename: Fiona H
authors.initials: FH
authors.lastname: Blackhall
authors.forename: Melania
authors.initials: M
authors.lastname: Pintilie
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Wigle
authors.forename: Igor
authors.initials: I
authors.lastname: Jurisica
authors.forename: Ni
authors.initials: N
authors.lastname: Liu
authors.forename: Nikolina
authors.initials: N
authors.lastname: Radulovich
authors.forename: Michael R
authors.initials: MR
authors.lastname: Johnston
authors.forename: Shaf
authors.initials: S
authors.lastname: Keshavjee
authors.forename: Ming-Sound
authors.initials: MS
authors.lastname: Tsao
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000601:surgery; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics* / Q000601:surgery; D020411:Oligonucleotide Array Sequence Analysis; D013510:Pulmonary Surgical Procedures; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
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