Effect of surgical procedures on prostate tumor gene expression profiles

Current surgical treatment of prostate cancer is typically accomplished by either open radical prostatectomy (ORP) or robotic-assisted laparoscopic radical prostatectomy (RALRP). Intra-operative procedural differences between the two surgical approaches may alter the molecular composition of resected surgical specimens, which are indispensable for molecular analysis and biomarker evaluation. The objective of this study is to investigate the effect of different surgical procedures on RNA quality and genome-wide expression signature. RNA integrity number (RIN) values were compared between total RNA samples extracted from consecutive LRP (n=11) and ORP (n=24) prostate specimens. Expression profiling was performed using the Agilent human whole-genome expression microarrays. Expression differences by surgical type were analyzed by Volcano plot analysis and gene ontology analysis. Quantitative reverse transcription (RT)-PCR was used for expression validation in an independent set of LRP (n=8) and ORP (n=8) samples. The LRP procedure did not compromise RNA integrity. Differential gene expression by surgery types was limited to a small subset of genes, the number of which was smaller than that expected by chance. Unexpectedly, this small subset of differentially expressed genes was enriched for those encoding transcription factors, oxygen transporters and other previously reported surgery-induced stress-response genes, and demonstrated unidirectional reduction in LRP specimens in comparison to ORP specimens. The effect of the LRP procedure on RNA quality and genome-wide transcript levels is negligible, supporting the suitability of LRP surgical specimens for routine molecular analysis. Blunted in vivo stress response in LRP specimens, likely mediated by CO(2) insufflation but not by longer ischemia time, is manifested in the reduced expression of stress-response genes in these specimens.