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MiRNA profiles in cell-free urine: The potential utility in identifying patients with pT0 disease prior to cystectomy
Shiv Patel, MD1, Kari Bailey, MD1, Drew Palmer, MD1, Travis Sullivan, MS1, James McKiernan, MD2, John A. Libertino, MD1, Kimberly Rieger-Christ, PhD1.
1Lahey Hospital and Medical Center, Burlington, MA, USA, 2Columbia University Medical Center, New York, NY, USA.
BACKGROUND:
Neoadjuvant chemotherapy prior to radical cystectomy has been shown to confer a survival advantage in patients with muscle-invasive bladder cancer. When combined with maximal endoscopic resection of visible tumor, 39% of patients can be rendered pathologic stage 0 (pT0) prior to cystectomy. Previous studies have shown differential expression of microRNA (miRNA) in the urine of patients with muscle invasive and non-muscle invasive bladder cancer. We aimed to identify differentially expressed miRNA in the urine of patients with varying tumor pathology stage at cystectomy.
METHODS:
Total RNA was isolated from cell-free urine of patients undergoing cystectomy for muscle-invasive transitional cell carcinoma of the bladder, as well as healthy control samples (HC) from patients with no history of cancer. Patients undergoing cystectomy were divided into three groups: pT0, pT1 and ≥pT2, consistent with the pathologic tumor stage of the specimen at the time of surgery. Pooled RNA isolates from each group were profiled via PCR array of 751 miRNA (Exiqon). Validation of miRNA expression levels was performed on individual samples by qRT-PCR.
RESULTS:
The number of miRNA detected within each group correlated with the severity of disease where 391 miRNAs were detected in the ≥pT2 group, 137 in the pT1 group, 124 in the pT0 group, and 73 among the HCs. Hierarchical cluster analysis revealed two main branches; one consisting of the HC and pT0 pools and the other comprised of the pT1 and pT2 pools. Additionally, 32 miRNA were expressed in the pT1 and pT2 pools, and not detected in the pT0 and HC pools. qRT-PCR validation confirmed differential expression of several miRNA between the two clustered groups.
CONCLUSIONS:
This study identified miRNA in cell-free urine differentiating patients with tumor present from those who were tumor free at the time of cystectomy. This miRNA profile may aid in the development of a noninvasive method of confirming response to neoadjuvant therapies, and may provide an adjunct to expectant management and surveillance strategies for the treatment of bladder cancer.
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