Association of genome-wide copy number alterations with metastasis of clear cell renal cell carcinoma.

Abstract

428 Background: About one-third of patients with clear cell renal cell carcinoma (ccRCC) exhibit metastasis at the time of diagnosis and show poor prognosis. The genetic and epigenetic alterations associated with metastasis in ccRCC have variably been studied, and their role in the metastatic process is unclear. The goals of the current study were to identify genomic copy number alterations (CNAs) associated with ccRCC metastasis and examine their clinical utility. Methods: In this IRB-approved study, genome-wide copy number profiling was performed on DNA from 144 ccRCC (81 primary and 63 metastatic lesions). Differential CNAs between primary and metastatic lesions and between different metastatic sites were identified using Fisher’s exact test. Associations between CNAs and overall survival (OS) were tested using the log rank statistic and Kaplan-Meier method. Genomic profiling data of 437 and 240 primary ccRCC (TCGA and PMID: 23797736, respecitively) were used for verification. Results: Between primary and metastatic lesions, 25 CNAs were significantly different (p<0.05). Of the 11 more frequent in metastatic lesions, nine retained significance when comparing stage IV and stage I TCGA ccRCC. For 368 TCGA locally-invasive tumors (stages I, II, and III), three CNAs (loss of 9p24.3-p13.3, 9p12-q11, and 9q21.12-q21.33) were associated with inferior survival (p=0.002). In the second dataset of 214 locally-invasive lesions, loss of 18q11.2-q23 correlated with shorter OS (p=0.025). Across metastatic lesions, nine CNAs were found to be significantly enriched in lung lesions and three in bone. In a subset of 127 ccRCC with known metastatic status at 5 years after diagnosis, two of these CNAs (gain of 7q36.1-36.3 in lung and loss of 22q13.2 in bone) were significantly enriched in the corresponding primary specimens. Conclusions: This study identified CNAs associated with ccRCC metastasis and common sites of metastasis that have the potential to serve as biomarkers to assist in better risk stratification of patients with this disease. Integrated analyses of genes mapping to the loci of genomic imbalance would further our understanding of the biology of metastasis in renal cancer.