Genomic CGH-assessed structural DNA alterations in rectal carcinoma as related to local recurrence following primary operation for cure

Abstract

Several factors determine overall outcome and possible local recurrence after curative surgery for rectal carcinoma. Surgical performance is usually believed to be the most pertinent factor, followed by adjuvant oncological treatment and tumor histopathology. However, chromosomal instability is common in colorectal cancer and tumor clones are assumed to differ in aggressiveness and potential of causing local recurrence. The aim of this study was, therefore, to evaluate if genetic alterations in primary rectal carcinoma are predictive of local recurrences. A large clinical database with linked bio-bank allowed for careful matching of two patient groups (R0) resected for rectal carcinoma. One group had developed early, isolated local recurrences and the other group seemed cured after 93 months follow-up. DNA from the primary tumors was analysed with array-CGH (comparative genomic hybridization) including 55,000 genomic probes. DNA from all primary tumors in both groups displayed previously reported and well-recognised DNA aberrations in colorectal carcinoma. Significant copy number gains were confirmed in the 4q31.1-31.22 region in DNA from tumors with subsequent local recurrence. Twenty-two affected genes in this region code for products with high relevance in tumor biology (p53 regulation, cell cycle activity, transcription). DNA from rectal carcinoma displayed well-known aberrations as described for colon carcinoma with no obvious prediction of local rectal recurrence. Gains in the 4q31.1-31.22 DNA region are highly potential for local recurrence despite R0 resection to be confirmed in larger patient materials.