Prognostic signatures of oligometastasis in colorectal cancer liver metastasis.

Abstract

3588 Background: Knowledge of molecular differences between limited metastasis (oligometastasis) and widespread metastases may provide biomarkers for selection of patients who will benefit from curative metastasis resection and provide useful prognostic information. In this study, we detect messenger RNA expressional patterns in patients with colorectal cancer liver metastasis (CRCLM) and identify networks of coding and noncoding RNAs corresponding to oligometastatic phenotype. Methods: RNA was prepared from frozen tumor tissue of 55 patients with CRCLM patients treated with liver resection and/or biopsy of their metastatic tumors with greater than 15 years of follow-up. Survival was calculated and stratified according to risk of recurrence. Cases were subject to RNA-Sequencing experiments with paired end sequencing. Results: RNA analysis with TopHat and Cuffdiff found significant differences in transcript expression according to recurrence for 667 genes (P < 0.05). Of these transcripts, 166 had a greater than 2-fold gene expression between groups when comparing mean Fragments Per Kilobase of transcript per Million mapped reads (FPKM) (P < 0.05). Unsupervised hierarchical clustering revealed distinct genomic patterns based on clinical outcome. A supervised gene expression analysis revealed a differential expression of genes in the Homeobox ( HOX) family (P < 0.05). Overexpression of individual members of the HOX gene family are associated with prognosis. Upregulation of the HOXD11 gene was associated with cure in 60% of cases while downregulation was associated with 5-year overall survivals of 16% (P = 0.023). Furthermore, when clusters of HOX family members were compared, we found that expression correlated with survival, underlining the importance of this gene family in oligometastasis biology. A high ratio of the HOXD cluster to HOXA cluster was associated with a long recurrence free survival (P = 0.002). Conclusions: Common genomic signatures characterize patients with liver oligometastasis from primary colorectal cancer. The HOX gene family strongly correlates with prognosis and represents a unique molecular subtype of patients. Further mechanistic studies of the HOX gene family in metastases are underway.