MicroRNAs as Regulators of Colorectal Cancer Hepatic Metastasis
Alexis Scherl, Jia Min Loo, Fung Ying Man, Alexander Nguyen, Sohail Tavazoie. Yale University School of Medicine, New Haven, CT; Rockefeller University, New York, NY
Background: Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the US. The mortality of CRC is largely attributable to hepatic metastasis, rather than the primary tumor. Current clinical therapies have limited efficacy due in part to our poor understanding of metastatic progression. Recently, microRNAs (miRNAs) have been shown to regulate cancer metastasis; therefore, the aim of this study is to identify miRNAs that function as regulators of CRC hepatic metastasis.
Design: A novel in vivo hepatic colonization selection model was utilized to derive human CRC cell lines with greater metastatic potential than the weakly metastatic parental cell lines. Array-based profiling was used to identify potential metastasis-associated miRNAs. Candidate miRNAs were then evaluated as regulators of metastasis utilizing in vivo tumor xenograft assays. Quantitative real-time RT-PCR (qRT-PCR) was employed to determine expression levels of the metastasis-associated miRNAs in human primary and metastatic tumors. To examine the biology of these miRNAs in the context of tumor formation, we conducted morphometric analysis of metastatic xenograft tumors. To assess the effect of miRNA silencing with respect to CRC cell survival in liver parenchyma, we developed a novel ex-vivo hepatic organotypic slice metastasis assay.
Results: We identified two miRNAs that are significantly downregulated in aggressively metastatic cell lines as compared to parental controls. Utilizing in vivo metastasis assays, silencing of these miRNAs resulted in increased hepatic metastatic tumor burden. Conversely, overexpression of these miRNAs decreased metastasis. qRT-PCR showed significantly decreased levels of miRNA expression in human metastatic tumors as compared to primary tumors. Histologically, tumor xenografts with miRNA silencing had increased tumor burden due to greater numbers of similarly sized tumor nodules, rather than due to larger sized individual nodules. As demonstrated in hepatic organotypic slice cultures, silencing of these miRNAs enhanced CRC cell survival in the liver microenvironment.
Conclusions: We have identified two previously uncharacterized miRNAs that function as endogenous regulators of hepatic CRC metastasis. Silencing of these miRNAs results in increased CRC metastasis in vivo, and decreased levels of these miRNAs are present in human CRC hepatic metastases as compared to primary tumors. These results demonstrate the clinical relevance of these metastasis-associated miRNAs, highlighting their potential as future therapeutic targets.
Monday, March 4, 2013 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 114, Monday Morning