P5-20-05: Peripheral Blood Transcriptomics and Doxorubicin Cardiotoxicity.
Authors: Todorova VK , Beggs ML , Dhakal IB , Hennings LJ , Makhoul I , Klimberg VS 
Published: June 2012

Background: Doxorubicin (DOX) cardiotoxicity is dose-dependent and unpredictable. Currently, the clinical methods used for detection of pre-symptomatic DOX-induced cardiotoxicity show low diagnostic sensitivity and identify the existing cardiomyopathy rather than prevent it. It has been reported that DOX cardiomyopathy can occur at low doses, suggesting the presence of increased phenotypic sensitivity by some individuals. Studies have found specific gene expression signatures of circulating blood cells in response to physiological and pathological changes, suggesting that they can be used as biosensors for diagnostic purposes. This study aimed to characterize the peripheral blood mononuclear cells (PBMC) gene expression profile associated with DOX-induced cardiotoxicity with an ultimate goal to identify biomarkers for early prediction of DOX cardiotoxicity. Materials and Methods. Twenty Sprague Dawley rats were randomized into 2 groups: DOX-treated (n=12) and controls (n=8). DOX-treated rats received a single intraperitoneal dose of 12 mg/kg DOX (similar to 65mg/m2 for humans) and the controls were injected with saline. All rats were sacrificed 48 hours after DOX administration and blood, and samples from the heart left ventricle (LV) were collected. Histopathological alterations were evaluated microscopically. RNAs was isolated from cardiac LV and PBMCs. Cardiac and PBMC genome-wide expression profiling were performed using Illumina Rat Ref-12 BeadChip microarrays. For statistical analysis the raw data were log2 transformed and median normalized. The differential analysis per gene was performed using a 2-sample (control vs. DOX-treated) Student's t-test. Statistical significance was set at false discovery rate (FDR)&lt;0.05. Differentially expressed genes were mapped to known metabolic/signaling pathways using MetaCore GENEGO software.

Results. A total of 1406 transcripts were differentially expressed in the hearts (247 upregulated and 1159 downregulated) and 1526 in PBMCs (271 upregulated and 1255 downregulated) between DOX-treated rats and control rats. Of these 1237 genes (92%) were similarly differentially regulated (179 upregulated and 1058 downregulated) both in the hearts and PBMCs. Fifty metabolic/signaling pathways were significantly affected by DOX-treatment. The top ten of these include oxidative phosphorylation; cell proliferation and differentiation; TGF, WNT and cytoskeletal remodeling; insulin signaling; cell adhesion; regulation of amino acid metabolism, cytoskeleton remodeling, PI3K/AKt signaling and CCR5 signaling in macrophages and T lymphocytes.

Discussion: The results from this study showed that PBMC gene expression profile reflected a similar pattern in the hearts of rats treated with DOX and provide a novel and important information about the feasibility of the PBMC as a surrogate marker for DOX cardiotoxicity. The data obtained lay a foundation for further clinical studies to identify the cardiotoxicity risk, predict DOX-treatment response and ultimately to allow the anti-cancer therapy to be tailored to individual patients.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-20-05.