BioProject

Intratumoral heterogeneity is a major barrier against effective cancer therapy. Human malignant mesothelioma (HMM) that is closely associated with asbestos exposure is extremely heterogeneous in morphology and molecular phenotype. Contrast to genetic mutations, the role of epigenetic modifications in the generation and maintenance of heterogeneous populations in cancers remains largely undetermined. The present study was performed to investigate underlying molecular mechanisms for the emergence of intratumoral heterogeneity by identifying the global microRNA expression profile of distinct subpopulations of MS1 cell line, a HMM cell line. More aggressive cancer cells could be enriched by side population (SP) assay in HMM [20]. The sorted SP and NSP subpopulations were subjected to the microarray analysis of miRNA expression to investigate differentially altered miRNA genes defining tumor heterogeneity in HMM. Total RNAs were isolated from the sorted subpopulations of HMM cells, SP and non-SP fractions. The expression profile of miRNAs was evaluated using Affymetrix GeneChip miRNA Arrays. After data extraction and normalization, the microRNAs defining the cell subpopulations were determined using bioinformatics softwares. A total of 95 miRNAs including 42 up-regulated and 53 down-regulated were identified based on the criteria of 2 fold difference and a p-value < 0.05. Functional ontology of the dysregulated miRNAs revealed that a large number of target genes were categorized into the regulation of various cellular processes, including cell proliferation, programmed cell death, cell migration, cellular response to stress, and stem cell maintenance. The data show that microRNAs are significantly involved in the generation and maintenance of intratumoral heterogeneity and their regulation could be an effective strategy to eradicate a more aggressive cancer cell subpopulation. This is the first to report the profile of miRNA expression in CSCs in HMM by using side population assay assisted with flow cytometry. It will be valuable to understand the regulatory function of HMM CSC miRNAs in generation and maintenance of intratumoral heterogeneity. Overall design: Total RNAs were isolated from the sorted subpopulations of HMM cells, SP and non-SP fractions. (no replicates)