Protein coding and noncoding gene signatures in two subtypes of exosomes released by LIM1863 human colon cancer cell line

Exosomes are 40~120 nm diameter vesicles of endocytic origin released by most cells and important in mediating cell-cell communication. As mRNA and noncoding RNA are two main functional RNA molecules in post transcription level and involves in many bio-activities including cancer progression and metastasis, it is important to understand the coding and noncoding genes contained within exosomes released by tumour cells. This study focused on the protein coding and noncoding genes enriched in two subtypes of exosomes (A33-enriched exosomes, A33-Exos and EpCAM-enriched exosomes, EpCAM-Exos) released by human colon cancer LIM1863 cell line. With high throughput sequencing technology and bioinformatics analyses, we demonstrate 350 protein coding genes (PCGs) and 222 noncoding genes (NCGs) are commonly enriched; 56 PCGs and 202 NCGs were specifically enriched in A33-Exos and 276 PCGs and 253 NCGs were enriched unique to EpCAM-Exos. A salient finding was the significant enrichment of TPT1, ribosomal protein genes and GAS5, a tumour noncoding gene, in exosomes. We further demonstrate differentially seven expressed genes (SCARB1, SCD, TPT1, EETF1G, BCL7C, RPS3, and RAB13) by qRT-PCR. Importantly, we correlated these findings with several matched tissue-derived tumour-normal samples showed TPT1 and ribosomal protein genes were up regulated in human tumour samples. Our findings provide a new insight of functional RNA molecules in exosomes and new select non-invasive biomarker candidates for colon cancer diagnosis and prognosis.

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