Prostate cancer has one of the highest incidence rates of all cancers in Australia. A significant proportion of prostate cancers are indolent and this has resulted in many men with indolent disease being unnecessarily treated. This is a major unmet need in the treatment of prostate cancer and thus new biomarkers that accurately predict outcomes are required. Tetraspanins have been shown to be involved in key cancer-related cellular processes, with studies showing that expression of the tetraspanins CD9 and CD151 correlate with prostate tumour type, stage and patient outcome. Further, tetraspanins are abundant on extracellular vesicles (EVs) that represent a source of biomarkers readily accessible by non-invasive means. This project seeks to determine how CD9 expression in prostate cancer influences the EV cargo to identify novel prognostic biomarkers.
CD9 expression was knocked down in RWPE1 (normal prostate cells) and increased in PC3 (bone metastasis from prostate cancer). EVs were collected after 48h by ultraconcentration from supplement-free cell culture media. Total RNA was extracted with Trizol and evaluated using total RNA Agilent 2100 bioanalyzer chips, RNA was converted to labelled cDNA and hybridized to Affymetrix Human Transcriptome arrays.
Increasing the expression of CD9 in PC3 cells resulted in increased incorporation of CD9 in EVs and the differential incorporation of 2532 transcripts. Whereas decreasing CD9 expression in RWPE1 cells and the resultant EVs altered the incorporation of 486 transcripts into the EVs. These transcripts therefore, represent novel potential EV biomarkers due to being differentially incorporated by expression of the metastasis suppressor CD9. From this it may be possible to identify a biomarker signature that will improve outcomes for prostate cancer patients.