A125: Circulating RNA in prostate cancer reveals novel androgen regulated genes that predict poor outcome

Benjamin Thomas1,Jonathan Kay2, Suraj Menon1, Sarah Vowler1, Sarah Dawson1, Hayley Luxton1, Thomas Johnson1, Charlie Massie1, Michelle Osbourne1, Anne Warren3, Keith Burling3, Andy Lynch1,Anne George4, Marie Corcoran4, Johannah Burge4, Sara Stearn4, Alastair Lamb1, Greg Shaw1, David Neal1, Hayley Whitaker3

1CRUK Cambridge Institute, Cambridge, UK,2University College London, London, UK,3Addenbrookes Hospital, Cambridge, UK,4University of Cambridge, Cambridge, UK,5University of Oxford, Oxford, UK

Presenting date: Monday 2 November

Background

Circulating DNA can be used to identify and monitor mutations present within cancerous tissue across multiple tumour types. Circulating RNA is potentially more labile and may more accurately reflect changes in gene expression during tumour development and treatment. Here we analysed the circulating RNA from the extremes of prostate disease; benign and metastatic disease to identify genes that are associated with metastasis and a poor outcome.

Method

Differentially expressed genes were identified in the discovery cohort of 22 control (PSA >3.8ng/ml, negative biopsy) and 10 metastatic samples using HT12 expression arrays. Genes were validated at the RNA and protein level using RT-PCR and immunohistochemistry on primary tissue. As the discovery cohort had poorly defined clinical characteristics genes were validated in two clinically well-defined cohorts; a hormone status cohort (hormone naive, stable disease treated with anti-androgens and hormone refractory) and risk stratified cohort defined by PSA, Gleason grade and stage. Androgen regulation of targets was confirmed by chIP.

Results

A four gene signature of FAM129A, MME, KRT7 and SOD2 was down-regulated in the circulating RNA of the discovery cohort but this was not always reflected in the tissue at the protein level. KRT7 and MME RNA expression could be used to discriminate between groups in the risk cohort. In the hormone status cohort FAM129A, SOD2 and MME mRNA expression was significantly reduced in patients with stable disease compared to naïve patients suggesting androgen regulation of these genes. MME RNA expression could also significantly distinguish between stable disease and hormone refractory patients. chIP data confirmed AR binding to all target promoters in at least one prostate cell line.

Conclusion

Circulating RNA can be used to detect changes associated with disease progression and hormone status. These genes could be analysed in a minimally invasive blood test to predict poor patient outcome.