Introduction and Objectives: XMRV is a novel human retrovirus associated with prostate cancer. Although other gammaretroviruses cause cancer in animals, it remains unknown if XMRV is a cause of disease.
However, indirect or direct modes of carcinogenesis by XMRV have been suggested depending on whether the virus was found in stroma or malignant epithelium.
To gain insight into the possible role of XMRV in these diseases we have identified genes that are induced in response to XMRV infection. [Genes whose expression is changed.]
Methods: Prostate cancer cell line DU145 was infected for 8, 24, 48 and 120 hours with XMRV. A comparison to uninfected DU145 cells cultured for the same periods of time served as controls. A population of total RNA was isolated using Qiagen RNeasy Mini Kit followed by digestion of DNA with DNAse treatment. XMRV infections at the different time points were monitored using real-time RT-PCR for env XMRV RNA.
The RNA samples were analyzed for gene expression using Sentrix humanRef-8 v3 expression bead chips from Illumina (Cleveland Clinic Genomics Core). To verify the results obtained by the array experiment, we determined induction of a subset of the regulated genes. Total RNA was reverse transcribed to cDNA using iScript Select cDNA Synthesis Kit from Bio-Rad (random primers method). Induction of selected genes by XMRV infection was verified by qPCR (Relative Quantification) from the cDNA pool using SYBR Green master mix. Fold-induction at each time point for the individual mRNAs was determined. In addition, pathway predictions were determined using Ingenuity Systems (content version 3002) software for genes induced by more than 2-fold following XMRV infection.
In gene expression profiling, we observed maximal gene induction between 24 and 48 hours post-infection.
For example, the pro-inflammatory cytokine IL8 gene, a potential contributing factor to androgen independent growth of late-stage prostate cancer, was consistently induced by XMRV infection by up to 6-fold.
Of the XMRV induced genes, pathway analysis indicated 10 genes are implicated in cell morphology, 11 genes in cellular development, 12 genes in cell-to-cell signaling and interaction, 11 genes in cellular movement and 13 genes in cellular growth and proliferation.
The chemokine IL-8 is one of the most highly induced genes in response to XMRV infection of prostate cancer cell line DU145.
XMRV induction of the 30 host genes identified in this study suggests a profound effect of the virus on fundamental cellular physiology and inflammation. These findings could be relevant to the possible pathogenic effects on XMRV in prostate cancer.
Source: The Journal of Urology, Apr 2011;vol 185(4)Supplement, #280, p. e113. By Lee M, Busho E, Das Gupta J, Klein E, Silverman R. The Cleveland Clinic, Cleveland, Ohio, USA.