Micro (mi)RNAs have recently been found to play an important role in cancer biology. In order to further understand how miRNAs affect prostate tumour progression, we evaluated miRNA expression in two invasive prostate tumour lines, PC3 and DU145. We then focused our evaluation on a novel miRNA, miR-105, whose levels were significantly decreased in both tumour cell lines as compared to normal prostate epithelial cells. As miR-105 levels were reduced in prostate tumour cell lines, we restored its expression following transfection of cells with mimic constructs to over-express miR-105 in both cell lines, in order to determine its effect on various tumourigenic properties. Over-expression caused decreased tumour cell proliferation, anchorage-independent growth and invasion in vitro and inhibited tumour growth in vivo. We further identified CDK6 as a putative target of miR-105, which likely contributed to its inhibition of tumour cell growth. Our results suggest that miR-105 inhibits tumour cell proliferation and may be an interesting target to regulate tumour growth or potentially used as a biomarker to differentiate between less and more aggressive tumours in patients.

Micro (mi)RNAs have recently been found to play an important role in cancer biology. In order to further understand how miRNAs affect prostate tumour progression, we evaluated miRNA expression in two invasive prostate tumour lines, PC3 and DU145. We then focused our evaluation on a novel miRNA, miR-105, whose levels were significantly decreased in both tumour cell lines as compared to normal prostate epithelial cells. As miR-105 levels were reduced in prostate tumour cell lines, we restored its expression following transfection of cells with mimic constructs to over-express miR-105 in both cell lines, in order to determine its effect on various tumourigenic properties. Over-expression caused decreased tumour cell proliferation, anchorage-independent growth and invasion in vitro and inhibited tumour growth in vivo. We further identified CDK6 as a putative target of miR-105, which likely contributed to its inhibition of tumour cell growth. Our results suggest that miR-105 inhibits tumour cell proliferation and may be an interesting target to regulate tumour growth or potentially used as a biomarker to differentiate between less and more aggressive tumours in patients.