Runx2 transcriptome of prostate cancer cells: insights into invasiveness and bone metastasis.
BACKGROUND
Prostate cancer (PCa) cells preferentially metastasize to bone at least in part by acquiring osteomimetic properties. Runx2, an osteoblast master transcription factor, is aberrantly expressed in PCa cells, and promotes their metastatic phenotype. The transcriptional programs regulated by Runx2 have been extensively studied during osteoblastogenesis, where it activates or represses target genes in a context-dependent manner. However, little is known about the gene regulatory networks influenced by Runx2 in PCa cells. We therefore investigated genome wide mRNA expression changes in PCa cells in response to Runx2.


RESULTS
We engineered a C4-2B PCa sub-line called C4-2B/Rx2 dox, in which Doxycycline (Dox) treatment stimulates Runx2 expression from very low to levels observed in other PCa cells. Transcriptome profiling using whole genome expression array followed by in silico analysis indicated that Runx2 upregulated a multitude of genes with prominent cancer associated functions. They included secreted factors (CSF2, SDF-1), proteolytic enzymes (MMP9, CST7), cytoskeleton modulators (SDC2, Twinfilin, SH3PXD2A), intracellular signaling molecules (DUSP1, SPHK1, RASD1) and transcription factors (Sox9, SNAI2, SMAD3) functioning in epithelium to mesenchyme transition (EMT), tissue invasion, as well as homing and attachment to bone. Consistent with the gene expression data, induction of Runx2 in C4-2B cells enhanced their invasiveness. It also promoted cellular quiescence by blocking the G1/S phase transition during cell cycle progression. Furthermore, the cell cycle block was reversed as Runx2 levels declined after Dox withdrawal.


CONCLUSIONS
The effects of Runx2 in C4-2B/Rx2 dox cells, as well as similar observations made by employing LNCaP, 22RV1 and PC3 cells, highlight multiple mechanisms by which Runx2 promotes the metastatic phenotype of PCa cells, including tissue invasion, homing to bone and induction of high bone turnover. Runx2 is therefore an attractive target for the development of novel diagnostic, prognostic and therapeutic approaches to PCa management. Targeting Runx2 may prove more effective than focusing on its individual downstream genes and pathways.
Baniwal
Sanjeev K
SK
Department of Biochemistry & Molecular Biology, University of Southern California, Los Angeles, CA, USA. baniwal@usc.edu
Khalid
Omar
O
Gabet
Yankel
Y
Shah
Ruchir R
RR
Purcell
Daniel J
DJ
Mav
Deepak
D
Kohn-Gabet
Alice E
AE
Shi
Yunfan
Y
Coetzee
Gerhard A
GA
Frenkel
Baruch
B
D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D014408:Biomarkers, Tumor / Q000235:genetics; D001859:Bone Neoplasms / Q000556:secondary*; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D054377:Chemokine CXCL12 / Q000235:genetics; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism*; D015891:Cystatins / Q000235:genetics; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D006801:Humans; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000235:genetics; D008840:Microfilament Proteins / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011471:Prostatic Neoplasms / Q000150:complications* / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053669:Syndecan-2 / Q000235:genetics
D033942:Adaptor Proteins, Vesicular Transport; D014408:Biomarkers, Tumor; C116891:CST7 protein, human; D054377:Chemokine CXCL12; D050659:Core Binding Factor Alpha 1 Subunit; D015891:Cystatins; D008840:Microfilament Proteins; C493709:RUNX2 protein, human; C508245:SDC2 protein, human; C478582:SH3PXD2A protein, human; C485188:TWF1 protein, human; D053669:Syndecan-2; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D020780:Matrix Metalloproteinase 9