Login to Access Video or Poster Abstract: MP28-03
Sources of Funding: none

Introduction

Chromodomain helicase DNA-binding protein 1 (CHD1) is a frequently deleted gene in prostate cancer (PCa). Our previous work demonstrated accelerated tumor growth as well as increased spontaneous lung metastasis of CHD1 depleted PC3 cells in a xenograft mouse model. In order to provide additional evidence for the role of CHD1 deletion in PCa metastasis and progression, we performed accompanying in vitro and in vivo experiments using ARCaP-M cells after shRNA-mediated KD of CHD1 and evaluated clinical outcomes of patients with CHD1 deletion after radical prostatectomy (RP).

Methods

ARCaP-M cells were stably transfected with shRNA against CHD1 by lentiviral transduction. The control cells were transfected with non-targeting shRNA. The resulting CHD1 status was assessed by western blot. In vivo, both cell lines were subcutaneously xenografted into immunodeficient pfp-/-/rag2-/- mice. At a tumor size of about 0.5 g, mice were sacrificed and primary tumors as well as right lungs were weighed and processed for histopathological analysis. DNA from the blood, left lungs, livers, brains and bone marrow were isolated for quantification of DTC and CTC by Alu-qPCR. MicroRNA (miRNA) expression in the mouse blood and mRNA expression in primary tumors were analyzed by microarray. To estimate the clinical impact of CHD1 deletion, we carried out FISH analysis in 6883 clinical PCa specimens and analyzed the pathologic and clinical follow-up of patients related to CHD1 deletion.

Results

We detected a stronger expression of CHD1 in ARCaP-M than previously reported for PC3 cells. KD of CHD1 resulted in effective down-regulation of CHD1 protein levels in ARCaP-M. After comparable growth periods in vivo, xenograft primary tumors with CHD1-KD were not significantly larger than control tumors. However, we observed increased levels of CTC in the mouse blood as well as a higher metastatic cell load in the lungs, livers and brains in the CHD1-depleted group, while the level of DTCs in the bone marrow was not changed and below the analytical limit of detection. Moreover, miRNA microarray analysis identified 24 miRNAs differentially expressed in CHD1-depleted mouse serum. In clinical multivariate analysis, CHD1 deletion was significantly linked to early PSA recurrence (p= 0.027), early metastasis (p= 0.001) and cancer specific mortality (p= 0.025) after RP. Overall survival was not affected by CHD1 status (p=0.41). We also observed more frequent metastases in the CHD1 deleted group (8% vs. 3,3 %, p<0.001), apart from the previous reported higher Gleason score (p<0.001) and advanced tumor stages of CHD1 deleted PCa specimens (p=0.005).

Conclusions

KD of CHD1 increases metastatic potential in two xenograft models of human PCa and leads to significant regulation of several miRNAs which could be involved in spontaneous dissemination of PCa cells. Moreover, multivariate analysis of oncological outcomes confirmed the significant association of CHD deletion with early BCR, early and more frequent metastasis as well as cancer specific mortality after surgery. This translational study demonstrates that CHD1 deletion predicts both histopathological tumor characteristics and disease progression by metastasis as well as cancer specific mortality after surgery and thereby supports the role of CHD1 deregulation for PCa progression.

Funding

none