NLK inhibits the transformation from prostatitis to prostate cancer through maintaining NF-κB/P53 functional balance

Abstract

Background and purpose: Prostate inflammation is an important promoter of carcinogenesis. However, the key underlying mechanisms remain unknown. Nemo-like kinase (NLK) expression is significantly lower in prostate cancer tissues than in benign tissues; downregulation of NLK expression can enhance the transcriptional activity of nuclear factor-κB (NF-κB) in prostate cancer cells. This study aimed to explore the effects of NLK in regulating the transformation from prostatitis to prostate cancer and its mechanisms, to provide effective molecular targets and a new theoretical basis for novel anti-inflammatory strategies in prostate cancer prevention. Methods: The cell model of transformation from prostatitis to prostate cancer (RWPE-1/THP-1) was established by co-culture of human prostate epithelial cells RWPE-1 and human acute monocytic leukemia cells THP-1. The proliferation and transformation abilities of model cells with the silence or overexpression of NLK were investigated by MTT experiment and soft agar experiment, respectively. The effects of the silence or overexpression of NLK on NF-κB activity in model cells were investigated by luciferase assay. The mRNA expression and protein levels of nuclear receptor-related factor 1 (Nurr1) and murine double minute 2 (MDM2) in model cells with the silence or overexpression of NLK were validated by real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) and Western blot, respectively. The effects of the silence or overexpression of NLK on P53 protein levels in model cells were investigated by Western blot. The co-localization of Nurr1 and P53 in RWPE-1 cells was investigated by immunofluorescence experiment. The interaction between Nurr1 and P53 in RWPE-1 cells was verified by co-immunoprecipitation assay. Results: Compared with the RWPE-1/THP-1 group, the proliferation and transformation abilities of model cells were decreased, the NF-κB activity was inhibited, the mRNA expression and protein levels of the Nurr1 and MDM2 were down-regulated, and the P53 protein levels were increased in RWPE-1 (NLK↑)/THP-1 group (P<0.05). In contrast, the proliferation and transformation abilities of model cells were increased, the NF-κB activity was enhanced, the mRNA expression and protein levels of the Nurr1 and MDM2 were up-regulated, and the P53 protein levels were reduced in RWPE-1 (NLK↓)/THP-1 group (P<0.05). Moreover, the Nurr1 and P53 were co-located in the nucleus of RWPE-1 cells and they interacted with each other. Conclusion: NLK can inhibit the transformation from prostatitis to prostate cancer, which may be related to maintaining NF-κB/P53 functional balance.

Keywords

• |prostate neoplasms|prostatitis|nemo-like kinase|malignant transformation