PDLIM2 suppression efficiently reduces tumor growth and invasiveness of human castration-resistant prostate cancer-like cells.
BACKGROUND
Although PDLIM2 gene may have a context-dependent role in various human malignancies and can be a potential therapeutic target, only a limited number of in vitro studies addressed the molecular functions of PDLIM2 in prostate cancer. Here, we aimed to explore the role of PDLIM2 and the effect of the PDLIM2 gene suppression on oncogenic phenotypes of human castration-resistant prostate cancer (CRPC)-like cells.


METHODS
We used human CRPC-like cell lines (PC3, DU145, and C4-2B) for our experiments. Transcription levels of PDLIM2 and relevant genes were measured by real time-PCR and protein expression was analyzed by western blot. Cell viability, proliferation, clonogenic growth, and tumor sphere formation were examined after a specific inhibition of PDLIM2 using RNA interference. Flow cytometry was used to examine apoptotic cell death and cell cycle disturbances. Wound healing and transwell migration assays were performed to investigate the invasion capabilities of CRPC-like cells. Additionally, key oncogenic signaling pathways were examined using western blot. Lastly, we evaluated the in vivo efficacy of PDLIM2 suppression on tumor growth of human CRPC xenografts in mice.


RESULTS
We observed a significant enhancement of PDLIM2 expression in human CRPC-like cell lines, while a specific inhibition of PDLIM2 reduced cell viability and proliferation due to apoptotic cell death. Conversely, PDLIM2 overexpression significantly reduced cell proliferation compared to the negative control in androgen-sensitive LNCaP cells. Moreover, PDLIM2 suppression led to a decrease of clonogenic growth and tumor sphere formation in three-dimensional cultures with the G2/M cell cycle arrest in human CRPC-like cells. PDLIM2 inhibition also attenuated cellular migration and invasion capabilities of human CRPC-like cells, and reduced the expression of mesenchymal marker. Among several oncogenic signaling pathways, only the MAPK/ERK signaling cascade was decreased by PDLIM2 inhibition and reciprocally, ERK inhibition down-regulated PDLIM2 expression. Importantly, PDLIM2 inhibition remarkably compromised tumor growth in a human CRPC xenograft model.


CONCLUSIONS
In summary, the suppression of PDLIM2 significantly reduced such oncogenic phenotypes as proliferation, clonogenicity, invasiveness, and tumor cell growth in human CRPC-like cells both in vitro and in vivo, indicating that PDLIM2 may be considered a novel therapeutic target gene for treating human CRPC.
Department of Urology, Seoul National University Bundang Hospital, Seongnam, Korea.
Minyong
M
Kang
Department of Urology, Seoul National University Hospital, Seoul, Korea.
Kyoung-Hwa
KH
Lee
Department of Urology, Seoul National University Hospital, Seoul, Korea.
Hye Sun
HS
Lee
Department of Urology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Yong Hyun
YH
Park
Department of Urology, Seoul National University Hospital, Seoul, Korea.
Chang Wook
CW
Jeong
Department of Urology, Seoul National University Hospital, Seoul, Korea.
Ja Hyeon
JH
Ku
Department of Urology, Seoul National University Hospital, Seoul, Korea.
Hyeon Hoe
HH
Kim
Department of Urology, Seoul National University Hospital, Seoul, Korea.
Cheol
C
Kwak
D000818:Animals; D014408:Biomarkers, Tumor / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D055785:Gene Knockdown Techniques / Q000379:methods; D006801:Humans; D060588:LIM Domain Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008840:Microfilament Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D009361:Neoplasm Invasiveness / Q000235:genetics; D064129:Prostatic Neoplasms, Castration-Resistant / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays / Q000379:methods
D014408:Biomarkers, Tumor; D060588:LIM Domain Proteins; D008840:Microfilament Proteins; C502929:PDLIM2 protein, human
castration-resistant prostate cancer; cytotoxicity; inhibition; tumor invasion