PMID:18360715

Citation	Possner, M, Heuser, M, Kaulfuss, S, Scharf, JG, Schulz, W, Hermann-Ringert, R and Thelen, P (2008) Functional analysis of NKX3.1 in LNCaP prostate cancer cells by RNA interference. Int. J. Oncol. 32:877-84
Abstract	The function of the androgen-regulated homeobox protein NKX3.1 in prostate cancer is controversial. NKX3.1 is necessary for correct prostate development and undergoes frequent allelic loss in prostate cancer. However, no mutations occur in the coding region and some particularly aggressive cancers over-express the protein. Nevertheless NKX3.1 is often referred to as candidate tumor suppressor gene. Recent findings suggest a function in protection against oxidative damage involved in prostate carcinogenesis. Thus NKX3.1 may act differently at various stages of prostate cancer. Unlike a classical tumor suppressor NKX3.1 is up-regulated by androgens and down-regulated by phytoestrogens. In this study we performed RNAi based functional analysis by knocking down NKX3.1 expression in LNCaP prostate cancer cells and analyzing the impact of NKX3.1 on gene expression and cell proliferation. Knock-down of NKX3.1 evoked a massive down-regulation of NKX3.1 expression, followed by reduction in mRNA expression of the androdrogen receptor (AR) and the insulin-like growth factor receptor (IGF-1R). Western blot analysis showed strong decreases of NKX3.1, AR, and IGF-1R protein expression. Concomitantly, cell proliferation decreased and expression of prostate-specific antigen (PSA) mRNA and its secretion were diminished, whereas expression of IGF binding protein 3 (IGFBP-3) and MMP tissue inhibitor 3 (TIMP-3) was up-regulated. In tumor cells not deprived of NKX3.1 expression this gene still has a function which might differ from its role in prostate development and carcinogenesis. NKX3.1 knock-down altered the expression of genes highly relevant in prostate cancer cell proliferation and apoptosis. In LNCaP NKX3.1 most probably plays the role of an androgen-regulated transcription factor whose down-regulation is paralleled by anti-proliferative and pro-apoptotic effects. Since NKX3.1 can regulate AR expression it may become a target for interference in hormone refractory prostate carcinoma.
Links	PubMed
Keywords	Cell Line, Tumor; Homeodomain Proteins/antagonists & inhibitors; Homeodomain Proteins/genetics; Homeodomain Proteins/physiology; Humans; Male; Prostatic Neoplasms/pathology; RNA Interference; Transcription Factors/antagonists & inhibitors; Transcription Factors/genetics; Transcription Factors/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HUMAN:NKX31	involved_in	GO:0045893: positive regulation of transcription, DNA-templated	ECO:0000315: mutant phenotype evidence used in manual assertion		P	has_input:(UniProtKB:P10275)|has_input:(UniProtKB:P08069)	Seeded From UniProt	complete
HUMAN:NKX31	involved_in	GO:0045892: negative regulation of transcription, DNA-templated	ECO:0000315: mutant phenotype evidence used in manual assertion		P	has_input:(UniProtKB:P07288)	Seeded From UniProt	complete
HUMAN:NKX31	involved_in	GO:0045892: negative regulation of transcription, DNA-templated	ECO:0000315: mutant phenotype evidence used in manual assertion		P	has_regulation_target:(UniProtKB:P07288)	Seeded From UniProt	complete
HUMAN:NKX31	involved_in	GO:0045893: positive regulation of transcription, DNA-templated	ECO:0000315: mutant phenotype evidence used in manual assertion		P	has_regulation_target:(UniProtKB:P10275)|has_regulation_target:(UniProtKB:P08069)	Seeded From UniProt	complete
HUMAN:NKX31	involved_in	GO:0008284: positive regulation of cell population proliferation	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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