Stains
NKX3.1

Authors: Satbir Thakur, Ph.D. (see Authors page)
Editor: Emeka Enwere, M.D.
Editorial Board Member Review: Lauren N. Stuart, M.D., M.B.A.

Revised: 23 May 2017, last major update April 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: NKX3.1
Cite this page: NKX3.1. PathologyOutlines.com website. http://pathologyoutlines.com/topic/stainsnkx3.html. Accessed August 21st, 2017.
Definition / general
  • Homeodomain containing transcription factor protein that is expressed specifically in prostate gland and binds to a consensus sequence 5’-TAAGT[AG]- 3’
  • Expression is regulated in an androgen specific manner
  • Loss of expression is commonly reported in human prostate carcinomas and prostatic intraepithelial neoplasia, due to allelic loss, promoter methylation and posttranscriptional silencing (Differentiation 2008;76:717)
  • Human NKX3.1 gene encodes a 234 amino acid protein and is homologous to the Drosophila bagpipe gene, which is essential in mesoderm development (Mol Cell Biol 2002;22:1495, Eur J Cell Biol 2010;89:273)
Essential features
  • Due to its highly restricted expression in prostate epithelial cells, NKX3.1 can be used as a diagnostic biomarker for prostate cancer and other metastatic lesions originating in the prostate
  • NKX3.1 (98.6%) shows better sensitivity than Prostate Specific Antigen (PSA) (94.2%) for identifying metastatic prostatic adenocarcinoma
Terminology
    Also known as
  • NK3 Homeobox 1
  • Homeobox Protein NK-3 Homolog A
  • NKX3-1
  • NKX3A
  • NK3 Transcription Factor Related, Locus 1 (Drosophila)
  • NK3 Transcription Factor Related, Locus 1
  • NK Homeobox (Drosophila), Family 3, A
  • NK3 Transcription Factor Homolog A
  • NK Homeobox, Family 3, A
  • Homeobox Protein Nkx-3.1
  • BAPX2
  • NKX3 (GeneCards - NKX3.1 Gene)
Pathophysiology
  • 3’NKX3.1 is a prostate specific gene encoding a transcription factor that plays an important role in prostate development and carcinogenesis (Mol Biol Rep 2010;37:1505)
    • Can act as a transcriptional activator or repressor, depending on the tissue and cellular context
    • Plays an important role in normal prostate development, regulating proliferation of glandular epithelium and in the formation of ducts in prostate
  • The expression of mammalian NKX3.1 is androgen dependent and is frequently reduced or lost in prostate cancer (Genes Dev 1999;13:966, Genomics 1997;43:69, Cancer Res 2000;60:6111)
  • Loss of NKX3.1 is an initiating event in the formation of prostate intraepithelial lesion (PIN), a precursor of prostate carcinoma (Mol Biol Rep 2010;37:1505)
  • Human NKX3.1 gene is located on chromosome 8p21, which is frequently reported to undergo loss of heterozygosity (LOH) during the progression of prostate cancer
    • LOH has been reported in 12 - 89% of high grade prostatic intraepithelial neoplasia and 35 - 86% of prostatic adenocarcinomas
    • The frequency of LOH on chromosome 8p increases with advancing disease grade (Am J Surg Pathol 2010;34:1097)
  • Conditional deletion of one or both alleles of NKX3.1 in transgenic mice leads to the development of preinvasive lesions that resemble human prostatic intraepithelial neoplasia (Mol Cell Biol 2002;22:1495)
  • Targeted disruption of NKX3.1 in mice results in defects in prostate branching morphogenesis, epithelial cell differentiation, growth and protein secretion (Genes Dev 1999;13:966)
  • In mice with targeted disruption of PTEN or Cdkn1b, loss of one or both alleles of NKX3.1 results in aggressive prostate tumorigenesis (Cancer Res 2003;63:3886, Am J Pathol 2004;164:1607)
  • Loss of function of NKX3.1 in mouse prostate results in downregulation of genes essential for prostate differentiation (Science 2016;352:1576)
  • Castration resistant NKX3.1 expressing cells (CARNs) in mice have been found to be bipotential in nature and self renewing
  • Single cell transplantation of CARNs reconstitutes prostate ducts in renal grafts; in these mice, NKX3.1 has been shown to be required for stem cell maintenance (Nature 2009;461:495)
  • In humans, loss of NKX3.1 expression has been shown to be strongly associated with hormone refractory disease and metastases in prostate cancer (Cancer Res 2000;60:6111)
  • In oral squamous cell carcinoma (OSCC), association between NKX3.1 loss and occult lymph node metastatic lesions has been observed; loss of NKX3.1 emerged as a significant risk factor to decrease the disease free and overall survival of OSCC patients (Int J Oncol 2012;40:1907)
  • NKX3.1 has been shown to increase p53 stability and activity in an MDM2 dependent manner by its association with HDAC1 (Cancer Cell 2006;9:367)
Interpretation
Uses by pathologists
  • Due to its highly restricted expression in prostate epithelial cells, NKX3.1 can be used as a diagnostic biomarker for prostate cancer and other metastatic lesions originating in the prostate (Am J Surg Pathol 2014;38:e6, Adv Anat Pathol 2015;22:149)
  • NKX3.1 (98.6%) shows better sensitivity than Prostate Specific Antigen (PSA) (94.2%) for identifying metastatic prostatic adenocarcinomas (Am J Surg Pathol 2010;34:1097)
Microscopic (histologic) images

Images hosted on PathOut server:
Images contributed by Debra Zynger, M.D.

Prostate needle cores with prostatic adenocarcinoma, H&E and NKX3.1

Metastatic prostatic adenocarcinoma to bone, H&E

Metastatic prostatic adenocarcinoma to bone, NKX3.1



Images contributed by Grzegorz Gurda MD, PhD, Gundersen Health Systems, Wisconsin:

Prostatic adenocarcinoma, Gleason 3+3, 90% staining, 4x, 10x, 20x

Nodular hyperplasia (BPH), 4x, 10x, 20x



Images hosted on other servers:

Immunohistochemical
staining for NKX3.1 in
normal and atrophy

Immunohistochemical
staining for NKX3.1 in
normal and PIN

Immunohistochemical
staining for NKX3.1 in
normal and carcinoma

NKX3.1 staining in normal prostate tissue

Soft tissue metastasis stained
with: (A) H&E, (B) NKX3.1, (C)
PSA, (D) PSAP
Positive staining - normal
  • Highly expressed in the prostate and at a lower level in the testis (GeneCards - NKX3.1 Gene, Prostate 2003;55:111)
  • Salivary gland tissue; bronchial submucosal glands; isolated regions of transitional epithelium in the ureter
Positive staining - disease
Negative staining
  • All other organs stain negatively for this protein
Board review question #1
    Which of the following would be expected to exhibit the weakest staining for NKX3.1?

  1. Bladder adenocarcinoma
  2. Normal prostatic epithelium
  3. Prostatic Intraepithelial Neoplasia (PIN)
  4. Primary prostate adenocarcinoma
  5. Prostate carcinoma nodal metastasis
Board review answer #1
A. Bladder adenocarcinoma. NKX3.1 staining is typically limited to prostate (benign and malignant) and some breast carcinomas.