The NKX3.1 gene is an androgen-regulated homeodomain gene located on chromosome 8p21.2, whose expression is predominantly localized to prostate epithelium. The NKX3.1 protein acts as a nuclear transcription factor that has a critical function in prostate development and tumour suppression, and is a negative regulator of epithelial cell growth in prostate tissue. Apart from prostate epithelium, NKX3.1 is found in testis, ureter, and pulmonary bronchial mucous glands.
+ The proportion of prostate adenocarcinomas being NKX3.1 positive in the literature is highly varying but with the newest antibodies and a sensitive visualization system more than 90% are positive.
-/+ NKX3.1 is found in a minority (~20%) of prostatic small cell carcinomas and breast carcinomas, particularly lobular carcinomas.
NKX3.1 is a highly sensitive and specific marker for prostate adenocarcinoma in line with other prostate markers like Prostate Specific Antigen (PSA) and Prostein (p501S), particularly useful in low differentiated tumours where PSA and/or Prostein may be weakly expressed or lost. NKX3.1 is a nuclear marker, which occasionally may allow for an easier interpretation than the above mentioned cytoplasmic markers.