A new member of the mouse NK family of homeobox genes that is related to Drosophila NK-3 has been identified. Expression of this gene, termed Nkx-3.1, is largely restricted to the prostate gland in adult animals. The level of Nkx-3.1 mRNA decreases markedly in response to castration, suggesting that its expression is androgendependent. In situ hybridization analyses demonstrated that expression of Nkx-3.1 in the prostate is confined to epithelial cells. In newborns, Nkx-3.1 mRNA is detected in the urethral epithelium that is being induced by the surrounding mesenchyme to invaginate to form prostatic buds. Together, these observations suggest that the Nkx-3.1 protein, which likely functions as a transcription factor, plays a prominent role both in the initiation of prostate development and in the maintenance of the differentiated state of prostatic epithelial cells.

BACKGROUND Hox genes encode transcriptional regulatory proteins that are largely responsible for establishing the body plan of all metazoan organisms. A subset of Hox genes is expressed during the period of organogenesis and into adulthood. hoxb‐13 is a recently‐described member of the Hox gene family that is expressed in the spinal cord, hindgut, and urogenital sinus during embryogenesis. METHODS Northern blot and in situ hybridization analyses of hoxb‐13 expression in adult mouse tissues were performed. RESULTS hoxb‐13 mRNA is restricted to the prostate gland and distal colon in adult animals. In situ hybridization of mouse prostate tissue demonstrated that hoxb‐13 is expressed in the epithelial cells of the ventral, dorsal, lateral, and anterior prostate lobes. Accumulation of hoxb‐13 mRNA is not diminished following castration. CONCLUSIONS These data demonstrate that hoxb‐13 expression is androgen‐independent in mouse prostate glands. The identification of hoxb‐13 as an androgen‐independent gene expressed in adult mouse prostate epithelial cells provides a new potential target for developing therapeutics to treat advanced prostate cancer. Prostate 41:203–207, 1999. © 1999 Wiley‐Liss, Inc.

Although lesions are expected to disappear with prolonged MPA treatment, this form of progestin therapy is hazardous because recurrence occurs frequently. Only strictly selected patients should therefore be indicated for long-term MPA treatment and careful evaluation before and after treatment should be performed.

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Seminal plasma inhibin-B level is a useful predictor of the presence of testicular sperm in men with non-obstructive azoospermia.