NKS-01

It is very important to examine the influence of inhibition of in situ estrogen production on the pathobiology of human sex steroid-dependent tumors in order to understand the clinical effects of aromatase inhibitors. We have examined the biological changes before and after aromatase inhibitor treatment in vitro (endometrial and ovarian cancer) and in vivo (breast cancer). First, we analyzed these changes using histoculture of 15 human endometrial cancers and 9 ovarian cancers. Five of the fifteen endometrial cancers and four of the nine ovarian cancers demonstrated decreased [3H]thymidine uptake or Ki67 labeling index after 14alpha-hydroxy-4-androstene-3,6,17-trione (NKS01) treatment. In ovarian cancer cases, the responsive cases tended to be associated with higher aromatase and estrogen receptor alpha (ER) expression compared with the other cases but this was not seen in the endometrial cancer cases. There were no changes in ER and aromatase expression before and after NKS01 treatment in either ovarian or endometrial cancer cases. We then studied the same primary human breast tumors before and after aminoglutethimide (AMG, n=3) and 4-hydroxyandrostenedione (4-OHA, n=3) treatment. Tumor aromatase activity increased in 3 cases and decreased or was unchanged in 3 cases but aromatase immunoreactivity in stroma and adipocytes was unaltered in 5 cases. There were no changes in the ER labeling index before or after treatment. Five of the six cases including the responsive cases tended to be associated with decreased cell proliferation or Ki67 expression and increased apoptosis when examined by the TUNEL method. These results indicate that aromatase inhibitors may exert their effects on human breast and other cancers through decreasing proliferation and increasing apoptosis, possibly without altering ER status.

The sexually dimorphic nucleus of the preoptic area (SDN‐POA) and the anteroventral periventricular nucleus of the preoptic area (AVPvN‐POA) are sexually dimorphic regions in the rat brain. These regions are sensitive to reproductive function‐related drugs, and thus applied for aromatase inhibitor evaluation in the present study. Effects of NKS01 (an aromatase inhibitor) and tamoxifen on the SDN‐POA and AVPvN‐POA were examined. Five mg of NKS01 or its vehicle was injected to SD male and female rats from days 1 to 14 (the day of birth = day 0). Other 10 males and 10 females received a single injection of 100 μg tamoxifen on day 1. Rats in each group were sacrificed at day 30 or 60. The SDN‐POA was examined at days 30 and 60, and the AVPvN‐POA at day 60. When NKS01 was given to male rats for the first 14 days of life, a significant reduction of SDN‐POA size was observed on day 60. When tamoxifen was given, SDN‐POA reduction in size was also observed at days 30 and 60 in male rats. As for the AVPvN‐POA, tamoxifen markedly reduced volume in female rats, resulting in polycystic ovaries at day 60. This may be due to an estrogenic property of tamoxifen. On the other hand, NKS01 was not significantly effective in the AVPvN‐POA, although the volume of the nucleus in NKS01 males was inclined to increase. From these results, as well as the SDN‐POA, the AVPvN‐POA may be useful to evaluate the side effect of reproductive function‐related drug.