NAV3, a Tumor Suppressor Gene, Is Decreased in Uterine Leiomyoma Tissue and Cells

NAV 3 is a tumor suppressor of unknown function in leiomyomas. The objective of this study is to assess NAV3 expression and its potential role in human uterine leiomyomas. NAV3 protein expression was examined in patient leiomyoma and patient-matched myometrial tissue samples by Western blot and immunohistochemistry. NAV3 mRNA and protein expression was assessed in leuprolide acetate- and cetrorelix-treated cell line leiomyoma samples. RNAseq analysis of placebo-treated leiomyoma compared with myometrium demonstrated the presence of transcripts encoding for several neuronal proteins. For NAV3, RNA sequence analysis demonstrated decreased expression in leiomyoma as compared with myometrium (0.86 +/- 0.03 fold). Presence of NAV3 mRNA was also decreased in leiomyoma surgical samples (0.43 fold +/- 0.05, p = 0.026) compared with patient-matched myometrium. Confirmatory qRT-PCR results on immortalized leiomyoma and myometrial cell lines similarly demonstrated a decrease in expression of NAV3 in leiomyomas (0.28 +/- 0.02, p = 0.00075). Immunohistochemical analysis demonstrated a significant decrease in NAV 3 protein in leiomyomas (H-score 154.7 +/- 6.2) as compared with myometrium (H-score; 312.5 +/- 14.7, p < 0.0001). Leuprolide acetate-treated leiomyoma cells demonstrated an increase in NAV 3 mRNA expression (1.53 +/- 0.13, p < 0.0001). Similarly, Western blot analysis on leuprolide-treated leiomyoma cells showed a non-significant increase in NAV 3 protein expression (1.26 +/- 0.09, p = 0.063). NAV 3, a tumor suppressor in numerous cancers, is decreased in leiomyoma cells and tissue compared with myometrium, and increased by GnRH analog treatment, suggesting that NAV3 may mediate steroid hormone-independent leiomyoma regulation by GnRH analogs.