Genetic susceptibility for C19 androgen induction of ovarian granulosa cell tumorigenesis in SWXJ strains of mice.

ABSTRACT

Susceptibility to pubertal onset, malignant granulosa cell (GC) tumors of the ovary is inherited in SWR/Bm and certain SWR-related SWXJ recombinant inbred strains of mice. In some SWXJ strains, GC tumors occur spontaneously (spontaneous strains), and in others GC tumors can only be induced by treatment with dehydroepiandrosterone (DHEA-dependent strains). A gene controlling susceptibility to both spontaneous and DHEA-induced GC tumorigenesis, Gct, has been assigned to Chromosome 4. Additional research on the role of steroids in GC tumorigenesis has revealed a second gene controlling response to C19 androgenic steroids. Spontaneous strains showed increased tumor frequency after treatment with testosterone (T), whereas DHEA-dependent strains showed no GC tumors following T treatment. Within treatment groups, serum steroid data from DHEA, T, and control treated mice showed no consistent differences between spontaneous and DHEA-dependent strains with respect to progesterone, DHEA, androstenedione, dihydrotestosterone, T, estrone, or estradiol. Thus, observed differences in GC tumor responsiveness to exogenous steroids were not due to different patterns of steroid metabolism among spontaneous and DHEA-dependent strains. Further studies on the range of effective C19 steroids were conducted using one spontaneous and one DHEA-dependent strain. The spontaneous strain showed increased GC tumor frequency in response to dihydrotestosterone and androsterone treatment, whereas the DHEA-dependent strain showed no response. This result suggests that spontaneous strains may be sensitive to a broad range of C19 steroids. To determine whether genetic differences in endogenous steroid levels have a role in spontaneous GC tumorigenesis, serum steroid levels were measured in SWR/Bm and SJL/Bm progenitor strains during the developmental period of risk between 22 and 38 days of age. With the exception of transiently increased DHEA at 22 days, there were no consistent differences in steroid levels analyzed. Thus, serum steroid profiles were not reliably prognostic for GC tumorigenesis. In conclusion, GC tumor induction in response to T treatment has co-segregated with susceptibility to spontaneous GC tumors in the SWXJ recombinant inbred strains. Thus, the second gene in our ovarian granulosa cell tumor model regulates responsiveness to T. We propose to name this gene spontaneous ovarian tumorigenesis (Sot), with alleles for susceptibility (s) carried by spontaneous strains and resistance (r) carried by DHEA-dependent strains.