Tumors which originate in the male reproductive tract frequently display hormone-responsive growth. However, for prostate cancer (the most common steroid regulated tumor in the male), nearly all advanced tumors ultimately fail to respond to androgen deprivation and presently there is no effective chemotherapy available for this disease. The events which de-regulate androgen-dependent growth of male reproductive tumors are of critical importance. Steroid hormones have been demonstrated to play a fundamental role in the initiation of tumor growth, as well as to regulate tumor growth and progression. This proposal seeks support to determine the events which lead to the progression of a male reproductive tumor (induced by steroid administration) from a slow proliferating androgen-regulated tumor to a rapidly proliferating hormonally autonomous state by defining the molecular mechanisms associated with steroid regulation of growth. To our knowledge, the DDT1MF-2 cell line (from ductus deferens) is the only androgen dependent cell line derived from a male reproductive tumor which progresses to a hormonally autonomous state following androgen ablation, despite the presence of a normal androgen receptor. Androgens regulate the expression of aFGF and v-sis in DDT1MF-2 cells. Since the responsive cells demonstrate a plasticity to respond to alternative growth stimuli in vitro, hormone autonomous growth could be through the activation of growth factor gene expression by stimuli other than androgens. These might include transcription factors (Nur77, fos). Another route to steroid autonomy is through activation of the cascade of events which lead to mitosis. Immediate early genes (such as Nur77, fos) are androgen-regulated in DDT1MF-2 cells. Since Nur77 is a member of the steroid receptor family, androgen control of its expression could have implications in neoplastic growth. Progression to hormone independence may result from differential regulation of transcription factors in hormone-responsive and -unresponsive state. The concentration of Nur77 transcripts is dramatically altered following androgen administration in DDT1MF-2 cells. These changes correlate with expression of aFGF as well as proliferation. We will focus on the mechanism of androgen regulation of Nur77 and c-fos in hormone-dependent and -independent DDT1MF-2 cells. We will define the effect of androgens on the transcription, half-life and steady state levels of Nur77 and c-fos mRNA and correlate the findings with the effect on DDT1MF-2 cell proliferation. The role of Nur77 and fos in hormone-regulated growth will be shown by transfection of expression vectors and anti-sense oligonucleotides. We will determine the DNA sequences required for androgen-regulated expression of Nur77 and fos as well as DDT1MF-2 growth by transfection of a series of fos-CAT and Nur77-CAT constructs which involve both the 5'and 3'flanking sequences and promoters. The androgen-regulated events which activate transcription of specific genes which lead to mitosis in hormone responsive tumor are unknown.
Our aim i s to define the molecular mechanism associated with this regulation of growth, as well as to define the events which lead to the progression of the tumor to an autonomous state.
| Lamb, D J; Ray, M (1995) Steroid-regulated growth of DDT1MF-2 cells is profoundly influenced by culture conditions. In Vitro Cell Dev Biol Anim 31:871-5 |
