This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Prostate cancer is the most common cancer diagnosed in the USA and the majority of prostate cancers diagnosed eventually progress from being androgen-dependent to androgen-independent. However, the precise molecular mechanisms underlying prostate cancer progression are unknown, which presents a major hurdle for the treatment of prostate cancer. The long-term goals of this research program are to elucidate the precise role of G-protein coupled endothelin A receptor (ETA R) signaling in prostate cancer progression from being androgen-dependent to androgen-independent and the molecular mechanisms whereby Regulator of G-protein Signaling 2 (RGS2) modulates the ETAR signaling in this progression. The LNCaP prostate cancer cell line has been chosen as a model in our preliminary studies. It grows slowly in an androgen-sensitive manner at low-passage but grows aggressively and loses androgen-dependence in high-passage, mimicking the progression of human prostate cancers. We found that increased ETA R and loss of RGS2 expression are associated with the loss of androgen-responsiveness in prostate cancer LNCaP cells, which both have been confirmed in human prostate tumor samples. Our preliminary studies also suggested that these two alterations may cooperatively promote prostate cancer progression. We will pursue these preliminary studies further through the following specific aims:
Aim 1. To determine molecular mechanisms whereby ETA R signaling promotes androgen-independent prostate cancer cell growth. We will investigate whether the hyperactive ERK activity triggered by ETA R signaling is responsible for androgen-independent prostate cancer cell proliferation. We will also silence androgen receptor by small interfering RNA to determine the importance of androgen receptor in ETA R signaling-triggered proliferation of prostate cancer cells.
Aim 2. To study the biological importance of RGS2 in prostate cancer progression. We will investigate whether RGS2 negatively modulates prostate cancer by either expressing inducible RGS2 in androgen-independent LNCaP cells or using siRNA to silence RGS2 in androgen-dependent LNCaP cells. We will also study the effects of manipulating RGS2 on the malignant growth of prostate cancer cells in culture and in athymic nude mice.
Aim 3. To determine the molecular mechanisms whereby dysregulation of RGS2 contributes prostate cancer progression. We will analyze how manipulating RGS2 expression negatively regulates the ETA R signaling and androgen-independent malignant cell growth in androgen receptor postitive LNCaP cells and in other androgen receptor negative prostate cancer cell lines. The significance of these studies, which are supported by strong preliminary data, resides in the fact that they will provide important information on the molecular mechanisms whereby increased ETA R and loss of RGS2 cooperatively promote prostate cancer progression. Therefore, development of medicines that increase the RGS2 expression, in combination with ETA R inhibitors, may prove more effective for the successful treatment of advanced prostate cancer patients. ?
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