Exploring the role of steroid transport genes in prostate cancer progression and response to therapy
Elahe Mostaghel, MD, PhD, Fred Hutchinson Cancer Research Center
Mechanisms responsible for the variable tissue response to androgen deprivation and the elevated tumoral androgen levels observed in CRPC have not been elucidated, but may reflect tumoral uptake and metabolism of adrenal androgens to T and DHT or de novo synthesis of androgens from the uptake of cholesterol or progesterone precursors. We hypothesize that steroid transport proteins expressed in prostate tumors impact the response of prostate cancer to hormone therapy by mediating import of steroidogenic substrates involved in tumor androgen metabolism.
The aims of this proposal are:
- To comprehensively evaluate expression of steroid transporter gene families in benign and neoplastic prostate tissue, including castration resistant prostate cancer metastases.
- To determine functional activity and impact of coding polymorphisms in candidate steroid transport genes on the uptake of steroidogenic substrates including progesterone, testosterone and DHEA.
- To determine the impact of candidate steroid transport gene expression and SNP genotype on prostate cancer outcomes and the response to androgen deprivation in localized and advanced disease.
Steroid transport proteins may serve as novel prognostic and predictive biomarkers of the PCa response to hormone therapy. Identification of transporter gene SNPs associated with enhanced steroid import or adverse clinical outcomes would allow pre-treatment stratification of patients in neoadjuvant, biochemical relapse or advanced disease settings who are at risk of poor response to standard ADT. Such patients could be targeted for enrollment in clinical studies utilizing more aggressive/novel hormonal therapies or studies incorporating non-hormonal based treatment strategies (e.g., trials evaluating early chemotherapy).
Characterization of microRNAs in urine for diagnosis and prognosis of prostate cancer
Daniel Lin, MD, Fred Hutchinson Cancer Research Center
There is a pressing need to develop improved biomarkers that not only detect early prostate cancer but also identify clinically aggressive disease. While considerable effort has focused on blood-borne biomarkers, recent efforts have turned to urine-based assays because urine represents a proximal source of prostate-derived cellular material. MicroRNAs are a class of recently discovered small RNA that regulate multiple cellular functions, and perturbations in microRNAs have also been associated with a variety of malignancies, including prostate cancer. We have found that microRNAs are present as stable entities in the circulation and also have identified them in urine by using quantitative reverse-transcription PCR (qRT-PCR).
We hypothesize that microRNAs found in urine are more sensitive/specific biomarkers for the detection of prostate cancer than circulating serum and plasma markers and that microRNAs may detect potentially lethal prostate cancer. We aim to characterize expression of microRNAs in post-digital rectal examination (DRE) urine and urine sediments from men undergoing prostate biopsy for suspicion of prostate cancer. We propose to collect post-DRE urine specimens and characterize microRNAs expression in the urine and urine sediments in 50 men: 20 with benign biopsies, 15 with Gleason 3+3 cancer, and 15 with Gleason 3+4 or greater cancer, oversampling available Gleason 8-10/4+3 cancers. Results from the proposed studies will yield important preliminary information to inform future work in discovery and validation of stable, urine-based molecular markers in prostate cancer.
Detection of grade 4 prostate cancer in urine of men with low grade cancer biopsies
Martin Gleave, MD, Colin Collins, PhD, University of British Columbia, Vancouver Prostate Centre
In many men with a diagnosis of low-grade (Gleason Grade 3) prostate cancer, the cancer will remain asymptomatic during the lifetime of the patient. For these men, active surveillance has emerged as a suitable option for delaying treatment. During regular follow-up, the most common reason for deciding to treat is the discovery of high-grade cancer. The frequency of occult high-grade (Gleason Grade 4) is approximately 30%. Thus, early detection of high-grade cancer would improve the safety of active surveillance programs, reduce patient anxiety and improve the quality of life of approximately 100,000 men per year in the U.S., who are newly diagnosed with prostate cancer. This pilot project will test the hypothesis that occult GG4 cancer can be detected in tissue and urine specimens obtained at initial diagnosis. The hypothesis is that genomic copy number profiles of Gleason Grade 3 cancers will differ depending on the presence or absence of Gleason Grade 4 cancer in the prostate. The hypothesis will be addressed in 2 specific aims:
- To determine whether the status of the 39 Genomic Evaluators of Metastatic Prostate Cancer (GEMCaP) biomarkers and total genomic instability in Gleason Grade 3 cancer is predictive of concurrent Gleason Grade 4 cancer in the same prostate;
- To establish methods to perform array comparative genomic hybridization (aCGH) with DNA isolated from urine and determine whether a urine-based test can be used to predict Gleason Grade 4 cancer in the prostate.
DNA samples from tissue and urine will be analyzed by aCGH for the frequency of genomic copy number gains and losses to measure overall genomic instability and the data will be used to assess copy number changes within GG3 cancers, to compare GG3 and GG4 cancers, and to detect GG4 cancer in urine.
A novel FISH assay to assess the prognostic significance of TMPRSS2-ERG fusion
Min Fang, MD, PhD, Fred Hutchinson Cancer Research Center
The heterogeneous nature of prostate cancer demands new methods of risk stratification in order to make optimal therapeutic decisions. The exciting discovery of the presence of TMPRSS2-ERG gene rearrangements in over 50% of prostate cancer begs for the knowledge whether this is a significant prognostic marker. Current literature gave inconsistent answers to this question. This pilot study aims to explore the prognostic significance of TMPRSS2-ERG fusion and its variants in prostate cancer using a tissue microarray including 100 samples each from patients with and without 5-year relapse. We developed a novel 4-color fluorescence in situ hybridization assay that overcomes the limitations of the previously reported methods for detecting TMPRSS2-ERG fusion variants. To further explore the role of TMPRSS2-ERG gene rearrangement in prostate cancer progression, especially from the androgen-dependent to androgen-independent state, we also propose to study the potential association of TMPRSS2-ERG fusion with androgen receptor (AR) gene amplification/expression status of X-chromosome aneuploiy. This pilot study will allow the validation of this new FISH assay that may serve as a useful tool for other SPORE projects, provide additional data for the prognostic significance of TMPRSS2-ERG fusion, and further identify genomically defined subgroups of prostate cancer for future research.
Role of TCA cycle enzymes MDH2-CS in prostate cancer development and chemosensitivity
David Qian, PhD, Oregon Health & Science University
Genomic information derived from prostate cancer cell lines and clinical samples can be utilized in cancer detection, staging, prognosis and development of individualized therapy. However, the successful utilizations of this knowledge require solid understanding in mechanisms. We have observed that genes encoding for mitochondrial MDH2 and citrate synthase (CS) are frequently overexpressed in prostate cancer patients. Patients with overexpression of CS and normal expression of MDH2 are associated with significantly longer relapse-free survival after neoadjuvant chemotherapy. Our hypothesis is that CS and MDH2 play important roles in prostate cancer oncogenesis and in mediating docetaxel cytotoxicity via a redox of dependent mechanism. Upregulation of CS increases prostate cancer cell sensitivity to docetaxel, whereas upregulation of MDH2 confers resistance. The specific aim for this proposal is to determine the roles of MDH2 and CS in oxidative metabolism, redox, proliferation and survival, and response to chemotherapy in the LNCaP cell line. To accomplish this aim, we will use shRNA to deplete either CS or MDH2, both of which are overexpressed in LNCaP. We will determine the impact of shRNA in ATP biosynthesis, oxidative stress. We will test whether CS and MDH2 provide LNCaP growth and survival advantages in the presence and absence of docetaxel-chemotherapy. Further, we will determine whether the activity of CS and MDH2 is mediated by their intermediate oxaloacetate (OAA). This study will provide us a refined hypothesis and preliminary data for an R01 type application, in which we seek to investigate how metabolic alterations impact prostate cancer development and response to existing therapies.