Molecular markers have been associated with prostate cancer patient outcome after definitive therapy with radical prostatectomy or radiotherapy (RT), but no model incorporating such markers has gained acceptance in the clinic. We have been investigating the expression of proteins related to apoptosis and the cell cycle, and have found 7 prostate cancer tissue biomarkers (Ki-67, p53, MDM2, bcl-2, bax, p16 and cox-2) measured using immunohistochemistry (IHC) that are predictive of outcome in patients enrolled in Radiation Therapy Oncology Group (RTOG) clinical trials, 86-10 and 92-02. The power of the clinical trials performed by the RTOG is that substantial numbers of men have been treated with standard techniques. Each of the 7 biomarkers has been tested individually with the standard clinical factors of PSA, Gleason score and T-stage, and assigned protocol treatment. The hypothesis is that by combining all of these markers together, along with clinical parameters, a model will be developed that is more strongly associated with distant metastasis (DM) and/or cause specific mortality (CSM), as compared to current models using clinical factors alone. For most of the 7 biomarkers that are the focus of this grant, image analysis has been used to quantify expression and has been found to result in associations that are as significant, or more so, as compared to manual determinations. Because these are relatively new methods of biomarker quantification, such as using mean intensity score, confirmation in an independent patient cohort is needed. A preliminary model indicates that Ki-67, MDM2, p16 and cox-2 have the most promise. Refinements in the model are in progress, with planned validation in a similar, but distinct, patient population treated in RTOG 94-13. The determination of gene expression at the protein level in archival tissue has limitations. Based on our prior experience, typical prostate needle biopsy specimens in patients with high-risk prostate cancer allow for about 7 markers to be quantified per case. We have focused on genes in the apoptotic pathway, but there are many other genes in other pathways that have potential. One way to broaden measurement of gene expression is to quantify mRNA levels. Our preliminary data show that high quality RNA may be obtained from as few as 500 cells extracted from a single 5?M thick tissue section.
The aims of this proposal are to 1) construct a model predictive of DM and/or CSM based on molecular marker expression by IHC, clinical factors and treatment;2) quantify biomarker expression by IHC in samples from RTOG 94-13, apply the model in Aim 1 and develop a new model for determining poor prognosis after RT+ short term androgen deprivation;and 3) confirm that the procedure we have developed for microarray analysis of RNA from archival prostate cancer needle biopsy tissue is robust and to begin to apply this technology to selected cases from RTOG 94-
We have identified 7 biomarkers (Ki-67, p53, MDM2, bcl-2, bax, p16 and cox-2) in which abnormal expression using immunohistochemistry (IHC) has been associated with worse patient outcome after radiotherapy, with or without androgen deprivation, in Radiation Therapy Oncology Group (RTOG 86-10 and 92-02) clinical trials. The objectives are to develop a model predictive of distant metastasis in which all of the biomarkers are considered together with clinical factors, apply the model to an independent population (RTOG 94-13) and contrast these results with mRNA gene expression profiles from formalin-fixed tissue (RTOG 94- 13). The IHC-based model has promise to be brought rapidly into the clinic to better select appropriate treatment, while the RNA-based approach has broader potential in the long-term.
| Heckman, Michael G; Tzou, Katherine S; Parker, Alexander S et al. (2013) Lack of Association between COX-2 Staining Level and Biochemical Recurrence Following Salvage Radiation Therapy for Recurrent Prostate Cancer. J Radiat Oncol 2:309-314 |
