Small Molecule Therapeutics Theranostic Agents for Photodynamic Therapy of Prostate Cancer by Targeting Prostate-Specific Membrane Antigen Xinning Wang 1 , Brian Tsui 2 , Gopolakrishnan Ramamurthy 1 , Ping Zhang 3 , Joseph Meyers 1 , Malcolm E. Kenney 3 , Jonathan Kiechle 4 , Lee Ponsky 4 , and James P. Basilion 1,5 Abstract Prostatectomy has been the mainstay treatment for men with localized prostate cancer. Surgery, however, often can result in major side effects, which are caused from damage and removal of nerves and muscles surrounding the prostate. A technology that can help surgeons more precisely identify and remove prostate cancer resulting in a more complete prostatectomy is needed. Prostate-specific membrane antigen (PSMA), a type II membrane antigen highly expressed in prostate cancer, has been an attractive target for imaging and therapy. The objective of this study is to develop low molecular weight PSMA-targeted photodynamic therapy (PDT) agents, which would provide image guidance for prostate tumor resection and allow for subsequent PDT to eliminate unresectable or remaining cancer cells. On the basis of our highly negatively charged, urea-based PSMA ligand PSMA-1, we synthesized two PSMA-targeting PDT conjugates named PSMA-1-Pc413 and PSMA-1-IR700. In in vitro cellular uptake experiments and in vivo animal imaging experiments, the two conjugates demonstrated selective and specific uptake in PSMA-positive PC3pip cells/tumors, but not in PSMA-negative PC3flu cells/tumors. Further in vivo photodynamic treatment proved that the two PSMA-1–PDT conjugates can effectively inhibit PC3pip tumor progression. The two PSMA-1–PDT conjugates reported here may have the potential to aid in the detection and resection of prostate cancers. It may also allow for the identification of unresectable cancer tissue and PDT ablation of such tissue after surgical resection with potentially less damage to surrounding tissues. Mol Cancer Ther; 15(8); 1834–44. Ó2016 AACR. Introduction PSA testing has allowed significantly more men to be diagnosed and treated for prostate cancer. Approximately 220,800 new diagnoses and 27,540 deaths from the disease are projected in 2015 in the United States (1). Over 90% of men have localized tumors at initial screenings and are candidates for radical pros- tatectomies (2). However, at surgery, cancer has been shown to extend outside the prostate (pathologic stage C) in 20% to 42% of patients (3), surgery fails to halt the disease in approximately 20% of the patients who undergo radical prostatectomy, and recur- rence rate of this disease is more than 60% (4–6). During radical prostatectomy, surgeons have difficulty acces- sing prostate cancer invasion; therefore, many malignant nodules escape detection, leading to disease recurrence. A retrospective multivariate analysis by Wright and colleagues of incomplete resection of prostate cancer in more than 65,000 patients who underwent radical prostatectomies (7) found that positive surgi- cal margins were associated with a 2.6-fold increased unadjusted risk of prostate cancer–specific mortality and are an independent predictor of mortality. This study also underscored the need for surgeons to optimize surgical techniques to achieve negative surgical margins to increase sound oncological outcomes. How- ever, surgical achievement of this without side effects is challeng- ing because the prostate is surrounded by many nerves and muscle fibers controlling different excretory and erectile functions that are difficult but necessary to avoid. In 1983, Walsh defined nerve locations around the prostate and inspired a number of "nerve- sparing" surgical approaches, including robotic-assisted laparo- scopic prostatectomy (8). Unfortunately, the success of these approaches to mitigate side effects is mixed, (9, 10) and surgical approaches are still associated with significant morbidity, for example, incontinence (3%–74%) and impotence (30%–90%; refs. 11–16). There remains an unmet clinical need to improve surgical techniques for identifying and removing cancerous tissue without damaging surrounding tissues during prostatectomy. Recently, Neuman and colleagues showed that the near-infrared (NIR) fluorescence probe YC-27 can improve the surgical treat- ment of prostate cancer and reduce the rate of positive surgical margins in real-time laparoscopic extirpative surgery (17). Photodynamic therapy (PDT) is a minimally invasive therapy used clinically in the treatment of cancers and other diseases (18–20). PDT uses photosensitizers which are pharmacologically inactive until exposed to light in the presence of oxygen. The active drug forms reactive oxygen species such as singlet oxygen to kill 1 Department of Radiology and NFCR Center for Molecular Imaging, Case Western Reserve University, Cleveland, Ohio. 2 School of Medi- cine, Case Western Reserve University, Cleveland, Ohio. 3 Department of Chemistry,Case Western Reserve University,Cleveland, Ohio. 4 Urol- ogy Institute, University Hospitals Case Medical Center, Cleveland, Ohio. 5 Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio. Note: Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/). Corresponding Author: James P. Basilion, Case Western Reserve University, 11100 Euclid Ave, Wearn Building B-44, Cleveland, OH 44106-5056. Phone: 216- 983-3264; Fax: 216-844-4986; E-mail: jxb206@case.edu doi: 10.1158/1535-7163.MCT-15-0722 Ó2016 American Association for Cancer Research. Molecular Cancer Therapeutics Mol Cancer Ther; 15(8) August 2016 1834 Downloaded from http://aacrjournals.org/mct/article-pdf/15/8/1834/1852973/1834.pdf by guest on 10 June 2022