Progesterone receptor (PR) is strongly associated with disease prognosis and therapeutic efficacy in hormone related diseases such as endometriosis and breast, ovarian, and uterine cancers. Receptor status is currently determined by immunohistochemistry assays. However, noninvasive PR imaging agents could improve disease detection and help elucidate pathological molecular pathways, leading to new therapies and animal disease models. A series of water-soluble PR-targeted magnetic resonance imaging (MRI) probes were synthesized using Cu(I)-catalyzed click chemistry and evaluated in vitro and in vivo. These agents demonstrated activation of PR in vitro and preferential accumulation in PR(+) compared to PR(−) human breast cancer cells with low toxicity. In xenograft tumor models, the agents demonstrated enhanced signal intensity in PR(+) tumors compared to PR(−) tumors. The results suggest that these agents may be promising MRI probes for PR(+) diseases.

Ovarian cancer is the most lethal gynecological disease affecting women in the US. The Cancer Genome Atlas Network identified p53 mutations in 96% of high-grade serous ovarian carcinomas, demonstrating its critical role. Additionally, the Transforming Growth Factor Beta (TGFβ) pathway is dysfunctional in various malignancies, including ovarian cancer. This study investigated how expression of wild-type, mutant, or the absence of p53 alters ovarian cancer cell response to TGFβ signaling, as well as the response of the ovarian surface epithelium and the fallopian tube epithelium to TGFβ. Only ovarian cancer cells expressing wild-type p53 were growth inhibited by TGFβ, while ovarian cancer cells that were mutant or null p53 were not. TGFβ induced migration in p53 null SKOV3 cells, which was not observed in SKOV3 cells with stable expression of mutant p53 R273H. Knockdown of wild-type p53 in the OVCA 420 ovarian cancer cells enhanced cell migration in response to TGFβ. Increased protein expression of DKK1 and TMEPAI, two pro-invasive genes with enhanced expression in late stage metastatic ovarian cancer, was observed in p53 knockdown and null cells, while cells stably expressing mutant p53 demonstrated lower DKK1 and TMEPAI induction. Expression of mutant p53 or loss of p53 permit continued proliferation of ovarian cancer cell lines in the presence of TGFβ; however, cells expressing mutant p53 exhibit reduced migration and decreased protein levels of DKK1 and TMEPAI.

This abstract is also being presented as a short talk in Session 8: Clinical Science Trials. A full abstract is printed in the Proffered Abstracts section (PR14) of the Conference Proceedings. Citation Format: Roshan Ara Ahmed, Benjamin Hopkins, Carmine Palermo, Steve A. Sastra, Zachary Rapp, Ramon Parsons, Kenneth P. Olive. PTEN-Long and gemcitabine combination treatment as a therapeutic for pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A86.

PTEN is the second most frequently altered tumor suppressor found in human cancer, and is downregulated in a majority of pancreatic tumors. PTEN-Long is an endogenously expressed translational variant of this tumor suppressor that is identical to PTEN with the exception of an additional N-terminal region that gives this variant the ability to cross the cell membrane. Purified PTEN-Long can be used therapeutically to restore lost PTEN function, and has provoked profound regressions in PTEN null xenograft models. Here we explore the effect of PTEN-Long therapy in pancreatic cancer, both in the presence and absence of endogenous PTEN. In preliminary data, we found that combining PTEN-Long with chemotherapy extended overall survival in a clinically predictive genetically engineered mouse model of PDA (K-rasLSL.G12D/+; p53LSL.R172H/+;PdxCre, called KPC). To explore PTEN-Long’s ability to enter various tissues we performed pharmacokinetic and pharmacodynamic experiments. We also utilized a surgical biopsy technique to obtain paired pre- and post-treatment tumor samples. These experiments demonstrated that PTEN-Long is able to alter canonical PTEN/PI3K signaling within pancreatic tumor tissues. Finally, we treated PTEN deficient mice (K-rasLSL.G12D/+; PTENFlox/+; PdxCre) with PTEN-Long in an attempt to model the therapeutic response of the ~5% of human pancreatic tumors that are genetically PTEN null. Longitudinal ultrasound imaging of the first of these mice suggests that these mice have more significant and prolonged regressions compared to KPC mice following PTEN-Long treatment. This abstract is also presented as Poster A86. Citation Format: Roshan Ara Ahmed, Benjamin Hopkins, Carmine Palermo, Steve A. Sastra, Zachary Rapp, Ramon Parsons, Kenneth P. Olive. PTEN-Long and gemcitabine combination treatment as a therapeutic for pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr PR14.

Expression of the PTEN tumor suppressor protein is frequently altered in human pancreatic tumors, and deletion of PTEN in genetically engineered mouse (GEM) models accelerates pancreatic tumorigenesis. However, efforts to target components of the PTEN pathway, through inhibitors of PI3-Kinases, AKT, or mTOR, have failed to provide significant survival benefit to date. We utilized a naturally occurring, membrane-permeable variant of the PTEN protein, called PTEN-Long, to restore PTEN-function in trans to established pancreatic tumors in the KPC GEM model of pancreatic ductal adenocarcinoma (PDA). Combination PTEN-Long + gemcitabine therapy prolonged overall survival by 2-fold in this model and led to frank regressions of varying duration in a subset of tumors. In order to study the mechanisms of response to PTEN-Long therapy, we utilized variants of the PTEN-Long protein that are functionally mutated in different ways. A phosphatase-dead variant of PTEN-Long failed to have any effect on tumor growth in KPC mice. Interestingly, a variant of PTEN-Long that is no longer membrane permeable actually reduced overall survival in combination with gemcitabine, perhaps indicating a role for the protein in the extracellular matrix. Finally, we compared the effect of PTEN-Long in KPC mice to that of the pan-PI3K inhibitor GDC-0449. In contrast to PTEN-Long + gemcitabine, GDC-0449 + gemcitabine failed to extend survival or produce tumor regressions. Investigating the distinctions between pan-PI3K inhibition and PTEN restoration, we noted disparate, indeed opposite, effects of these two therapies on blood glucose maintenance and insulin levels, strongly that PTEN can function though additional, non-canonical intermediates beyond phospho-inositides. With the development of a clinical grade PTEN-Long material under way, we believe that these studies highlight the potential therapeutic utility of PTEN restoration therapy in PDA. These experiments provide the opportunity to dissect non-canonical aspects of PTEN signalling through in vivo structure/function analysis in GEM models of pancreatic cancer. Citation Format: Benjamin Hopkins, Carmine Palermo, Roshan A. Ahmed, Stephen A. Sastra, Ramon Parsons, Kenneth P. Olive. Non-canonical effects of PTEN restoration therapy contribute to improved survival in a GEM model of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A90.