Currently funded: Targeting Chemoresistance in CCNE-1-Amplified Ovarian Cancer

Wolf Ruprecht Wiedemeyer, PhD (Cedars Sinai Medical Center)
Cedars-Sinai Medical Center

The putative oncogene CCNE1 (cyclin E1) is frequently amplified in human high-grade serous ovarian cancer. CCNE1-amplified cancers tend to be wildtype for BRCA1 and BRCA2 and are associated with shorter survival and resistance to platinum-based chemotherapy (“anti-BRCAness” phenotype). Previous work has focused on the development of a cyclin-dependent kinase (CDK) inhibitor-based strategy to target CCNE1-dependent ovarian cancers. Cyclin E1 is an activating cofactor for CDK, which stimulate cell cycle progression through RB-dependent induction of E2F transcriptional activity (cyclin E-RB-E2F signaling).
In genetic and pharmacological targeting approaches, ovarian cancer cells developed resistance after initial response to cyclin E inhibition by acquiring de novo genetic changes in the receptor tyrosine kinase (RTK) signaling pathway. CDKi-resistant cells, as well as cells expressing a mutant form of the RTK, ERBB2, compensated for loss of cyclin E function by increased cyclin D-dependent signaling. These results suggest that currently available CDKi may be insufficient as single agents in ovarian cancer therapy. However, CDKi-resistant cells were significantly more sensitive to the chemotherapeutic agent cisplatin. Moreover, acute CDKi treatment resulted in transcriptional down.regulation of BRCA1. Therefore, we hypothesize that CDKi may improve response to cisplatin in CCNE1-amplified ovarian cancers via induction of the BRCAness phenotype as a result of reduced BRCA1 function.
This proposal will address this question mechanistically by comparing BRCA1-mediated DNA repair capacity in CDKi-treated and untreated cells. Genetic depletion of BRCA1 may phenocopy CDKi-induced sensitivity to cisplatin. Furthermore, chromatin immunoprecipitation (ChIP) experiments will determine if BRCA1 is a direct downstream target of cyclin E-RB-E2F signaling. ChIP is expected to reveal physical binding of the BRCA1 promoter by cyclin E1-associated E2F proteins. In order to translate these findings into clinical applications, synergy between CDKi and cisplatin will be assessed in a preclinical xenograft model. Due to the availability of clinically tested CDKi such as Dinaciclib, currently in phase 3 clinical trial, our findings will have immediate translational potential if proven correct.

Towards Individualized Therapy for Ovarian Cancer

Sandra Orsulic, PhD
Cedars-Sinai Medical Center

Advanced ovarian clear cell carcinoma (CCC) is a distinct histologic subtype of epithelial ovarian cancer that is largely refractory to current chemotherapy regimens. Given the poor response to chemotherapy, there is a great need to identify and validate new therapeutic targets for ovarian CCC. Exploiting addictions and vulnerabilities in tumors with distinguishable molecular features offers an opportunity to develop individualized therapies that may be more effective than the current “one size fits all” approach. Comparative studies of gynecologic and renal tumors have demonstrated that ovarian CCC clusters closer to renal and endometrial CCC than other ovarian subtypes, indicating that certain molecular events may be common to clear cell tumors regardless of the organ of origin. Thus, it has been suggested that clear cell histology-based, rather than organ-based, therapeutic approaches would be more effective in the treatment of CCC. The practicality of this approach is exemplified by the gastrointestinal stromal tumor (GIST) in which histologic classification led to the discovery of a novel treatment paradigm. We postulate that some of the genes that are highly expressed in ovarian CCC are drivers of cancer progression and could serve as therapeutic targets.
Our aims are to validate these targets and assess the efficacy of their inhibitors using human ovarian CCC lines in orthotopic mouse models. We anticipate that our preclinical results will help move ovarian cancer treatment towards therapies tailored to specific cancer subtypes. Specifically, our comprehensive validation of genes that are over-expressed in ovarian CCC will provide a rational basis for clinical trials in patients with CCC.

A combination therapy of JO-1 and chemotherapy in ovarian cancer models

André Lieber, MD, PhD
University of Washington

Epithelial cells maintain several intercellular junctions, a feature which is often conserved in epithelial cancers in situ. Epithelial junctions decrease intratumoral dissemination of anticancer drugs, including monoclonal antibodies, T-cells, and chemotherapy drugs. We have created a small recombinant protein derived from adenovirus serotype 3. This protein binds to DSG2 and triggers transient opening of epithelial junctions. We therefore named the protein JO-1 (“junction opener -1”). In a number of xenograft tumor models, we have shown that JO-1 increased the efficacy of monoclonal antibody (e.g. Herceptin and Erbitux) therapy. In these models, JO-1 triggered the cleavage and subsequent internalization of DSG2 in tumor cells. At the same time, it activated an epithelial-to-mesenchymal transition, which resulted in a decrease of E-cadherin in tight junctions. Transient opening of tight junctions enhanced the penetration of Herceptin and Erbitux in tumors. Epithelial junctions not only represent a physical barrier to therapeutic monoclonal antibodies and T-cells but they also decrease intratumoral dissemination of hydrophilic chemotherapy drugs with high molecular weights and/or hydration radius.
The goal of this proposal is to generate preclinical efficacy and safety data for treatment of ovarian cancer with JO-1 as a monotherapy or in combination with chemotherapy. The Specific Aims are: 1. Generate preclinical safety and pharmacokinetic data for intravenous JO-1 injection in DSG2 transgenic mice. 2. Study effect of JO-1 in syngeneic ovarian cancer model. 3. Test combinations of JO-1 with six major chemotherapy drugs, including Docetaxel, Doxorubicin, Irinotecan, Paclitaxel (Taxol®), Paclitaxel Albumin Bound Particles (Abraxane®), and Doxorubicin HCL liposome (Doxil®) to generate efficacy data supporting the use of the combinations in the clinic. These efficacy studies will be performed in the syngeneic 1D8-DSG2 tumor model as well as in xenograft models using a series for primary human ovarian cancer cell lines to establish tumors.
JO-1 co-therapy has the potential to enhance the efficacy of chemotherapeutics in ovarian cancer patients. It might also allow for lowering the effective dose of drugs, which in turn will reduce adverse side effects. This approach of providing a recombinant viral protein to selectively open intercellular junctions through transient activation of intracellular signaling is unique.