Abstract B15: Patient-derived Pancreatic Adenocarcinoma cells: A new model system to define chemotherapy resistance mechanisms and to improve targeted personalized treatment

Background: Pancreatic adenocarcinoma (PA) is the fourth leading cause of cancer related death in the USA. Patients diagnosed with this disease can expect a 1-year survival rate of approximately 10%. One of the main reasons of the high mortality observed within PA is failure on first-line therapies. Current PA treatment involves Gemcitabine, a nucleoside analog that showed improvement in overall survival. Recently this drug has been used in combination with nab-paclitaxel, 5-FU, Erlotinib and MEK inhibitors. However, a growing number of patients have shown resistance to these regimes. A more comprehensive understanding of resistance mechanisms will enhance treatment choice and clinical responses, and this remains an area of intense investigation. However much of the data available on PA drug targets and efficacy come from commercially available pancreatic cell lines, a main limitation in PA research, as these lines do not accurately represent a given patients9 tumor, underscoring the need for the development and use of patient-specific primary epithelial PA cells. In our current study we present the use of patient-derived primary PA cells as a model system for basic and translational research as well as personalized therapeutic approaches. Methods: Patients9 biopsies were collected after surgery and long-term cultures of PA cells were established using the conditional reprogramming of cells (CRC) approach. To date, six primary lines have been continuous culture for over 6 month. KRAS and p53 sequencing verified the PA origin of both the patient sample and the matched CRC lines. CRC karyotyping was also performed to confirm the absence of normal cells as well as to validate the long-term genomic integrity of the lines in culture. In order to evaluate patient-specific differences in treatment response, the IC509s for gemcitabine, nab-paclitaxel (Abraxane) and the MEK inhibitor, Trametinib, were determined. To better understand treatment resistance mechanisms, new drug resistance approaches were developed and multiple drug-resistant clones per primary cell line were established, and their resistance verified. Gemcitabine activity was also evaluated in combination with Abraxane and Trematenib in both parental and resistant-clone cell lines. In addition, novel three-dimensional (3D) organoid cultures have been established from the two dimensional (2D) CRC cultures in order to verify the constancy of the model. Results: We established KRAS-mutant primary cell lines derived from patients9 PA specimens. The cell lines9 karyotype showed stability over multiple passages covering more than 6 months in continuous 2D culture. Five Abraxane resistant clones have been derived to date from two different parent cell lines and two gemcitabine resistant clones derived from one of these cell lines. The clones tested were 3 to 1000 times less sensitive to the drugs when compared to the parents. Notably, the Abraxane resistant clones also showed a greater resistance to Gemcitabine as compared to the parent line. In addition, the PA lines also showed an overall increasing sensitivity to Gemcitabine when pre- or co-treated with Trematenib. Molecular and genetic analyses are being performed to identify potential biomarkers of high therapeutic value. Conclusion: Taken together, the ease of culture, the genetic stability, the medium to high throughput ability to identify differences between patients sensitivity to FDA approved drugs, all confirm the power of this technology for on-demand in vitro use in PA research. Our approach now enables the high-resolution experiments necessary to better understand the underlying drug sensitivity and resistance mechanisms that directly affect clinical outcomes. Citation Format: Erika M. Parasido, Praathibha Sripadhan, Richard Schlegel, Michael J. Pishvaian, Jonathan Brody, Jordan Winter, Christopher Albanese. Patient-derived Pancreatic Adenocarcinoma cells: A new model system to define chemotherapy resistance mechanisms and to improve targeted personalized treatment. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr B15.