Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly and clinically burdensome malignancies with a five-year survival rate 5%. PDACs are notoriously aggressive, prone to rapid conversion to metastatic phenotype, have remarkable desmoplastic features with strong prevalence of stromal components hindering therapeutic access, and are moreover difficult to diagnose at early stages. Thus, we are executing studies to meet the stated objectives to develop, utilize, and provide to the community several tractable preclinical PDAC models for therapeutic and biomarker discovery. CAPR recent progress on internal initiatives includes generation and full characterization of three relevant Cre-inducible missense p53 GEM strains in which the non-recombined allele expresses wild type p53 prior to a Cre-driven conversion to a mutant isoform expressing one. The p53aa172 inducible mutant strain has been bred with PDX-Cre and KRASG12D-lsl mice to generate animals that are similar to the KPC model, with the exception that they harbor no null allele prior to expression of p53-172. Development of PDA in these mice (KPwt-172C) is similar to that of KPC mice, except that ectopic tumors do not develop and PDA develops with shortened latency. Furthermore, orthotopic KPC-PDA GDA models have been established from several KPC-derived primary tumors and shown to develop PDA with characteristics of the parental malignancy. In addition, the metastatic rate is increased to about 70 %, thus potentially enabling studies on mechanisms and treatment of metastatic disease. This high metastatic rate makes this model ideal for evaluating therapies for metastatic disease. As one of the most visible preclinical resource for intramural CCR investigators, CAPR pancreatic program is involved in multiple collaborative initiatives with CCR PI labs. For example, the pancreatic team has recently finalized a large, multi-modular collaborative project with Dr. Udo Rudloff's lab pursuing a comprehensive IND-enabling characterization of metarrestin compound employing both de novo and syngeneic orthotopic transplant models of pancreatic adenocarcinoma (PDAC). Ten integrated preclinical assessment studies interrogating bioavalability, in vivo toxicity, a spectrum of molecular responses to treatment, as well as efficacy as monotherapy and in combination with gemcitabine standard of care, have been completed and will be used to support the upcoming IND submission for metarrestin. The results of this collaborative effort are being written up as two publications co-authored by CAPR scientists. Expanding collaborative relations with Dr. Rudloff's section of the Thoracic and Gastrointestinal Oncology branch, CAPR also commenced a second, committee-approved joint study to evaluate another molecule - a biosimilar peptide compound RP-182 - which has shown promise as a potential microenvironment re-modelling factor in PDAC. At present, a pilot multi-organ PK study has been completed to explore bioavailability in PDAC-affected tissues and circulation. Another CCR PI-initiated collaborative PDAC study is ongoing with Dr. Martin Schnermann's lab. In this project, CAPR joined efforts with drug development chemists to assess a novel strategy of attacking this lethal malignancy with photo-activated formulations synthesized to selectively release an anti-cancer drug payload in disease-affected tissues upon near-IR irradiation. CAPR is currently assisting Dr. Schnermann's team in optimizing tissue distribution of the SiPc-based compounds. CAPR is also initiating collaboration with Dr. William Stetler-Stevenson's lab to assess the ability of TIMP-2 recombinant polypeptide to suppress the cancer growth and metastatic dissemination of PDAC in the autochthonous KPC mouse model. A joint project with Dr. Peter Johnson's lab has recently been launched to investigate the biological significance of Perinuclear Signaling Complexes (PSC) characteristic for Ras-driven malignancies in carcinogenic progression, and to validate these intriguing intracellular structures as possible drug targets to ameliorate aggressive cancers featuring deregulated Ras pathways. Continuing to deliver on its collaboration with Dr. Christine Alewine, CAPR researchers established an allelic series of genetically modified mouse models expressing either chimeric mouse/human mesothelin (MSLN) protein under the transcriptional control of the endogenous mMSLN locus, or a fully human MSLN ortholog in a narrow expression domain in the thyroid gland. Having undergone extensive molecular characterization, these validated new tools provide immunocompetent recipient animals tolarized against hMSLN protein or lacking MSLN expression in either a constitutive or conditional manner, and will now be used for syngeneic allografting studies with PDAC cells expressing chimMSLN protein to prepare cohorts of tumor bearing animals to assess the efficacy of recombinant immunotoxins designed to recognize human MSLN protein.
