Abstract 5713
Background
Historically, immunotherapies have been tested in syngeneic mouse models and until now only limited CRC syngeneic cells are available. Animal models with functioning human immune systems are critically needed to more accurately evaluate checkpoint blockers delivery, therapeutic response, and to better define biomarker expression in the presence of a competent immune system.
Methods
To better address the efficacy of immune checkpoint therapy specifically in relation to presence of a BRAFmutation, we developed a novel platform for the generation of somatic mosaic models of CRC enabling (i) high-throughput generation of genetically complex syngeneic models of cancer, (ii) tracing studies through fluorescence reporters.
Results
Cdx2Cre/+ mice, expressing the Cre recombinaseunder the control of a human Cdx2 promoter/enhancer sequence have been crossed with the R26LSL-Cas9-Gfp strain to generate models allowing for tissue specific activation of Cas9 and Gfpreporter only in CDX2 positive cells. This strain has been crossed with BRAFFSF-V600E mice to generate the final model. 6-8 weeks old mice have then been transduced with AAV constructs expressing the FLPO recombinasethat can be activated by Cre recombinase and sgRNAs targeting APC, TP53, MLH1, MSH2and ARID1Aalone or combined, in order to model MSI CRC (APC-TP53-MLH1and ARID1A-MLH1conditional mosaic knock-outs) and MSS CRC (APC-TP53 conditional mosaic knock-out). Viral particles have been surgically delivered via subserosal cecal injection and mice monitored for tumor formation by IVIS imaging. 35 mice injected with 3 combinations of tumor suppressors provide a diverse immunology repetoire. Cell lines isolated from genetically modified mice will provide a physiologic relevant and feasible means to study the mechanisms of response and resistance to immunotherapies and to understand biological and molecular differences between BRAFmutated MSI and MSS tumors.
Conclusions
This project focuses on the identification and characterization of the functional drivers of CMS1CRC tumors leveraging in vivomosaic genome editing technologies and functional genetic labeling of malignant sub-populations emerging during disease progression and in response to therapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
MD Anderson Cancer Center.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
5043 - Comprehensive results of a Phase Ib study with a HER2/neu B-cell peptide vaccine administered with cisplatin and 5-fluorouracil or capecitabine chemotherapy show safety, immunogenicity and clinical response in patients with HER2/Neu overexpressing advanced gastric cancer
Presenter: Ursula Wiedermann
Session: Poster Display session 3
Resources:
Abstract
4506 - Single intravenous preoperative administration of the oncolytic virus Pexa-Vec to prime anti-tumor immunity
Presenter: Adel Samson
Session: Poster Display session 3
Resources:
Abstract
1631 - Randomized phase 2 clinical trial of NY-ESO-1 protein vaccine combined with cholesteryl pullulan (CHP-NY-ESO-1) in resected esophageal cancer patients
Presenter: Shinichi Kageyama
Session: Poster Display session 3
Resources:
Abstract
4244 - T cell repertoire sequencing reveals dynamics of response to dendritic cell vaccine plus dasatinib for checkpoint blockade resistant metastatic melanoma
Presenter: Luca Quagliata
Session: Poster Display session 3
Resources:
Abstract
5791 - Ixovex, a novel oncolytic E1B-mutated adenovirus
Presenter: Mohiemen Anwar
Session: Poster Display session 3
Resources:
Abstract
4170 - Anti-CSPG4 DNA vaccination as a promising strategy for the treatment of CSPG4+ tumors: a comparative oncology trial
Presenter: Federica Riccardo
Session: Poster Display session 3
Resources:
Abstract
5780 - Antitumor activity, immunogenicity and safety of a novel PD-1 vaccine in combination with two chimeric HER-2 peptide vaccine in syngeneic Balb/c, C57Bl/6 models and in beagle dogs
Presenter: Pravin Kaumaya
Session: Poster Display session 3
Resources:
Abstract
5860 - Maternal immunization against ALK as a weapon to fight neuroblastoma
Presenter: Giuseppina Barutello
Session: Poster Display session 3
Resources:
Abstract
4720 - Phase 1 study evaluating safety, pharmacokinetics (PK), pharmacodynamics, and preliminary efficacy of ABBV-428, first-in-class mesothelin (MSLN)-CD40 bispecific, in patients (pts) with advanced solid tumors
Presenter: Jason Luke
Session: Poster Display session 3
Resources:
Abstract
5717 - Anti-PD-L1/IL-15 fusion protein generates robust adaptive immune gene signatures in tumors leading to tumor inhibition and memory responses
Presenter: Stella Martomo
Session: Poster Display session 3
Resources:
Abstract