Abstract A148: Modeling patient responses to targeted therapy with rAAV mediated gene editing.
Authors: Little Annette S. , Hunt Jessica , Hughes David , Feltell Ruth , Gitterman Daniel , Leah Rachel , Astley Holly , Mangena Ramu , Grimshaw Kyla , Torrance Christopher 
Published: August 2014

Abstract
Successful drug development in oncology requires a deeper understanding of the functional consequences of the diverse genetic changes observed in human cancers. For example, responses to epidermal growth factor receptor (EGFR) inhibitors are observed in patients whose tumors express EGFR alleles with activating mutations, rather than in tumors overexpressing EGFR. Furthermore, antibodies against EGFR are ineffective in tumors bearing certain activating alleles of KRAS.
Horizon Discovery has used its proprietary rAAV gene engineering technology to generate isogenic cell lines covering a range of mutations commonly found in cancer patients. Use of a non-tumorigenic ‘clean’ cell line background such as MCF10A allows specific evaluation of the mutations without any confounding factors due to the presence of other genetic alterations. Mutations introduced into cancer cell line backgrounds allow the contextual evaluation of a cancer related gene. Here we describe the use of isogenic cell line panels as powerful tools for investigating sensitivity and resistance markers to cancer therapeutics.
Some 50% of human tumors exhibit p53 loss or inactivation. To investigate how p53 loss in combination with other common cancer-driving mutations may influence therapeutic responses, we have generated a suite of MCF10A isogenic cell lines covering some of the major cancer genotypes, either in isolation or on a TP53 (-/-) background. These genotypes include EGFR (delE746-A750/+), EGFR (L858R/+), KRAS (G12V/+), BRAF (V600E/+), BRAF (V600K/+) and PIK3CA (H1047R/+). Thus, we have been able to investigate the interaction effects of discrete mutations in molecularly defined, but more tumor-like cell models.
One data highlight arose from the profiling of the EGFR mutant panel using small molecule EGFR inhibitors; in isolation, the introduction of common activating EGFR mutations L858R or deletion of E746-A750 led to increased sensitivity, recapitulating clinical findings. However, combining EGFR mutation with loss of p53 further enhanced the cell response. Through systematic profiling of this panel to targeted therapeutic agents such as gefinitib, selumetinib, vemurafenib, and pictilisib, we have identified interesting differential sensitivities, which can be directly attributable to introduction of a given mutation.
Results such as these can enable better patient stratification for anticancer agents, and allow incorporation of molecular markers into clinical trial design for personalised therapeutic regimens.
Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A148.
Citation Format: Annette S. Little, Jessica Hunt, David Hughes, Ruth Feltell, Daniel Gitterman, Rachel Leah, Holly Astley, Ramu Mangena, Kyla Grimshaw, Christopher Torrance. Modeling patient responses to targeted therapy with rAAV mediated gene editing. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A148.