Abstract B167: KRAS gene mutations are associated with tumor resistance toward the LN1222/AD736 p38 inhibitor
Authors: Vuaroqueaux Vincent , Kelter Gerhard , Hendriks Hans R , Laufer Stefan , Fiebig Heinz-Herbert 
Published: August 2018

The p38 MAPK pathway, also called stress activated protein kinase pathway, is involved in basic cellular processes of inflammation and acts on cell growth, proliferation, differentiation, migration, and apoptosis. p38 MAP kinase activation occurs by environmental stress and proinflammatory cytokines signaling and is frequently deregulated in cancers. p38 MAP kinase inhibition has been suggested for treatment of the cancer; a number of inhibitors have been developed and some are in an early phase of clinical evaluation. The present study aimed to investigate the antitumor activity and discover potential predictive biomarkers for the novel p38 inhibitor LN1222/AD736 in a large and diverse series of tumor models. Cancer cell inhibition was tested in vitro by means of a propidium-based monolayer assay in a total of 222 human tumor cell lines, covering 29 different types of solid tumors including 70 derived from PDX. To illuminate molecular determinants of drug sensitivity, we conducted a biomarker discovery study using the molecular profiles of cell lines, which included whole exome mutations, gene copy number variations, and gene expression profiles as determined by next-generation sequencing, Affymetrix SNP6.0 and Affymetrix U133 2plus. Throughout the 222 cell lines, the IC50 and IC70 geometric means were 0.33 μM and 1.3 μM, respectively. High antitumor potency (IC70 &lt;500 nΜ) was found in 121 out of 222 cell lines (54%), and the cell line sensitivity toward LN1222/AD736 was well dichotomized into very sensitive (&lt;500 nM) and very resistant (&gt;30 μM) models. Very sensitive cell lines were observed in leukemia and lymphoma as well as a wide variety of solid tumors including sarcoma (soft tissues and osteosarcoma), prostate, bladder, breast, melanoma, colon, NSCLC, and kidney tumor models, irrespective of the cancer type. Molecular analyses showed that tumor models had comparable expression patterns of the four different isoforms of p38 mRNA (MAPK11, 12, 13, and 14) with those of the patient’s tumors (TCGA data set). None of the four isoforms was found significantly predictive for tumor sensitivity to LN1222/AD736 (Lima test and Spearman correlation analyses). Interestingly, the biomarker discovery screening associated KRAS gene mutations (24 of 127 model tested (20%)) as a strong factor for resistance toward LN1222/AD736, only wild type KRAS models were sensitive (Wilcoxon test p&lt;0.0001). In parallel, we identified a subset of 80 differentially expressed genes that discriminates groups of tumors with a high response rate by using unsupervised hierarchical clustering (p&lt;0.0001). The ingenuity pathway analysis indicates that part of these genes are related to inflammation and cell survival. These biomarker data will be evaluated in an independent data set of tumors treated with p38 inhibitors. Our results demonstrate that the p38 inhibitor LN1222/AD736 had antitumor activity in a wide range of tumors and may represent a relevant treatment option for tumors with wild type KRAS. Extending the analysis in vitro and in vivo in tumor types in which activity was seen and testing combinations of LN1222/AD736 and other compounds targeting the MAPK pathway are needed to refine the evaluation. The biomarker findings should be tested and validated in larger cohort.

Citation Format: Vincent Vuaroqueaux, Gerhard Kelter, Hans R Hendriks, Stefan Laufer, Heinz-Herbert Fiebig. KRAS gene mutations are associated with tumor resistance toward the LN1222/AD736 p38 inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B167.