Survival of pancreatic cancer cells lacking KRAS function

Abstract

Activating mutations in the proto-oncogene KRAS are a hallmark of pancreatic ductal adenocarcinoma (PDAC), an aggressive malignancy with few effective therapeutic options. Despite efforts to develop KRAS-targeted drugs, the absolute dependence of PDAC cells on KRAS remains incompletely understood. Here we model complete KRAS inhibition using CRISPR/Cas-mediated genome editing and demonstrate that KRAS is dispensable in a subset of human and mouse PDAC cells. Remarkably, nearly all KRAS deficient cells exhibit phosphoinositide 3-kinase (PI3K)-dependent mitogen-activated protein kinase (MAPK) signaling and induced sensitivity to PI3K inhibitors. Furthermore, comparison of gene expression profiles of PDAC cells retaining or lacking KRAS reveal a role of KRAS in the suppression of metastasis-related genes. Collectively, these data underscore the potential for PDAC resistance to even the very best KRAS inhibitors and provide insights into mechanisms of response and resistance to KRAS inhibition.

Endocrine-exocrine signaling drives obesity-associated pancreatic ductal adenocarcinoma

“…To elucidate potential non-mutational mechanisms of PDAC progression, we performed bulk RNA-sequencing (RNA-seq) on pancreata from obese KCO and non-obese KC and KPC mice exhibiting comparable tumor burden (Table S6), permitting analyses of both tumor cells and their microenvironment in cancer pathogenesis. Using Independent Component Analysis (ICA), an unsupervised blind source separation technique (Hyvarinen and Oja, 2000;Muzumdar et al, 2017), we identified gene expression signatures associated with inflammation and fibrosis as upregulated in KCO compared to KC/KPC mice (Figures 4A-D and Tables S7-S8), likely representing obesity-associated alterations in the tumor microenvironment. We confirmed abundant extracellular matrix deposition and immune cell infiltration by histologic analyses of KCO tumor sections ( Figure 4E).…”

“…All reads that passed quality metrics were mapped to UCSC mm9 mouse genome build (http://genome.ucsc.edu/) using RSEM (v1.2.12) (http://deweylab.github.io/RSEM/). All RNAseq analyses were conducted in R. High-resolution signature analyses between tumors from obese (KCO and KCO treated with AAV-GFP) and non-obese (KC and KPC) models were performed using a blind source separation methodology based on Independent Component Analysis (ICA), as previously described (Hyvarinen and Oja, 2000;Muzumdar et al, 2017).…”

“…Unfortunately, no effective direct KRAS inhibitors are currently approved for clinical use (Papke and Der, 2017). Moreover, our recent work has demonstrated that PDAC cells can survive genetic ablation of KRAS both in vitro and in vivo Muzumdar et al, 2017), arguing that resistance will subvert even the very best KRAS inhibitors. Alternative paradigms beyond genetic factors therefore need to be explored to develop novel therapeutic and preventative strategies in PDAC.…”

Novel Targets in Pancreatic Cancer Therapy - Current Status and Ongoing Translational Efforts

“…Nevertheless, developing direct inhibitors of oncogenic KRAS signaling has been found to be extremely challenging and, as of to date, no suitable inhibitors are available for routine application outside of early clinical and preclinical studies [30,31,32,33,34,35,36]. Moreover, accumulating preclinical evidence already suggests that, although being a potentially powerful therapeutic approach, pharmacological inhibition of oncogenic KRAS signaling alone will likely not be sufficient to fully eradicate and cure metastatic pancreatic cancer [27,29]. …”

“…At the same time PDAC cells appear to maintain dependence on oncogenic Ras signaling for survival and proliferation [26,27,28]. Therefore, pharmacologically inhibiting oncogenic KRAS signaling has been suggested for a long time and is still considered as the Holy Grail in the quest for targeted therapeutic approaches directed against pancreatic cancer by many authors [29]. Nevertheless, developing direct inhibitors of oncogenic KRAS signaling has been found to be extremely challenging and, as of to date, no suitable inhibitors are available for routine application outside of early clinical and preclinical studies [30,31,32,33,34,35,36].…”