Targeting RAS for Cancer Treatment: What a Long, Strange Trip It's Been

Kirsten rat sarcoma viral oncogene homolog (KRAS) is the most frequently mutated oncogene detected in 30% of all human cancers. Drugs that can impede the function of oncogenic KRAS offer exceptional therapeutic value. However, direct targeting KRAS is challenging due to its protein structure that lacks deep binding pockets for small-molecule inhibitors. Despite the recent success in targeting the G12C allele, targeted therapy for another hotspot mutant – G12V mutant KRAS has not been described. Here, we utilize CRISPR-Cas9 based genome-wide knockout screens and leverage a high-throughput microfluidic cell sorting platform to identify genes that regulate mutant KRAS harboring G12V mutation. The screens were conducted in two colorectal cancer cell lines HT29 and SW480, expressing wild-type KRAS and homozygous G12V KRAS, respectively. We have identified a list of genes whose loss-of-function reduces wild-type or mutant G12V KRAS protein expression. Our top gene identified from the mutant KRAS screen - denoted as selective-mutant KRAS modulator (SMKM) has shown promising results in selectively decreasing G12V KRAS protein expression. Through multiple assays including live cell imaging, western blot, flow cytometry, and proteomic analysis in SMKM knockout cells and SMKM inhibitor-treated cells. We found highly selective reduction in G12V KRAS protein expression. More importantly, genetically or pharmacologically inhibiting SMKM has demonstrated anti-tumor activity. We conducted cell viability assays including CellTiter-glo, MTT, and clonogenic assay. We treated a panel of G12V KRAS mutant and wild-type KRAS cell lines with SMKM inhibitor and found significantly reduced cell viability in G12V KRAS mutant cell lines across colorectal and lung cancer. To further demonstrate the downstream impact on mutant KRAS signaling, secondary assays including western blot and Lumit immunoassay were conducted. We observe a reduction in the aberrant phospho-ERK and phospho-AKT signaling in SMKM inhibitor treated cells. Our in vivo efficacy trial using heterozygous G12V KRAS lung cancer NCI-H441 xenograft model has shown SMKM inhibition significantly reduces tumor growth and increases the survival rate. Together, these data indicate the feasibility of selectively targeting G12V KRAS with SMKM inhibition. Lastly, our results provide a first-in-class small molecule oral inhibitor based selective protein clearance as an effective anti-G12V mutant KRAS therapeutic strategy. Citation Format: Xiyue Hu, Randy Singh, Shana Kelley. Phenotypic CRISPR genome-wide screening for the discovery of genetic regulators of allele-specific mutant KRAS [abstract]. In: Proceedings of the AACR Special Conference: Targeting RAS; 2023 Mar 5-8; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Res 2023;21(5_Suppl):Abstract nr B014.

Sensitive Detection of KRAS Mutations in Archived Formalin-Fixed Paraffin-Embedded Tissue Using Mutant-Enriched PCR and Reverse-Hybridization

Analysis of EGFR, KRAS and P53 mutations in lung cancer using cells in the curette lavage fluid obtained by bronchoscopy

The Ras/Raf/MAPK Pathway

Early detection and treatment of ovarian cancer: shifting from early stage to minimal volume of disease based on a new model of carcinogenesis

Anti-EGFR therapy is approved by US Food and Drug Administration (FDA) as mono-therapy or as part of combination chemotherapy for metastatic colorectal carcinoma. Monoclonal anti-EGFR antibodies cetuximab and panitumumab have shown benefits for those patients with wild-type KRAS gene. Patients with KRAS mutation in codon 12 or 13 are unresponsive to targeted anti-EGFR therapy. Mutations of BRAF, the main downstream target gene of KRAS, also negatively impact the patients’ response to the therapy. On the contrary, EGFR gene amplification in colon cancer predicts a better response to anti-EGFR therapy. The correlation of EGFR amplification with KRAS and BRAF mutation status is not only of academic interests but also of clinical importance. Previous studies have shown that EGFR mutation is mutually exclusive with KRAS and BRAF mutations in lung cancer. However, there is limited data on colorectal cancer so far. In this study, 28 colorectal cancer samples are tested for KRAS and BRAF mutations by PCR and for EGFR gene copy number by fluorescence in situ hybridization (FISH). EGFR high-copies, KRAS mutation and BRAF mutation are found in 15 (54%), 13 (46%) and 3 (11%) samples, respectively. A pattern is seen between KRAS mutations (13 positive samples) and BRAF mutations (3 positive samples). However, high EGFR high copy number is not mutually-exclusive with KRAS or BRAF mutations. Six samples with KRAS mutations and 2 with BRAF mutation show co-existing high EGFR copy number. These account for 29% of total cases tested. Five cases are triple negative for EGFR, KRAS and BRAF alterations. The results from our study indicate that high EGFR copy number with concurrent KRAS or BRAF mutations is quite common in colon cancer and the therapeutic response with anti-EGFR agents in this patient population requires further investigation.

KRAS mutations appear with high frequency in colorectal, lung and pancreatic cancers, which are the three leading causes of new cancer deaths worldwide. Mutant KRAS is preferentially bound to GTP resulting in continuous cell proliferation. Mutant KRAS exposes cells to oncogenic forms of stress (i.e. genotoxic, metabolic, proteostatic stress), which disrupt proliferation and tissue homeostasis. To cope with stress, cells engage pro-adaptive mechanisms, which act in favor of mutant KRAS to transform cells. An important adaptation mechanism to stress acts at the level of mRNA translation and involves the functional interplay between the translation initiator factors eIF2 and eIF2B. Phosphorylated eIF2 mediates a translational and transcriptional reprogramming to promote adaptation under stress, a process that is antagonized by the guanine exchange function (GEF) of eIF2B. We demonstrate the physical interaction between mutant KRAS and eIF2B by mass spectrometry. Using genetic approaches, we show that eIF2B is required for the survival and proliferation of tumor cells with KRAS mutations via the stimulation of MAPK signaling. We also show that eIF2B contributes to increased resistance of tumor cells to pharmacological inhibition of mutant KRAS forms. Genetic inactivation of eIF2B promotes the formation of mutant KRAS-GDP complexes whereas its pharmacological stimulation facilitates mutant KRAS-GTP complex formation in tumor cells; this data supports a potential GEF function for eIF2B towards mutant KRAS. Cell imaging experiments provide strong evidence for the implication of eIF2B in the association of mutant KRAS with the plasma membrane of tumor cells. Our findings reveal a stimulatory role of eIF2B in mutant KRAS signaling and provide a previously unidentified link between mutant KRAS and mRNA translation with implications in the growth and treatment of cancers with KRAS mutations. Citation Format: Hyungdong Kim, Nour Ghaddar, Laleh Ebrahimi Ghahnavieh, Shuo Wang, Kwang-Jin Cho, Atsuo Sasaki, Antonis E. Koromilas. Translation initiation factor 2B (eIF2B) stimulates mutant KRAS function in cancer [abstract]. In: Proceedings of the AACR Special Conference: Targeting RAS; 2023 Mar 5-8; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Res 2023;21(5_Suppl):Abstract nr A022.

Like most cancer types, lung cancer is caused predominantly by somatic genome alterations. In lung adenocarcinoma, the most common histological type of lung cancer, these alterations are known to occur in multiple pathways including the p53 pathway, the receptor tyrosine kinase (RTK)/Ras/Raf/MAP kinase (MAPK) pathway and PI3 kinase pathway, the Rb1/cell cycle pathway, the Swi/Snf pathway, the Myc pathway, and the telomerase pathway, among others. Genome-wide association studies comparing polymorphisms in germline DNA from patients with lung cancer and from unaffected control subjects have led to the identification of multiple germline risk alleles for lung adenocarcinoma, including the HLA locus, the telomerase catalytic subunit gene locus, and, notably, the nicotinic acetylcholine receptor locus, where polymorphisms appear to modulate individual propensity for smoking. The components of inherited lung cancer risk, particularly in nonsmokers, are not fully understood, but there appear to be variations in lung adenocarcinoma mutations in distinct ancestry groups, which may be related to inherited factors. In particular, the frequency of somatic EGFR and KRAS mutations in lung cancer varies by ethnicity. Somatic EGFR mutation rates are higher in lung cancers from patients with East Asian ancestry and lower in lung cancers from patients with European or African ancestry. Somatic KRAS and STK11 mutation rates show the opposite pattern, higher in lung cancers from patients with European or African ancestry and lower in lung cancers from patients with East Asian ancestry. In patients from Latin America, somatic lung cancer EGFR mutation frequencies vary by country, with higher frequencies in Peru, intermediate frequencies in Mexico, Colombia, Costa Rica and Brazil, and lower frequencies in Argentina. To explore the relationship between the somatic genome in lung cancer and ethnicity related germline risk, we performed cancer gene panel sequencing of DNA from over 1,000 lung cancers from Mexico and Colombia, countries with significant population admixture. We developed methods to infer ancestry from the tumor DNA sequence based on coverage of single nucleotide polymorphisms. This study revealed associations between ancestry and somatic lung cancer genomic alterations, including tumor mutational burden, and specific driver mutations in EGFR, KRAS, and STK11. A local ancestry score was more strongly correlated with EGFR mutation frequency compared with global ancestry correlation, suggesting that germline genetics, rather than environmental exposure, could underlie these disparities. Our study suggests that the variation in EGFR and KRAS somatic mutation frequency in lung cancer is associated with genetic ancestry in patients from Latin America, and suggests further studies to identify germline alleles that underpin this association. If we find a germline locus or loci that could impact the development of lung cancers with EGFR and/or KRAS mutation, this might help in improving lung cancer prevention and screening for populations of Latin American origin and others. Furthermore, multiple studies now highlight the importance of EGFR mutation screening and EGFR-directed targeted therapy for lung cancer patients in Latin America and with origins in Latin America. Citation Format: Matthew L. Meyerson. Somatic mutations, germline risk and ancestry in lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr PL03-02.

Lung cancer is the leading cause of cancer-related mortality in the United States. Improved ways to treat and prevent lung cancer are needed. Increased epidermal growth factor receptor (EGFR) expression frequently occurs in lung carcinogenesis. Treatment with the EGFR-tyrosine kinase inhibitor (EGFR-TKI) erlotinib prolongs survival, especially in patients whose lung cancers harbor activating EGFR mutations. However, patients with non-small cell lung cancers (NSCLCs) that harbor KRAS mutations can be less responsive. Therefore, there is a need for improved NSCLC treatments irrespective of KRAS or EGFR mutation status. Previous studies showed that the rexinoid bexarotene causes cyclin D1 proteasomal degradation. The EGFR-TKI erlotinib also represses cyclin D1, but via different mechanisms. The combination of bexarotene with erlotinib was explored. Initial effects of this combination on tumor growth and cyclin D1 expression were examined in murine transgenic lung cancer cell models with or without KRAS/p53 mutations. Findings were translated into both early stage window of opportunity (14 patients enrolled) and advanced stage (42 patients enrolled) phase II NSCLC trials. In the window of opportunity trial, cyclin D1 was measured in pre-versus post-treatment NSCLC biopsies and in buccal swabs. EGFR and phospho-EGFR immunohistochemical expression was assessed in the paired tumor biopsies. KRAS and EGFR mutations were also examined. A phase II trial in heavily pre-treated stage IV NSCLC cases was performed with early PET responses evaluated. Findings reveal significant repression of cyclin D1 expression and lung cancer cell growth. Intriguingly, cyclin D1, EGFR and phospho-EGFR immunohistochemical expression profiles were reduced while necrosis and inflammatory cellular responses were induced in the window of opportunity trial independent of the presence of KRAS or EGFR mutations. Cyclin D1 was repressed in post-treatment buccal swabs. The refractory NSCLC trial (2 median relapses, 21% with prior EGFR-inhibitor therapies) had 3 major clinical responses (2 had KRAS or EGFR mutations) with prolonged survival (583, 665, and 1460+ days). Median survival was 22 weeks (16 weeks for controls). Hypertriglyceridemia or rash significantly increased median overall survival to 24 weeks. Early PET response did not reliably predict clinical response. In summary, combining bexarotene with erlotinib can repress cyclin D1 and confer in vitro and clinical anti-tumor responses (including induced tumor necrosis and inflammatory changes) independent of EGFR or KRAS mutations present in the lung cancers. Notably, survival increased in the treated stage IV NSCLC patients when hypertriglyceridemia or rash developed. Clinical activity of this regimen is encouraging and warrants further study for lung cancer therapy or chemoprevention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-412. doi:10.1158/1538-7445.AM2011-LB-412

The tumour molecular profile predicts the activity of epidermal growth factor receptor (EGFR) inhibitors in non-small-cell lung cancer (NSCLC). However, tissue availability and tumour heterogeneity limit its assessment. We evaluated whether [(18)F]FDG PET might help predict KRAS and EFGR mutation status in NSCLC. Between January 2005 and October 2011, 340 NSCLC patients were tested for KRAS and EGFR mutation status. We identified patients with stage III and IV disease who had undergone [(18)F]FDG PET/CT scanning for initial staging. SUVpeak, SUVmax and SUVmean of the single hottest tumour lesions were calculated, and their association with KRAS and EGFR mutation status was assessed. A receiver operator characteristic (ROC) curve analysis and a multivariate analysis (including SUVmean, gender, age and AJCC stage) were performed to identify the potential value of [(18)F]FDG PET/CT for predicting KRAS mutation. From 102 patients staged using [(18)F]FDG PET/CT, 28 (27%) had KRAS mutation (KRAS+), 22 (22%) had EGFR mutation (EGFR+) and 52 (51%) had wild-type KRAS and EGFR profiles (WT). KRAS+ patients showed significantly higher [(18)F]FDG uptake than EGFR+ and WT patients (SUVmean 9.5, 5.7 and 6.6, respectively; p < 0.001). No significant differences were observed in [(18)F]FDG uptake between EGFR+ patients and WT patients. ROC curve analysis for KRAS mutation status discrimination yielded an area under the curve of 0.740 for SUVmean (p < 0.001). The multivariate analysis showed a sensitivity and specificity of 78.6% and 62.2%, respectively, and the AUC was 0.773. NSCLC patients with tumours harbouring KRAS mutations showed significantly higher [(18)F]FDG uptake than WT patients, as assessed in terms of SUVpeak, SUVmax and SUVmean. A multivariate model based on age, gender, AJCC stage and SUVmean might be used as a predictive marker of KRAS mutation status in patients with stage III or IV NSCLC.

Background: KRAS is one of the best characterized genes in cancer but, despite great efforts made in the past three decades, it remains practically undruggable. KRAS is frequently mutated in the three first cancer leading cause of death in the western countries, which are lung, colorectal (CRC) and pancreatic cancers and has been associated to aggressive phenotypes and reduced response to treatment. Unlike in CRC, where mutated KRAS role seems defined, in non-small-cell lung cancer (NSCLC), which accounts for the 85% of all lung cancers, its role as predictive or prognostic factor has not been established yet and the only definition of KRAS status seems not to be sufficient to shed light on this open question. KRAS has been found mutated mostly at codon 12, in about 20% of NSCLCs and in smokers, but the result of this process is a pool of mutations differing for the replaced basis and for the percentage the substitutions have been observed in other types of cancer. In fact, while in CRC the most common KRAS mutation is the G12D, the G12C substitution is the most abundant in NSCLC. It has been assumed that different KRAS mutations in the same position could differently impact on drug response. We generated an isogenic system in NCI-H1299 cell line with KRAS most common mutations found in NSCLC patients (G12C, G12D and G12V) to test this hypothesis. The G12C clone resulted resistant in vitro and in vivo to cisplatin, which constitutes the standard first line regimen in NSCLC. Methods: The effect of cisplatin on signalling pathways and DNA damage response was determined by western blotting, immunofluorescence and Real-Time PCR. Platinum adducts on DNA were revealed by DRC-ICP-MS. Results: The MAPK and PI3K pathways modulation induced by cisplatin did not seem to account for the different cisplatin sensitivities observed among the clones. Factors involved in processes like cisplatin intracellular uptake and inactivation have been investigated, but the slight differences observed did not explain the behavior of clones treated with cisplatin. Even if cisplatin showed a similar ability to enter the cells and to reach the DNA, concordant results seemed to indicate that an increased removal of platinum bound to DNA might be responsible for the resistance of G12C clone. A reduced G2/M cell cycle phase block was observed in the G12C clone compared to all the others after cisplatin treatment. This observation was supported by a much faster reduction of the levels of platinum adducts on DNA in G12C cells and, at the same time, by a barely detectable H2AX activation following treatment. We hypothesized that a DNA repair mechanism, able to faster remove platinum from DNA before the formation of double strand cross-links, could be involved in the resistance of G12C clone. Preliminary experiments on Nucleotide Excision Repair and Fanconi Anemia repair mechanisms, which have been associated to the removal of adducts from DNA, excluded these systems as responsible for cisplatin resistance. Conclusions: Altogether these data reveal the possibility that KRAS mutations differently influence the response to cisplatin in NSCLC. Further studies are ongoing to address this point. Understanding the molecular factors involved in the different response of KRAS clones to cisplatin could be useful in the clinical setting to improve the limited efficacy on KRAS mutated NSCLC patients of this drug, which nevertheless still represents the best available therapy. Supported by CARIPLO (2010-0794) and AIRC (IG 12915). Citation Format: Elisa Caiola, Roberta Frapolli, Massimo Broggini, Marina Chiara Garassino, Gabriella Farina, Mirko Marabese. Studies on the molecular mechanisms responsible for cisplatin resistance associated to KRAS G12C mutation in NSCLC. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A54. doi: 10.1158/1557-3125.RASONC14-A54

Progress in Making Ras as a Druggable Target.

Objective To investigate the epidermal growth factor receptor (EGFR), KRAS and BRAF mutations and their correlation with clinicopathological characteristics in non-small-cell lung cancer (NSCLC). Methods The mutations of exon 18, exon 19, exon 20 and exon 21 of the EGFR, codon 12, codon 13 of the KRAS and codon 600 of the BRAF gene in 143 cases of NSCLC were detected by gene sequencing. The relationship between the mutations and clinicopathological features was analyzed by SPSS 16.0. Results EGFR mutation was detected in 57 cases (39.9 %), including 2 mutations in exon 18, 25 in exon 19, 3 in exon 20, 24 in exon 21 and 3 multiple point mutations. KRAS mutation was found in 25 cases (17.5 %), including 23 in codon 12 and 2 in codon 13. BRAF V600E mutation was detected only in 2 cases (1.4 %). No patient harboring multiple EGFR, KRAS and BRAF mutations was found. EGFR mutation rate was related to gender, smoking history, histological types, differentiation and tumor size (P 0.05). There was no association between KRAS mutation and clinicopathological features including gender, smoking history, histological types, differentiation, tumor size, lymph node metastasis and pTNM stage (P> 0.05). Conclusions The frequency of EGFR mutation in NSCLC is high, and usually occurs in female, non-smokers, smaller tumors, better differentiation and adenocarcinomas. The frequency of KRAS mutation is not associated with the clinicolpathological features. The frequency of BRAF mutation is very low, and EGFR, KRAS and BRAF gene mutations do not occur at the same time.These results contribute to the target therapy of NSCLC. Key words: Carcinoma, non-small-cell lung; Epidermal growth factor receptor; KRAS; BRAF; Clinicopathological characteristics

As many as 40 percent of non-small cell lung cancers (NSCLC) either lack actionable targets for implementing targeted therapy and using immune-oncology agents, or progress following targeted therapy. Patients with such tumors depend on DNA damaging/alkylating agents. Very few available agents have nanomolar potency, with the majority being weakly cytotoxic (IC50&amp;gt; 20µM). Cisplatin based therapies also associate with high rates of drug resistance development, resulting from mutations such as those that affect NRF2 pathway. Newer drugs that will be more potent and remain efficacious in NSCLC with such mutations could lead to better alternate therapies. LP-184, currently in preclinical development, demonstrates highly potent anticancer activity in the NCI-60 cell line panel, with NSCLC emerging as the most prominent sensitive cancer type (4/10 top sensitive cell lines were NSCLC). Using the pattern matching tool from the NCI CellMiner™ platform LP-184 stands out as a unique molecule and is strongly anti-correlated in drug activity with approved DNA alkylating agents such as oxaliplatin, ifosfamide and carmustine. LP-184 activity is dependent upon the expression of Prostaglandin Reductase 1 (PTGR1). PTGR1 is upregulated in tumors with deregulated NRF2, including tumors with mutations in KEAP1. We hypothesized LP-184 to be efficacious in lung cancers with KEAP1 mutations. LP-184 activity was assessed in an expanded panel of 20 NSCLC cell lines. Overall, LP-184 exhibited high activity in 16/20 NSCLC cell lines (mean IC50 570 nM, median IC50 371 nM). LP-184 IC50 values are 10-3800 fold lower than those seen for cisplatin, paclitaxel and pemetrexed. When activity of LP-184 in the cell lines was correlated with presence or absence of KEAP1 and/ or KRAS mutations, 5/7 cell lines with KEAP1 mutations and 4/5 cell lines with KRAS mutations, as well as 4/5 cell lines with dual KEAP and KRAS mutations were sensitive to LP-184. Machine learning (ML) methods were further used to develop an LP-184-specific gene signature predictive of response. Using this 40 gene signature, LP-184 showed predicted nanomolar potency in 85 of 129 NSCLC cell lines (65%) in the Cancer Cell Line Encyclopedia (CCLE) with mean IC50 100 nM and median IC50 87 nM. Of these 85, 24 cell lines have KEAP1 mutations and 25 cell lines have KRAS mutations, with 10 overlapping cell lines having both KEAP1 and KRAS mutations. In conclusion, LP-184 stands out as a unique anticancer agent that demonstrates nanomolar potency against NSCLC cell lines. ML-based gene signature of response allows biomarker-guided selection of lung cancers that might benefit the most with this agent. LP-184 could thus provide focused clinical value in the treatment of lung cancer. Citation Format: Aditya Kulkarni, Jean Philippe Richard, Umesh Kathad, Michael Seddon, Terri Lehman, Rama Modali, Panna Sharma. LP-184, a molecule with nanomolar potency, exhibits strong activity in lung cancers with KEAP1 and KRAS mutations [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4185.

Background: LKB1 and KRAS are the most commonly mutated genes in non-small cell lung cancer (NSCLC), each present in up to 35% of patient tumors. KRAS mutations have been associated with resistance to EGFR tyrosine kinase inhibitors, but it is not established to what extent KRAS or LKB1 mutations may predict response to other systemic treatments, including PI3K/Akt and MEK inhibitors. Methods: IC50s for cytotoxic chemotherapies and targeted drugs were determined by MTS assay in a large panel of NSCLC cell lines with known mutational status. Cells lines with and without mutations were compared by t-test and linear mixed model to determine the effect of single and double mutations. Protein expression in cell lines was measured by reverse phase protein array. Results: LKB1 mutations strongly predicted resistance to Akt inhibition by MK2206 (p=0.004), but not to PI3K inhibitors BAY80-6949, GDC0941, or 8-amino-adenosine (p&amp;gt;0.24). In contrast, KRAS mutations were strongly associated with resistance to PI3K inhibitors BAY80-6949 (p≤0.0001) and GDC0941 (p=0.034) and to Akt inhibition by MK2206 (p=0.047). Conversely, there was a trend towards greater sensitivity in the KRAS mutated cells to the MEK inhibitor BAY86-9766. Resistance to PI3K inhibition in KRAS mutated lines was largely abrogated by the combination of BAY80-6949 and BAY86-9766. Co-existing LKB1 and KRAS mutations were present in 18% of cell lines, but were not significantly more resistant to PI3K/Akt inhibitors, nor did they predict greater MEK inhibitor sensitivity. There was no association between KRAS or LKB1 mutations and response to cytotoxic chemotherapies, including docetaxel, pemetrexed, or platinum doublets. At the protein level, LKB1 mutant cell lines had significantly higher expression of IGF1R (p&amp;lt;0.0001 by t-test), compared to wild type cell lines, which may represent an alternative signaling pathway contributing to resistance in mutant cell lines. Conclusions: KRAS and LKB1 mutations are associated with greater resistance to PI3K/Akt inhibitors, although there are some differences in resistance with specific drugs. These findings suggest that these mutations may have potential as predictive biomarkers and warrant further investigation prospectively in clinical trials of PI3K, Akt, and MEK inhibitors. In addition, the observation of increased protein expression of IGFR1 in LKB1 mutated lines supports a rationale for combining PI3K/Akt and IGF1R inhibitors as a strategy to overcome resistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5605. doi:1538-7445.AM2012-5605