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Identifying novel targets of oncogenic EGF receptor signaling in lung cancer through global phosphoproteomics

ABSTRACT: Mutations in the epidermal growth factor receptor (EGFR) kinase domain occur in 10-30% of lung adenocarcinoma. Leucine to arginine substitution at amino acid position 858 (L858R) accounts for around 50% of EGFR-tyrosine kinase inhibitor (TKI) sensitizing mutations. A second site mutation in the gatekeeper residue (T790M) accounts for around 60% of acquired resistance to EGFR-TKIs. We sought to identify the immediate direct and indirect targets of these mutant EGFRs in lung adenocarcinoma and their modulation by erlotinib, the first generation, and most widely used EGFR-directed TKI. We undertook stable isotope labeling of amino acids in cell culture (SILAC), phosphopeptide enrichment, and quantitative mass spectrometry to identify dynamic changes of phosphorylation downstream of mutant EGFRs in lung adenocarcinoma cells harboring L858R or L858R/T790M mutations and their modulation by erlotinib inhibition. Phosphorylation at the majority of phosphosites identified exhibited no change upon either EGF stimulation or erlotinib inhibition. Only around 7% of phosphosites identified and quantified showed increased phosphorylation upon EGF stimulation in either cell line. However, while phosphorylation at 61% of these phosphosites decreased upon erlotinib inhibition in the TKI sensitive H3255 cells, only 24% of such sites exhibited decreased phosphorylation upon erlotinib inhibition in the TKI resistant H1975 cells. Top canonical pathways that were inhibited upon erlotinib treatment in sensitive cells, but not the resistant cells include EGFR, Insulin receptor, HGF, MAPK, mTOR, p70S6K and JAK/STAT signaling. We identified phosphosites in proteins of the autophagy network, such as ULK1 (S623) that is constitutive phosphorylated in these lung adenocarcinoma cells, but phosphorylation is inhibited upon erlotinib treatment in sensitive cells, but not resistant cells. Finally, kinase-substrate prediction analysis from our data indicated that substrates of basophilic kinase families, AGC, CAMK and STE were significantly enriched and those of proline directed kinase families, CMGC and CK were significantly depleted among substrates that exhibit increased phosphorylation upon EGF stimulation and reduced phosphorylation upon TKI inhibition. This is the first study to date to examine global phosphorylation changes upon erlotinib treatment of lung adenocarcinoma cells and results from this study provide new insights into signaling downstream of mutant EGFRs in lung adenocarcinoma.

INSTRUMENT(S): LTQ Orbitrap, LTQ Orbitrap Elite

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Lung, Permanent Cell Line Cell

DISEASE(S): Lung Adenocarcinoma

SUBMITTER: Udayan Guha

LAB HEAD: Udayan Guha

PROVIDER: PXD001101 | Pride | 2015-01-30

REPOSITORIES: Pride

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Identifying novel targets of oncogenic EGF receptor signaling in lung cancer through global phosphoproteomics.

Zhang Xu X Belkina Natalya N Jacob Harrys Kishore Charles HK Maity Tapan T Biswas Romi R Venugopalan Abhilash A Shaw Patrick G PG Kim Min-Sik MS Chaerkady Raghothama R Pandey Akhilesh A Guha Udayan U

Proteomics 20150101 2-3

Mutations in the epidermal growth factor receptor (EGFR) kinase domain occur in 10-30% of lung adenocarcinoma and are associated with tyrosine kinase inhibitor (TKI) sensitivity. We sought to identify the immediate direct and indirect phosphorylation targets of mutant EGFRs in lung adenocarcinoma. We undertook SILAC strategy, phosphopeptide enrichment, and quantitative MS to identify dynamic changes of phosphorylation downstream of mutant EGFRs in lung adenocarcinoma cells harboring EGFR(L858R) ...[more]

PMID: 25404012

Similar Datasets

Project description:Lung cancer is the leading cause of cancer death. Mutations in the kinase domain of EGFR, a predominant driver oncogene, such as L858R missense mutation and a series of deletions spanning the conserved sequence 747LREA750, are associated with sensitivity to tyrosine kinase inhibitors (TKIs). However, patients receiving EGFR-TKIs (gefitinib and erlotinib) develop drug-resistance due to a secondary mutation at the gatekeeper residue (T790M) in about 50-60% of cases, urging for new drug development. Afatinib, a FDA approved second-generation EGFR-TKI that was developed to circumvent T790M-mediated resistance, has not been very effective in clinical trials. In this study, we performed a global phosphoproteomic screen to identify targets that undergo mutant EGFR-dependent tyrosine phosphorylation and their modulation by erlotinib or afatinib. We undertook stable isotope labeling of amino acids in cell culture (SILAC), phosphopeptide enrichment, and quantitative mass spectrometry to identify dynamic changes of phosphorylation downstream of mutant EGFRs in lung adenocarcinoma cells harboring L858R or L858R/T790M mutations and their modulation by erlotinib and afatinib inhibition. We identified and quantified 397, 429, 223, and 594 phosphotyrosine sites in H3255, 11-18,PC9, and H1975 cell lines that were grown in presence of FBS and in presence/absence of TKIs, respectively. These account for a total of 907 unique phospho-tyrosine sites in 496 proteins. Among them, 187 phosphotyrosine sites were found to be in 89 kinases, which may serve as intermediary regulatory kinases in EGFR signalling pathway. Further analysis indicated that in TKI-sensitive H3255 and 11-18 cells, there were 58/111 and 65/101 tyrosine sites that were hypophosphorylated in presence of erlotinib and afatinib, respectively. However, in TKI-resistant H1975 cells, 189 and 264 tyrosine sites were hypophosphorylated in presence of erlotinib and afatinib respectively, indicating that the afatinib-specific additional sites could be validated for identifying potentially new drug targets to counter TKI-resistance. Ingenuity pathway analysis (IPA) of proteins with altered phosphorylation sites demonstrated that several canonical pathways including ephrin receptor signalling and integrin signalling pathways were enriched, which may play important roles in cell growth and proliferation. However, upon EGF stimulation of serum starved H3255 cells in presence or absence of TKIs, 99 tyrosine sites that were hyperphosphorylated upon EGF stimulation were inhibited in presence of erlotinib or afatinib. But in H1975 cells treated with erlotinib, 48 of the above sites were either unchanged or were hyperphosphorylated. These sites include EGFR (Y1197/869/998), JAK1 (Y1034), FRK (Y497), GAB1 (Y657/689), MAPK1 (Y187), MAPK3 (Y204), MET (Y1252/1253). Furthermore, a total of 112 sites that were observed to be hypophosphorylated upon EGF stimulation in H1975 cells, were found to be hyperphosphorylated upon erlotinib inhibition. This could possibly be due to the activation of downstream phosphatases with EGF stimulation. We are now performing in-depth bioinformatic analysis and validation experiments using functional genomics to understand the role of targets of mutant EGFR signalling in lung cancer.

Project description:Lung cancer continues to be the leading cause of cancer mortality worldwide. The treatment of lung cancer patients harboring mutant EGFR with orally administered EGFR TKIs has been a paradigm shift. Osimertinib and rociletinib are two 3rd generation irreversible EGFR TKIs targeting the EGFR T790M mutation. Osimertinib is the current standard care for patients with EGFR mutations due to increased efficacy, lower side effects, and enhanced brain penetrance. Unfortunately, all patients develop resistance to it. Genomic approaches have primarily been used to interrogate resistance mechanisms. Here, we have characterized the proteome and phosphoproteome of a series of isogenic EGFR mutant lung adenocarcinoma cell lines that are either sensitive or resistant to these drugs. To our knowledge, this is the most comprehensive proteomic dataset resource to date to investigate 3rd generation EGFR TKI resistance in lung adenocarcinoma. We have interrogated this unbiased global quantitative proteomic and phosphoproteomic dataset to uncover alterations in signaling pathways, and to reveal a proteomic signature of EMT and kinases / phosphatases with altered protein expression and phosphorylation in the TKI resistant cells. We validated the significant role of SHP2 in the activation of RAS/MAPK and PI3K/AKT signaling pathways. Furthermore, we performed anticorrelation analyses of this phosphoproteomic dataset with the published drug-induced P100 phosphoproteomic datasets from the Library of Integrated Network-Based Cellular Signatures (LINCS) program to predict drugs with the potential to overcome EGFR TKI resistance. We identified that dactolisib, a PI3K/mTOR inhibitor, in combination with osimertinib, may overcome osimertinib resistance both in vitro and in vivo. Introduction Lung cancer continues to be the leading cause of cancer mortality in the world (1). Many lung adenocarcinoma patients with activating epidermal growth factor receptor (EGFR) mutations initially respond dramaticlly to the first- or second-generation EGFR tyrosine kinase inhibitors (TKIs). However, they eventually develop resistance. The most common mechanism of acquired resistance is the EGFR T790M gatekeeper site residue mutation (2). Osimertinib, a third generation irreversible EGFR TKI has been approved by the FDA to treat patients harboring the EGFR T790M mutation who have developed resistance to first- and second- generation EGFR TKIs (3). Recently, osimertinib was also approved for the front-line treatment of patients harboring EGFR mutations (4). Rociletinib is another irreversible inhibitor targeting the EGFR T790M mutation, which has minimal activity against wild-type EGFR. Both drugs have therapeutic benefits and have demonstrated activity in tumors with T790M-mediated resistance to other EGFR tyrosine kinase inhibitors (5, 6). Further development of rociletinib was ceased in 2016 due to less than expected efficacy, poor brain penetration leading to tumor progression in brain tissues and off-target effects on IGFR activation leading to hyperglycemia (7, 8). Although 3rd-generation TKIs provide clinical benefit to most patients with EGFR mutations, some patients, demonstrating primary resistance, still do not respond to these inhibitors. Complete responses are rare, and all patients eventually develop resistance, suggesting primary and acquired resistance mechanisms decrease the efficacy of the drugs (9, 10). Genomic approaches have been used primarily to interrogate osimertinib resistance mechanisms (9, 11-15). Several mechanisms of osimertinib resistance have been identified (16), including novel second site EGFR mutations, activated bypass pathways such as MET amplification, HER2 amplification, RAS mutations, BRAF mutations, PIK3CA mutations, and novel fusion events (17). However, the resistance mechanism is complex and still not fully understood. Previously, we have used SILAC-based quantitative phosphoproteomics to identify the global dynamic modification which occur upon treatment of TKI-sensitive and -resistant lung adenocarcinoma cells with the 1st and 2nd generation EGFR TKIs, erlotinib and afatinib. Utilizing this strategy, we identified the targets of mutant EGFR signaling pathways responsible for TKI resistance, and possible off-target effects of the drugs (18, 19). In this study, we employed SILAC-based quantitative mass spectrometry to characterize alterations in the proteome and phosphoproteome which occur upon acquired resistance and sought to identify novel mechanisms of resistance to the third generation EGFR TKIs, osimertinib and rociletinib. To our knowledge, this is the most comprehensive 3rd generation EGFR TKI resistant proteome and phosphoproteome analysis resource available to date.

Project description:Introduction: The clinical benefit of EGFR tyrosine kinase inhibitor (TKI) treatment in non-small cell lung cancer (NSCLC) patients with activating EGFR mutations is temporary, as virtually all patients develop acquired EGFR TKI resistance that occurs via diverse mechanisms. Here, we identified increased FGFR1 expression as such a resistance mechanism and using pathways analysis and drug combination testing we identified a novel combination treatment to control growth of these resistant tumors. Methods: Novel erlotinib-resistant NSCLC cell lines were generated and analyzed by mass spectrometry-based proteomics to identify altered pathways associated with erlotinib resistance. The altered pathways were further analyzed in gefitinib and osibenib resistant cell lines. Small molecule inhibitor combinations were used to block the altered pathways and investigate growth reduction in vitro and in two xenograft mouse models. FGFR1 mRNA levels were examined in pre- and (post?)- EGFR TKI treatment clinical tumor samples. Results: Proteomic analysis revealed increased expression of FGFR1 and AXL as well as increased Akt and ERK1/2 activation in a panel of novel erlotinib-resistant HCC827 cell lines. Combined treatment with erlotinib or osimertinib and a panel of small molecule inhibitors targeting AXL/MET, FGFRs, Akt, PI3K/mTOR, MEK or ERK1/2 showed that the most prominent re-sensitization to EGFR TKI occurred with the pan-FGFR inhibitor, PD173074. Interestingly, simultaneous blockade of components of the Akt pathway using specific Akt or dual PI3K-mTOR inhibitors combined with inhibitors targeting the FGFR family exhibited the most efficient growth inhibition of FGFR1 overexpressing EGFR TKI-resistant cell lines. Phosphorylation of proteins downstream of Akt, including PRAS40, FOXO and S6 ribosomal protein, were completely abrogated by PD173074 combined with the Akt inhibitor GSK2141795 . Combination treatment with PD173074 and an Akt inhibitor exhibited synergistic growth inhibition in vivo in two FGFR1 overexpressing NSCLC EGFR TKI-resistant animal models. Conclusion: The significant growth inhibition in vitro and in vivo observed with PD173074 combined with Akt compared to either drug alone imply that inhibition of several key targets may be beneficial in controlling erlotinib-resistant NSCLC. The complete abrogation of PRAS40, FOXO and S6 phosphorylations by PD173074 combined with an Akt inhibitor indicates that the Akt pathway is no longer active.

			Action	DRS
	H1975_MaxQuantresults.zip	Other
	H1975_pST_BR1_F1.raw	Raw
	H1975_pST_BR1_F10.raw	Raw
	H1975_pST_BR1_F11.raw	Raw
	H1975_pST_BR1_F12.raw	Raw