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J.G. Izzo
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ORAL 21 - Biology - Moving Beyond the Oncogene to Oncogene-Modifying Genes (ID 118)
- Event: WCLC 2015
- Type: Oral Session
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:A. Katz, M.S. Tsao
- Coordinates: 9/08/2015, 10:45 - 12:15, Mile High Ballroom 4a-4f
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ORAL21.02 - Landscape and Functional Significance of KRAS Co-Mutations in Lung Adenocarcinoma (LUAC) (ID 3224)
10:56 - 11:07 | Author(s): J.G. Izzo
- Abstract
- Presentation
Background:
The biological heterogeneity of KRAS-mutant LUAC represents a major impediment to the successful implementation of targeted therapeutic strategies for this clinically challenging group of lung cancer patients. Through integrative, multi-platform analysis of large scale omics data we recently identified three major subsets of KRAS-mutant LUAC defined on the basis of co-occurring genomic alterations in STK11/LKB1 (KL subgroup), TP53 (KP) and CDKN2A/B (KC), the latter coupled with low expression of the TTF1 transcription factor. We further demonstrated subset-specific molecular dependencies, patterns of immune system engagement and therapeutic vulnerabilities. Here, we extend these findings through comprehensive analysis of a wide panel of KRAS co-mutations and assess the impact of key co-mutations on facets of the malignant phenotype including flux through the MAPK and PI3K/AKT pathways and heterotypic interactions with the host immune system.
Methods:
Our datasets consisted of 431 tumors from TCGA (122 KRAS-mutant), 41 additional chemo-naive KRAS-mutant LUACs (PROSPECT dataset) and 36 platinum-refractory KRAS-mutant LUACs from the BATTLE-2 clinical trial. Significant KRAS co-mutations were identified on the basis of a P value threshold of ≤0.05 (Fisher’s exact test) coupled with a baseline prevalence of ≥3%. RNASeq data were downloaded directly from the TCGA site. Expression profiling of PROSPECT tumors was performed using the Illumina Human WG-6 v3 BeadChip Array whereas BATTLE-2 tumors were profiled using the GeneChipâHuman Gene 1.0 ST Array from Affymetrix. Generation of MAPK and PI3K proteomic scores, based on Reverse Phase Protein Array (RPPA) data, has been previously reported.
Results:
Our analysis identified somatic mutations in 31 genes as significantly co-mutated with KRAS in LUAC samples. Among them, co-mutations in STK11/LKB1 (P=0.00011) and ATM (P=0.0004) predominated. Somatic mutations in ERBB4 (P=0.0059), encoding a member of the ErbB family of receptor tyrosine kinases and MAP3K4 (P=0.0017) were also enriched in KRAS-mutant LUAC. We assessed the impact of KRAS co-mutations on the amplitude and directionality of signaling downstream of mutant KRAS using the proteomic “MAPK score“ and “PI3K score” as surrogates of effector pathway activation. Interestingly, co-mutations in ERBB4 were associated with significantly suppressed flux through the MAPK pathway (P=0.0024, t-test). Somatic mutations in other genes, including CAMSAP2, were associated with suppressed signaling through both the MAPK (P=0.00876, t-test) and PI3K-AKT (P=0.0032, t-test) cascades. Finally, within KRAS-mutant tumors, co-mutations in NLRC5, a master transcriptional regulator of MHC Class I molecules were associated with reduced mRNA expression of several of its classical target genes. In addition, low mRNA expression of NLRC5 correlated strongly with reduced expression of key components of the antigen presentation pathway across multiple independent datasets of chemotherapy naïve and platinum refractory KRAS-mutant tumors and cell lines. Thus, in addition to cell autonomous effects, co-mutations can also impinge on the reciprocal relationship between malignant cells and their immune microenvironment.
Conclusion:
Our work identifies a compendium of KRAS co-mutations that impact classical and emerging cancer hallmarks, including evasion of the host immune response. Systematic interrogation of the functional impact of prevalent KRAS co-mutations is essential for the development of personalized treatment approaches for this heterogeneous group of tumors.
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ORAL 42 - Drug Resistance (ID 160)
- Event: WCLC 2015
- Type: Oral Session
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:R.C. Doebele, J.V. DeGregori
- Coordinates: 9/09/2015, 18:30 - 20:00, Mile High Ballroom 4a-4f
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ORAL42.04 - Rictor Alterations Elicit Mechanisms of Survival Advantage and Resistance to Targeted Therapy in Non-Small Cell Lung Cancer (NCSLC) (ID 2991)
19:02 - 19:13 | Author(s): J.G. Izzo
- Abstract
- Presentation
Background:
Rictor (RPTOR independent companion of MTOR, complex 2) is a highly conserved protein and is a critical component for assembly and functionality of the mTORC2 complex. Alterations of the PI3K/mTOR/AKT pathway are hallmark of many cancer types, underscoring the potential important role of Rictor. The goal of our current study was to characterize the functional consequences of genomic alterations of Rictor in advanced refractory NSCLC. Our preliminary data suggest that Rictor alterations have the potential to, not only signal canonically (via activation of AKT), but also provide cancer cells with alternate, more advantageous oncogenic signaling via non-canonical mechanisms.
Methods:
We correlated genomic data (DNA next generation sequencing (NGS), Foundation Medicine, Inc) gene expression profiling, and clinical outcome in the context of the ongoing BATTLE-2 clinical trial of targeted therapies in chemo-refractory NSCLC(198 cases). We further (1) surveyed early stage NSCLC cases(230 cases) in The Cancer Genome Atlas (TCGA) database to perform two-way hierarchical clustering comparing gene expression profiling in amplified vs diploid cases; (2) utilized a single-nucleotide polymorphism array to select Rictor amplified and diploid NSCLC cell lines; (3) assessed Rictor protein and RNA expression by Western blot and qRT-PCR, respectively; (4) performed Rictor knockdown (siRNA), and (5) performed drug sensitivity to targeted therapies by MTS assay.
Results:
In the Battle-2 cases, we identified 15% of Rictor alterations (9% gene amplifications, 6.6% mutations, non-concomitant). Among the mutations, 1 was mapped to an N-terminal phosphorylation site, while all others are of unknown significance to date. Rictor alterations were significantly associated with lack of 8-week disease control in the AKTi+MEKi therapeutic arm. In the TCGA we found: (1) 10% Rictor amplifications and 3% mutations; (2) significant correlation between amplification and elevated Rictor gene expression; (3) a putative functional gene expression signature associated with Rictor amplification. In diploid cell lines we found concordance between AKT phosphorylation and activation of other downstream mTORC2 targets (i.e. SGK1 and PKCα), but in Rictor amplified cell lines we witnessed a discordant activation of these pathways. Furthermore, following Rictor knockdown in our amplified cell lines, a significant reduction of colony formation, migratory, and invasive potential was seen in a pathway-differential manner. Thus, suggesting that Rictor amplifications may provide survival advantage in select cancer cells by tipping the signaling balance toward a non-canonical oncogenic pathway (AKT-independent[I1] ).Also in a differential pathway manner, Rictor gene amplification and overexpression contributed to resistance to a number of targeted therapies
Conclusion:
Rictor alterations may constitute a potential novel mechanism of targeted therapy resistance via the activation of non-canonical signaling pathways. These alterations could define new molecular NSCLC subtypes with distinct biology that expose unique avenues for therapeutic implication. Ongoing studies are exploring therapeutic vulnerabilities, non-canonical signaling and Rictor mutations.
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