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P. Tong
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MINI 09 - Drug Resistance (ID 107)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:L. Villaruz, J. Minna
- Coordinates: 9/07/2015, 16:45 - 18:15, 205+207
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MINI09.10 - Tumor Angiogenesis in LKB1-Mutant Non-Small Cell Lung Cancer (NSCLC) (ID 3059)
17:40 - 17:45 | Author(s): P. Tong
- Abstract
- Presentation
Background:
LKB1 is a critical regulator of cell growth, metabolism and EMT, and it is mutated in 20-30% of non-small cell lung cancers (NSCLC). LKB1 mutations co-occur with KRAS-activating mutations in 7%-10% of all NSCLC and results in an aggressive phenotype and a worse response to chemotherapy compared to KRAS-mutated tumors. Because LKB1 activates AMPK (AMP-activated protein kinase) which functions as a cellular energy sensor, LKB1-deficient cells are unable to appropriately sense metabolic and energetic stress. LKB1 is also known to regulate angiogenesis, but the mechanism(s) by which this occurs remains unclear. Bevacizumab, the human anti-VEGF antibody approved for the treatment of NSCLC, improves the progression-free and overall survival of NSCLC patients combined with chemotherapy, but often the benefit is transient, and therapeutic resistance occurs. Our laboratory has previously identified phenotypical differences in vasculature patterns in A549 NSCLC tumors resistant to bevacizumab (LKB1 mutant), when compared to H1975 tumors, (LKB1 wild-type). In addition, LKB1 mutant NSCLC cell lines are highly vulnerable to agents acting on energetic pathways. These results may indicate that loss of LKB1 in NSCLC could alter the tumor vasculature and regulate sensitivity to anti-angiogenic therapies. Here, we investigate the hypothesis that combinations of energetic-depleting compounds along with blockade of tumor angiogenesis would be more effective in NSCLC LKB1 mutant tumors.
Methods:
mRNA and protein expression of 584 angiogenesis-related genes were analyzed in wild-type and LKB1 mutant NSCLC (TCGA, RPPA and PROSPECT databases). In vitro validation was performed using qPCR, immunohistochemistry and western blot analysis as well as pairs of isogenic LKB1 mutant cell lines with overexpressed or silenced LKB1. Endothelial cells were incubated with conditioned medium of wild-type and LKB1 mutant NSCLC cell lines, and tube formation matrigel, proliferation and migration (Boyden chamber) assays were performed.
Results:
We identify a group of new and classic angiogenesis-related molecules: VEGFA, VEGFR1, KDR, NRP1, PDGFB, PDGFRA-B, HIF-1A, C-KIT, VCAM1, hypoxia related molecules: HIF1AN, EGLN1, HIF3A, CA12, EPAS1 and immune related molecules: TNFSF11, NFKB1, CD47, PDL1 differentially expressed in LKB1-wild type and LKB1 mutant NSCLC (p<0.05 and fold-change ≥ or ≤1.5). LKB1 mutant cell lines showed higher protein expression of phospho-cKIT, a tyrosine-kinase receptor involve in cell proliferation and angiogenesis, and CA12 (Carbonic anhydrase 12), a known HIF-1α regulated molecule, involved in maintaining cellular pH homeostasis. Also, LKB1 mutant cells exhibit different quantitative vascular patterns in matrigel assays like number of nodes, junctions, length and branching of the endothelial matrix (p<0.05). Human endothelial cells exhibited an increase rate of proliferation and migration when incubated with conditioned medium from LKB1 mutant NSCLC cell lines compared with conditioned media from LKB1-wild type NSCLC cell lines (p<0.05).
Conclusion:
There are biological differences in vasculature patterns in LKB1 mutant NSCLC tumors and in LKB1 mutant cell lines comparing with wild-type LKB1. These differences are translated in biological alterations of human endothelial cells in vitro suggesting an important role of LKB1 in resistance to anti-angiogenic treatments in vivo.
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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): P. Tong
- 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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