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MINI 09 - Drug Resistance (ID 107)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
MINI09.10 - Tumor Angiogenesis in LKB1-Mutant Non-Small Cell Lung Cancer (NSCLC) (ID 3059)
16:45 - 18:15 | Author(s): D. Xia
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.
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.
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).
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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