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D. Hayakawa
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P2.02 - Biology/Pathology (ID 616)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Moderators:
- Coordinates: 10/17/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P2.02-012 - The Epigenetic Role of LSD1+8a in Small Cell Lung Cancer (ID 8848)
09:30 - 09:30 | Author(s): D. Hayakawa
- Abstract
Background:
Small cell lung cancer (SCLC) is a neuroendocrine tumor which account for 15% of all lung cancers. SCLC is characterized by rapid progression which led metastasis to distant organs and represented poor prognosis. Although there were various molecular targeted therapies in SCLC that were already under investigation, results have been disappointing. The focus on biological pathways has recently shifted from genetic to epigenetic regulations. Histone methylation is one of the epigenetic mechanism which has pivotal role in gene expression, cell cycle and differentiation. Lysine-specific demethylase 1 (LSD1)/KDM1 is a histone modifier that is expressed in certain human cancers including SCLC. LSD1+8a is one of the isoform of LSD1 that was reported to be restricted in neural tissues and it plays critical role in neuronal differentiation. The aim of this study is to elucidate the epigenetic role of LSD1+8a in SCLC.
Method:
The expression of LSD1 and LSD1+8a mRNAs were analyzed by qPCR in several cancer cell lines. Neuroendocrine markers were detected by qPCR in several SCLC cell lines. The Pearson correlation test was performed to investigate the correlation between LSD1+8a and neuroendocrine markers. siRNA against specific to exon 8a was designed and knockdown LSD1+8a isoform specifically. Cell proliferation assays following knockdown of LSD1+8a were performed in LSD1+8a expressed SCLC cell lines.
Result:
LSD1 mRNA was expressed in majority of SCLC cell lines, interestingly LSD1+8a mRNA was detected in small subset of SCLC cell lines. There were positive correlations of LSD1+8a and neuroendocrine marker genes such as chromogranin A (CHGA), enolase2 (ENO2), neural cell adhesion molecule (NCAM) and synaptophysin (SYP) in human cancer cell lines. The suppression of LSD1+8a by siRNA drove to decrease expression of neuroendocrine marker genes in SCLC and inhibited cell proliferation in LSD1+8a expressed cell.
Conclusion:
LSD1+8a could play an important role in SCLC.
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P3.02 - Biology/Pathology (ID 620)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Moderators:
- Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P3.02-024 - Role of FBXW7 in the Maintenance of Quiescent Cancer Stem Cells Resistant to Gefitinib in EGFR Mutation-Positive Non-Small Cell Lung Cancer (ID 8160)
09:30 - 09:30 | Author(s): D. Hayakawa
- Abstract
Background:
Accumulating evidence indicates that quiescent cancer stem cells (CSCs) are involved in the resistance to gefitinib in non-small cell lung cancer (NSCLC) as non-mutational mechanism. We have previously reported that gefitinib-resistant persisters (GRPs) highly expressed stemness factors and had characteristic features of the CSCs phenotype. Recent studies demonstrate that FBXW7, a type of F-box protein, plays an important role in the maintenance of quiescent CSC by mediating the degradation of c-Myc protein by ubiquination. The aim of this study is to figure out the role of FBXW7 in the resistance to gefitinib in NSCLC with EGFR mutation.
Method:
NSCLC cell lines, PC9 and HCC827, harboring sensitive-EGFR mutation were exposed to high concentration of gefitinib in order to develop GRPs. We tried to knockdown FBXW7 gene expression, and evaluated their sensitivity to gefitinib and CD133-positive stem cell population in GRPs. We also introduced FUCCI plasmid via lentiviral infection in the cells and then investigated the cell cycle and G0-phase cells in GRPs. Furthermore, we established gefitinib-resistant tumor (GRT) model by injecting PC9 cells into NOG-mice followed by gefitinib administration after tumor growth, and evaluated mRNA and protein expression of quiescence-related markers including FBXW7 in vivo.
Result:
In vitro, GRPs showed high expression of stem cell marker CD133 and quiescence-related markers including FBXW7 and low expression of c-Myc at protein level. Cell cycle analysis revealed that majority of GRPs existed in G0/G1 phase. Silencing of FBXW7 gene reduced CD133-positive cell population in GRPs. Knockdown of FBXW7 also increased susceptibility of cells to gefitinib, reversed population of G0/G1-arrest cells to G2/S/M cells, and decreased cell number of GRPs. In vivo, GRTs after gefitinib treatment revealed high expression of FBXW7 and low expression of c-Myc.
Conclusion:
These findings suggest that FBXW7 may play a pivotal role in the maintenance of quiescent CSCs resistant to gefitinib in EGFR mutation-positive NSCLC.
