RESUMO
Thyroid transcription factor-1 (TTF-1, encoded by the NKX2-1 gene) is highly expressed in small-cell lung carcinoma (SCLC) and lung adenocarcinoma (LADC), but how its functional roles differ between SCLC and LADC remains to be elucidated. Here, we compared the genome-wide distributions of TTF-1 binding regions and the transcriptional programs regulated by TTF-1 between NCI-H209 (H209), a human SCLC cell line, and NCI-H441 (H441), a human LADC cell line, using chromatin immunoprecipitation-sequencing (ChIP-seq) and RNA-sequencing (RNA-seq). TTF-1 binding regions in H209 and H441 cells differed by 75.0% and E-box motifs were highly enriched exclusively in the TTF-1 binding regions of H209 cells. Transcriptome profiling revealed that TTF-1 is involved in neuroendocrine differentiation in H209 cells. We report that TTF-1 and achaete-scute homolog 1 (ASCL1, also known as ASH1, an E-box binding basic helix-loop-helix transcription factor, and a lineage-survival oncogene of SCLC) are coexpressed and bound to adjacent sites on target genes expressed in SCLC, and cooperatively regulate transcription. Furthermore, TTF-1 regulated expression of the Bcl-2 gene family and showed antiapoptotic function in SCLC. Our findings suggest that TTF-1 promotes SCLC growth and contributes to neuroendocrine and antiapoptotic gene expression by partly coordinating with ASCL1.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Carcinoma Pulmonar de Células não Pequenas/genética , Proliferação de Células/genética , Neoplasias Pulmonares/genética , Carcinoma de Pequenas Células do Pulmão/genética , Fator Nuclear 1 de Tireoide/metabolismo , Apoptose/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Carcinoma Pulmonar de Células não Pequenas/mortalidade , Linhagem Celular Tumoral , Sobrevivência Celular/genética , Sequenciamento de Cromatina por Imunoprecipitação , Regulação Neoplásica da Expressão Gênica/genética , Ontologia Genética , Estudo de Associação Genômica Ampla , Humanos , Imuno-Histoquímica , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/mortalidade , Motivos de Nucleotídeos , Prognóstico , Ligação Proteica , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Interferência de RNA , RNA-Seq , Carcinoma de Pequenas Células do Pulmão/metabolismo , Carcinoma de Pequenas Células do Pulmão/mortalidade , Análise Serial de TecidosRESUMO
Transforming growth factor-ß (TGF-ß) induces apoptosis in many types of cancer cells and acts as a tumor suppressor. We performed a functional analysis of TGF-ß signaling to identify a molecular mechanism that regulated survival in small cell lung cancer cells. Here, we found low expression of TGF-ß type II receptor (TßRII) in most small cell lung cancer cells and tissues compared to normal lung epithelial cells and normal lung tissues, respectively. When wild-type TßRII was overexpressed in small cell lung cancer cells, TGF-ß suppressed cell growth in vitro and tumor formation in vivo through induction of apoptosis. Components of polycomb repressive complex 2, including enhancer of zeste 2 (EZH2), were highly expressed in small cell lung cancer cells; this led to epigenetic silencing of TßRII expression and suppression of TGF-ß-mediated apoptosis. Achaete-scute family bHLH transcription factor 1 (ASCL1; also known as ASH1), a Smad-dependent target of TGF-ß, was found to induce survival in small cell lung cancer cells. Thus, EZH2 promoted small cell lung cancer progression by suppressing the TGF-ß-Smad-ASCL1 pathway.
RESUMO
The co-culture of TF-1 leukemia cells and MS-5 stromal cells produces a cobblestone area which partially mimics the leukemia stem cell niche. The adhering leukemia cells are shown to become less sensitive to cytarabine, etoposide and daunorubicin. These changes are associated with an increased proportion of the G0/G1 phase, increased upregulation of cyclin-dependent kinase inhibitors, and increased levels of Bcl-2, but not with any change in the expression of BAX or drug transporters such as ABCG2 and MDR1, compared to monocultured leukemic cells. In addition, we demonstrate using a bioimaging technique that daunorubicin accumulates in the lysosomes of the adherent leukemic cells and that V-ATPase is activated. These findings suggest that adhesion alone can lead to drug resistance in leukemic stem cells by various mechanisms.
