Upregulation of CXCR4 is functionally crucial for maintenance of stemness in drug-resistant non-small cell lung cancer cells

• Published in: Oncogene Vol. 32; no. 2; pp. 209 - 221
• Main Authors: Jung, M-J, Rho, J-K, Kim, Y-M, Jung, J E, Jin, Y B, Ko, Y-G, Lee, J-S, Lee, S-J, Lee, J C, Park, M-J
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.01.2013; Nature Publishing Group
• Subjects: 1-Phosphatidylinositol 3-kinase; 631/67/1059/2326; 631/67/71; 631/80/86; 692/699/67/1612/1350; AKT protein; Animals; Apoptosis; Cancer; Cancer cells; Carcinoma, Non-Small-Cell Lung - drug therapy; Carcinoma, Non-Small-Cell Lung - metabolism; Carcinoma, Non-Small-Cell Lung - pathology; Care and treatment; Cell Biology; Cell Line, Tumor; Chemokine CXCL12 - metabolism; CXCR4 protein; Data processing; Development and progression; Drug resistance; Drug Resistance, Neoplasm; Female; Heterocyclic Compounds - pharmacology; Human Genetics; Humans; Internal Medicine; Lung cancer; Lung cancer, Non-small cell; Lung Neoplasms - drug therapy; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Medicine; Medicine & Public Health; Mice; Mice, Nude; Mice, SCID; Neoplastic Stem Cells - drug effects; Neoplastic Stem Cells - physiology; Non-small cell lung carcinoma; Oncology; original-article; Phosphatidylinositol 3-Kinase - metabolism; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt - metabolism; PTEN Phosphohydrolase - genetics; PTEN Phosphohydrolase - metabolism; PTEN protein; Pyridines - pharmacology; Receptors, CXCR4 - antagonists & inhibitors; Receptors, CXCR4 - genetics; Receptors, CXCR4 - metabolism; RNA Interference; RNA, Small Interfering; SDF-1 protein; Secretion; Signal Transduction; siRNA; Stat3 protein; STAT3 Transcription Factor - antagonists & inhibitors; STAT3 Transcription Factor - genetics; STAT3 Transcription Factor - metabolism; Stem cells; TOR protein; TOR Serine-Threonine Kinases - metabolism; Transfection; Tumor cell lines; Tumorigenicity; Tyrphostins - pharmacology; Up-Regulation; South Korea; non-small cell lung cancer; CXCR4; STAT3 signaling; tumorigenicity; cancer stem cell; PI3K/PTEN/Akt/mTOR signaling
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2012.37

The hypothesis of cancer stem cells has been proposed to explain the therapeutic failure in a variety of cancers including lung cancers. Previously, we demonstrated acquisition of epithelial–mesenchymal transition, a feature highly reminiscent of cancer stem-like cells, in gefitinib-resistant A549 cells (A549/GR). Here, we show that A549/GR cells contain a high proportion of CXCR4+ cells that are responsible for having high potential of self-renewal activity in vitro and tumorigenicity in vivo . A549/GR cells exhibited strong sphere-forming activity and high CXCR4 expression and SDF-1α secretion compared with parent cells. Pharmacological inhibition (AMD3100) and/or siRNA transfection targeting CXCR4 significantly suppressed sphere-forming activity in A549 and A549/GR cells, and in various non-small cell lung cancer (NSCLC) cell lines. A549/GR cells showed enhanced Akt, mTOR and STAT3 (Y705) phosphorylation. Pharmacological inhibition of phosphatidyl inositol 3-kinase or transfection with wild-type PTEN suppressed phosphorylation of Akt, mTOR and STAT3 (Y705), sphere formation, and CXCR4 expression in A549/GR cells, whereas mutant PTEN enhanced these events. Inhibition of STAT3 by WP1066 or siSTAT3 significantly suppressed the sphere formation, but not CXCR4 expression, indicating that STAT3 is a downstream effector of CXCR4-mediated signaling. FACS-sorted CXCR4+ A549/GR cells formed many large spheres, had self-renewal capacity, demonstrated radiation resistance in vitro and exhibited stronger tumorigenic potential in vivo than CXCR4− cells. Lentiviral-transduction of CXCR4 enhanced sphere formation and tumorigenicity in H460 and A549 cells, whereas introduction of siCXCR4 suppressed these activities in A549/GR cells. Our data indicate that CXCR4+ NSCLC cells are strong candidates for tumorigenic stem-like cancer cells that maintain stemness through a CXCR4-medated STAT3 pathway and provide a potential therapeutic target for eliminating these malignant cells in NSCLC.