Tumorigenicity Of Non-small Cell Lung Cancer Cells Research Articles

GOLPH3/CKAP4 promotes metastasis and tumorigenicity by enhancing the secretion of exosomal WNT3A in non-small-cell lung cancer

Cancer metastasis is the main cause of mortality associated with non-small-cell lung cancer (NSCLC), accounting for up to 70% of deaths among patients. The mechanisms underlying distal metastasis remain largely unknown. Golgi phosphoprotein 3 (GOLPH3) correlates negatively with overall survival in multiple tumors. In this study, we evaluated the function of GOLPH3 in NSCLC distal metastasis. GOLPH3 was expressed at high levels in samples from patients with NSCLC and was positively associated with clinicopathologic characteristics including clinical stage (P < 0.001), T (P = 0.001), N (P = 0.007), and M (P = 0.001) classification. Functionally, Transwell and wound-healing assays suggested that GOLPH3 overexpression enhances NSCLC cell migration and invasion abilities. Tumor-sphere formation and flow cytometry assays demonstrated that GOLPH3 overexpression enhances a stem cell-like phenotype of NSCLC cells. Metastasis models established by tail vein and intracardiac injection confirmed the pro-metastatic function of GOLPH3 in vivo. A subcutaneous tumor formation model confirmed that GOLPH3 overexpression increased the tumorigenicity of NSCLC cells. Mechanistically, gene set enrichment analysis revealed a positive association of GOLPH3 mRNA expression with WNT-activated gene signatures. Luciferase-reporter and nuclear extract assays showed that GOLPH3 overexpression enhances metastasis and tumorigenicity through activation of the WNT/β-catenin pathway. Immunoprecipitation-mass spectrometry and gene ontology analysis demonstrated that GOLPH3 interacts with cytoskeleton-associated protein 4 (CKAP4) in exosome-mediated distal metastasis. We found that GOLPH3 decreased the amount of plasma membrane-localized CKAP4 and increased the amount of exosome-localized CKAP4 to promote the formation of CKAP4-containing exosomes. Furthermore, we demonstrated that CKAP4 binds exosomal WNT3A to enhance its secretion. Therefore, the GOLPH3/CKAP4 axis plays a crucial role in promoting exosomal-WNT3A secretion to enhance and maintain the stem-like phenotype and metastasis in NSCLC, thus indicating the therapeutic potential of GOLPH3 in patients with NSCLC metastasis.

Epigenetic silencing of microRNA-199a-5p promotes the proliferation of non-small cell lung cancer cells by increasing AKAP1 expression.

MicroRNA (miR)-199a-5p expression is downregulated in a variety of malignancies, including non-small cell lung cancer (NSCLC), and its low expression is associated with a poor prognosis. However, to the best of our knowledge, the mechanism underlying miR-199a-5p downregulation in NSCLC and its target effectors remain to be elucidated. The present study revealed the downregulation of miR-199a-5p expression in NSCLC tissues and cell lines compared with in para-carcinoma tissues and a lung epithelial cell line. Further experiments indicated that the methylation levels of the miR-199a promoter were markedly higher in NSCLC tissues compared with in para-carcinoma tissues. The DNA methyltransferase inhibitor 5-Aza-2′-deoxycytidine markedly increased the expression levels of miR-199a-5p in NSCLC cells. Furthermore, it was identified that miR-199a-5p mimics transfection decreased the expression levels of A-kinase anchoring protein 1 (AKAP1) at both the mRNA and protein levels by targeting the 3′ untranslated region of AKAP1 mRNA. The in vitro experiments demonstrated that miR-199a-5p overexpression inhibited the proliferation and tumorigenicity of NSCLC cells, whereas overexpression of AKAP1 partially recovered the malignant phenotypes, suggesting that AKAP1 may be a downstream effector targeted by miR-199a-5p. Collectively, the present findings indicated that miR-199a-5p may be a novel regulator of AKAP1, and that miR-199a-5p may be a potential tumor suppressor in NSCLC.

Elevated Heme Synthesis and Uptake Underpin Intensified Oxidative Metabolism and Tumorigenic Functions in Non–Small Cell Lung Cancer Cells

Tumors of human non-small cell lung cancer (NSCLC) are heterogeneous but exhibit elevated glycolysis and glucose oxidation relative to benign lung tissues. Heme is a central molecule for oxidative metabolism and ATP generation via mitochondrial oxidative phosphorylation (OXPHOS). Here, we showed that levels of heme synthesis and uptake, mitochondrial heme, oxygen-utilizing hemoproteins, oxygen consumption, ATP generation, and key mitochondrial biogenesis regulators were enhanced in NSCLC cells relative to nontumorigenic cells. Likewise, proteins and enzymes relating to heme and mitochondrial functions were upregulated in human NSCLC tissues relative to normal tissues. Engineered heme-sequestering peptides (HSP) reduced heme uptake, intracellular heme levels, and tumorigenic functions of NSCLC cells. Addition of heme largely reversed the effect of HSPs on tumorigenic functions. Furthermore, HSP2 significantly suppressed the growth of human NSCLC xenograft tumors in mice. HSP2-treated tumors exhibited reduced oxygen consumption rates (OCR) and ATP levels. To further verify the importance of heme in promoting tumorigenicity, we generated NSCLC cell lines with increased heme synthesis or uptake by overexpressing either the rate-limiting heme synthesis enzyme ALAS1 or uptake protein SLC48A1, respectively. These cells exhibited enhanced migration and invasion and accelerated tumor growth in mice. Notably, tumors formed by cells with increased heme synthesis or uptake also displayed elevated OCRs and ATP levels. These data show that elevated heme flux and function underlie enhanced OXPHOS and tumorigenicity of NSCLC cells. Targeting heme flux and function offers a potential strategy for developing therapies for lung cancer. SIGNIFICANCE: These findings show that elevated heme availability due to increased heme synthesis and uptake causes intensified oxygen consumption and ATP generation, promoting tumorigenic functions and tumor growth in NSCLC. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/10/2511/F1.large.jpg.

Tumor-suppressive effects of microRNA-181d-5p on non-small-cell lung cancer through the CDKN3-mediated Akt signaling pathway in vivo and in vitro.

The involvement of several microRNAs (miRs) in the initiation and development of tumors through the suppression of the target gene expression has been highlighted. The aberrant expression of miR-181d-5p and cyclin-dependent kinase inhibitor 3 (CDKN3) in non-small-cell lung cancer (NSCLC) was then screened by microarray analysis. In the present study, we performed a series of in vivo and in vitro experiments for the purpose of investigating their roles in NSCLC and the underlying mechanism. There was a high expression of CDKN3, whereas miR-181d-5p was downregulated in NSCLC. Quantitative RT-PCR, Western blot analysis, and dual-luciferase reporter gene assay further identified that CDKN3 could be negatively regulated by miR-181d-5p. Moreover, the upregulation of miR-181d-5p or silencing of CDKN3 could inactivate the Akt signaling pathway. A549 with the lowest miR-181d-5p and H1975 with the highest CDKN3 among the five NSCLC cell lines (H1299, A549, H1975, NCI-H157, and GLC-82) were adopted for in vitro experiments, in which expression of miR-181d-5p and CDKN3 was altered by transfection of miR-181d-5p mimic/inhibitor or siRNA-targeting CDKN3. Afterwards, cell proliferation, apoptosis, invasion, migration, and angiogenesis, as well as epithelial-mesenchymal transition (EMT), were evaluated, and tumorigenicity was assessed. In addition, an elevation in miR-181d-5p or depletion in CDKN3 led to significant reductions in proliferation, invasion, migration, angiogenesis, EMT, and tumorigenicity of NSCLC cells, coupling with increased cell apoptosis. In conclusion, this study highlights the tumor-suppressive effects of miR-181d-5p on NSCLC via Akt signaling pathway inactivation by suppressing CDKN3, thus providing a promising therapeutic strategy for the treatment of NSCLC.

Hypermethylation of miRNA-589 promoter leads to upregulation of HDAC5 which promotes malignancy in non-small cell lung cancer.

Histone deacetylases (HDACs) are crucial for regulating chromatin activity, which plays a critical role in cell proliferation, differentiation, and apoptosis of various cancers. Therefore, HDAC inhibitors have been applied as effective therapeutic agents for cancer treatment. However, the expression profiles and regulatory mechanisms of histone deacetylases in lung cancer are not well understood. In the present study, aberrant high levels of HDAC5 were observed in non-small cell lung cancer (NSCLC) and further analysis indicated a negative relationship between HDAC5 and a tumor suppressor, miR‑589‑5p, in NSCLC specimens. Consistently, miR‑589‑5p reduced the expression of HDAC5 by targeting the 3'UTR of HDAC5 mRNA in NSCLC cells. Considering the loss of miR‑589‑5p in NSCLC, the methylation status of the miR-589 gene promoter was examined. The hypermethylation of the miR-589 gene promoter was more significant in NSCLC cells compared with lung epithelial cells, and methylation inhibition by 5-aza-2-deoxycytidine (5-Aza-dC) decreased HDAC5 expression. Furthermore, several downstream gene clusters of HDAC5 were studied in the present investigation. As a result, miR‑589‑5p/HDAC5 pathway was found to regulate a number of cell cycle and epithelial-mesenchymal transition (EMT)-related genes in NSCLC cells. In vitro and invivo phenotype experiments revealed a critical role of miR‑589‑5p/HDAC5 pathway in the migration, invasion, and tumorigenicity of NSCLC cells. These findings demonstrate a novel mechanism for deregulation of HDAC5 in NSCLC and suggest that miR‑589‑5p/HDAC5 pathway may represent a new prognostic biomarker and therapeutic target against NSCLC.

Up-regulation of SRPK1 in non-small cell lung cancer promotes the growth and migration of cancer cells.

Dys-regulation of serine-arginine protein kinase 1 (SRPK1) has been reported in non-small cell lung cancer (NSCLC). However, its functions in the progression of NSCLC remain poorly understood. In this study, the expression of SRPK1 in NSCLC tissues was determined using real-time PCR, and the roles of SRPK1 in the progression of NSCLC were investigated. It was found that both the mRNA level and the protein level of SRPK1 were up-regulated in NSCLC tissues. Forced expression of SRPK1 promoted the growth and migration of NSCLC cells, while knocking down the expression of SRPK1 inhibited the growth, migration, and tumorigenicity of NSCLC cells. Mechanism studies showed that SRPK1 activated the transcriptional activity of beta-catenin/T-cell factor (TCF) complex, and knocking down the expression of SRPK1 attenuated the expression of target genes of beta-catenin/T-cell factor (TCF) complex. In addition, silencing the expression of SRPK1 down-regulated the phosphorylation of GSK3beta. Taken together, SRPK1 might play an oncogenic role in NSCLC, and SRPK1 might be a therapeutic target for NSCLC.

Abstract LB-023: Caspase-9b directly interacts with cIAP1 to drive agonist-independent NF-κB activation and tumorigenesis in non-small cell lung cancer

Abstract Caspase-9 has two isoforms with opposing functions, pro-apoptotic caspase-9a (C9a) and anti-apoptotic caspase-9b (C9b). C9b expression has been reported to augment the anchorage-dependent growth (AIG) and tumorigenic capacity of non-small cell lung cancer (NSCLC) cells. The mechanism of this biological observation was revealed in this study. Specifically, C9b was demonstrated to have a dual caspase-9a-independent function in regulating the survival/oncogenic nuclear factor κB (NF-κB) pathway. In particular, C9b was shown to activate the canonical arm and inhibit of the non-canonical arm of the NF-κB pathway by destabilizing NF-κB inhibitor alpha (IκB-α) and NF-κB-inducing kinase (NIK). Importantly, this new role for C9b contributes to the enhanced survival and AIG of NSCLC cells conferred by C9b expression. The link between C9b expression and NF-κB activation was also validated in human NSCLC tumors. Further mechanistic studies revealed a direct association of C9b with the cellular inhibitor of apoptosis 1 (cIAP1), a regulatory factor in both arms of the NF-κB network, via its IAP-binding motif (IBM). Through this interaction, C9b induces the E3 ligase activity of cIAP1, which regulates NF-κB activation, and promotes the viability, AIG and tumorigenicity of NSCLC cells. Hence, C9b/cIAP1 interaction is a new attractive molecular target for developing therapeutics to treat NSCLC. Citation Format: Ngoc T. Vu, Margaret A. Park, Michael D. Shultz, Amy C. Ladd, Charles E. Chalfant. Caspase-9b directly interacts with cIAP1 to drive agonist-independent NF-κB activation and tumorigenesis in non-small cell lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-023. doi:10.1158/1538-7445.AM2015-LB-023

Caspase‐9b Directly Interacts with c‐IAP1 to Drive an Agonist‐Independent Activation of the NF‐κB Pathway and the Enhancement of Tumorigenicity in Non‐Small Cell Lung Cancer

Caspase-9 has two isoforms with opposing functions, pro-apoptotic caspase-9a (C9a) and anti-apoptotic caspase-9b (C9b). C9b expression has been reported to augment the anchorage-dependent growth and tumorigenic capacity of non-small cell lung cancer (NSCLC) cells; however, the mechanism of this biological observation was unknown. Herein for the first time, C9b is shown to have a dual function in regulating the survival/oncogenic nuclear factor κB (NF-κB) pathway, which is independent from modulating C9a activation. In particular, C9b is shown to activate the canonical arm and inhibit of the non-canonical arm of the NF-κB pathway by destabilizing NF-κB inhibitor alpha (IκB-α) and NF-κB-inducing kinase (NIK). Importantly, this new role for C9b contributes to the enhanced survival and anchorage-independent growth of NSCLC cells conferred by C9b expression. Further mechanistic studies demonstrated a direct association of C9b with the cellular inhibitor of apoptosis 1 (c-IAP1), a regulatory factor in both arms of the NF-κB network, via its IAP-binding motif (IBM). Through this interaction, C9b induces the E3 ligase activity of c-IAP1, which regulates NF-κB activation, and promotes the viability, anchorage-independent growth and tumorigenicity of NSCLC cells. Lastly, the link between C9b expression and NF-κB activation was validated in human NSCLC tumors. Overall, a novel tumorigenic mechanism has been identified by which alternative mRNA processing leads to generation of a protein isoform that regulates the NF-κB signaling independent of external agonist.

TAZ is a novel oncogene in non-small cell lung cancer

Transcriptional coactivator with PDZ-binding motif (TAZ) is a transcriptional coactivator involved in the differentiation of stem cell as well as the development of multiple organs. Recently, TAZ has also been identified as a major component of the novel Hippo-LATS tumor suppressor pathway and to function as an oncogene in breast cancer. We show for the first time that TAZ is an oncogene in non-small cell lung cancer (NSCLC). Our results show that TAZ is overexpressed in NSCLC cells and that lentivirus-mediated overexpression of TAZ in HBE135 immortalized human bronchial epithelial cells causes increased cell proliferation and transformation, which can be restored back to its original levels by knockdown of TAZ. In addition, short-hairpin RNA (shRNA)-mediated knockdown of TAZ expression in NSCLC cells suppresses their proliferation and anchorage-independent growth in vitro, and tumor growth in mice in vivo, which can be reversed by re-introduction of shRNA-resistant TAZ into TAZ-knockdown NSCLC cells. These results indicate that TAZ is an oncogene and has an important role in tumorigenicity of NSCLC cells. Therefore, TAZ may present a novel target for the future diagnosis, prognosis and therapy of lung cancer.

Ect2 links the PKCι–Par6α complex to Rac1 activation and cellular transformation

Protein kinase Cι (PKCι) promotes non-small cell lung cancer (NSCLC) by binding to Par6α and activating a Rac1-Pak-Mek1,2-Erk1,2 signaling cascade. The mechanism by which the PKCι-Par6α complex regulates Rac1 is unknown. Here we show that Ect2, a guanine nucleotide exchange factor (GEF) for Rho family GTPases, is coordinately amplified and overexpressed with PKCι in NSCLC tumors. RNAi-mediated knock down of Ect2 inhibits Rac1 activity and blocks transformed growth, invasion and tumorigenicity of NSCLC cells. Expression of constitutively active Rac1 (RacV12) restores transformation to Ect2-deficient cells. Interestingly, the role of Ect2 in transformation is distinct from its well-established role in cytokinesis. In NSCLC cells, Ect2 is mislocalized to the cytoplasm where it binds the PKCι-Par6α complex. RNAi-mediated knock down of either PKCι or Par6α causes Ect2 to redistribute to the nucleus, indicating that the PKCι-Par6α complex regulates the cytoplasmic localization of Ect2. Our data indicate that Ect2 and PKCι are genetically and functionally linked in NSCLC, acting to coordinately drive tumor cell proliferation and invasion through formation of an oncogenic PKCι-Par6α-Ect2 complex.