SBC-3 Cells Research Articles

EphA2 inhibition suppresses proliferation of small-cell lung cancer cells through inducing cell cycle arrest

Small-cell lung cancer (SCLC) is characterized by one of neuroendocrine tumors, and is a clinically aggressive cancer due to its rapid growth, early dissemination, and rapid acquisition of multidrug resistance to chemotherapy. Moreover, the standard chemotherapeutic regimen in SCLC has not changed for three decades despite of the dramatic therapeutic improvement in non-SCLC. The development of a novel therapeutic strategy for SCLC has become a pressing issue. We found that expression of Eph receptor A2 (EphA2) is upregulated in three of 13 SCLC cell lines and five of 76 SCLC tumor samples. Genetic inhibition using siRNA of EphA2 significantly suppressed the cellular proliferation via induction of cell cycle arrest in SBC-5 cells. Furthermore, small molecule inhibitors of EphA2 (ALW–II–41-27 and dasatinib) also exclusively inhibited proliferation of EphA2-positive SCLC cells by the same mechanism. Collectively, EphA2 could be a promising candidate as a therapeutic target for SCLC.

Dysfunction of Poly (ADP-Ribose) Glycohydrolase Induces a Synthetic Lethal Effect in Dual Specificity Phosphatase 22-Deficient Lung Cancer Cells.

Poly (ADP-ribose) glycohydrolase (PARG) is the main enzyme responsible for catabolism of poly (ADP-ribose) (PAR), synthesized by PARP. PARG dysfunction sensitizes certain cancer cells to alkylating agents and cisplatin by perturbing the DNA damage response. The gene mutations that sensitize cancer cells to PARG dysfunction-induced death remain to be identified. Here, we performed a comprehensive analysis of synthetic lethal genes using inducible PARG knockdown cells and identified dual specificity phosphatase 22 (DUSP22) as a novel synthetic lethal gene related to PARG dysfunction. DUSP22 is considered a tumor suppressor and its mutation has been frequently reported in lung, colon, and other tumors. In the absence of DNA damage, dual depletion of PARG and DUSP22 in HeLa and lung cancer A549 cells reduced survival compared with single-knockdown counterparts. Dual depletion of PARG and DUSP22 increased the apoptotic sub-G1 fraction and upregulated PUMA in lung cancer A549, PC14, and SBC5 cells, and inhibited the PI3K/AKT/mTOR pathway in A549 cells, suggesting that dual depletion of PARG and DUSP22 induced apoptosis by upregulating PUMA and suppressing the PI3K/AKT/mTOR pathway. Consistently, the growth of tumors derived from double knockdown A549 cells was slower compared with those derived from control siRNA-transfected cells. Taken together, these results indicate that DUSP22 deficiency exerts a synthetic lethal effect when combined with PARG dysfunction, suggesting that DUSP22 dysfunction could be a useful biomarker for cancer therapy using PARG inhibitors. SIGNIFICANCE: This study identified DUSP22 as a novel synthetic lethal gene under the condition of PARG dysfunction and elucidated the mechanism of synthetic lethality in lung cancer cells.

Abstract 766: Mutual negative regulation of EZH2 and miR-4448 for tumor progression via epithelial mesenchymal transition in small cell lung cancer

Abstract Enhancer of zeste homolog 2 (EZH2) is a catalytic component of polycomb repressive complexes, promotes tumor progression and metastasis. Expression levels of EZH2 are associated with clinical outcomes in a variety of tumors. High expression levels of EZH2 have been reported in cell lines and tissues of small cell lung cancer (SCLC), which is characterized by its invasiveness and metastatic potentials. Epithelial-mesenchymal transition (EMT) is well recognized to contribute to aggressiveness of SCLC, and microRNA (miRNA) is known to be associated with both EMT and the biological characteristics of SCLC. The aim of this study was to identify a novel miRNA defining EZH2-assciated EMT and tumor aggressiveness in SCLC. Immunohistochemistry and quantitative PCR showed that EZH2 expressions levels were decreased in three types of SCLC cell lines and tumor tissues from 34 patients with SCLC. Small interfering RNA (siRNA) against EZH2 suppressed its expression and EMT in SBC3 and SBC5 cell lines, both of which had high EZH2 expression levels as SCLC cell lines. Comprehensive miRNA expression analysis was used to compare changes of miRNA expression between EZH2 siRNA-transfected cells and mock-transfected cells. As a result, miR-4448 expression was significantly decreased in SBC3 and SBC5 cells transfected with EZH2 siRNA. Cell growth assay and cell invasion assay revealed that overexpression of miR-4448 inhibited cellular proliferation and invasion potential. Furthermore, we confirmed that overexpression of miR-4448 abrogated EMT and decreased EZH2 expression. In conclusion, EZH2 and miR-4448 mutually suppressed these expressions and functions, which was associated with tumor progression via EMT in SCLC. The findings of this study suggest that miR-4448 may play a crucial role in the biological characteristics of SCLC. Citation Format: Nobuyuki Koyama, Yuichi Ishikawa, Yuki Iwai, Kazutetsu Aoshiba, Hiroyuki Nakamura, Koichi Hagiwara. Mutual negative regulation of EZH2 and miR-4448 for tumor progression via epithelial mesenchymal transition in small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 766.

Abstract 4639: SLC7A11 expression confers cancer stem-like properties in small cell lung cancer cells

Abstract Small Cell Lung Cancer (SCLC) which accounts for 15 % of primary lung cancers is known to grow fast and metastasize easily to whole body at early stages. However, the standard care of SCLC has not been changed for over 10 years and effective treatment remains to be developed. System xc(-) comprises xCT (SLC7A11) and CD98hc subunits and is a major plasma membrane antiporter responsible for the cellular uptake of cystine in exchange for intracellular glutamate. Recently, we studied the impact of xCT inhibitor sulfasalazine (SSZ) in various cancers and found that SCLC cells manifest low level of xCT and are highly sensitive to SSZ treatment compared with non-small cell lines. Furthermore, we found that xCT expression in SCLC cells is regulated by the cellular density and the tumorsphere culture which is known to enhance the cancer stem cell properties also enhances the xCT expression in these cells. To examine the functional relevance of xCT expression to cancer stem-like properties in SCLC cells, we established the stably xCT-expressing SBC-5 cells (SBC5-xCT). Similar to other SCLC cell lines, parental SBC5 cells were not able to proliferate from single-cell level, however, SBC5-xCT cells were found to possess an ability to proliferate from single-cell level. Furthermore, SBC5-xCT cells manifested higher resistance to an anticancer agent cisplatin and higher ability of tumor-initiation than parental SBC5 cells. Our findings establish a new functional role for xCT in the promotion of cancer stem-like properties in SCLC cells. Citation Format: Shohei Kamenori, Kentaro Suina, Juntaro Yamasaki, Subaru Shintani, Yuji Otsuki, Yuki Hirata, Shogo Okazaki, Kenji Tsuchihashi, Oltea Sampetrean, Yoichiro Mitsuishi, Fumiyuki Takahashi, Kazuhisa Takahashi, Hideyuki Saya, Osamu Nagano. SLC7A11 expression confers cancer stem-like properties in small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4639.

Abstract 4509: Overexpression of CADM1 enhances malignant features of small-cell lung cancer

Abstract Small-cell lung cancer (SCLC) is one of the representative intractable cancers with the 5-year survival of less than 10 %. Novel approaches to the treatment of SCLC are required because recurrence arises inevitably after the initial chemotherapy. CADM1 was originally identified as a tumor suppressor of non-small cell lung cancer (NSCLC) which encodes a member of immunoglobulin superfamily cell adhesion molecules. CADM1 consists of an extracellular domain with three immunoglobulin-like loops, a trans-membrane domain and a short cytoplasmic domain containing a protein 4.1-binding motif (4.1BM) and a PDZ-II-binding motif. We have reported that CADM1 is highly expressed in 90% of human SCLC cell lines and promotes subcutaneous tumor formation of SCLC cells in nude mice. In this study, we performed clinicopathological evaluation of CADM1 in SCLC and analyzed the molecular mechanisms of malignant progression of SCLC by overexpressing CADM1. Firstly, we performed immunohistochemical analysis of CADM1 expression in high-grade neuroendocrine tumor (HGNEC) of the lung, including SCLC and large cell neuroendocrine carcinoma (LCNEC). We found that CADM1 protein was expressed in 75% (33/44) of SCLC tumors and correlated with the nodal involvement in lung HGENC. To understand pathological significance of CADM1 overexpression in SCLC, we introduced a full-length CADM1 and its mutants in the extracellular or intracellular domain into SCLC cells, SBC5, lacking endogenous CADM1 expression and assessed their malignant features in comparison with control SBC5 cells. CADM1 expression significantly enhanced colony formation in soft agar and subcutaneous tumor formation in nude mice of SBC5, whereas a mutant in 4.1BM did not. Then, we screened chemical library of 170 small molecules of known function to identify compounds which inhibit anchorage-independent growth of SCLC cells enhanced by CADM1. Inhibitors of PI3K, Akt and PKA significantly suppressed cell growth of SBC5, suggesting that CADM1 activates PI3K/Akt and PKA signaling pathways through its 4.1BM and promotes anchorage-independent growth of SCLC cells. We also found that orthotopic injection of NCI-N417 cells overexpressing CADM1 into the lung of nude mice significantly enhanced their metastasis to mediastinal lymph nodes. These results suggest that CADM1 enhances tumor growth and metastasis of SCLC cells probably by activating PI3K/Akt and PKA pathways through its binding proteins at 4.1BM. Citation Format: Toko Funaki, Takeshi Ito, Yoshinori Murakami. Overexpression of CADM1 enhances malignant features of small-cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4509.

Lung Cancer Derived Circulating miR-21 Promotes Bone Metastasis by Activating Differentiation of Monocytes to Osteoclasts

Background: Osteoclastogenesis is a key process in osteolytic bone metastasis (BM). Previous studies indicated that miRNAs could regulate cancer progression and osteoclastogenesis. Our purpose was to investigate the roles of lung cancer cells-derived circulating miR-21 on osteoclastogenesis and its clinical significance in BM patients. Methods: The difference of miRNA expression in two lung cancer cell lines SBC-5 (with characteristic BM ability) and SBC-3 (without BM ability) were analyzed. Circulating miR-21 levels of lung cancer patients with or without BM were compared. The effects of conditioned media from lung cancer cell lines or patients' plasma with different miR-21 levels on osteoclastogenesis were investigated. The diagnostic performance of circulating miR-21 in BM patients was evaluated. Findings: We found that miR-21 expression was specifically higher in SBC-5 than that in SBC-3 cells. The supernatants of SBC-5 cells with higher level miR-21 promoted osteoclastogenesis. Moreover, we demonstrated that the circulating miR-21 level was significantly higher in BM patients than that in non-BM patients. The plasma from BM patients with higher level miR-21 could also promot osteoclastogenesis. Mechanistically, lung cancer cells-derived circulating miR-21 could be transferred into osteoclast precursor cells and promot osteoclastogenesis probably by inhibiting PTEN (Phosphatase and tensin homologue). Finally, we indecated that circulating miR-21 had a potential for the diagnosis of BM. Interpretation: Our findings suggested circulating miR-21 played important roles in BM of lung cancer and may service as a biomarker to diagnose BM in lung cancer patients. Funding: This work was supported by grants from the National Natural Science Foundation of China (No. 81572639, 81770875, 81370969), Department of Science and Technology of Sichuan Province (2018SZ0142), and Sichuan University (2018SCUH0093). Declaration of Interest: No potential conflicts of interest were disclosed. Ethical Approval: The study was approved by the hospital research ethics committee of West China Hospital of Sichuan University and conducted in accordance with the International Ethical Guidelines for Biomedical Research Involving Human Subjects. All patients included in this study had signed the informed consent form.

Liprin-α4 as a New Therapeutic Target for SCLC as an Upstream Mediator of HIF1α.

Small-cell lung cancer (SCLC) remains one of deadliest types of cancers. Cis-diamminedichloroplatinum (CDDP) is a key chemotherapeutic agent for SCLC, however, its therapeutic effect is limited. Recently, hypoxia in the cancer microenvironment has been suggested to influence the effect of cancer therapy. Using small interfering RNA inhibition of leukocyte common antigen-related interacting protein alpha 4 (liprin-α4), and of hypoxia-inducible factor (HIF)-1α, proliferation, invasion, migration and chemosensitivity were investigated in SBC-5 SCLC cells, under normoxia and hypoxia. Liprin-α4 was found to contribute to proliferation, but not migration and invasion of SBC-5 cells both under normoxia and hypoxia. Inhibition of liprin-α4 increased chemosensitivity of SBC-5 cells under hypoxia. Liprin-α4 signaling occurs through mitogen-activated protein kinase pathways via activation of HIF1α expression. Inhibition of HIF1α reduced proliferation and increased chemosensitivity of SBC-5 cells under hypoxia. Liprin-α4 inhibition may enhance the effect of CDDP and liprin-α4 might be a novel therapeutic target in SCLC.

RBPJ and MAML3: Potential Therapeutic Targets for Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is still a deadly type of cancer for which there are few effective therapeutic strategies. Development of a new molecule targeting agent is urgently desired. Previously we showed that recombination signal binding protein for immunoglobulin-kappa-J region (RBPJ) and mastermind-like 3 (MAML3) are new therapeutic targets for pancreatic cancer. In the present study, we analyzed whether RBPJ/MAML3 inhibition could also be a new therapeutic strategy for SCLC. Using silencing of RBPJ/MAML3, proliferation, invasion, migration and chemosensitivity of SBC-5 cells were investigated. RBPJ/MAML3 inhibition reduced Smoothened and HES1 expression, suggesting that RBPJ/MAML3 signaling was through Hedgehog and NOTCH pathways. In the analysis of cell functions, RBPJ/MAML3 inhibition significantly reduced proliferation and invasiveness via reduction of expression of matrix metalloproteinases. On the other hand, RBPJ/MAML3 inhibition also reduced chemosensitivity to cis-diamminedichlo-roplatinum and gemcitabine. These results suggest that RBPJ and MAML3 could be new therapeutic targets for SCLC, however, chemosensitivity may be reduced in combinational use with other chemo-therapeutic agents.

Biological effects of BMP7 on small-cell lung cancer cells and its bone metastasis

Small-cell lung cancer(SCLC) is typically fatal if untreated. It is characterized by early and widespread metastases, and has the ability to rapidly develop resistance to chemotherapy. Bone morphogenetic protein7(BMP7), a member of the BMP family of signaling molecules, has been implicated in various types of cancer, particularly prostate cancer and breast cancer. However, there is little knowledge of the function of BMP7 in SCLC. The aim of the present study was to investigate the biological function of recombinant human (rh)BMP7 on SCLC cells and the underlying molecular basis for this regulatory mechanism. The effect of rhBMP7 on SCLC cell lines and associated signaling pathways was investigated. Results suggested that rhBMP7 significantly inhibited the proliferation, motility and invasion of SBC-3 and SBC-5 cells. However, rhBMP7 exhibited no effect on the apoptosis of SBC-5 cells, but promoted apoptosis of SBC-3 cells. Furthermore, cell cycle analysis revealed that rhBMP7 was able to increase the proportion of cells in G1phase and decrease the S phase proportion. Total and membrane BMP receptor(BMPR)IA and BMPRIB were highly expressed in SBC-5 cells, whereas cytoplasmic BMPRIA and BMPRIB expression was higher in SBC-3 cells. However, activinA receptor typeI expression was higher in SBC-3 cells in total and cytoplasmic proteins. Furthermore, following stimulation with rhBMP7, Smad2, Smad4 and p21 were downregulated. We hypothesized that rhBMP7 inhibited the progressiveness of SCLC cells by inducing G1phase arrest and inhibiting Sphase entry. The results of the present study indicated that BMP7 serves a key function in regulating the progression of SCLC.

Effects of DKK1 overexpression on bone metastasis of SBC-3 cells.

Among all malignancies, lung cancer is the leading cause of cancer-related deaths in China. Bone metastasis is one of the most common complications and one of the most important factors affecting the prognosis of lung cancer patients, which resulting in very poor therapeutic effects. Previously, we have demonstrated that the expression levels of Dickkopf1 (DKK1), a protein involved in cell regulation and proliferation, was dramatically higher in cells that have a tendency to metastasize and invade the bone tissue (SBC-5 cells) compared with cells that do not (SBC-3 cells). Downregulation of DKK1 in SBC-5 cells inhibited cell malignancy in vitro, and the formation of bone metastasis in vivo. However, whether upregulating DKK1 would be sufficient to induce aggressive tumor behavior (proliferation, migration, invasion and metastasis) in SBC-3 cells remained to be investigated. The present study aimed to examine the role of DKK1 in SBC-3 cells, as well as to investigate the SBC-3 ability to metastasize and invade the bone tissue. The results demonstrated that upregulation of DKK1 in SBC-3 cells enhanced cell proliferation, colony formation, cell migration and invasion in vitro, as well as bone metastasis in vivo. These results indicate that DKK1 may be an important regulator in the development of small cell lung cancer (SCLC), and targeting DKK1 may be an effective method for preventing and/or treating skeletal metastases in SCLC cases.

Hedgehog Inhibition Upregulates TRK Expression to Antagonize Tumor Suppression in Small Cell Lung Cancer Cells.

Previously we have shown that tropomyosin-related kinase B (TRKB) and Hedgehog (Hh) signalling pathways induce malignant phenotypes in many cancer types. However, results from small cell lung cancer (SCLC) clinical trials using TRK and Hh inhibitors have been disappointing. One reason for this may be the existence of crosstalk between TRKB and Hh signalling pathways. In this study, we detected negative crosstalk between the TRKB and Hh-GLI1 signalling pathways. The human small cell lung carcinoma cell line, SBC-5, was used. Using small interfering RNA to inhibit TRKB and Hh signalling, whether TRKB and Hh signaling contribute to proliferation and invasiveness in SBC-5 cells were investigated. TRKB expression in GLI1 siRNA-transfected SBC-5 cells was higher than that of control cells. GLI1-knockdown alone did not affect invasiveness of SBC-5 cells. However, combined knockdown of TRKB and GLI1 significantly decreased invasiveness. Moreover, combined TRKB and GLI1 knockdown inhibited proliferation and migration to a greater extent than when either was inhibited alone. These results suggest that Hh inhibition increases TrkB expression to counter tumor suppression in SBC-5 cells. The combined use of TRKB and Hh inhibitors may, therefore, be useful for the treatment of refractory SCLC.

RETRACTED: Effects of lentivirus-mediated silencing of Periostin on tumor microenvironment and bone metastasis via the integrin-signaling pathway in lung cancer

The study aims to investigate the effects of Periostin gene silencing on tumor microenvironment and bone metastasis via the integrin-signaling pathway in lung cancer (LC). LC patients were divided into bone metastasis and non-bone metastasis groups; Healthy volunteers were selected as normal group. ELISA was performed to detect serum Periostin levels and plasma calcium ion concentration. SBC-5 cells were assigned into blank group (without transfection), negative control (NC) group (transfected with empty plasmid), si-Periostin group (transfected with si-Periostin plasmid), si-Integrin-αvβ3 group (transfected with Integrin-αvβ3 siRNA plasmid) and si-Periostin+si-Integrin-αvβ3 group (transfected with si-Periostin and si-Integrin-αvβ3 plasmid). qRT-PCR and Western blotting were performed to determine mRNA and protein expression of Periostin, metastasis-associated factors of tumor microenvironment and integrin signaling pathway-related proteins. CCK-8, scratch test and transwell assay were applied to detect cell proliferation, migration and invasion respectively. Nude mouse models of LC bone metastasis were established. TRAP Staining was employed to measure the number of osteoclasts. Bone metastasis group exhibited higher levels of Periostin compared to normal and non-bone metastasis groups. Si-Periostin, si-Integrin-αvβ3 and si-Periostin+si-Integrin-αvβ3 groups showed decreased Periostin expression, proliferation rate, migration distance, invasive cells, and expressions of metastasis-associated factors of tumor microenvironment and integrin signaling pathway-related proteins compared to blank and NC groups. Similarly, number of osteoclasts and expression of integrin signaling pathway-related proteins were decreased, and bone injury and calcium ion concentration were reduced. The study demonstrated that down-regulation of Periostin expression modulated tumor microenvironment and inhibited bone metastasis by blocking integrin-signaling pathway in LC.

The effect of RCAN1 on the biological behaviors of small cell lung cancer.

Bone is the third most common site of cancer metastasis. In total, 30%-40% of lung cancer cases can develop skeletal metastasis for which no effective therapy in clinic is available. RCAN1 (regulator of calcineurin 1) is an important regulator in angiogenesis which is vital to tumor growth. In this study, we investigated the changes of biological behaviors in SBC-5 and SBC-3 cells after the RCAN1 expression level was changed. Briefly, overexpression of RCAN1 significantly attenuated their malignancy, including decreased ability of proliferation, colony formation, migration, invasion, and bone adherence. Furthermore, the cell cycle progression was impeded. Although the opposite changes were observed in SBC-3 cells after the RCAN1 expression was suppressed by RNA interference, the apoptosis rate was not affected by the expression level of RCAN1 in these cells. So, our research revealed that RCAN1 was involved in the development of small cell lung cancer, and it might be a cancer-inhibiting gene for the formation of bone metastases in small cell lung cancer.

The Biological Effects of Dickkopf1 on Small Cell Lung Cancer Cells and Bone Metastasis.

The bone is among the most common sites of metastasis in patients with lung cancer. Over 30%–40% of lung cancers can develop bone metastasis, and no effective therapeutic methods exist in clinic cases. Wnt/β-catenin signaling and Dickkopf1 (DKK1) play important roles in the progression of lung cancer, which preferentially metastasizes to the skeleton. However, the role of DKK1 in osteotropism of small cell lung cancer (SCLC) remains to be elucidated. This study aimed to define the role of DKK1 in SCLC bone metastasis and investigate the underlying mechanisms. Our results demonstrated that the expression level of DKK1 was dramatically higher in bone metastatic SCLC cells (SBC-5 cell line) compared with that in cells without bone metastatic ability (SBC-3 cell line). Therefore, we hypothesized that DKK1 was involved in the bone metastasis of SCLC. We then suppressed the DKK1 expression in SBC-5 cells by RNAi and found that downregulation of DKK1 can inhibit cell proliferation, colony formation, cell migration, and invasion, but increase the apoptosis rate. Downregulation of DKK1 did not affect the cell cycle progression of SBC-5 cells in vitro. In vivo, downregulated DKK1 in SBC-5 cells resulted in attenuated bone metastasis. These results indicated that DKK1 may be an important regulator in bone metastases of SCLC, and targeting DKK1 may be an effective method to prevent and treat skeleton metastases in SCLC cases.

Abstract 4763: Targeted therapy by MET inhibitors against small-cell lung cancer with aberrant activation of HGF/MET pathway

Abstract Small-cell lung cancer (SCLC) is one of the most aggressive malignancy, characterized by rapid growth and metastatic spread to multiple organs. Approximately 70% of SCLC patients have distant metastases at the diagnosis. Recent studies reported some genomic aberrations in SCLC and several molecular target drugs have been evaluated in clinical trials. However, no molecular target agents have been approved yet for SCLC. Hepatocyte growth factor (HGF), also known as scatter factor, is only one ligand for MET receptor. HGF/MET pathway plays the crucial role in the growth of various types of cancers. The purpose of this study is to examine the role of HGF/MET pathway activation in SCLC and to evaluate therapeutic potential of MET inhibitors, including crizotinib and golvatinib, against metastasized SCLC. We used eight human SCLC cell lines. Expression of HGF and MET was evaluated by ELISA and western blot, respectively. Cell viability was examined by MTT assay. Four cell lines produced discernible levels of HGF and four cell lines expressed phosphorylated MET, respectively. MET inhibitors, crizotinib and golvatinib, remarkably inhibited the viability of three cell lines, SBC-5, DMS273 and DMS273B1. Knockdown of either MET or HGF by specific siRNA suppressed the growth of these cell lines, indicating that HGF/MET pathway activation is essential for survival of these SCLC cell lines. These observations suggest that MET-TKIs may be useful for a subset of SCLC with aberrant HGF/MET pathway activation. We recently established in vivo imaging model of multiple organ metastasis (including liver and bone metastases) with SBC-5 cells. We are now evaluating the anti-metastatic effect of MET-TKIs, crizotinib and golvatinib, in the in vivo imaging model. At the annual meeting, we will present the results of MET-TKI treatment and discuss their potential against multiple-organ metastasis produced by SCLC with aberrant HGF/MET pathway activation. Citation Format: Hirokazu Taniguchi, Shinji Takeuchi, Koji Fukuda, Tadaaki Yamada, Shuichi Sakamoto, Manabu Kawada, Seiji Yano. Targeted therapy by MET inhibitors against small-cell lung cancer with aberrant activation of HGF/MET pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4763.

M3 Muscarnic Receptor Antagonist Mediates Cell Proliferation Apoptosis and Adhesion in Small Cell Lung Cancer

背景与目的研究表明毒蕈碱胆碱受体3（muscarinic receptor 3, M3R）在多种肿瘤的发生、发展中发挥重要的作用。本研究旨在探讨M3R在人小细胞肺癌（small cell lung cancer, SCLC）细胞株SBC3的表达，M3R拮抗剂对细胞增殖、凋亡及粘附的影响。方法体外培养SBC3细胞，RT-PCR和Western blot检测M3R的表达。MTT法及流式细胞法检测M3R拮抗剂（4-diphenylacetoxy-N-methylpiperidine methiodide, 4-DAMP）对细胞增殖和凋亡的影响。流式细胞法检测细胞整合素的表达及碘化乙酰胆碱（acetylcholine iodide, Ach）和4-DAMP对整合素表达的影响。纤维结合蛋白（Fn）包被的96孔板用以研究Ach、4-DAMP及整合素抗体对细胞粘附的作用。结果SBC3细胞表达M3R，4-DAMP浓度依懒性抑制细胞增殖。与对照组比较，10-4 M 4-DAMP能够明显地增加SBC3细胞凋亡。SBC3细胞表达αvβ1和α5β1整合素，10-4 M Ach刺激细胞粘附（P＜0.01）的作用几乎被10-5 M 4-DAMP、5 μg/mL抗-β1抗体或抗-αv和α5抗体完全阻断（P＜0.01），但Ach及4-DAMP不影响αv、α5和β1的表达水平。结论SBC3细胞表达M3R，M3R拮抗剂能抑制细胞的增殖并促进凋亡。其抑制粘附的作用是通过抑制细胞含β1的整合素（αvβ1和α5β1）的功能实现的。

Organ‐specific efficacy of HSP90 inhibitor in multiple‐organ metastasis model of chemorefractory small cell lung cancer

Small-cell lung cancer (SCLC) accounts for nearly 15% of lung cancer cases and exhibits aggressive clinical behavior characterized by rapid growth and metastatic spread to multiple organs. About 70% of patients with SCLC present with extensive disease and distant metastases at diagnosis. HSP90 is a 90-kDa molecular chaperone whose association is required for the stability and function of its numerous "client proteins." Here, we assessed the therapeutic potential of the HSP90 inhibitor 17-DMAG in SCLC. Notably, 17-DMAG hindered the viability of human SCLC cell lines-regardless of their chemosensitivity-via the decreased expression of client proteins, including the proto-oncogene c-Raf (also known as RAF1). In an in vivo imaging model of SCLC multiple-organ metastasis with the human SCLC cell line SBC-5, treatment with 17-DMAG remarkably inhibited the formation of metastatic sites in the liver, but was ineffective in hindering the progression of bone lesions. The latter was likely the result of activation of osteoclasts. IGF-1, which is supposed to be rich in bone environment, preserved c-Raf expression and maintained viability of SBC-5 cells treated with 17-DMAG. Furthermore, the combined use of a bisphosphonate with 17-DMAG significantly attenuated the progression of metastases in both the liver and the bone. These findings suggest that therapeutic effects of HSP90 inhibitors may be organ-specific and should be carefully monitored in SCLC clinical trials.

Abstract 1323: Both programmed cell death protein 1 and programmed death-ligand 1 molecules can be expressed on the cell surface of small-cell lung cancer

Abstract Background: Programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1) play a major role in suppressing the immune system by forming the PD-1/PD-L1 complex, which transmits an inhibitory signal to reduce T-cell activity. PD-L1 is often expressed in various malignant tumors. On the other hand, PD-1 is generally observed in activated lymphocytes and myeloid-derived dendritic cells. Of the malignant cells, only Jurkat cells (under special conditions) and angioimmunoblastic T-cell lymphoma tissue cells express PD-1 on their surface. Purpose: To clarify whether PD-1/PD-L1 complex participates in the immunotolerance on small-cell lung cancer (SCLC) cells. Materials and methods: We examined the expression levels of PD-1 and PD-L1 on the cell surface of SCLC cell lines using flowcytometry and reverse transcription polymerase chain reaction. Subsequently, the soluble PD-L1 (sPD-L1) concentration was measured using enzyme-linked immunosorbent assay, and the cell growth inhibitory effect of IFN-γ was determined by direct cell counting using a hemocytometer and Trypan blue staining. Results: Among the four SCLC cell lines examined, only SBC-3 cells expressed both PD-1 and PD-L1. The sPD-L1 concentrations in culture medium gradually increased according to cell growth. Although IFN-γ alone inhibited the growth of SBC-3 cells, PD-L1 expression on the cell surface was not induced by IFN-γ. Conclusions: We demonstrated that both PD-1 and PD-L1 molecules are co-expressed on the surface of SCLC cells. Although the biological implications of this remain unclear, we speculate that PD-1 and its ligand on the SCLC cells may participate in the growth inhibition of tumor cells as is reported in cytotoxic T cells. Citation Format: Hiromichi Yamane, Hideko Isozaki, Nobuaki Ochi, Kenichiro Kudo, Yoshihiro Honda, Tomoko Yamagishi, Toshio Kubo, Katsuyuki Kiura, Nagio Takigawa. Both programmed cell death protein 1 and programmed death-ligand 1 molecules can be expressed on the cell surface of 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 1323. doi:10.1158/1538-7445.AM2015-1323

Notch1 controls cell chemoresistance in small cell lung carcinoma cells.

Small cell lung carcinoma (SCLC) is characterized by a high rate of relapse and failure of chemotherapy because of the emergence of drug resistant cells. Notch signaling controls carcinogenesis in several human malignancies and could be involved in the resistance of cells to several chemotherapeutic agents. Herein, we analyzed the role of Notch1 signaling in the resistance of human SCLC cells to doxorubicin. Small interfering ribonucleic acid technology was used to knock down (KD) Notch1 in H69AR and SBC-3 SCLC cells. We detected the effect of inhibiting Notch1 on the expression of drug resistant related molecules: multidrug resistance-associated protein (MRP-1) and anti-apoptotic factor B-cell lymphoma-2, as well as to cell adhesion molecule E-cadherin, which contributes to the adhesion of SCLC cells to the extracellular matrix and confers chemoresistance in a process known as cell adhesion-mediated drug resistance (CAM-DR). We also observed the effect of KD Notch1 on cell survival under high concentrations of doxorubicin treated media. H69AR and SBC-3 cells expressed Notch1 protein and grew as adherent aggregates, which confer resistance to high concentrations of doxorubicin. On inhibiting Notch1, we observed activation of the apoptotic pathway in cells, possibly resulting from the loss of CAM-DR and, thus, SBC-3 cells showed a loss of chemoresistant ability. However, in H69AR cells with KD Notch1, the expression of MRP-1 was increased and, thus, sustained the chemoresistant ability of cells. The Notch1 signaling pathway is involved in mediating the drug resistance phenotype of SCLC cells.

Control of the MYC-eIF4E axis plus mTOR inhibitor treatment in small cell lung cancer.

BackgroundMammalian target of rapamycin (mTOR) inhibitors have anti-tumor effects against renal cell carcinoma, pancreatic neuroendocrine cancer and breast cancer. In this study, we analyzed the antitumor effects of mTOR inhibitors in small cell lung cancer (SCLC) cells and sought to clarify the mechanism of resistance to mTOR inhibitors.MethodsWe analyzed the antitumor effects of three mTOR inhibitors including everolimus in 7 SCLC cell lines by MTS assay. Gene-chip analysis, receptor tyrosine kinases (RTK) array and Western blotting analysis were performed to identify molecules associated with resistance to everolimus.ResultsOnly SBC5 cells showed sensitivity to everolimus by MTS assay. We established two everolimus resistant-SBC5 cell lines (SBC5 R1 and SBC5 R10) by continuous exposure to increasing concentrations of everolimus stepwise. SPP1 and MYC were overexpressed in both SBC5 R1 and SBC5 R10 by gene-chip analysis. High expression levels of eukaryotic translation initiation factor 4E (eIF4E) were observed in 5 everolimus-resistant SCLC cells and SBC5 R10 cells by Western blotting. MYC siRNA reduced eIF4E phosphorylation in SBC5 cells, suggesting that MYC directly activates eIF4E by an mTOR-independent bypass pathway. Importantly, after reduction of MYC or eIF4E by siRNAs, the SBC5 parent and two SBC5-resistant cells displayed increased sensitivity to everolimus relative to the siRNA controls.ConclusionThese findings suggest that eIF4E has been shown to be an important factor in the resistance to everolimus in SCLC cells. Furthermore, a link between MYC and mTOR-independent eIF4E contribute to the resistance to everolimus in SCLC cells. Control of the MYC-eIF4E axis may be a novel therapeutic strategy for everolimus action in SCLC.