Targeting the epigenetic processes to enhance antitumor immunity in small cell lung cancer.

Dysregulation of the epigenetic processes, such as DNA methylation, histone modifications, and modulation of chromatin states, drives aberrant transcription that promotes initiation and progression of small cell lung cancer (SCLC). Accumulating evidence has proven crucial roles of epigenetic machinery in modulating immune cell functions and antitumor immune response. Epigenetics-targeting drugs such as DNA methyltransferase inhibitors, histone deacetylase inhibitors, and histone methyltransferase inhibitors involved in preclinical and clinical trials may trigger antitumor immunity. Herein, we summarize the impact of epigenetic processes on tumor immunogenicity and antitumor immune cell functions in SCLC. Furthermore, we review current clinical trials of epigenetic therapy against SCLC and the mechanisms of epigenetic inhibitors to boost antitumor immunity. Eventually, we discuss the opportunities of developing therapeutic regimens combining epigenetic agents with immunotherapy for SCLC.

PD-L1 upregulation promotes drug-induced pulmonary fibrosis by inhibiting vimentin degradation.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with high mortality and limited therapeutic options. The immune checkpoint PD1/PD-L1 axis is related to the pathogenesis of pulmonary fibrosis, and upregulated expression levels of PD-L1 have been demonstrated in IPF patients. However, the mechanism of PD-L1 in pulmonary fibrosis is not fully understood. Here, we demonstrated upregulated expression of PD-L1 in fibrotic lung tissues and sera of IPF patients. Bleomycin (BLM) treatment induced PD-L1 upregulation, EMT (Epithelial-Mesenchymal Transition) and fibrosis-like morphology changes in human pulmonary alveolar epithelial cells (HPAEpiCs). Silencing PD-L1 attenuated BLM-induced EMT and fibrosis-like morphology changes in HPAEpiCs. In addition, we identified that PD-L1 directly binds to vimentin and inhibits vimentin ubiquitination, thereby increasing vimentin levels in HPAEpiCs. Silencing of vimentin inhibited BLM- and PD-L1-induced fibrosis in HPAEpiCs. The correlation between PD-L1 and EMT or vimentin expression was further confirmed in clinical samples and animal models. Finally, we used BLM- and paraquat-induced pulmonary fibrosis animal models to confirm the anti-pulmonary fibrosis effects of PD-L1 silencing. Taken together, our findings suggest that upregulated PD-L1 stimulates EMT of alveolar epithelial cells by increasing vimentin levels by inhibiting vimentin ubiquitination, thereby contributing to pulmonary fibrosis.

PD-L1P146R is prognostic and a negative predictor of response to immunotherapy in gastric cancer.

Cancer cells evade immune detection via programmed cell death 1/programmed cell death-ligand 1 (PD-1/PD-L1) interactions that inactivate T cells. PD-1/PD-L1 blockade has become an important therapy in the anti-cancer armamentarium. However, some patients do not benefit from PD-1/PD-L1 blockade despite expressing PD-L1. Here, we screened 101 gastric cancer (GC) patients at diagnosis and 141 healthy control subjects and reported one such subpopulation of GC patients with rs17718883 polymorphism in PD-L1, resulting in a nonsense P146R mutation. We detected rs17718883 in 44% of healthy control subjects, and rs17718883 was associated with a low susceptibility to GC and better prognosis in GC patients. Structural analysis suggests that the mutation weakens the PD-1:PD-L1 interaction. This was supported by co-culture experiments of T cells, with GC cells showing that the P146R substitution results in interferon (IFN)-γ secretion by T cells and enables T cells to suppress GC cell growth. Similar results with animal gastric tumor models were obtained in vivo. PD-1 monoclonal antibody treatment did not enhance the inhibitory effect of T cells on GC cells expressing PD-L1P146Rin vitro or in vivo. This study suggests that rs17718883 is common and may be used as a biomarker for exclusion from PD-1/PD-L1 blockade therapy.

miR-491 Inhibits Osteosarcoma Lung Metastasis and Chemoresistance by Targeting αB-crystallin.

Dysregulated microRNAs (miRNAs) play an important role in osteosarcoma (OS) progression. In the present study, we investigate the clinical significance of serum miR-491 level and the potential role of miR-491 in OS lung metastasis and chemoresistance. Clinical data show that the level of miR-491 was decreased in serum from OS patients compared with healthy control subjects, and that a decreased serum miR-491 level is correlated with increased metastasis, poor chemoresponse, and lower survival rate in OS patients. In vitro and in vivo experiments show that overexpression of miR-491 suppresses OS cell lung metastasis, whereas it enhances cisplatin (CDDP)-induced tumor growth inhibition and apoptosis. In contrast, inhibition of miR-491 stimulates OS cell lung metastasis and suppresses CDDP-induced tumor growth inhibition and apoptosis. Furthermore, we demonstrate that miR-491 exerts its role by directly targeting αB-crystallin (CRYAB) in OS. Our findings suggest that serum level of miR-491 has potential as a biomarker for predicting OS progression and prognosis of OS patients. Additionally, restoration of miR-491 may be a novel strategy for inhibiting OS lung metastasis and overcoming OS cell resistance to chemotherapy.

miR-382 inhibits osteosarcoma metastasis and relapse by targeting Y box-binding protein 1.

Lung metastasis and relapse in osteosarcoma (OS) patients indicate poor prognosis. Here, we identified significantly decreased expression of miR-382 in highly metastatic OS cell lines and relapsed OS samples compared to their parental cell lines and primary OS samples, respectively. In addition, our clinical data showed that the miR-382 expression level was inversely associated with relapse and positively associated with metastasis-free survival in OS patients. The overexpression of miR-382 suppressed epithelial-mesenchymal transition (EMT) and metastasis. This overexpression also decreased the cancer stem cell (CSC) population and function in OS cells. In contrast, inhibition of miR-382 stimulated EMT and metastasis and increased CSC population in OS cells. In addition, our in vivo experiments showed that the overexpression of miR-382 inhibited CSC-induced tumor formation, and the combination of miR-382 with doxorubicin prevented disease relapse in OS patients. Furthermore, we demonstrated that miR-382 exerted its tumor-suppressing potential by directly targeting Y box-binding protein 1 (YB-1) in OS. Taken together, our findings suggest that miR-382 functions as a tumor suppressor function and that the overexpression of miR-382 is a novel strategy to inhibit tumor metastasis and prevent CSC-induced relapse in OS.

MicroRNA miR-214 regulates ovarian cancer cell stemness by targeting p53/Nanog.

Previous studies have shown aberrant expression of miR-214 in human malignancy. Elevated miR-214 is associated with chemoresistance and metastasis. In this study, we identified miR-214 regulation of ovarian cancer stem cell (OCSC) properties by targeting p53/Nanog axis. Enforcing expression of miR-214 increases, whereas knockdown of miR-214 decreases, OCSC population and self-renewal as well as the Nanog level preferentially in wild-type p53 cell lines. Furthermore, we found that p53 is directly repressed by miR-214 and that miR-214 regulates Nanog through p53. Expression of p53 abrogated miR-214-induced OCSC properties. These data suggest the critical role of miR-214 in OCSC via regulation of the p53-Nanog axis and miR-214 as a therapeutic target for ovarian cancer.

Downregulation of pro-surfactant protein B contributes to the recurrence of early-stage non-small cell lung cancer by activating PGK1-mediated Akt signaling.

Recurrence is one of the main causes of treatment failure in early-stage non-small cell lung cancer (NSCLC). However, there are no predictors of the recurrence of early-stage NSCLC, and the molecular mechanism of its recurrence is not clear. In this study, we used clinical sample analysis to demonstrate that low levels of expression of precursor surfactant protein B (pro-SFTPB) in primary NSCLC tissue compared to their adjacent tissues are closely correlated with recurrence and poor prognosis in early-stage NSCLC patients. In vitro and in vivo experiments showed that downregulation of pro-SFTPB expression activates the Akt pathway by upregulating PGK1, which promotes metastasis and tumorigenicity in NSCLC cells. We then demonstrated that pro-SFTPB suppresses the formation of the ADRM1/hRpn2/UCH37 complex by binding to ADRM1, which inhibits PGK1 deubiquitination, thus accelerating ubiquitin-mediated PGK1 degradation. In summary, our findings indicate that low expression of pro-SFTPB in primary NSCLC compared to their adjacent tissue has potential as a predictor of recurrence and poor prognosis in early-stage NSCLC. Mechanistically, downregulation of pro-SFTPB attenuates inhibition of ADRM1-deubiquitinated PGK1, resulting in elevated levels of PGK1 protein; this activates the Akt pathway, ultimately leading to the progression of early-stage NSCLC.

SAMD9 Promotes Postoperative Recurrence of Esophageal Squamous Cell Carcinoma by Stimulating MYH9-Mediated GSK3ß/ß-Catenin Signaling.

Recurrence is a challenge to survival after the initial treatment of esophageal squamous cell carcinoma (ESCC). But, its mechanism remains elusive and there are currently no biomarkers to predict postoperative recurrence. Here, the possibility of sterile alpha motif domain-containing protein 9 (SAMD9) as a predictor of postoperative recurrence of ESCC is evaluated and the molecular mechanisms by which SAMD9 promotes ESCC recurrence are elucidated. The authors found that the high level of SAMD9 is correlated with postoperative recurrence and poor prognosis of ESCC. Overexpression of SAMD9 promotes tumor stemness, angiogenesis, and EMT, while downregulation of SAMD9 reduced these phenotypes. Mechanistically, it is found that SAMD9 stimulated ubiquitination-mediated glycogen synthase kinase-3 beta (GSK-3ß) degradation by interaction with myosin-9 (MYH9) and TNF receptor-associated factor 6 (TRAF6), which in turn activated Wnt/ß-catenin pathway. Further, the authors demonstrated that silencing SAMD9 inhibited lung metastasis and tumor formation in vivo. Finally, the authors found that silencing MYH9 or ß-catenin, or overexpressing GSK-3ß inhibited SAMD9-stimulated ESCC cell stemness, EMT, angiogenesis, metastasis, and tumorigenicity. Together, the findings indicate that the SAMD9/MYH9/GSK3ß/ß-catenin axis promotes ESCC postoperative recurrence and that SAMD9 is a crucial target for ESCC therapy. Additionally, SAMD9 has the potential as a predictor of postoperative recurrence in ESCC.

CXCR4 knockdown enhances sensitivity of paclitaxel via the PI3K/Akt/mTOR pathway in ovarian carcinoma.

Epithelial ovarian cancer (EOC) is the deadliest gynecological malignancy. EOC control remains difficult, and EOC patients show poor prognosis regarding metastasis and chemotherapy resistance. The aim of this study was to estimate the effect of CXCR4 knockdown-mediated reduction of cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) stemness and enhancement of chemotherapy sensitivity in EOC. Mechanisms contributing to these effects were also explored. Our data showed distinct contribution of CXCR4 overexpression by dependent PI3K/Akt/mTOR signaling pathway in EOC development. CXCR4 knockdown resulted in a reduction in CSCs and EMT formation and enhancement of chemotherapy sensitivity in tumor cells, which was further advanced by blocking CXCR4-PI3K/Akt/mTOR signaling. This study also documented the critical role of silencing CXCR4 in sensitizing ovarian CSCs to chemotherapy. Thus, targeting CXCR4 to suppress EOC progression, specifically in combination with paclitaxel (PTX) treatment, may have clinical application value.

Proteomic analysis of endogenous conjugated linoleic acid biosynthesis in lactating rats and mouse mammary gland epithelia cells (HC11).

This study was conducted to investigate the amount of CLA synthesized endogenously by rat mammary tissues in response to TVA (a precursor for cis-9, trans-11 CLA endogenous synthesis) treatment as well as the differences in the protein expression of genes encoding the biosynthesis of CLA in rat mammary tissue and mouse mammary gland epithelia cells (HC11). Treatment with TVA resulted in improved CLA productivity. Furthermore, 2-DE revealed two spots in samples of mammary tissues and one spot in samples of mammary gland epithelia cells (HC11) that were consistently altered in the TVA treatment groups when compared with the control group (non-fatty acid). The mRNA expression patterns of three of the proteins (PDI, PRDX2, LAMR1), as measured by real-time PCR, were similar to the pattern of protein abundance. In addition, the expression of SCD mRNA in the mammary tissue of rats and HC11 cell treated with TVA was higher than in the control group. Our results suggest that the identified proteins may be related to CLA biosynthesis in mammary tissue.

Inhibiting the redox function of APE1 suppresses cervical cancer metastasis via disengagement of ZEB1 from E-cadherin in EMT.

BACKGROUND: Metastasis is a major challenge in cervical cancer treatment. Previous studies have shown that the dual functional protein apurinic/apyrimidinic endonuclease 1 (APE1) promotes tumor metastasis and is overexpressed in cervical cancer. However, the biological role and mechanism of APE1 in cervical cancer metastasis have rarely been studied. METHODS: We used gene set enrichment analysis (GSEA) to determine the APE1-related signaling pathways in cervical cancer. To investigate the role and mechanism of APE1 in cervical cancer metastasis and invasion, immunohistochemistry, immunofluorescence, western blotting, secondary structure prediction, coimmunoprecipitation, luciferase reporter, and electrophoretic mobility shift assays were performed. The inhibitory effects of the APE1 redox function inhibitor APX3330 on cervical cancer metastasis were evaluated using animal models. RESULTS: Clinical data showed that high expression of APE1 was associated with lymph node metastasis in cervical cancer patients. GSEA results showed that APE1 was associated with epithelial to mesenchymal transition (EMT) in cervical cancer. Ectopic expression of APE1 promoted EMT and invasion of cervical cancer cells, whereas inhibition of APE1 suppressed EMT and invasion of cervical cancer cells in a redox function-dependent manner. Notably, APE1 redox function inhibitor APX3330 treatment dramatically suppressed cervical cancer cell lymph node and distant metastasis in vivo. Furthermore, we found that APE1 enhanced the interaction between ZEB1 and the E-cadherin promoter by binding to ZEB1, thereby suppressing the expression of E-cadherin, a negative regulator of EMT. CONCLUSION: Our findings help to elucidate the role played by APE1 in cervical cancer metastasis and targeting APE1 redox function may be a novel strategy for inhibiting cervical cancer metastasis.

Low dietary inorganic phosphate stimulates lung tumorigenesis through altering protein translation and cell cycle in K-ras(LA1) mice.

Recent surveys indicate that Pi intake has increased steadily as Pi-containing foods have increased. Our previous study demonstrated that high dietary Pi strongly stimulated lung tumorigeneis. In order to answer the issue whether low Pi may be chemopreventive, we examined the effects of low Pi on lung cancer. Eighteen 5-wk-old male K-ras(LA1) lung cancer model mice were randomly allocated to 2 groups. One group was fed a normal diet (0.5% Pi) and other group was fed low Pi (0.1% Pi) diet for 4 wk. Lung cancer development was evaluated by histopathological examination, Western blot, kinase assay, and immunohistochemistry. Low Pi increased the expression of sodium-dependent phosphate co-transporter 2b, and activated Akt signal with decreased PTEN expression in the lungs of K-ras(LA1) mice. Low Pi increased the Akt/mTOR-mediated protein translation through upregulating the phosphorylation of p70S6K and 4E-BP1. In addition, low Pi stimulated cell cycling as evidenced by altered cell cycle regulators such as cyclin D1 and D3. Finally, low Pi increased lung tumorigenesis in K-ras(LA1) mice compared to the normal diet group. Our results clearly demonstrated that low Pi also promoted lung tumorigenesis, thus suggesting that an appropriate intake of dietary Pi may be critical for lung cancer prevention as well as treatment.

High dietary inorganic phosphate increases lung tumorigenesis and alters Akt signaling.

RATIONALE: Phosphate (Pi) is an essential nutrient to living organisms. Recent surveys indicate that the intake of Pi has increased steadily. Our previous studies have indicated that elevated Pi activates the Akt signaling pathway. An increased knowledge of the response of lung cancer tissue to high dietary Pi may provide an important link between diet and lung tumorigenesis. OBJECTIVES: The current study was performed to elucidate the potential effects of high dietary Pi on lung cancer development. METHODS: Experiments were performed on 5-week-old male K-ras(LA1) lung cancer model mice and 6-week-old male urethane-induced lung cancer model mice. Mice were fed a diet containing 0.5% Pi (normal Pi) and 1.0% Pi (high Pi) for 4 weeks. At the end of the experiment, all mice were killed. Lung cancer development was evaluated by diverse methods. MEASUREMENT AND MAIN RESULTS: A diet high in Pi increased lung tumor progression and growth compared with normal diet. High dietary Pi increased the sodium-dependent inorganic phosphate transporter-2b protein levels in the lungs. High dietary consumption of Pi stimulated pulmonary Akt activity while suppressing the protein levels of tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 as well as Akt binding partner carboxyl-terminal modulator protein, resulting in facilitated cap-dependent protein translation. In addition, high dietary Pi significantly stimulated cell proliferation in the lungs of K-ras(LA1) mice. CONCLUSIONS: Our results showed that high dietary Pi promoted tumorigenesis and altered Akt signaling, thus suggesting that careful regulation of dietary Pi may be critical for lung cancer prevention as well as treatment.

NNK-mediated upregulation of DEPDC1 stimulates the progression of oral squamous cell carcinoma by inhibiting CYP27B1 expression.

Oral squamous cell carcinoma (OSCC) is a prevalent and malignant cancer. However, the molecular mechanism of OSCC progression is not fully understood. In this study, we observed that the DEP domain containing 1 (DEPDC1) protein was overexpressed in OSCC tissues and that the increased expression of DEPDC1 was closely associated with tumor size and poor clinical outcomes in OSCC patients. The results of functional investigations demonstrated that DEPDC1 stimulates OSCC cell proliferation by inhibiting cytochrome P450 family 27 subfamily B member (CYP27B1) expression. Furthermore, we observed that upregulated DEPDC1 expression was closely associated with smoking status in OSCC patients. The results of in vitro experiments showed that the tobacco compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) stimulates DEPDC1 expression by promoting the methylation of its gene body by increasing DNMT1 expression in OSCC cells. Notably, the silencing of DEPDC1 dramatically inhibited OSCC growth by inhibiting cell proliferation and inducing apoptosis in vivo. These findings suggest that smoking causes DEPDC1 overexpression in OSCC through DNMT1-regulated DNA methylation and that upregulated DEPDC1 stimulates OSCC cell proliferation by inhibiting CYP27B1 expression. Our results establish a new mechanism of OSCC progression and highlight DEPDC1 as a candidate prognostic biomarker and therapeutic target in OSCC.

Bleomycin induces epithelial-to-mesenchymal transition via bFGF/PI3K/ESRP1 signaling in pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a fatal and chronic disease with a high rate of infection and mortality; however, its etiology and pathogenesis remain unclear. Studies have revealed that epithelial-mesenchymal transition (EMT) is a crucial cellular event in IPF. Here, we identified that the pulmonary fibrosis inducer bleomycin simultaneously increased the expression of bFGF and TGF-ß1 and inhibited epithelial-specific regulatory protein (ESRP1) expression in vivo and in vitro. In addition, in vitro experiments showed that bFGF and TGF-ß1 down-regulated the expression of ESRP1 and that silencing ESRP1 promoted EMT in A549 cells. Notably, we determined that bFGF activates PI3K/Akt signaling, and treatment with the PI3K/Akt inhibitor LY294002 inhibited bleomycin-induced cell morphology changes and EMT. In addition, the effects of LY294002 on bleomycin-induced EMT were inhibited by ESRP1 silencing in A549 cells. Taken together, these findings suggest that bleomycin induced EMT through down-regulating ESRP1 by simultaneously increasing bFGF and TGF-ß1 in pulmonary fibrosis. Additionally, our findings indicated that bFGF inhibits ESRP1 by activating PI3K/Akt signaling.

KRASQ61H Preferentially Signals through MAPK in a RAF Dimer-Dependent Manner in Non-Small Cell Lung Cancer.

Assembly of RAS molecules into complexes at the cell membrane is critical for RAS signaling. We previously showed that oncogenic KRAS codon 61 mutations increase its affinity for RAF, raising the possibility that KRASQ61H, the most common KRAS mutation at codon 61, upregulates RAS signaling through mechanisms at the level of RAS assemblies. We show here that KRASQ61H exhibits preferential binding to RAF relative to PI3K in cells, leading to enhanced MAPK signaling in in vitro models and human NSCLC tumors. X-ray crystallography of KRASQ61H:GTP revealed that a hyperdynamic switch 2 allows for a more stable interaction with switch 1, suggesting that enhanced RAF activity arises from a combination of absent intrinsic GTP hydrolysis activity and increased affinity for RAF. Disruption of KRASQ61H assemblies by the RAS oligomer-disrupting D154Q mutation impaired RAF dimerization and altered MAPK signaling but had little effect on PI3K signaling. However, KRASQ61H oligomers but not KRASG12D oligomers were disrupted by RAF mutations that disrupt RAF-RAF interactions. KRASQ61H cells show enhanced sensitivity to RAF and MEK inhibitors individually, whereas combined treatment elicited synergistic growth inhibition. Furthermore, KRASQ61H tumors in mice exhibited high vulnerability to MEK inhibitor, consistent with cooperativity between KRASQ61H and RAF oligomerization and dependence on MAPK signaling. These findings support the notion that KRASQ61H and functionally similar mutations may serve as predictive biomarkers for targeted therapies against the MAPK pathway. SIGNIFICANCE: These findings show that oncogenic KRASQ61H forms a cooperative RAS-RAF ternary complex, which renders RAS-driven tumors vulnerable to MEKi and RAFi, thus establishing a framework for evaluating RAS biomarker-driven targeted therapies.

Fabrication of a novel core-shell gene delivery system based on a brush-like polycation of alpha, beta-poly (L-aspartate-graft-PEI).

PURPOSE: A novel core-shell gene delivery system was fabricated in order to improve its gene transfection efficiency, particularly in the presence of serum. MATERIALS AND METHODS: alpha, beta-poly (L-aspartate-graft-PEI) (PAE) was simply synthesized by ring-opening reaction of poly (L-succinimide) with low molecular weight (LMW) linear polyethylenimine (PEI, Mn = 423). PAE/DNA nanoparticles were characterized. Condensation and protection ability of plasmid by PAE were confirmed by agarose gel electrophoresis assay. Cytotoxicity of the polymer and polymer/DNA nanoparticles were measured by MTS assay. Gene transfection efficiencies were evaluated both in vitro and in vivo. RESULTS: Core-shell nanoparticles assembled between DNA and PAE showed positive zeta potential, narrow size distribution, and spherical compact shapes with size below 250 nm when N/P ratio is above 10. Cytotoxicity of PAE was rather lower than that of PEI 25K, while the most efficient gene transfection and serum resistant ability of PAE/DNA complexes were higher than that of PEI 25K. Bafilomycin A1 treatment suggested "proton sponge" mechanism of PAE-mediated gene transfection. PAE/pEGFP-N2 nanoparticles also showed good gene expression in vivo and were dominantly distributed in kidney, liver, spleen and lung after intravenous administration. CONCLUSIONS: The results demonstrated the potential use of PAE as an effective gene carrier.

Poly(ester amine)-mediated, aerosol-delivered Akt1 small interfering RNA suppresses lung tumorigenesis.

RATIONALE: The low efficiency of conventional therapies in achieving long-term survival of patients with lung cancer calls for the development of novel therapeutic options. Recent advances in aerosol-mediated gene delivery have provided the possibility of an alternative for the safe and effective treatment of lung cancer. OBJECTIVES: To demonstrate the feasibility and emphasize the importance of noninvasive aerosol delivery of Akt1 small interfering RNA (siRNA) as an effective and selective option for lung cancer treatment. METHODS: Nanosized poly(ester amine) polymer was synthesized and used as a gene carrier. An aerosol of poly(ester amine)/Akt1 siRNA complex was delivered into K-ras(LA1) and urethane-induced lung cancer models through a nose-only inhalation system. The effects of Akt1 siRNA on lung cancer progression and Akt-related signals were evaluated. MEASUREMENTS AND MAIN RESULTS: The aerosol-delivered Akt1 siRNA suppressed lung tumor progression significantly through inhibiting Akt-related signals and cell cycle. CONCLUSIONS: The use of poly(ester amine) serves as an effective carrier, and aerosol delivery of Akt1 siRNA may be a promising approach for lung cancer treatment and prevention.

Synergistic effect of ERK inhibition on tetrandrine-induced apoptosis in A549 human lung carcinoma cells.

Tetrandrine (TET), a bis-benzylisoquinoline alkaloid from the root of Stephania tetrandra, is known to have anti-tumor activity in various malignant neoplasms. However, the precise mechanism by which TET inhibits tumor cell growth remains to be elucidated. The present studies were performed to characterize the potential effects of TET on phosphoinositide 3-kinase/Akt and extracellular signal-regulated kinase (ERK) pathways since these signaling pathways are known to be responsible for cell growth and survival. TET suppressed cell proliferation and induced apoptosis in A549 human lung carcinoma cells. TET treatment resulted in a down-regulation of Akt and ERK phosphorylation in both time-/concentration-dependent manners. The inhibition of ERK using PD98059 synergistically enhanced the TET-induced apoptosis of A549 cells whereas the inhibition of Akt using LY294002 had a less significant effect. Taken together, our results suggest that TET: i) selectively inhibits the proliferation of lung cancer cells by blocking Akt activation and ii) increases apoptosis by inhibiting ERK. The treatment of lung cancers with TET may enhance the efficacy of chemotherapy and radiotherapy and increase the apoptotic potential of lung cancer cells.