XB130 Mediates Cancer Cell Proliferation and Survival through Multiple Signaling Events Downstream of Akt

XB130, a novel adaptor protein, mediates RET/PTC chromosome rearrangement-related thyroid cancer cell proliferation and survival through phosphatidyl-inositol-3-kinase (PI3K)/Akt pathway. Recently, XB130 was found in different cancer cells in the absence of RET/PTC. To determine whether RET/PTC is required of XB130-related cancer cell proliferation and survival, WRO thyroid cancer cells (with RET/PTC mutation) and A549 lung cancer cells (without RET/PTC) were treated with XB130 siRNA, and multiple Akt down-stream signals were examined. Knocking-down of XB130 inhibited G(1)-S phase progression, and induced spontaneous apoptosis and enhanced intrinsic and extrinsic apoptotic stimulus-induced cell death. Knocking-down of XB130 reduced phosphorylation of p21Cip1/WAF1, p27Kip1, FOXO3a and GSK3β, increased p21Cip1/WAF1protein levels and cleavages of caspase-8 and-9. However, the phosphorylation of FOXO1 and the protein levels of p53 were not affected by XB130 siRNA. We also found XB130 can be phosphorylated by multiple protein tyrosine kinases. These results indicate that XB130 is a substrate of multiple protein tyrosine kinases, and it can regulate cell proliferation and survival through modulating selected down-stream signals of PI3K/Akt pathway. XB130 could be involved in growth and survival of different cancer cells.     

Effects of bufalin on the proliferation of human lung cancer cells and its molecular mechanisms of action

Bufalin, a naturally occurring small-molecule compound from Traditional Chinese Medicine (TCM) Chansu showed inhibitory effects against human prostate, hepatocellular, endometrial and ovarian cancer cells, and leukemia cells. However, whether or not bufalin has inhibitory activity against the proliferation of human non–small cell lung cancer (NSCLC) cells is unclear. The aim of this study is to study the effects of bufalin on the proliferation of NSCLC and its molecular mechanisms of action. The cancer cell proliferation was measured by MTT assay. The apoptosis and cell cycle distribution were analyzed by flow cytometry. The protein expressions and phosphorylation in the cancer cells were detected by Western blot analysis. In the present study, we have demonstrated that bufalin suppressed the proliferation of human NSCLC A549 cell line in time- and dose-dependent manners. Bufalin induced the apoptosis and cell cycle arrest by affecting the protein expressions of Bcl-2/Bax, cytochrome c, caspase-3, PARP, p53, p21WAF1, cyclinD1, and COX-2 in A549 cells. In addition, bufalin reduced the protein levels of receptor expressions and/or phosphorylation of VEGFR1, VEGFR2, EGFR and/or c-Met in A549 cells. Furthermore, bufalin inhibited the protein expressions and phosphorylation of Akt, NF-κB, p44/42 MAPK (ERK1/2) and p38 MAPK in A549 cells. Our results suggest that bufalin inhibits the human lung cancer cell proliferation via VEGFR1/VEGFR2/EGFR/c-Met–Akt/p44/42/p38-NF-κB signaling pathways; bufalin may have a wide therapeutic and/or adjuvant therapeutic application in the treatment of human NSCLC.     

Corilagin inhibits breast cancer growth via reactive oxygen species‐dependent apoptosis and autophagy

Corilagin is a component of Phyllanthus urinaria extract and has been found of possessing anti‐inflammatory, anti‐oxidative, and anti‐tumour properties in clinic treatments. However, the underlying mechanisms in anti‐cancer particularly of its induction of cell death in human breast cancer remain undefined. Our research found that corilagin‐induced apoptotic and autophagic cell death depending on reactive oxygen species (ROS) in human breast cancer cell, and it occurred in human breast cancer cell (MCF‐7) only comparing with normal cells. The expression of procaspase‐8, procaspase‐3, PARP, Bcl‐2 and procaspase‐9 was down‐regulated while caspase‐8, cleaved PARP, caspase‐9 and Bax were up‐regulated after corilagin treatment, indicating apoptosis mediated by extrinsic and mitochondrial pathways occurred in MCF‐7 cell. Meanwhile, autophagy mediated by suppressing Akt/mTOR/p70S6K pathway was detected with an increase in autophagic vacuoles and LC3‐II conversion. More significantly, inhibition of autophagy by chloroquine diphosphate salt (CQ) remarkably enhanced apoptosis, while the caspase inhibitor z‐VAD‐fmk failed in affecting autophagy, suggesting that corilagin‐induced autophagy functioned as a survival mechanism in MCF‐7 cells. In addition, corilagin induced intracellular reactive oxygen species (ROS) generation, when reduced by ROS scavenger NAC, apoptosis and autophagy were both down‐regulated. Nevertheless, in SK‐BR3 cell which expressed RIP3, necroptosis inhibitor Nec‐1 could not alleviate cell death induced by corilagin, indicating necroptosis was not triggered. Subcutaneous tumour growth in nude mice was attenuated by corilagin, consisting with the results in vitro. These results imply that corilagin inhibits cancer cell proliferation through inducing apoptosis and autophagy which regulated by ROS release.     

Sepiapterin regulates cell proliferation and migration: its association with integrin α3β1 and p53 in human lung cancer cells

Tetrahydrobiopterin (BH₄) has been known to be an essential cofactor for nitric oxide synthase as well as the aromatic amino acid hydroxylases, which are involved in regulation of cellular fates including proliferation, migration and differentiation. In the present study, we report that sepiapterin, a stable form of BH₄ precursor, modulates proliferation and migration in human lung cancer cells. Sepiapterin induction of cell proliferation in p53 wild-type A549 cells, but not in p53-deficient H1299 cells, is accompanied by enhanced expression of cell cycle-related proteins such as cyclin-dependent kinase 4 (Cdk4), cyclin D and cyclin E, and reduced expression of Cdk inhibitor p21^WAF1/Cip1, demonstrating that sepiapterin-induced mitogenic responses might be associated with p53 expression status in lung cancer cells. In addition, sepiapterin enhances cell migration in A549 cells, but not H1299 cells. Finally, we show that sepiapterin induces A549 cell proliferation and migration through the activation of Akt and p70^S6K signaling pathways, as evidenced by using Akt and p70^S6K inhibitor. Collectively, these findings indicate that sepiapterin might play differential roles in regulation of cellular fates, depending on the status of p53 expression in lung cancer.     

Targeting PKCε by miR-143 regulates cell apoptosis in lung cancer

Non-small cell lung cancer (NSCLC) is one of the most common causes for lung cancer and cancer-related death. The imbalance between cell proliferation and apoptosis was suggested to play an important role in cancer pathogenesis and PKCε is one of the widely recognized targets. Here, we demonstrate that miR-143 is aberrantly downregulated in NSCLC tissue and negatively correlates with expression of PKCε. We show that miR-143 specifically targets the 3′-UTR of PKCε and regulates its expression. Treatment with miR-143 inhibitor mimics cell proliferation and apoptosis imbalance in NSCLC, while inhibition of PKCε can reverse it. Our findings suggest that targeting PKCε overexpression in NSCLC should be beneficial for lung cancer therapy.     

PPARbeta/delta agonist stimulates human lung carcinoma cell growth through inhibition of PTEN expression: the involvement of PI3K and NF-kappaB signals

Recent studies suggest that activation of peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) promotes cancer cell survival. We previously demonstrated that a selective PPARbeta/delta agonist, GW501516, stimulated human non-small cell lung carcinoma (NSCLC) cell growth. Here, we explore the mechanisms responsible for this effect. We show that GW501516 decreased phosphate and tensin homolog deleted on chromosome 10 (PTEN), a tumor suppressor known to decrease cell growth and induce apoptosis. Activation of PPARbeta/delta and phosphatidylinositol 3-kinase (PI3K)/Akt signaling was associated with inhibition of PTEN. GW501516 increased NF-kappaB DNA binding activity and p65 protein expression through activation of PPARbeta/delta and PI3K/Akt signals and enhanced the physical interactions between PPARbeta/delta and p65 protein. Conversely, inhibition of PI3K and silencing of p65 by small RNA interference (siRNA) blocked the effect of GW501516 on PTEN expression and on NSCLC cell proliferation. GW501516 also inhibited IKBalpha protein expression. Silencing of IKBalpha enhanced the effect of GW501516 on PTEN protein expression and on cell proliferation. It also augmented the GW501516-induced complex formation of PPARbeta/delta and p65 proteins. Overexpression of PTEN suppressed NSCLC cell growth and eliminated the effect of GW501516 on phosphorylation of Akt. Together, our observations suggest that GW501516 induces the proliferation of NSCLC cells by inhibiting the expression of PTEN through activation of PPARbeta/delta, which stimulates PI3K/Akt and NF-kappaB signaling. Overexpression of PTEN overcomes this effect and unveils PPARbeta/delta and PTEN as potential therapeutic targets in NSCLC.     

KLHL38 involvement in non-small cell lung cancer progression via activation of the Akt signaling pathway

Lung cancer is the leading cause of cancer-related death worldwide. KLHL38 has been reported to be upregulated during diapause but downregulated after androgen treatment during the reversal of androgen-dependent skeletal muscle atrophy. This study aimed to clarify the role of KLHL38 in non-small cell lung cancer (NSCLC). KLHL38 expression was evaluated in tumor and adjacent normal tissues from 241 patients with NSCLC using immunohistochemistry and real-time PCR, and its association with clinicopathological parameters was analyzed. KLHL38 levels positively correlated with tumor size, lymph node metastasis, and pathological tumor-node-metastasis stage (all P < 0.001). In NSCLC cell lines, KLHL38 overexpression promoted PTEN ubiquitination, thereby activating Akt signaling. It also promoted cell proliferation, migration, and invasion by upregulating the expression of genes encoding cyclin D1, cyclin B, c-myc, RhoA, and MMP9, while downregulating the expression of p21 and E-cadherin. In vivo experiments in nude mice further confirmed that KLHL38 promotes NSCLC progression through Akt signaling pathway activation. Together, these results indicate that KLHL38 is a valuable candidate prognostic biomarker and potential therapeutic target for NSCLC.Subject terms: Lung cancer, Oncogenesis     

Baicalein inhibits cell growth and increases cisplatin sensitivity of A549 and H460 cells via miR‐424‐3p and targeting PTEN/PI3K/Akt pathway

Lung cancer is the leading cause of death in individuals with malignant disease. Non‐small‐cell lung cancer (NSCLC) is the most common type of lung cancer, and chemotherapy drugs such as cisplatin are the most widely used treatment for this disease. Baicalein is a purified flavonoid compound that has been reported to inhibit cancer cell growth and metastasis and increase sensitization to chemotherapeutic drugs via different pathways. Therefore, we assessed the effects of baicalein on the proliferation, apoptosis and cisplatin sensitivity in the NSCLC A549 and H460 cell lines and determined the pathways through which baicalein exerts its effects. Baicalein was slightly toxic to normal human bronchial NHBE cells but inhibited growth, induced apoptosis and increased cisplatin sensitivity in A549 and H460 cells. Baicalein down‐regulated miR‐424‐3p, up‐regulated PTEN expression and down‐regulated expression of PI3K and p‐Akt in A549 and H460 cells. Dual‐luciferase reporter assay demonstrated that PTEN is a target gene of miR‐424‐3p, and overexpression of miR‐424‐3p or silencing of PTEN partially attenuated the effects of baicalein on A549 and H460 cells. Taken together, we concluded that baicalein inhibits cell growth and increases cisplatin sensitivity to A549 and H460 cells via down‐regulation of miR‐424‐3p and targeting the PTEN/PI3K/Akt pathway.     

Silencing of Twist1 sensitizes NSCLC cells to cisplatin via AMPK-activated mTOR inhibition

Twist1 is highly expressed in primary and metastatic non-small cell lung cancer (NSCLC), and thus acts as a critical target for lung cancer chemotherapy. In the current study, we investigated the underlying mechanism initiated by silencing of Twist1 that sensitizes NSCLC cells to cisplatin. Silencing of Twist1 triggered ATP depletion, leading to AMP-activated protein kinase (AMPK)-activated mammalian target of rapamycin (mTOR) inhibition in NSCLC cells. AMPK-induced mTOR inhibition, in turn, resulted in downregulation of ribosome protein S6 kinase 1 (S6K1) activity. Downregulation of mTOR/S6K1 reduced Mcl-1 protein expression, consequently promoting sensitization to cisplatin. Overexpression of Mcl-1 reduced PARP cleavage induced by cisplatin and Twist1 siRNA, suggesting that this sensitization is controlled through Mcl-1 expression. Interestingly, cells treated with Twist1 siRNA displayed upregulation of p21^Waf1/CIP1, and suppression of p21^Waf1/CIP1 with specific siRNA further enhanced the cell death response to cisplatin/Twist1 siRNA. In conclusion, silencing of Twist1 sensitizes lung cancer cells to cisplatin via stimulating AMPK-induced mTOR inhibition, leading to a reduction in Mcl-1 protein. To our knowledge, this is the first report to provide a rationale for the implication of cross-linking between Twist1 and mTOR signaling in resistance of NSCLC to anticancer drugs.     

Berberine Targets AP-2/hTERT,NF-κB/COX-2, HIF-1α/VEGF and Cytochrome-c/Caspase Signaling to Suppress Human Cancer Cell Growth

Berberine (BBR), an isoquinoline derivative alkaloid isolated from Chinese herbs, has a long history of uses for the treatment of multiple diseases, including cancers. However, the precise mechanisms of actions of BBR in human lung cancer cells remain unclear. In this study, we investigated the molecular mechanisms by which BBR inhibits cell growth in human non-small-cell lung cancer (NSCLC) cells. Treatment with BBR promoted cell morphology change, inhibited cell migration, proliferation and colony formation, and induced cell apoptosis. Further molecular mechanism study showed that BBR simultaneously targeted multiple cell signaling pathways to inhibit NSCLC cell growth. Treatment with BBR inhibited AP-2α and AP-2β expression and abrogated their binding on hTERT promoters, thereby inhibiting hTERT expression. Knockdown of AP-2α and AP-2β by siRNA considerably augmented the BBR-mediated inhibition of cell growth. BBR also suppressed the nuclear translocation of p50/p65 NF-κB proteins and their binding to COX-2 promoter, causing inhibition of COX-2. BBR also downregulated HIF-1α and VEGF expression and inhibited Akt and ERK phosphorylation. Knockdown of HIF-1α by siRNA considerably augmented the BBR-mediated inhibition of cell growth. Moreover, BBR treatment triggered cytochrome-c release from mitochondrial inter-membrane space into cytosol, promoted cleavage of caspase and PARP, and affected expression of BAX and Bcl-2, thereby activating apoptotic pathway. Taken together, these results demonstrated that BBR inhibited NSCLC cell growth by simultaneously targeting AP-2/hTERT, NF-κB/COX-2, HIF-1α/VEGF, PI3K/AKT, Raf/MEK/ERK and cytochrome-c/caspase signaling pathways. Our findings provide new insights into understanding the anticancer mechanisms of BBR in human lung cancer therapy.     

Induction of apoptosis by tumor suppressor FHIT via death receptor signaling pathway in human lung cancer cells

FHIT is a novel tumor suppressor gene located at human chromosome 3p14.2. Restoration of wild-type FHIT in 3p14.2-deficient human lung cancer cells inhibits cell growth and induces apoptosis. In this study, we analyzed potential upstream/downstream molecular targets of the FHIT protein and found that FHIT specifically targeted and regulated death receptor (DR) genes in human non-small-cell lung cancer (NSCLC) cells. Exogenous expression of FHIT by a recombinant adenoviral vector (Ad)-mediated gene transfer upregulated expression of DR genes. Treatment with a recombinant TRAIL protein, a DR-specific ligand, in Ad-FHIT-transduced NSCLC cells considerably enhanced FHIT-induced apoptosis, further demonstrating the involvement of DRs in FHIT-induced apoptosis. Moreover, we also found that FHIT targeted downstream of the DR-mediated signaling pathway. FHIT overexpression disrupted mitochondrial membrane integrity and activated multiple pro-apoptotic proteins in NSCLC cell. These results suggest that FHIT induces apoptosis through a sequential activation of DR-mediated pro-apoptotic signaling pathways in human NSCLC cells.     

miR-605-5p promotes invasion and proliferation by targeting TNFAIP3 in non–small-cell lung cancer

Lung cancer is an significant cause of death worldwide, and non–small-cell lung cancer (NSCLC) is the most common type of lung cancer. MicroRNAs (miRNAs) have been identified to play key roles in NSCLC development. Recently, it has been reported that miR-605-5p is a cancer-related miRNA in several types of tumors. In this study, we study the role of miR-605-5p in NSCLC cells. We find that miR-605-5p is upregulated in NSCLC cells. Overexpression of miR-605-5p significantly promotes lung cancer invasion and migration in H460 and H1299 cells. Besides this, miR-605-5p also promotes lung cancer cell carcinoma proliferation and metastasis in vivo. However, downregulation of miR-605-5p inhibits cell invasion and migration by inhibiting lung cancer cell carcinoma proliferation and metastasis. In addition, the luciferase report assay identifies 3′-untranslated region tumor necrosis factor α-induced protein 3 (TNFAIP3) as a target of miR-605-5p. Silencing of TNFAIP3 promotes invasion and proliferation in lung cancer. In addition, the knockdown of TNFAIP3 restores the significant decrease in invasion and proliferation in miR-605-5p-inhibitor–transfected lung cancer cells. In conclusion, miR-605-5p promotes invasion and proliferation by targeting TNFAIP3 in NSCLC, and may provide possible biomarkers for NSCLC therapy.     

GINS2 facilitates epithelial-to-mesenchymal transition in non-small-cell lung cancer through modulating PI3K/Akt and MEK/ERK signaling

Non-small-cell lung cancer (NSCLC) is a cancer with high morbidity and mortality. We aimed to define the effect of Go-Ichi-Ni-San complex subuint 2 (GINS2) acting on NSCLC. The expressions of GINS2 in NSCLC tissues and cells were detected using real-time quantitative polymerase chain reaction, western blot, and immunohistochemistry (IHC). The relationship between GINS2 expression and NSCLC prognosis or clinicopathologic features was analyzed through statistical analysis. The overexpressed or downexpressed plasmids of GINS2 were transfected into NSCLC cell lines, and then cell proliferation, invasion, and migration viability were, respectively, determined by Cell Counting Kit-8 assay, transwell, and wound healing assay. The epithelial–mesenchymal transition (EMT) was observed and the EMT-related proteins were measured using IHC and western blot. The function of GINS2 in vivo was assessed by mice model. The related proteins of mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) and phosphoinositide-3-kinase/protein kinase B (PI3K/Akt) pathways were evaluated using western blot. GINS2 expression was upregulated in NSCLC tissues and cell lines, and its high expression was correlated with the poor prognosis and several clinicopathologic features, such as TMN stages (tumor size, lymph node, and metastasis) and clinical stages. GINS2 enhanced NSCLC cell proliferation, migration, and invasion viability in vivo and in vitro. GINS2 also promoted NSCLC cells EMT. In addition, GINS2 could regulate phosphorylated proteins of PI3K p85, Akt, MEK, and ERK expressions, it revealed that GINS2 effected on PI3K/Akt and MEK/ERK pathways. GINS2 promoted cell proliferation, migration, invasion, and EMT via modulating PI3K/Akt and MEK/ERK signaling pathways. It might be a target in NSCLC treatment.     

P42 Ebp1 functions as a tumor suppressor in non-small cell lung cancer

Although the short isoform of ErbB3-binding protein 1 (Ebp1), p42 has been considered to be a potent tumor suppressor in a number of human cancers, whether p42 suppresses tumorigenesis of lung cancer cells has never been clarified. In the current study we investigated the tumor suppressor role of p42 in non-small cell lung cancer cells. Our data suggest that the expression level of p42 is inversely correlated with the cancerous properties of NSCLC cells and that ectopic expression of p42 is sufficient to inhibit cell proliferation, anchorage-independent growth, and invasion as well as tumor growth in vivo. Interestingly, p42 suppresses Akt activation and overexpression of a constitutively active form of Akt restores the tumorigenic activity of A549 cells that is ablated by exogenous p42 expression. Thus, we propose that p42 Ebp1 functions as a potent tumor suppressor of NSCLC through interruption of Akt signaling. [BMB Reports 2015; 48(3): 159-165]     

A novel antagonist to the inhibitors of apoptosis (IAPs) potentiates cell death in EGFR-overexpressing non-small-cell lung cancer cells

In the effort to develop an efficient chemotherapy drug for the treatment of non-small-cell lung cancer (NSCLC), we analyzed the anti-tumorigenic effects of a novel small molecule targeting the inhibitor of apoptosis (IAPs), HM90822B, on NSCLC cells. HM90822B efficiently decreased IAP expression, especially that of XIAP and survivin, in several NSCLC cells. Interestingly, cells overexpressing epidermal growth factor receptor (EGFR) due to the mutations were more sensitive to HM90822B, undergoing cell cycle arrest and apoptosis when treated. In xenograft experiments, inoculated EGFR-overexpressing NSCLC cells showed tumor regression when treated with the inhibitor, demonstrating the chemotherapeutic potential of this agent. Mechanistically, decreased levels of EGFR, Akt and phospho-MAPKs were observed in inhibitor-treated PC-9 cells on phosphorylation array and western blotting analysis, indicating that the reagent inhibited cell growth by preventing critical cell survival signaling pathways. In addition, gene-specific knockdown studies against XIAP and/or EGFR further uncovered the involvement of Akt and MAPK pathways in HM90822B-mediated downregulation of NSCLC cell growth. Together, these results support that HM90822B is a promising candidate to be developed as lung tumor chemotherapeutics by targeting oncogenic activities of IAP together with inhibiting cell survival signaling pathways.Resistance to apoptosis is a hallmark of many solid tumors, including lung cancer, and is, therefore, an important target mechanism for controlling cancer proliferation. The inhibitor of apoptosis (IAP) is a family of proteins containing one or more conserved cysteine and histidine-rich baculoviral IAP repeat (BIR) in their N-terminal domains and a C-terminal RING (really interesting new gene) domain. The BIR domains of IAPs form zinc figure-like structures that bind to active caspases to block caspase activity, while the RING domain acts as an ubiquitin ligase to facilitate proteasome degradation of caspases. Several IAPs have been identified in mammals, including X-linked IAP (XIAP), cellular IAP-1 and -2 (cIAP-1 and cIAP-2) and survivin. Among these IAP proteins, XIAP is a central regulator of both the death receptor- and mitochondria-mediated apoptosis pathways. Consistent with their role in the inhibition of apoptosis, XIAP and survivin are highly expressed in a diverse array of tumors and are often associated with resistance to apoptosis and low sensitivity to chemotherapy drugs in some tumor types.^{1, 2, 3}Recent studies have shown that inhibition of the expression level or function of survivin and/or XIAP with anti-sense RNA, short interfering RNA (siRNA), dominant-negative mutants, or small molecules induces apoptotic cell death in tumor cells but not in normal cells.⁴ Several chemical IAP antagonists, such as AT-406, LCL-161, GDC-0152, TL-32711, LBW242 and HGS-1029, which mimic the interactions of IAP proteins with secondary mitochondria-derived activator of caspase (SMAC) N-terminal peptide (an endogenous antagonist of IAP proteins), have been developed and are currently being evaluated in clinical settings.^{5, 6, 7, 8} The elucidation of the mechanism of antagonism and identification of biomarkers that indicate apoptotic cell death in tumors are key issues in the development of IAP antagonists. As such, the role of IAPs in regulating the apoptotic response and as molecular targets for achieving selective therapeutic effects in tumor cells has attracted great attention in an effort to identify peptide antagonists or small-molecule inhibitors.Lung cancer is the leading cause of cancer-related death worldwide, with more than one million mortalities each year. Almost 85% of all lung cancer cases are diagnosed as non-small-cell lung cancers (NSCLC), which are further classified histologically as adenocarcinoma, squamous cell carcinoma or large cell carcinoma. Platinum-based chemotherapy represents the recommended standard first-line systemic treatment for advanced NSCLC, although the results of this approach are limited to a modest increase in survival rates. Epidermal growth factor receptor (EGFR) is often hyper-activated in many lung cancers due to the presence of a mutation in the kinase domain, causing the activation of multiple cell survival signals, especially Akt and mitogen-activated protein kinase (MAPK) pathways. This finding has led to the development of targeted therapeutics against the kinase, such as erlotinib and gefitinib, which becomes one of the most promising strategies for cancer treatment. The targeted therapeutics has often failed, however, due to the development of resistance through multiple mechanisms, indicating that additional adjuvants are necessary to achieve effective results.In this study, we investigated the therapeutic potential of HM90822B, originally synthesized to inhibit IAP activity, on NSCLC cells and in a xenograft mouse model and analyzed the cellular effects of the drug to elucidate its mechanism of action. Our results showed that HM90822B inhibits cell growth resulting in cell cycle arrest and apoptosis by targeting XIAP and survivin in conjunction with the inhibition of EGFR-MAPK pathway, primarily AKT, p38 and c-jun phosphorylation. These results indicate that the IAP inhibitor HM90822B is a promising therapeutics for the treatment of NSCLC.     

Distinctive regulation and function of PI 3K/Akt and MAPKs in doxorubicin-induced apoptosis of human lung adenocarcinoma cells

Regulation and function of PI 3K/Akt and mitogen-activated protein kinases (MAPKs) in doxorubicin-induced cell death were investigated in human lung adenocarcinoma cells. Doxorubicin induced dose-dependent apoptosis of human lung adenocarcinoma NCI-H522 cells. Prior to cell death, both Akt and the MAPK family members (MAPKs: ERK1/2, JNK, and p38) were activated in response to the drug treatment. The kinetics of the inductions for Akt and MAPKs are, however, distinct. The activation of Akt was rapid and transient, activated within 30 min of drug addition, then declined after 3 h, whereas the activations of three MAPKs occurred later, 4 h after addition of the drug and sustained until cell death occurred. Inhibition of PI 3K/Akt activation had no effect on MAPKs' activation, suggesting that the two pathways are independently activated in response to the drug treatment. Inhibition of PI 3K/Akt and p38 accelerated and enhanced doxorubicin-induced cell death. On the contrary, inhibition of ERK1/2 or JNK had no apparent effect on the cell death. Taken together, these results suggest that PI 3K/Akt and MAPKs signaling pathways are all activated, but with distinct mechanisms, in response to doxorubicin treatment. Activation of PI 3K/Akt and p38 modulates apoptotic signal pathways and inhibits doxorubicin-induced cell death. These responses of tumor cells to cancer drug treatment may contribute to their drug resistance. Understanding of the mechanism and function of the responses will be beneficial for the development of novel therapeutic approaches for improvement of drug efficacy and circumvention of drug resistance.