Resistant Human Lung Cancer Cell Research Articles

Self-Assembly of Erlotinib-Platinum(II) Complexes for Epidermal Growth Factor Receptor-Targeted Photodynamic Therapy.

Due to cell mutation and self-adaptation, the application of clinical drugs with early epidermal growth factor receptor (EGFR)-targeted inhibitors is severely limited. To overcome this limitation, herein, the synthesis and in-depth biological evaluation of an erlotinib-platinum(II) complex as an EGFR-targeted anticancer agent is reported. The metal complex is able to self-assemble inside an aqueous solution and readily form nanostructures with strong photophysical properties. While being poorly toxic toward healthy cells and upon treatment in the dark, the compound was able to induce a cytotoxic effect in the very low micromolar range upon irradiation against EGFR overexpressing (drug resistant) human lung cancer cells as well as multicellular tumor spheroids. Mechanistic insights revealed that the compound was able to selectively degrade the EGFR using the lysosomal degradation pathway upon generation of singlet oxygen at the EGFR. We are confident that this work will open new avenues for the treatment of EGFR-overexpressing tumors.

Root Extract of Trichosanthes kirilowii Suppresses Metastatic Activity of EGFR TKI-Resistant Human Lung Cancer Cells by Inhibiting Src-Mediated EMT

The roots of Trichosanthes kirilowii (TK) have been used in traditional oriental medicine for the treatment of respiratory diseases. In this study, we investigated whether an ethanolic root extract of TK (ETK) can regulate the metastatic potency of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-resistant human lung cancer cells. The relative migration and invasion abilities of erlotinib-resistant PC9 (PC9/ER) and gefitinib-resistant PC9 (PC9/GR) cells were higher than those of parental PC9 cells. Mesenchymal markers were overexpressed, whereas epithelial markers were downregulated in resistant cells, suggesting that resistant cells acquired the EMT phenotype. ETK reduced migration and invasion of resistant cells. The expression levels of N-cadherin and Twist were downregulated, whereas Claudin-1 was upregulated by ETK, demonstrating that ETK suppresses EMT. As a molecular mechanism, Src was dephosphorylated by ETK. The anti-metastatic effect of ETK was reduced by transfecting PC9/ER cells with a constitutively active form of c-Src. Dasatinib downregulated N-cadherin, Twist, and vimentin, suggesting that Src regulates EMT in resistant cells. Notably, CuB played a key role in mediating the anti-metastatic activity of ETK. Collectively, our results demonstrate that ETK can attenuate the metastatic ability of EGFR-TKI-resistant lung cancer cells by inhibiting Src-mediated EMT.

Novel Mitochondria-Based Targeting Restores Responsiveness in Therapeutically Resistant Human Lung Cancer Cells.

Cisplatin and tyrosine kinase inhibitors (TKI) are recommended to treat non-small cell lung cancer (NSCLC). However, ubiquitously acquired drug resistance in patients with NSCLC diminishes their therapeutic efficacy. Strategies for overcoming cisplatin and TKI resistance are an unmet medical need. We previously described a group of near-infrared heptamethine carbocyanine fluorescent dyes, referred to as DZ, with tumor-homing properties via differentially expressed organic anion-transporting polypeptides on cancer cells. This group of organic dyes can deliver therapeutic payloads specifically to tumor cells in the form of a chemical conjugate. We synthesized DZ-simvastatin (DZ-SIM) initially to target cholesterol biosynthesis in lung cancer cells. DZ-SIM killed both cisplatin-sensitive and cisplatin-resistant as well as EGFR-TKI-sensitive and EGFR-TKI-resistant lung cancer cells. This conjugate specifically accumulated in and effectively inhibited the growth of xenograft tumors formed by NSCLC cells resistant to first-generation (H1650) and third-generation (PC9AR) EGFR TKIs. DZ-SIM induced cell death by targeting mitochondrial structure and function. We concluded that DZ-SIM could be a promising novel therapy for overcoming drug resistance in patients with NSCLC.

Synergistic combination therapy of lung cancer using lipid-layered cisplatin and oridonin co-encapsulated nanoparticles

Lung cancer treatment using cisplatin (DDP) in combination with other drugs are effective for the treatment of non-small cell lung cancer (NSCLC). The aim of this study was to prepare a layer-by-layer nanoparticles (NPs) for the co-loading of DDP and oridonin (ORI) and to evaluate the antitumor activity of the system in vitro and in vivo. Novel DDP and ORI co-loaded layer-by-layer NPs (D/O-NPs) were constructed. The mean diameter, surface change stability and drug release behavior of NPs were evaluated. In vitro cytotoxicity of D/O-NPs was investigated against DDP resistant human lung cancer cell line (A549/DDP cells), and in vivo anti-tumor efficiency of D/O-NPs was tested on mice bearing A549/DDP cells xenografts. D/O-NPs have a diameter of 139.6 ± 4.4 nm, a zeta potential value of +13.8 ± 1.6 mV. D/O-NPs could significantly enhance in vitro cell toxicity and in vivo antitumor effect against A549/DDP cells and lung cancer animal model compared to the single drug loaded NPs and free drugs. The results demonstrated that the D/O-NPs could be used as a promising lung cancer treatment system.

Indole Curcumin Reverses Multidrug Resistance by Reducing the Expression of ABCB1 and COX2 in Induced Multidrug Resistant Human Lung Cancer Cells

Background: Drug resistance by the cancer cells towards current chemotherapeutic approaches poses a great challenge. In the present study, an indole analogue of a well-known plant derived anticancer molecule, curcumin, was tested for its Multidrug Resistance (MDR) reversing potential in induced multi drug resistant A549 cell line. Materials and Methods: Human lung cancer cell line A549 was made Multidrug Resistant (MDR) by prolonged treatment with low dosage of Docetaxel, an established anticancer drug. The MDR induction was confirmed by morphological evidence, Hoechst 33342 staining, MTT assay, Rhodamine123 staining and RT-PCR of ABCB1 gene. Protein expression studies were carried out using western blotting technique Results and Discussions: The induced MDR A549 cells exhibited significant increase in the gene expression of ABCB1 gene at the transcriptional level. Retention and efflux studies with Pglycoprotein (P-gp) substrate Rh123 indicated that indole curcumin inhibited P-gp mediated efflux of Rhodamine. Furthermore, treatment of MDR A549 cells with indole curcumin showed downregulation of gene expression of ABCB1 and COX 2. This was also confirmed from the decreased protein expression of COX 2. Conclusion: The results of the present study indicate that indole curcumin reverses multi drug resistance by downregulating the expression of ABCB1 and COX 2 genes. Thus, indole curcumin may act as a potent modulator for ABCB1 and COX 2 mediated MDR in lung cancer.

Anti-cancer effects of the root of SB in epidermal growth factor receptor-tyrosine kinase inhibitors resistant human lung cancer cells

Anti-cancer effects of the root of SB in epidermal growth factor receptor-tyrosine kinase inhibitors resistant human lung cancer cells

The root of TK triggered apoptosis in epidermal growth factor receptor-tyrosine kinase inhibitors resistant human non-small cell lung cancer cells

The root of TK triggered apoptosis in epidermal growth factor receptor-tyrosine kinase inhibitors resistant human non-small cell lung cancer cells

Maackia amurensis agglutinin induces apoptosis in cultured drug resistant human non-small cell lung cancer cells.

The emergence of multi drug resistance in non-small cell lung cancer (NSCLC) patients is a major challenge towards the efficacy of chemotherapy. Thus, there is an urgent need for the newer, better clinically targeted strategies to treat this disease. Earlier studies from our laboratory revealed the apoptotic activity of Maackia amurensis agglutinin (MAA) in human NSCLC cells. In this study, the effect of MAA on drug resistant NSCLC cells was investigated. Two Paclitaxel-resistant NSCLC sub-lines (A549/PTX100 and NCI-H460/PTX100) were developed from A549 & NCI-H460 cell lines respectively. The generation of drug resistance phenotype was confirmed by the expression of cell surface MDR-1. Both the drug resistant sub-lines showed distinct morphological alterations. MAA interacted with the cell-surface protein(s) of apparent Mr ~66kDa and induced apoptosis in both the sub-lines through intrinsic/mitochondrial pathway, involving reduction in mitochondrial trans-membrane potential, up-regulation of Bax, unaltered/decreased expression of Bcl-XL, release of mitochondrial cytochrome c into the cytosol and activation of pro-caspases (-9&-3). Our findings highlighted the potential of this plant agglutinin to serve as an apoptosis inducing agent in drug resistant NSCLC cells.

Self-assembled Lipid Nanoparticles for Ratiometric Codelivery of Cisplatin and siRNA Targeting XPF to Combat Drug Resistance in Lung Cancer.

DNA damage repair through the nucleotide excision repair (NER) pathway is one of the major reasons for the decreased antitumor efficacy of platinum-based anticancer drugs that have been widely applied in the clinic. Inhibiting the intrinsic NER function may enhance the antitumor activity of cisplatin and conquer cisplatin resistance. Herein, we report the design, optimization, and application of a self-assembled lipid nanoparticle (LNP) system to simultaneously deliver a cisplatin prodrug together with siRNA targeting endonuclease xeroderma pigmentosum group F (XPF), a crucial component in the NER pathway. The LNP is able to efficiently encapsulate both the platinum prodrug and siRNA molecules with a tuned ratio. Both platinum prodrug and XPF-targeted siRNA are efficiently carried into cells and released; the former damages DNA and the latter specifically downregulates both mRNA and protein levels of XPF to potentiate the platinum drug, leading to enhanced expression levels of apoptosis markers and improved cytotoxicity in both cisplatin-sensitive and -resistant human lung cancer cells. Our results demonstrate an effective approach to utilize a multi-targeted nanoparticle system that can specifically silence an NER-related gene to promote apoptosis induced by cisplatin, especially in cisplatin-refractory tumors.

The Biguanides Metformin and Buformin in Combination with 2-Deoxy-glucose or WZB-117 Inhibit the Viability of Highly Resistant Human Lung Cancer Cells.

The biguanides metformin (MET) and to a lesser extent buformin (BUF) have recently been shown to exert anticancer effects. In particular, MET targets cancer stem cells (CSCs) in a variety of cancer types but these compounds have not been extensively tested for combination therapy. In this study, we investigated in vitro the anticancer activity of MET and BUF alone or in combination with 2-deoxy-D-glucose (2-DG) and WZB-117 (WZB), which are a glycolysis and a GLUT-1 inhibitor, respectively, in H460 human lung cancer cells growing under three different culture conditions with varying degrees of stemness: (1) routine culture conditions (RCCs), (2) floating lung tumorspheres (LTSs) that are enriched for stem-like cancer cells, and (3) adherent cells under prolonged periods (8-12 days) of serum starvation (PPSS). These cells are highly resistant to conventional anticancer drugs such as paclitaxel, hydroxyurea, and colchicine and display an increased level of stemness markers. As single agents, MET, BUF, 2-DG, and WZB-117 potently inhibited the viability of cells growing under RCCs. Both MET and BUF showed a strong synergistic effect when used in combination with 2-DG. A weak potentiation was observed when used with WZB-117. Under RCCs, H460 cells were more sensitive to MET and BUF and WZB-117 compared to nontumorigenic Beas-2B cells. While LTSs were less sensitive to each single drug, both MET and BUF in combination with 2-DG showed a strong synergistic effect and reduced cell viability to similar levels compared to the parental H460 cells. Adherent cells growing under PPSS were also less sensitive to each single drug, and MET and BUF showed a strong synergistic effect on cell viability in combination with 2-DG. Overall, our data demonstrates that the combination of BGs with either 2-DG or WZB-117 has “broad-spectrum” anticancer activities targeting cells growing under a variety of cell culture conditions with varying degrees of stemness. These properties may be useful to overcome the chemoresistance due to intratumoral heterogeneity found in lung cancer.

Cytosolic PKM2 stabilizes mutant EGFR protein expression through regulating HSP90-EGFR association.

This corrects the article DOI: 10.1038/onc.2015.397.

Stephania Tetrandra and Ginseng-Containing Chinese Herbal Formulation NSENL Reverses Cisplatin Resistance in Lung Cancer Xenografts.

Chinese Herbal Formulation, supplement energy and nourish lung (SENL), effectively enhances chemotherapeutic efficacy in lung cancer treatment and reverses multi-drug resistance (MDR) in lung cancer cells in vitro. The present study is designed to assess the effect of a New SENL (NSENL, modification of SENL) formulation on resistance to chemotherapy of cisplatin (DDP)-resistant human lung cancer cell line (A549/DDP) xenografts in nude mice. We assessed six constituents in NSENL by high performance liquid chromatography (HPLC). BALB/c nude mice harboring A549/DDP cell xenografts were established to assess the antitumor effect of NSENL and its impact on the expression of MDR related genes. The six constituents in NSENL, including ginsenoside Rg1, ginsenoside Rb1, ginsenoside Rg3, astragaloside IV, ophiopogonin D and tetrandrine were quantitated simultaneously by HPLC. The combination of NSENL with DDP significantly inhibited tumor growth at a rate of up to 66.8% ([Formula: see text]). In addition, NSENL as monotherapy or combined with DDP downregulated multidrug resistance-associated protein 1 (MRP1), basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor 1 (FGFR1) at both the mRNA and protein levels ([Formula: see text]), reduced glutathione S-transferase π (GST-π) protein expression and tumor microvascular density as well as decreased phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) ([Formula: see text]). These findings demonstrated that NSENL can reverse MDR in A549/DDP cells in vivo, an effect possibly associated with downregulation of MDR-associated genes as well as inhibition of bFGF/FGFR and phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR signaling pathways.

P3.02c-021 PD 0332991, a Selective Cyclin D Kinase 4/6 Inhibitor, Sensitizes Lung Cancer Cells to Killing by EGFR TKIs: Topic: Targeted Therapy

The acquired resistance of EGFR-TKIs in non-small cell lung cancer (NSCLC) is a big challenge in the targeted therapy. It is necessary to investigate whether CDK4/6 inhibitor PD 0332991 could contribute to reverse the drug resistance of EGFR TKI resistant human lung cancer cell in vitro and in vivo and to explore the underlying mechanisms. Cell viability, proliferation, cell cycle and apoptosis were measured by MTT assay, EDU assay, cell cycle and apoptosis assay, respectively. The underlying mechanisms were assessed by real-time PCR, western-blot and microarray analysis. Tumor xenograft animal study was performed to verify the effect of PD 0332991 in vivo. Lung adenocarcinoma patients with acquired resistance to EGFR-TKIs were given a tentative treatment of PD 0332991. Our study showed that PD 0332991 could potentiate significantly the gefitinib induced growth inhibition of both EGFR-TKI sensitive PC-9 and EGFR-TKI resistant PC-9/AB2 cells, through down-regulating the proliferation, inducing cell apoptosis and G0/G1 cell cycle arrest. In the mice experiments in vivo, we found the mice treated by PD 0332991 and gefitinib showed a fastest tumor regression, and a most delayed relapse pattern. The tumor from the mice treated by the combination showed a significantly down-regulated proliferation, an up-regulated apoptosis and a less angiogenesis confirmed by Ki67, TUNEL and CD34 staining, respectively. In addition, we reported an adenocarcinoma patient with gefitinib resistance had a remarkable clinical remission after administrated with PD 0332991. Our research showed, for the first time, that PD 0332991 could contribute EGFR-TKI resistant NSCLC cells to overcome the acquired resistance in vivo and in vitro. This might provide a novel treatment strategy for the patients with EGFR-TKI resistance.

Therapeutic effects of gold nanoparticles synthesized using Musa paradisiaca peel extract against multiple antibiotic resistant Enterococcus faecalis biofilms and human lung cancer cells (A549)

Botanical-mediated synthesis of nanomaterials is currently emerging as a cheap and eco-friendly nanotechnology, since it does not involve the use of toxic chemicals. In the present study, we focused on the synthesis of gold nanoparticles using the aqueous peel extract of Musa paradisiaca (MPPE-AuNPs) following a facile and cheap fabrication process. The green synthesized MPPE-AuNPs were bio-physically characterized by UV-Vis spectroscopy, FTIR, XRD, TEM, Zeta potential analysis and EDX. MPPE-AuNPs were crystalline in nature, spherical to triangular in shape, with particle size ranging within 50nm. The biofilm inhibition activity of MPPE-AuNPs was higher against multiple antibiotic resistant (MARS) Gram-positive Enterococcus faecalis. Light and confocal laser scanning microscopic observations evidenced that the MPPE-AuNPs effectively inhibited the biofilm of E.faecalis when tested at 100μgmL-1. Cytotoxicity studies demonstrated that MPPE-AuNPs were effective in inhibiting the viability of human A549 lung cancer cells at higher concentrations of 100μgmL-1. The morphological changes in the MPPE-AuNPs treated A549 lung cancer cells were visualized under phase-contrast microscopy. Furthermore, the ecotoxicity of MPPE-AuNPs on the freshwater micro crustacean Ceriodaphnia cornuta were evaluated. Notably, no mortality was recorded in MPPE-AuNPs treated C.cornuta at 250μgmL-1. This study concludes that MPPE-AuNPs are non-toxic, eco-friendly and act as a multipurpose potential biomaterial for biomedical applications.

Bufalin inhibits gefitinib resistant NCI-H460 human lung cancer cell migration and invasion in vitro

Ethnopharmacological relevanceBufalin, a component of Chan Su (frog), has been shown to have biological activities including anti-tumor effects. Gefitinib has been used as an anti-cancer drug in lung cancer patients; however, some patients eventually become gefitinib resistant. Aim of the studyIn this study, we investigated anti-metastasis effects of bufalin in gefitinib resistant NCI-H460 lung cancer cells. Materials and methodsThe effects of the bufalin in gefitinib resistant NCI-H460 lung cancer cells were investigated on cell viability using flow cytometry. The adhesion capacity, wound healing assay, invasion and migration assay, and Western blot analysis were used to understand the molecular mechanisms in this study ResultsUnder sub-lethal concentrations (from 2.5 up to 10nM), bufalin significantly inhibits cell adhension, migration and invasion nature of gefitinib resistant H460 cells. Western blotting assay revealed that bufalin depressed some of the key metastasis-related proteins, such as SOS-1, MMP-2 and Rho A underwent significant reduction. Phosphorylated Focal adhesion kinase (p-FAK), phosphorylated extracellular signal-regulated kinase (p-ERK1/2), Ras and E-cadherin were significantly reduced at 48h treatment. However, phosphorylated p38 (p-p38), phosphorylated c-Jun NH2-terminal kinase (p-JNK1/2) and NF-κBp65 were increased. ConclusionsBased on these observations, we suggest that bufalin can be used in anti-metastasis of gefitinib resistant NCI-H460 lung cancer cells in the future.

Structure activity relationship of annonaceous acetogenins against multidrug resistant human lung cancer cell line A549/Taxol in vitro

10 kinds of annonaceous acetogenins were selected for antitumor activity testing against human lung cancer cell line A549/Taxol and the structure activity relationship was analyzed.MTT assay was used to detect the inhibitory activities of 10 kinds of annonaceous acetogenins and positive drugs against A549/Taxol cells, respectively uvariamicin-Ⅲ(1), uvariamicin-Ⅱ(2), annosquacin D(3), desacetyluvaricin(4), annosquatin A(5), squamostatin D(6), bullatacin(7), squamocin(8), motrilin(9), annosquatin B(10), verapamil and cisplatin. Annonaceous acetogenins showed significant inhibitory activities against A549/Taxol cells, and were more potent than the positive drug verapamil and cisplatin.The more carbon atoms between the tetrahydrofuran ring and the lactone ring of annonaceous acetogenins exhibited more potency.Besides,ACGs with two substituted hydroxyl showed more potency than the compounds with three substituted hydroxyl in the bis-adjacent-THF ACGs. Furthermore, ACGs with three substituted hydroxyl showed more potency than the compounds with four substituted hydroxyl among the no bis-adjacent-THF ACGs.

Cytosolic PKM2 stabilizes mutant EGFR protein expression through regulating HSP90-EGFR association.

Secondary mutation of epidermal growth factor receptor (EGFR) resulting in drug resistance is one of the most critical issues in lung cancer therapy. Several drugs are being developed to overcome EGFR tyrosine kinase inhibitor (TKI) resistance. Here, we report that pyruvate kinase M2 (PKM2) stabilized mutant EGFR protein by direct interaction and sustained cell survival signaling in lung cancer cells. PKM2 silencing resulted in markedly reduced mutant EGFR expression in TKI-sensitive or -resistant human lung cancer cells, and in inhibition of tumor growth in their xenografts, concomitant with downregulation of EGFR-related signaling. Mechanistically, PKM2 directly interacted with mutant EGFR and heat-shock protein 90 (HSP90), and thus stabilized EGFR by maintaining its binding with HSP90 and co-chaperones. Stabilization of EGFR relied on dimeric PKM2, and the protein half-life of mutant EGFR decreased when PKM2 was forced into its tetramer form. Clinical levels of PKM2 positively correlated with mutant EGFR expression and with patient outcome. These results reveal a previously undescribed non-glycolysis function of PKM2 in the cytoplasm, which contribute to EGFR-dependent tumorigenesis and provide a novel strategy to overcome drug resistance to EGFR TKIs.

Structure–activity relationships of diverse ACGs against multidrug resistant human lung cancer cell line A549/Taxol

Fifteen annonaceous acetogenins (ACGs) with different stereochemical structures and configuration, representing three main classes of bis-adjacent-tetrahydrofuran (THF), bis-nonadjacent-THF, and mono-THF ACGs, were selected to tested for their inhibition activity on A549/Taxol cell line, which is multidrug resistant (MDR). The present study showed that some tested compounds showed significant activity toward A549/Taxol cells, and were more potent than the positive control Verapamil. For example, squamostatin-D (14) (IC50 value=16.19μM) was 7.8 times more active than Verapamil (IC50 value=127.09μM). Those ACGs with more carbons between the THF ring and the γ-unsaturated lactone were more potent. Moreover, ACGs with stereochemical arrangement of erythro were more active than those of threo, the compounds with THF ring configuration of cis seemed to be superior to those of trans. However, if all other structural features were identical, the ACGs with more hydroxyls on the aliphatic chain were not more potent towards A549/Taxol, which was not in accordance with previous studies. Furthermore, bis-nonadjacent-THF ACGs whose molecular weight is 622, with three hydroxyl groups located at carbon 16, 19, 24 and stereochemical arrangement of erythro possibly produced notable cytotoxicity. Based on the above conclusions, we proposed a compound model that may be a promising anti-MDR cancer candidate drug in the future clinical trial.

Microarray expression profile of long non-coding RNAs in EGFR-TKIs resistance of human non-small cell lung cancer.

The application of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) is limited by drug resistance in non-small cell lung cancer (NSCLC). Long non-coding RNAs (lncRNAs) are known to be involved in tumor development and metastasis, as well as chemotherapy resistance. To gain insight into the molecular mechanisms of EGFR-TKIs resistance, EGFR-TKIs‑sensitive and ‑resistant human lung cancer cells were analyzed by lncRNA microarray. In the present study, we found a total of 22,587 lncRNAs expressed in lung cancer cells. Of these, the expression level of 1,731 lncRNAs was upregulated >2-fold compared with gefitinib-sensitive cells while that of 2,936 was downregulated. Bioinformatics analysis (GO and pathway analyses) revealed that some classical pathways participating in cell proliferation and apoptosis were aberrantly expressed in these cells (P-value cut-off was 0.05). Enhancer-like lncRNAs and their nearby coding genes were analyzed. Six lncRNAs were identified as potential enhancers. Several lncRNAs were validated in lung cancer cell lines using RT-qPCR. To the best of our knowledge, the results showed for the first time that differentially expressed lncRNAs responded to EGFR-TKIs resistance in NSCLC cells. LncRNAs may therefore be novel candidate biomarkers and potential targets for EGFR-TKIs therapy in the future.

Knockdown of Merm1/Wbscr22 attenuates sensitivity of H460 non-small cell lung cancer cells to SN-38 and 5-FU without alteration to p53 expression levels.

Merm1/Wbscr22 is a novel metastasis promoter that has been shown to be involved in tumor metastasis, viability and apoptosis. To the best of our knowledge, there are currently no studies suggesting the possible correlation between the expression of Merm1/Wbscr22 in tumor cells and chemosensitivity to antitumor agents. In the present study, two human non-small cell lung cancer cell lines, H1299 and H460, were used to investigate whether Merm1/Wbscr22 affects chemosensitivity to antitumor agents, including cisplatin (CDDP), doxorubicin (ADM), paclitaxel (PTX), mitomycin (MMC), 7-Ethyl-10-hydroxycamptothecin (SN-38; the active metabolite of camptothecin) and 5-fluorouracil (5-FU). Merm1/Wbscr22 knockdown cell lines (H1299-shRNA and H460-shRNA) and negative control cell lines (H1299-NC and H460-NC) were established by stable transfection, and the efficiency of Merm1/Wbscr22 knockdown was confirmed by western blotting, immunofluorescence microscopy and quantitative polymerase chain reaction. The results demonstrated that shRNA-mediated knockdown of Merm1/Wbscr22 did not affect cell proliferation in vitro and in vivo. The H460 cells harboring wild type p53 were markedly more sensitive to all six antitumor agents as compared with the p53-null H1299 cells. Downregulation of Merm1/Wbscr22 did not affect H1299 sensitivity to any of the six antitumor agents, whereas attenuated H460 sensitivity to SN-38 and 5-FU, without significant alteration in p53 at both mRNA and protein levels, was identified. The reduced H460 sensitivity to SN-38 was further confirmed in vivo. SN-38 demonstrated significant tumor growth inhibitory activity in both H460 and H460‑NC tumor xenograft models, but only marginally suppressed the H460-shRNA xenograft tumor growth. Furthermore, CDDP (4, 10, 15 µg/ml)-resistant human non-small lung cancer cells A549 (A549-CDDPr-4, 10, 15) expressed significant amounts of Merm1/Wbscr22 protein, as compared with the parental A549 cells. In conclusion, shRNA-mediated knockdown of Merm1/Wbscr22 attenuates H460 sensitivity to SN-38 and 5-FU, suggesting Merm1/Wbscr22 is involved in chemosensitivity to SN-38 and 5-FU in H460 cells. No direct correlation between the p53 expression level and altered chemosensitivity was identified.