Integrin beta1 over-expression associates with resistance to tyrosine kinase inhibitor gefitinib in non-small cell lung cancer

The epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) such as gefitinib and erlotinib have been widely used in treating patients with advanced non-small cell lung cancer (NSCLC). However, acquired resistance to EGFR TKI almost occurs in every patient eventually. To identify its potential mechanism, we established a human NSCLC cell line PC9/AB2 which was 576-fold decrease in gefitinib sensitivity compared with its parental PC9 cell lines. No EGFR-T790M mutation or abnormal expression of c-Met protein was found in PC9/AB2 cells. Over-expression of integrin β1 was found, accompanied with increase of the cells' adhesion and migration. To further confirm the role of integrin β1 in gefitinib acquired resistance, we transferred its siRNA-expressing plasmid and its whole cDNA expressing plasmid into PC9/AB2 and into PC9 cells, respectively. The sensitivity of NSCLC cells to gefitinib was negatively correlated with integrin β1 expression levels. All these data suggest that up-regulation of integrin β1 might be an important factor for gefitinib resistance in NSCLC cell line PC9/AB2.     

LncRNA DUXAP9‐206 directly binds with Cbl‐b to augment EGFR signaling and promotes non‐small cell lung cancer progression

Long noncoding RNAs (lncRNAs) are involved in the pathology of various tumours, including non‐small cell lung cancer (NSCLC). However, the underlying molecular mechanisms of their specific association with NSCLC have not been fully elucidated. Here, we report that a cytoplasmic lncRNA, DUXAP9‐206 is overexpressed in NSCLC cells and closely related to NSCLC clinical features and poor patient survival. We reveal that DUXAP9‐206 induced NSCLC cell proliferation and metastasis by directly interacting with Cbl‐b, an E3 ubiquitin ligase, and reducing the degradation of epidermal growth factor receptor (EGFR) and thereby augmenting EGFR signaling in NSCLC. Notably, correlations between DUXAP9‐206 and activated EGFR signaling were also validated in NSCLC patient specimens. Collectively, our findings reveal the novel molecular mechanisms of DUXAP9‐206 in mediating the progression of NSCLC and DUXAP9‐206 may serve as a potential target for NSCLC therapy.     

Effect of simvastatin on the resistance to EGFR tyrosine kinase inhibitors in a non-small cell lung cancer with the T790M mutation of EGFR

Although non-small cell lung cancer (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFR) are highly responsive to EGFR tyrosine kinase inhibitors (TKIs) including gefitinib and erlotinib, development of acquired resistance is almost inevitable. Statins show antitumor activity, but it is unknown whether they can reverse EGFR-TKIs resistance in NSCLC with the T790M mutation of EGFR. This study investigated overcoming resistance to EGFR-TKI using simvastatin. We demonstrated that addition of simvastatin to gefitinib enhanced caspase-dependent apoptosis in T790M mutant NSCLC cells. Simvastatin also strongly inhibited AKT activation, leading to suppression of β-catenin activity and the expression of its targets, survivin and cyclin D1. Both insulin treatment and AKT overexpression markedly increased p-β-catenin and survivin levels, even in the presence of gefitinib and simvastatin. However, inhibition of AKT by siRNA or LY294002 treatment decreased p-β-catenin and survivin levels. To determine the role of survivin in simvastatin-induced apoptosis of gefitinib-resistant NSCLC, we showed that the proportion of apoptotic cells following treatment with survivin siRNA and the gefitinib–simvastatin combination was greater than the theoretical additive effects, whereas survivin up-regulation could confer protection against gefitinib and simvastatin-induced apoptosis. Similar results were obtained in erlotinib and simvastatin-treated HCC827/ER cells. These findings suggest that survivin is a key molecule that renders T790M mutant NSCLC cells resistant to apoptosis induced by EGFR-TKIs and simvastatin. Overall, these data indicate that simvastatin may overcome EGFR-TKI resistance in T790M mutant NSCLCs via an AKT/β-catenin signaling-dependent down-regulation of survivin and apoptosis induction.     

MUC3A induces PD-L1 and reduces tyrosine kinase inhibitors effects in EGFR-mutant non-small cell lung cancer

The immune checkpoint ligand programmed death-ligand 1 (PD-L1) and the transmembrane mucin (MUC) 3A are upregulated in non-small cell lung cancer (NSCLC), contributing to the aggressive pathogenesis and poor prognosis. Here, we report that knocking down the oncogenic MUC3A suppresses the PD-L1 expression in NSCLC cells. MUC3A is a potent regulator of epidermal growth factor receptor (EGFR) stability, and MUC3A deficiency downregulates the activation of the PI3K/Akt and MAPK pathways, which subsequently reduces the expression of PD-L1. Furthermore, knockdown of MUC3A and tyrosine kinase inhibitors (TKIs) in EGFR-mutant NSCLC cells play a synergistic effect on inhibited proliferation and promoted apoptosis in vitro. In the BALB/c nude mice xenograft model, MUC3A deficiency enhances EGFR-mutated NSCLC sensitivity to TKIs. Our study shows that transmembrane mucin MUC3A induces PD-L1, thereby promoting immune escape in NSCLC, while downregulation of MUC3A enhances TKIs effects in EGFR-mutant NSCLC. These findings offer insights into the design of novel combination treatment for NSCLC.     

Harnessing the lysosome-dependent antitumor activity of phenothiazines in human small cell lung cancer

Phenothiazines are a family of heterocyclic compounds whose clinical utility includes treatment of psychiatric disorders as well as chemotherapy-induced emesis. Various studies have demonstrated that these compounds possess cytotoxic activities in tumor cell lines of different origin. However, there is considerable confusion regarding the molecular basis of phenothiazine-induced cell death. Lung cancer (LC) remains one of the most prevalent and deadly malignancies worldwide despite considerable efforts in the development of treatment strategies, especially new targeted therapies. In this work, we evaluated the potential utility of phenothiazines in human LC. We show that phenothiazines as single treatment decreased cell viability and induced cell death preferentially in small cell lung carcinoma (SCLC) over non small cell lung carcinoma (NSCLC) cell lines. Sensitivity to phenothiazines was not correlated with induction of apoptosis but due to phenothiazine-induced lysosomal dysfunction. Interestingly, the higher susceptibility of SCLC cells to phenothiazine-induced cell death correlated with an intrinsically lower buffer capacity in response to disruption of lysosomal homeostasis. Importantly, this effect in SCLC occurred despite mutation in p53 and was not influenced by intrinsic sensitivity/resistance toward conventional chemotherapeutic agents. Our data thus uncovered a novel context-dependent activity of phenothiazines in SCLC and suggest that phenothiazines could be considered as a treatment regimen of this disease, however, extended cell line analyses as well as in vivo studies are needed to make such conclusion.     

The positive impact of cytological specimens for EGFR mutation testing in non‐small cell lung cancer: a single South East Asian laboratory’s analysis of 670 cases

B. Pang, D. Matthias, C.W. Ong, A.N. Dhewar, S. Gupta, G.L. Lim, M.‐E. Nga, J.E. Seet, A. Qasim, T.‐M. Chin, R. Soo, R. Soong and M. Salto‐Tellez The positive impact of cytological specimens for EGFR mutation testing in non‐small cell lung cancer: a single South East Asian laboratory’s analysis of 670 cases Objectives: To compare the rejection rates of non‐small cell lung cancer (NSCLC) samples obtained by differing sampling methods for testing by Sanger sequencing for epidermal growth factor receptor (EGFR) mutations. To assess the association between unsatisfactory outcomes and the quantity of DNA extracted from cytological versus histological samples. Methods: Six hundred and seventy NSCLC samples referred to our centre from 2008 to 2010 were reviewed as a consequence of sample rejection, presence of EGFR mutations, cytological versus histological sampling methods, DNA quantity and the unsatisfactory genotyping rate. Results: Eighty samples were rejected for testing in similar proportions of histological and cytological samples (11.9% versus 10.9%) usually (n = 75) because the amount of cellular material was judged insufficient in small biopsies or cytology samples. The remaining 590 samples on which EGFR testing was attempted yielded 51 (8.6%) unsatisfactory test outcomes caused by failure of the polymerase chain reaction (PCR) (n = 47 cases), uninterpretable Sanger chromatograms (n = 3 cases) and insufficient DNA extracted for PCR (n = 1 case). The difference in rates of unsatisfactory outcomes between cytological samples (seven of 147 samples or 4.7%) versus tissue samples (44 of 443 samples or 9.9%) was clinically relevant but not statistically significant (Mann–Whitney test; P < 0.081). There was no association between the concentration of DNA extracted and the likelihood of an unsatisfactory analysis; which was similar in all types of sections (large and small) while 0% of 37 cytology slides were unsatisfactory. Conclusions: Utilizing cytology samples for EGFR testing avoids unnecessary patient re‐biopsing and yields a clinically superior satisfactory rate to the overall satisfactory rate of tissue biopsies of NSCLC. The quality rather than quantity of DNA extracted may be a more important determinant of a satisfactory result.     

Novel irreversible EGFR tyrosine kinase inhibitor 324674 sensitizes human colon carcinoma HT29 and SW480 cells to apoptosis by blocking the EGFR pathway

Background

Epidermal growth factor receptor (EGFR) is widely expressed in multiple solid tumors including colorectal cancer by promoting cancer cell growth and proliferation. Therefore, the inhibition of EGFR activity may establish a clinical strategy of cancer therapy.

Methods

In this study, using human colon adenocarcinoma HT29 and SW480 cells as research models, we compared the efficacy of four EGFR inhibitors in of EGFR-mediated pathways, including the novel irreversible inhibitor 324674, conventional reversible inhibitor AG1478, dual EGFR/HER2 inhibitor GW583340 and the pan-EGFR/ErbB2/ErbB4 inhibitor. Cell proliferation was assessed by MTT analysis, and apoptosis was evaluated by the Annexin-V binding assay. EGFR and its downstream signaling effectors were examined by western blotting analysis.

Results

Among the four inhibitors, the irreversible EGFR inhibitor 324674 was more potent at inhibiting HT29 and SW480 cell proliferation and was able to efficiently induce apoptosis at lower concentrations. Western blotting analysis revealed that AG1478, GW583340 and pan-EGFR/ErbB2/ErbB4 inhibitors failed to suppress EGFR activation as well as the downstream mitogen-activated protein kinase (MAPK) and PI3K/AKT/mTOR (AKT) pathways. In contrast, 324674 inhibited EGFR activation and the downstream AKT signaling pathway in a dose-dependent manner.

Conclusion

Our studies indicated that the novel irreversible EGFR inhibitor 324674 may have a therapeutic application in colon cancer therapy.     

The EGFR inhibitor gefitinib suppresses ligand-stimulated endocytosis of EGFR via the early/late endocytic pathway in non-small cell lung cancer cell lines

The drug gefitinib (Iressa), which is a specific inhibitor of EGFR tyrosine kinase, has been shown to suppress the activation of EGFR signaling for survival and proliferation in non-small cell lung cancer (NSCLC) cell lines. A recent study demonstrated rapid down-regulation of ligand-induced EGFR in a gefitinib-sensitive cell line and inefficient down-regulation of EGFR in a gefitinib-resistant cell line in the exponential phase of growth; this implies that each cell type employs a different unknown down-regulation mechanism occurs. However, the mechanism of drug sensitivity to gefitinib remains unclear. In this study, to further substantiate the effect of gefitinib on the EGFR down-regulation pathway and to understand the detailed internalization mechanism of gefitinib-sensitive PC9 and gefitinib-resistant QG56 cell lines, we examined the internalization of Texas red-EGF in the absence or presence of gefitinib in both cell lines. The distribution of internalized Texas red-EGF, early endosomes, and late endosomes/lysosomes was then assessed by confocal immunofluorescence microscopy. Here, we provide novel evidence that efficient endocytosis of EGF–EGFR occurs via the endocytic pathway in the PC9 cells, because the internalized Texas red-EGF-positive small punctate vesicles were transported to the late endosomes/lysosomes and then degraded within the lysosomes after 60 min of internalization. Additionally, gefitinib exerted a strong inhibitory effect on the endocytosis of EGFR in PC9 cells, and the internalization rate of EGFR from the plasma membrane via the early endosomes to the late endosomes/lysosomes was considerably delayed. This indicates that gefitinib efficiently suppresses ligand-stimulated endocytosis of EGFR via the early/late endocytic pathway in PC9 cells. In contrast, the internalization rate of ligand-induced EGFR was not significantly changed by gefitinib in QG56 cells because even in the absence of gefitinib, internalized EGFR accumulation was noted in the early and late endosomes after 60 min of internalization instead of its delivery to the lysosomes in QG56 cells. This suggests that the endocytic machinery of EGFR might be basically impaired at the level of the early/late endosomes. Taken together, this is the first report demonstrating that the suppressive effect of gefitinib on the endocytosis of EGFR is much stronger with PC9 cells than QG56 cells. Thus, impairment in some steps of the EGF–EGFR traffic out of early endosomes toward the late endosomes/lysosomes might confer gefitinib-resistance in NSCLC cell lines. Iressa is a trademark of the AstraZeneca group of companies.     

Bombesin production by human small cell carcinoma of the lung

A series of continuous cell lines of human small cell carcinoma of the lung (SCCL) have been evaluated for the production of bombesin (BN). In early established cultures BN was detected in the medium of 9 out of 11 cell lines and in 6 out of 7 cell homogenates examined. Levels in the medium were frequently higher in cultures of later passages compared to earlier passages of the same line and low levels developed in the two previously negative cell lines. Plasma concentrations were greater than 80 pmol/l in 2 out of 27 (7%) randomly selected patients with SCCL. A culture (DMS 406) established from the tumor of a patient with the highest plasma level (1240 pmol/l) was the highest producer in vitro. The results indicate that BN, which has been demonstrated immunocytochemically to be present in normal bronchial mucosal cells, is frequently produced by SCCL in vitro but elevated plasma levels are infrequently found in patients with this neoplasm.     

Cx31.1 acts as a tumour suppressor in non-small cell lung cancer (NSCLC) cell lines through inhibition of cell proliferation and metastasis

Reduced connexin expression and loss of gap junction function is a characteristic of many cancers, including lung cancer. However, there are little reports about the relation between Cx31.1 and lung cancer. This study was conducted to investigate the effect of Cx31.1 on non-small cell lung cancer (NSCLC). We found that the Cx31.1 was down-regulated in NSCLC cell lines, and the expression levels were reversely related with their metastatic potential. We ectopically expressed Cx31.1 in H1299 NSCLC cell line to examine the influence of Cx31.1 overexpression. The results showed that overexpression of Cx31.1 in H1299 cells reduced cell proliferation, induced a delay in the G(1) phase, inhibited anchorage-independent growth and suppressed cell migration and invasion. The cell cycle delay and cell migration and invasion suppressive effects of Cx31.1 were partially reversed by siRNA targeting mRNA of Cx31.1. Moreover, xenografts of Cx31.1 overexpressing H1299 cells showed reduced tumourigenicity. These results suggested that Cx31.1 has tumour-suppressive properties. Further investigation indicated that cyclin D3 may be responsible for Cx31.1-induced G(1) phase delay. Importantly, Cx31.1 increased the expression of epithelial markers, such as cytokeratin 18, and decreased expression of mesenchymal markers, such as vimentin, indicating a Cx31.1-mediated partial shift from a mesenchymal towards an epithelial phenotype. We concluded that Cx31.1 inhibit the malignant properties of NSCLC cell lines, the mechanisms under this may include regulation of EMT.     

S100B promotes the proliferation, migration and invasion of specific brain metastatic lung adenocarcinoma cell line

Brain metastasis frequently occurs in cancer patients and is associated with a poor prognosis. We previously reported that S100B was highly expressed in PC14/B, a specific brain metastatic lung adenocarcinoma cell line, which suggests that it is associated with brain metastasis of lung cancer. However, the role of S100B in brain metastasis remains to be elucidated. In this study, using PC14/B cell line, we found that siRNA mediated depletion of S100B in PC14/B cells led to notable differences in cell proliferation, apoptosis, cell cycle progression, colony formation ability, cell migratory and invasive activity compared with the mock-transfected cells. Therefore, our data suggest that S100B promotes the brain metastasis of lung adenocarcinoma by promoting cell proliferation, preventing apoptosis and increasing cell migration and invasion.     

Ceramide kinase regulates growth and survival of A549 human lung adenocarcinoma cells

Ceramide-1-phosphate (C1P) is emerging as a new addition to the family of bioactive sphingolipid metabolites. At low concentrations, C1P enhanced survival of NIH 3T3 fibroblasts and A549 lung cancer cells, while at high concentrations, it reduced survival and induced apoptosis. Apoptosis correlated with degradation of C1P to pro-apoptotic ceramide. To examine the role of endogenous C1P, expression of ceramide kinase, the enzyme that produces C1P, was downregulated, which reduced cellular proliferation, progression into S phase and enhanced apoptosis induced by serum starvation. Our results suggest that ceramide kinase determines the balance between pro-apoptotic ceramide and anti-apoptotic C1P to regulate cell fate, reminiscent of its function in plants.     

Crosstalk between Epidermal Growth Factor Receptors (EGFR) and integrins in resistance to EGFR tyrosine kinase inhibitors (TKIs) in solid tumors

Cell adhesion to the extracellular matrix (ECM) is important in a variety of physiological and pathologic processes, including development, tumor invasion, and metastasis. Integrin-mediated attachment to ECM proteins has emerged to cue events primitively important for the transformed phenotype of human cancer cells. Cross-talk between integrins and growth factor receptors takes an increasingly prominent role in defining adhesion, motility, and cell growth. This functional interaction has expanded beyond to link integrins with resistance to Tyrosine kinase inhibitors (TKIs) of Epidermal Growth Factor Receptors (EGFRs). In this regard, integrin-mediated adhesion has two separate functions one as a clear collaborator with growth factor receptor signaling and the second as a basic mechanism contributing in Epithelial to Mesenchymal Transition (EMT) which affects response to chemotherapy. This review provides an overview of these mechanisms and describes treatment options for selectively targeting and disrupting integrin interaction to EGFR for cancer therapy.     

The function of BED finger domain of Zbed3 in regulating lung cancer cell proliferation

Zbed3, a BED finger domain-containing protein was found to promote cancer proliferation by regulating β-catenin expression through interacting with Axin. But whether and how BED finger domain function in regulating cancer proliferation is unknown. We constructed five mutants of Zbed3, which lacks the Axin-Zbed3 binding site, and the 43 to 52, 69 to 77, 87 to 92, and 97 to 104 sequences in BED finger domain, respectively and named them as Z-A, Z1, Z2, Z3, and Z4. Transfection of both wild-type of Zbed3 and the mutants Z1, Z3, and Z4 (P < 0.05), but not Z2 (P > 0.05) significantly upregulated β-catenin expression in NCI-H1299 cells. Overexpression of both wild-type of Zbed3 and the mutants Z1, Z3, and Z4 (P < 0.05) but not Z2 (P > 0.05) significantly promoted cancer cell proliferation and invasion. The ability of proliferation (P < 0.05) but not invasion (P < 0.05) of cancer cells transfected with Z1 and Z4 was significantly lower than that with wild-type Zbed3 and Z3. Overexpression of wild-type Zbed3 (P < 0.05) but not the mutant Z-A, which lacks the binding site with Axin and Z2 (P > 0.05) significantly upregulated the interaction of Axin and Zbed3, β-catenin expression and the activity of Wnt signaling. Both overexpression of wild-type Zbed3 and the mutant Z1 and Z4 significantly upregulated the activity of Wnt signaling and promoted cancer cell proliferation (P < 0.05) but only overexpression of wild-type Zbed3 (P < 0.05), but not the mutant Z1, and Z4 (P > 0.05), significantly upregulated the expression of proliferating cell nuclear antigen (PCNA) in NCI-H1299 cells. These results indicate that Zbed3 may promote lung cancer cell proliferation through regulating PCNA expression besides regulating β-catenin expression and BED finger domain can impact on this function.     

The genomic alterations of lung adenocarcinoma and lung squamous cell carcinoma can explain the differences of their overall survival rates

In the US, lung carcinoma accounted for over 150,000 deaths in 2018 and the advances in increasing survival rates are still limited. In this study, we investigated the cohorts with lung adenocarcinoma (LUAD) or lung squamous cell carcinoma (LUSC) from The Cancer Genome Atlas to figure out the risk factors and genomic alterations that affected their prognosis. The histoclinical factors that differed between LUAD and LUSC were identified and the risk factors affecting the overall survival were figured out for both LUAD and LUSC. Next, the patterns of nucleotides substitutions and the mutational signatures were extracted to illustrate whether different mutational processes performed for them. Finally, the genes that had different frequencies of mutation were identified. LUAD and LUSC presented differences in histoclinical factors including age at the time of diagnosis, sex, smoking history, pathological T classification, and overall survival. This was caused by the distinct genomic alterations including the transition-to-transversion ratios, mutational signatures, and the frequently mutated genes. We proposed that the mutational signature associated with aging could be used to predict the prognosis of patients with LUAD. On the other hand, the AID/APOBEC family was associated with the prognosis of LUSC. Finally, SNTG1 and LRRK2 might be important in LUAD and LUSC, respectively.     

New pemetrexed‐peptide conjugates: synthesis,characterization and in vitro cytostatic effect on non‐small cell lung carcinoma (NCI‐H358) and human leukemia (HL‐60) cells

Pemetrexed (Pem) is a novel antimetabolite type of anticancer drug that demonstrated promising clinical activity in a wide variety of solid tumors, including non‐small cell lung carcinoma and malignant pleural mesothelioma. It inhibits enzymes involved in the folate pathway, for which the presence of its free carboxylic groups is necessary. The heteroaromatic ring system of Pem has a modifiable amino group, which opens a possibility to apply a new strategy to conjugate Pem to carrier molecules. Considering this as well as the necessity of untouched carboxylic groups of Pem in the new conjugates, we developed a new synthesis strategy. Here, we describe the synthesis and the characterization of new Pem‐peptide conjugates in which cell‐penetrating octaarginine or/and lung‐targeting H‐Ile‐Glu‐Leu‐Leu‐Gln‐Ala‐Arg‐NH₂ peptide is attached to the drug by thioether bond. The conjugates characterized by RP‐HPLC and MS exhibited cytostatic effect in vitro on non‐small cell lung carcinoma as well as on human leukemia cell lines. The IC₅₀ values of the conjugates were similar, but the conjugates with H‐Ile‐Glu‐Leu‐Leu‐Gln‐Ala‐Arg‐NH₂ sequence were slightly more effective. Our data show that the in vitro cytostatic effect of the free Pem was essentially maintained after conjugation with cell‐penetrating or cell‐targeting peptides. Thus, the conjugation strategy reported could lead to the development of a new generation of active Pem conjugates. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Clinical relevance and functional implications for human leucocyte antigen‐g expression in non‐small‐cell lung cancer

HLA‐G has been documented both in establishment of anti‐tumour immune responses and in tumour evasion. To investigate the clinical relevance of HLA‐G in non‐small‐cell lung cancer (NSCLC), expression status and potential significance of HLA‐G in NSCLC were analysed. In this study, HLA‐G expression in 101 NSCLC primary lesions and plasma soluble HLA‐G (sHLA‐G) from 91 patients were analysed with immunohistochemistry and ELISA, respectively. Correlations between HLA‐G status and various clinical parameters including survival time were evaluated. Meanwhile, functional analysis of transfected cell surface HLA‐G expression and plasma sHLA‐G form NSCLC patients on natural killer (NK) cell cytolysis were performed. Data revealed that HLA‐G was expressed in 41.6% (42/101) NSCLC primary lesions, while undetectable in adjacent normal lung tissues. HLA‐G expression in NSCLC lesions was strongly correlated to disease stages (P= 0.002). Plasma sHLA‐G from NSCLC patients was markedly higher than that in normal controls (P= 0.004), which was significantly associated with the disease stages (I versus IV, P= 0.025; II versus IV, P= 0.029). Patient plasma sHLA‐G level (≥median, 32.0 U/ml) had a significantly shorter survival time (P= 0.044); however, no similar significance was observed for the lesion HLA‐G expression. In vitro data showed that both cell surface HLA‐G and patient plasma sHLA‐G could dramatically decrease the NK cell cytolysis. Our findings indicated that both lesion HLA‐G expression and plasma sHLA‐G in NSCLC is related to the disease stage and can exert immunosuppression to the NK cell cytolysis, indicating that HLA‐G could be a potential therapeutic target. Moreover, plasma sHLA‐G in NSCLC patients could be used as a prognosis factor for NSCLC.     

Endogenous thrombopoietin promotes non‐small‐cell lung carcinoma cell proliferation and migration by regulating EGFR signalling

Thrombopoietin (TPO) is a haematopoietic cytokine mainly produced by the liver and kidneys, which stimulates the production and maturation of megakaryocytes. In the past decade, numerous studies have investigated the effects of TPO outside the haematopoietic system; however, the role of TPO in the progression of solid cancer, particularly lung cancer, has not been well studied. Exogenous TPO does not affect non‐small‐cell lung cancer (NSCLC) cells as these cells show no or extremely low TPO receptor expression; therefore, in this study, we focused on endogenous TPO produced by NSCLC cells. Immunohistochemical analysis of 150 paired NSCLC and adjacent normal tissues indicated that TPO was highly expressed in NSCLC tissues and correlated with clinicopathological parameters including differentiation, P‐TNM stage, lymph node metastasis and tumour size. Suppressing endogenous TPO by small interfering RNA inhibited the proliferation and migration of NSCLC cells. Moreover, TPO interacted with the EGFR protein and delayed ligand‐induced EGFR degradation, thus enhancing EGFR signalling. Notably, overexpressing TPO in EGF‐stimulated NSCLC cells facilitated cell proliferation and migration, whereas no obvious changes were observed without EGF stimulation. Our results suggest that endogenous TPO promotes tumorigenicity of NSCLC via regulating EGFR signalling and thus could be a therapeutic target for treating NSCLC.