Downregulation of CPA4 inhibits non small-cell lung cancer growth by suppressing the AKT/c-MYC pathway

Carboxypeptidase A4 negatively regulates HGS-ETR1/2-induced pyroptosis by forming a positive feedback loop with the AKT signalling pathway

Pyroptosis, a mode of inflammatory cell death, has recently gained significant attention. However, the underlying mechanism remains poorly understood. HGS-ETR1/2 is a humanized monoclonal antibody that can bind to DR4/5 on the cell membrane and induce cell apoptosis by activating the death receptor signalling pathway. In this study, by using morphological observation, fluorescence double staining, LDH release and immunoblot detection, we confirmed for the first time that HGS-ETR1/2 can induce GSDME-mediated pyroptosis in hepatocellular carcinoma cells. Our study found that both inhibition of the AKT signalling pathway and silencing of CPA4 promote pyroptosis, while the overexpression of CPA4 inhibits it. Furthermore, we identified a positive regulatory feedback loop is formed between CPA4 and AKT phosphorylation. Specifically, CPA4 modulates AKT phosphorylation by regulating the expression of the AKT phosphatase PP2A, while inhibition of the AKT signalling pathway leads to a decreased transcription and translation levels of CPA4. Our study reveals a novel mechanism of pyroptosis induced by HGS-ETR1/2, which may provide a crucial foundation for future investigations into cancer immunotherapy.

Angiopoietin-1 promotes triple-negative breast cancer cell proliferation by upregulating carboxypeptidase A4

Angiopoietin-1 (ANG1) is a pro-angiogenic regulator that contributes to the progression of solid tumors by stimulating the proliferation, migration and tube formation of vascular endothelial cells, as well as the renewal and stability of blood vessels. However, the functions and mechanisms of ANG1 in triple-negative breast cancer (TNBC) are unclear. The clinical sample database shows that a higher level of ANG1 in TNBC is associated with poor prognosis compared to non-TNBC. In addition, knockdown of ANG1 inhibits TNBC cell proliferation and induces cell cycle G1 phase arrest and apoptosis. Overexpression of ANG1 promotes tumor growth in nude mice. Mechanistically, ANG1 promotes TNBC by upregulating carboxypeptidase A4 (CPA4) expression. Overall, the ANG1-CPA4 axis can be a therapeutic target for TNBC.

Recent Developments and Challenges in Molecular-Targeted Therapy of Non-Small-Cell Lung Cancer

Treatment of lung cancer with conventional therapies, which include radiation, surgery, and chemotherapy results in multiple undesirable adverse or side effects. The major clinical challenge in developing new drug therapies for lung cancer is resistance, which involves mutations and disturbance in various signaling pathways. Molecular abnormalities related to epidermal growth factor receptor (EGFR), v-Raf murine sarcoma viral oncogene homolog B1 (B-RAF) Kirsten rat sarcoma virus (KRAS) mutations, translocation of the anaplastic lymphoma kinase (ALK) gene, mesenchymal-epithelial transition factor (MET) amplification have been studied to overcome the resistance and to develop new therapies for non-small cell lung cancer (NSCLC). But, inevitable development of resistance presents limits the clinical benefits of various new drugs. Here, we review current progress in the development of molecularly targeted therapies, concerning six clinical biomarkers: EGFR, ALK, MET, ROS-1, KRAS, and B-RAF for NSCLC treatment.

Knockdown of carboxypeptidase A4 (CPA4) inhibits gastric cancer cell progression via cell cycle arrest and apoptosis

Background

Gastric cancer is one of the most prevalent cancers, with a low survival rate at the later stages. Carboxypeptidase A4 (CPA4) is associated with the aggressiveness and growth in cancer. However, its regulatory role in gastric cancer remains unknown. Therefore, we investigated the role of CPA4 in gastric cancer progression in vitro.

Methods

The human gastric adenocarcinoma cell line (AGS cell line) was used in the present study. CPA4 knockdown lentiviruses were constructed. Western blot analysis was performed to evaluate the protein expression levels of epithelial-mesenchymal transition (EMT) transcription factors, EMT biomarkers, and proteins involved in the Wnt signaling pathway, mitogen-activated protein kinase (MAPK) signaling pathway, and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was carried out to evaluate the mRNA expression level of CPA4. The String database was employed for protein-protein interaction (PPI) network analysis. Cell colony formation, proliferation, migration, invasion, apoptosis, and cell cycle analyses were performed using corresponding kits.

Results

CPA4 is highly expressed in gastric cancer cell lines. Overexpressed CPA4 was associated with the induction of EMT. Knockdown of CPA4 inhibited cell colony formation, proliferation, migration, and invasion of gastric cancer cells. Knockdown of CPA4 also promoted cell apoptosis of gastric cancer cells.

Conclusions

Knockdown of CPA4 inhibited cell progression via arresting the cell cycle and inducing EMT in gastric cancer.

STIL Promotes Tumorigenesis of Bladder Cancer by Activating PI3K/AKT/mTOR Signaling Pathway and Targeting C-Myc

SCL/TAL1 interrupting locus (STIL) regulates centriole replication and causes chromosome instability, which is closely related to malignant tumors. The purpose of our study was to investigate the role of STIL in bladder cancer (BC) tumorigenesis for the first time. The public database indicated that STIL is highly expressed and correlated with the cell cycle in BC. Immunohistochemistry staining showed that STIL expression is significantly elevated in BC tissues compared with paracancer tissues. CRISPR-Cas9 gene editing technology was used to induce BC cells to express STIL-specific sgRNA, revealing a significantly delayed growth rate in STIL knockout BC cells. Moreover, cell cycle arrest in the G0/G1 phase was triggered by decreasing STIL, which led to delayed BC cell growth in vitro and in vivo. Mechanically, STIL knockout inhibited the PI3K/AKT/mTOR pathway and down-regulated the expression of c-myc. Furthermore, SC79 (AKT activating agent) partially reversed the inhibitory effects of STIL knockout on the proliferation and migration of BC cells. In conclusion, STIL enhanced the PI3K/AKT/mTOR pathway, resulting in increased expression of c-myc, ultimately promoting BC occurrence and progression. These results indicate that STIL might be a potential target for BC patients.

The BRCT Domain from the Homologue of the Oncogene PES1 in Leishmania major (LmjPES) Promotes Malignancy and Drug Resistance in Mammalian Cells

Around 15% of cancer cases are attributable to infectious agents. Epidemiological studies suggest that an association between leishmaniasis and cancer does exist. Recently, the homologue of PES1 in Leishmania major (LmjPES) was described to be involved in parasite infectivity. Mammalian PES1 protein has been implicated in cellular processes like cell cycle regulation. Its BRCT domain has been identified as a key factor in DNA damage-responsive checkpoints. This work aimed to elucidate the hypothetical oncogenic implication of BRCT domain from LmjPES in host cells. We generated a lentivirus carrying this BRCT domain sequence (lentiBRCT) and a lentivirus expressing the luciferase protein (lentiLuc), as control. Then, HEK293T and NIH/3T3 mammalian cells were infected with these lentiviruses. We observed that the expression of BRCT domain from LmjPES conferred to mammal cells in vitro a greater replication rate and higher survival. In in vivo experiments, we observed faster tumor growth in mice inoculated with lentiBRCT respect to lentiLuc HEK293T infected cells. Moreover, the lentiBRCT infected cells were less sensitive to the genotoxic drugs. Accordingly, gene expression profiling analysis revealed that BRCT domain from LmjPES protein altered the expression of proliferation- (DTX3L, CPA4, BHLHE41, BMP2, DHRS2, S100A1 and PARP9), survival- (BMP2 and CARD9) and chemoresistance-related genes (DPYD, Dok3, DTX3L, PARP9 and DHRS2). Altogether, our results reinforced the idea that in eukaryotes, horizontal gene transfer might be also achieved by parasitism like Leishmania infection driving therefore to some crucial biological changes such as proliferation and drug resistance.

Cadmium Toxicity Is Regulated by Peroxisome Proliferator-Activated Receptor δ in Human Proximal Tubular Cells

Cadmium (Cd) is a toxic heavy metal that is widely present in the environment. Renal proximal tubule disorder is the main symptom of Cd chronic poisoning. Our previous study demonstrated that Cd inhibits the total activities of peroxisome proliferator-activated receptor (PPAR) transcription factors in human and rat proximal tubular cells. In this study, we investigated the involvement of PPAR in Cd renal toxicity using the HK-2 human proximal tubular cell line. Among PPAR isoform genes, only PPARD knockdown significantly showed resistance to Cd toxicity in HK-2 cells. The transcriptional activity of PPARδ was decreased not only by PPARD knockdown but also by Cd treatment. DNA microarray analysis showed that PPARD knockdown changed the expression of apoptosis-related genes in HK-2 cells. PPARD knockdown decreased apoptosis signals and caspase-3 activity induced by Cd treatment. PPARD knockdown did not affect the intracellular Cd level after Cd treatment. These results suggest that PPARδ plays a critical role in the modification of susceptibility to Cd renal toxicity and that the apoptosis pathway may be involved in PPARδ-related Cd toxicity.

Proteomic Changes in the Monolayer and Spheroid Melanoma Cell Models of Acquired Resistance to BRAF and MEK1/2 Inhibitors

Extracellular signal-regulated kinase-1/2 (ERK1/2) pathway inhibitors are important therapies for treating many cancers. However, acquired resistance to most protein kinase inhibitors limits their ability to provide durable responses. Approximately 50% of malignant melanomas contain activating mutations in BRAF, which promotes cancer cell survival through the direct phosphorylation of the mitogen-activated protein kinase MAPK/ERK 1/2 (MEK1/2) and the activation of ERK1/2. Although the combination treatment with BRAF and MEK1/2 inhibitors is a recommended approach to treat melanoma, the development of drug resistance remains a barrier to achieving long-term patient benefits. Few studies have compared the global proteomic changes in BRAF/MEK1/2 inhibitor-resistant melanoma cells under different growth conditions. The current study uses high-resolution label-free mass spectrometry to compare relative protein changes in BRAF/MEK1/2 inhibitor-resistant A375 melanoma cells grown as monolayers or spheroids. While approximately 66% of proteins identified were common in the monolayer and spheroid cultures, only 6.2 or 3.6% of proteins that significantly increased or decreased, respectively, were common between the drug-resistant monolayer and spheroid cells. Drug-resistant monolayers showed upregulation of ERK-independent signaling pathways, whereas drug-resistant spheroids showed primarily elevated catabolic metabolism to support oxidative phosphorylation. These studies highlight the similarities and differences between monolayer and spheroid cell models in identifying actionable targets to overcome drug resistance.

Comprehensive Analysis of CPA4 as a Poor Prognostic Biomarker Correlated with Immune Cells Infiltration in Bladder Cancer

Simple Summary

The overexpression of Carboxypeptidase A4 (CPA4) has been observed in plenty of types of cancer and has been elucidated to promote tumor growth and invasion; however, its role in bladder urothelial carcinoma (BLCA) is still unclear. Therefore, we aimed to show the prognostic role of CPA4 and its relationship with immune infiltrates in BLCA. We confirmed that the overexpression of CPA4 is associated with shorter overall survival, disease-specific survival, progress-free intervals, and higher dead events. Moreover, we found that several infiltrating immune cells (Th1cell, Th2 cell, T cell exhaustion, and Tumor-associated macrophage) were correlated with the expression of CPA4 in bladder cancer using TIMER2 and GEPIA2. In conclusion, CPA4 may be a novel and great prognostic biomarker based on bioinformation analysis in BLCA.

Abstract

Carboxypeptidase A4 (CPA4) has shown the potential to be a biomarker in the early diagnosis of certain cancers. However, no previous research has linked CPA4 to therapeutic or prognostic significance in bladder cancer. Using data from The Cancer Genome Atlas (TCGA) database, we set out to determine the full extent of the link between CPA4 and BLCA. We further analyzed the interacting proteins of CPA4 and infiltrated immune cells via the TIMER2, STRING, and GEPIA2 databases. The expression of CPA4 in tumor and normal tissues was compared using the TCGA + GETx database. The connection between CPA4 expression and clinicopathologic characteristics and overall survival (OS) was investigated using multivariate methods and Kaplan–Meier survival curves. The potential functions and pathways were investigated via gene set enrichment analysis. Furthermore, we analyze the associations between CPA4 expression and infiltrated immune cells with their respective gene marker sets using the ssGSEA, TIMER2, and GEPIA2 databases. Compared with matching normal tissues, human CPA4 was found to be substantially expressed. We confirmed that the overexpression of CPA4 is linked with shorter OS, DSF(Disease-specific survival), PFI(Progression-free interval), and increased diagnostic potential using Kaplan–Meier and ROC analysis. The expression of CPA4 is related to T-bet, IL12RB2, CTLA4, and LAG3, among which T-bet and IL12RB2 are Th1 marker genes while CTLA4 and LAG3 are related to T cell exhaustion, which may be used to guide the application of checkpoint blockade and the adoption of T cell transfer therapy.

Insufficient ablation promotes the metastasis of residual non-small cell lung cancer (NSCLC) cells via upregulating carboxypeptidase A4

BACKGROUND

Thermal ablation is a potentially curative therapy for early-stage non-small cell lung cancer (NSCLC). Early recurrence after thermal ablation necessitates our attention.

METHODS

The invasion and migration abilities of NSCLC after sublethal heat stimulus were observed in vitro and in vivo. Sublethal thermal stimulus molecular changes were identified by RNA sequencing. A xenograft model of NSCLC with insufficient ablation was established to explore the epithelial-to-mesenchymal transition (EMT) and metastasis-related phenotypes alteration of residual tumors.

RESULTS

In vitro, the invasion and migration abilities of NSCLC cells were enhanced 72 h after 44 °C and 46 °C thermal stimulus. Epithelial-mesenchymal transition (EMT) phenotypes were also upregulated under these conditions. RNA sequencing revealed that the expression of carboxypeptidase A4 (CPA4) was significantly upregulated after thermal stimulus. Significant upregulation of CPA4 and EMT phenotypes was also found in the xenograft model of insufficient NSCLC ablation. The EMT process and invasion and migration abilities can be reversed by silencing CPA4.

CONCLUSIONS

This study demonstrates that sublethal heat stimulus caused by insufficient ablation can promote EMT and enhance the metastatic capacity of NSCLC. CPA4 plays an important role in these biological processes. Inhibition of CPA4 might be of great significance for improving early-stage NSCLC survival after ablation.

Non-coding RNA in cancer

Majority of the human genome is transcribed to RNAs that do not encode proteins. These non-coding RNAs (ncRNAs) play crucial roles in regulating the initiation and progression of various cancers. Given the importance of the ncRNAs, the roles of ncRNAs in cancers have been reviewed elsewhere. Thus, in this review, we mainly focus on the recent studies of the function, regulatory mechanism and therapeutic potential of the ncRNAs including microRNA (miRNA), long ncRNA (lncRNA), circular RNA (circRNA) and PIWI interacting RNA (piRNA), in different type of cancers.

Carboxypeptidase A4 negatively correlates with p53 expression and regulates the stemness of breast cancer cells

Background: Triple-negative breast cancer (TNBC) is an aggressive cancer subtype lacking effective treatment options, and p53 is the most frequently mutated or deleted gene. Carboxypeptidase A4 (CPA4) is an extracellular metallocarboxypeptidase, which was closely associated with aggressiveness. Although a recent study indicated that CPA4 could induce epithelial‑mesenchymal transition in breast cancer cells, no studies investigated its stemness-related function and the correlation between CPA4 and p53 in TNBC. In this study, we aimed to investigate the CPA4 levels in breast cancer tissues and analyze its association with p53, and study its roles in cancer stemness maintenance. Methods: CPA4 mRNA level and its prognostic value were analyzed by using online database UALCAN (http://ualcan.path.uab.edu) and Kaplan-Meier plotter (www.kmplot.com), respectively. The expression of CPA4, p53 and ALDH1A1 in breast cancer and adjacent normal tissues were evaluated by IHC using the corresponding primary antibodies on a commercial tissue array (Shanghai Biochip Co., Ltd., Shanghai, China). siRNA knockdown was used to study the function of proliferation, colony formation assay and sphere formation in serum-free medium. Results: Analysis of the UALCAN datasets identified that CPA4 mRNA levels were elevated in TNBC, especially in the TP53-mutant subgroup. Furthermore, high levels of CPA4 mRNA were significantly associated with unfavourable overall survival OS in breast cancer patients. Immunohistochemistical analysis demonstrated that CPA4 levels were elevated in 32.1% of breast cancer samples (45/140), and the positive rates of ALDH1A1 and p53 in the breast cancer tissues were 25% (35/140) and 50% (70/140), respectively. Statistical analysis revealed high levels of CPA4 was significantly associated with TNBC phenotype. Correlation analysis indicated that CPA4 over-expression was positively associated with ALDH1A1 (P<0.01) and negatively correlated with p53 (P<0.05). In Kaplan-Meier survival analysis, either high CPA4 or ALDH1A1 levels was significantly correlated with poor survival in breast cancer patients. Functional studies demonstrated that down-regulation of CPA4 significantly inhibited TNBC cell proliferation, colony-formation assays in soft agar and sphere formation in serum-free medium. Conclusion: This study demonstrated for the first time that CPA4 was negatively correlates with p53 expression and inhibition of CPA4 could reduce the number of breast cancer cells with stemness property. It might be a potential target for the TNBC treatment.

Knockdown of circ0082374 inhibits cell viability, migration, invasion and glycolysis in glioma cells by miR-326/SIRT1

Circular RNAs (circRNAs) play important roles in the development and treatment of glioma. However, the role and mechanism of circRNA carboxypeptidase A4 (circ0082374) in glioma are largely unknown. Forty-two glioma patients and 28 normal patients were recruited. Glioma cell lines A172 and U251 were used for functional assays. The expression levels of circ0082374, microRNA-326 (miR-326) and sirtuin 1 (SIRT1) were examined via quantitative real-time polymerase chain reaction or western blot. Cell viability, migration, invasion and glycolysis were measured via cell counting kit-8, trans-well, oxygen consumption rate and western blot, respectively. The target correlation of circ0082374/miR-326 or miR-326/SIRT1 was explored via dual-luciferase reporter, RNA immunoprecipitation and pull-down assays. The role of circ0082374 in vivo was investigated via xenograft model. We found circ0082374 expression was elevated in glioma tissues and cells. Knockdown of circ0082374 suppressed the viability, migration, invasion and glycolysis in glioma cells. miR-326 was a target of circ0082374 and miR-326 knockdown attenuated the inhibitive role of circ0082374 silence in glioma progression. SIRT1 was a target of miR-326 and circ0082374 could promote SIRT1 expression by sponging miR-326. Silence of SIRT1 reversed the promoting effect of circ0082374 on glioma progression. Knockdown of circ0082374 reduced xenograft tumor growth by miR-326/SIRT1 in vivo. Collectively, silence of circ0082374 repressed the viability, migration, invasion and glycolysis in glioma cells by regulating miR-326 and SIRT1 in a ceRNA mechanism, providing a new mechanism for the pathogenesis of glioma.

CPA4 Promotes EMT in Pancreatic Cancer via Stimulating PI3K-AKT-mTOR Signaling

Background

Carboxypeptidase A4 (CPA4), as a novel tumor biomarker, is prevalently observed in various cancers. However, the potential role of CPA4 in pancreatic cancer (PC), to our knowledge, has not been fully clarified.

Materials and Methods

We systematically explored the detailed function of CPA4 in epithelial to mesenchymal transition (EMT) stimulated PC in human clinical samples and in vitro.

Results

CPA4 was overexpressed in clinical PC samples that was positively related with tumor size (P=0.026), T stage (P=0.011), lymph-node metastasis (P=0.026) and a worse prognosis for PC patients (P=0.001). Interestingly, CPA4 was inversely correlated with E-cadherin (r=−0.372, P=0.003) in clinical samples and PC cell lines which cooperatively contributed to a worse prognosis (P=0.005) for PC patients. CPA4 overexpression enhanced EMT in AsPC-1 and Capan-2 cells, which promoted EMT-like cellular morphology and cell invasion and migration. Meanwhile, CPA4 overexpression activated EMT and PI3K-AKT-mTOR signaling, following with the downregulation of E-cadherin and β-catenin, and the upregulation of N-cadherin, vimentin, p-PI3K (Tyr458), p-AKT (Ser473) and p-mTOR (Ser2448). However, PI3K inhibitor LY294002 reversed CPA4 overexpression-stimulated EMT in vitro. Moreover, CPA4 was co-immunoprecipitated with AKT in two PC cells with CPA4 high expression. Conversely, CPA4 silencing inhibited EMT in PANC-1 cells. CPA4 overexpression or silencing promoted or inhibited cell proliferation and drug resistance in Capan-2 and PANC-1 cells via regulating Bcl2/Bax and cleaved-caspase3 signaling. However, LY294002 reversed CPA4 overexpression-stimulated cell proliferation and drug resistance in vitro in Bcl2/Bax and caspase3-dependent apoptosis.

Conclusion

CPA4 overexpression contributes to aggressive clinical stage of PC patients and promotes EMT in vitro via activation of PI3K-AKT-mTOR signaling.

Carboxypeptidase A4 promotes cardiomyocyte hypertrophy through activating PI3K-AKT-mTOR signaling

Carboxypeptidase A4 (CPA4) is a member of the metallocarboxypeptidase family. Current studies have identified the roles of CPA4 in cancer biology and insulin sensitivity. However, the roles of CPA4 in other diseases are not known. In the present study, we investigated the roles of CPA4 in cardiac hypertrophy. The expression of CPA4 was significantly increased in the hypertrophic heart tissues of human patients and isoproterenol (ISO)-induced hypertrophic heart tissues of mice. We next knocked down Cpa4 with shRNA or overexpressed Cpa4 using adenovirus in neonatal rat cardiomyocytes and induced cardiomyocyte hypertrophy with ISO. We observed that Cpa4 overexpression promoted whereas Cpa4 knockdown reduced ISO-induced growth of cardiomyocyte size and overexpression of hypertrophy marker genes, such as myosin heavy chain β (β-Mhc), atrial natriuretic peptide (Anp), and brain natriuretic peptide (Bnp). Our further mechanism study revealed that the mammalian target of rapamycin (mTOR) signaling was activated by Cpa4 in cardiomyocytes, which depended on the phosphoinositide 3-kinase (PI3K)-AKT signaling. Besides, we showed that the PI3K-AKT-mTOR signaling was critically involved in the roles of Cpa4 during cardiomyocyte hypertrophy. Collectively, these results demonstrated that CPA4 is a regulator of cardiac hypertrophy by activating the PI3K-AKT-mTOR signaling, and CPA4 may serve as a promising target for the treatment of hypertrophic cardiac diseases.

Downregulation of OSR1 Promotes Colon Adenocarcinoma Progression via FAK-Mediated Akt and MAPK Signaling

Introduction

Odd-skipped related transcription factor 1 (OSR1) is a newly identified tumor suppressor in many tumor types. However, the role and mechanism of OSR1 in colon adenocarcinoma (COAD) remain unknown.

Methods

OSR1 expression was detected in COAD tissues and cells. COAD cells with OSR1 overexpression or knockdown were analyzed by in vitro CCK-8, transwell and flow cytometry assays, and by in vivo xenograft model.

Results

OSR1 expression was downregulated in COAD and low expression level of OSR1 was positively correlated with tumor stage and lymph node metastasis. Furthermore, low OSR1 expression was significantly associated with poor overall survival (OS) and distant metastasis-free survival (DMFS). Lentivirus-mediated restoration of OSR1 expression-inhibited proliferation, invasion and migration while induced cell cycle arrest and apoptosis in COAD cells in vitro, and inhibited tumor growth in vivo. In contrast, OSR1 knockdown promoted proliferation, invasion and migration in COAD cells in vitro. Mechanistically, OSR1 exerted anticancer effects by inhibiting FAK-mediated activation of Akt and MAPK pathways.

Conclusion

Our findings suggest that OSR1 functions as a tumor suppressor in COAD by suppressing FAK-mediated activation of Akt and MAPK pathways.

Downregulation of CPA4 inhibits non small-cell lung cancer growth by suppressing the AKT/c-MYC pathway

Carboxypeptidase A4 (CPA4) is a member of the metallocarboxypeptidase family. A previous study indicated that CPA4 may participate in the modulation of peptide hormone activity and hormone-regulated tissue growth and differentiation. However, the role of CPA4 in lung tumorigenesis remains unclear. Our study revealed that CPA4 expression was higher in both lung cancer cells and tumor tissues. We performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays, colony-formation assays, and Cellomics ArrayScan Infinity analysis to demonstrate that CPA4 knockdown inhibited non small-cell lung cancer (NSCLC) cell proliferation. Conversely, ectopic expression of CPA4 enhanced lung cancer cell proliferation. Consistent with these observations, we generated xenograft tumor models to confirm that CPA4 downregulation suppressed NSCLC cell growth. Mechanistically, we revealed that CPA4 downregulation may induce apoptosis and G1-S arrest by suppressing the protein kinase B/c-MYC pathway. These results suggest that CPA4 has an oncogenic effect on lung cancer growth. Taken together, we identified a novel gene in lung cancer that might provide a basis for new therapeutic targets.