Cisplatin-resistant Lung Adenocarcinoma Research Articles

WDHD1 Leads to Cisplatin Resistance by Promoting MAPRE2 Ubiquitination in Lung Adenocarcinoma.

Ubiquitin ligases have been shown to regulate drug sensitivity. This study aimed to explore the role of the ubiquitin ligase WD repeat and HMG-box DNA binding protein 1 (WDHD1) in regulating cisplatin sensitivity in lung adenocarcinoma (LUAD). A quantitative analysis of the global proteome identified differential protein expression between LUAD A549 cells and the cisplatin-resistant strain A549/DDP. Public databases revealed the relationship between ubiquitin ligase expression and the prognosis of patients with LUAD. Quantitative real-time polymerase chain reaction and Western blotting were used to estimate the WDHD1 expression levels. Analysis of public databases predicted the substrate of WDHD1. Western blotting detected the effect of WDHD1 on microtubule-associated protein RP/EB family member 2 (MAPRE2) and DSTN. Functional analysis of MAPRE2 verified the interaction between WDHD1 and MAPRE2, as well as the interacting sites by methyl-thiazolyl-tetrazolium assay and flow cytometry, immunoprecipitation, protein stability, and immunofluorescence. Cell and animal experiments confirmed the effect of WDHD1 and MAPRE2 on cisplatin sensitivity in LUAD. Clinical data evaluated the impact of WDHD1 expression level on cisplatin sensitivity. Quantitative analysis of the global proteome revealed ubiquitin-dependent protein catabolism to be more active in A549/DDP cells than in A549 cells. WDHD1 expression was higher in A549/DDP cells than in A549 cells, and knocking out WDHD1 increased the sensitivity of A549/DDP cells to cisplatin. WDHD1 overexpression negatively correlated with the overall survival of LUAD patients. We observed that MAPRE2 was upregulated when WDHD1 was knocked out. A MAPRE2 knockout in A549 cells resulted in increased cell viability while decreasing apoptosis when the A549 cells exposed to cisplatin. WDHD1 and MAPRE2 were found to interact in the nucleus, and WDHD1 promoted the ubiquitination of MAPRE2. Following cisplatin exposure, the WDHD1 and MAPRE2 knockout groups facilitated cell proliferation and migration, inhibited apoptosis in A549/DDP cells, decreased apoptosis, and increased tumor size and growth rate in animal experiments. Immunohistochemistry showed that Ki67 levels increased, and levels of apoptotic indicators significantly decreased in the WDHD1 and MAPRE2 knockout groups. Clinical data confirmed that WDHD1 overexpression negatively correlated with cisplatin sensitivity. Thus, the ubiquitin ligase WDHD1 induces cisplatin resistance in LUAD by promoting MAPRE2 ubiquitination.

Analysis of lncRNA UCA1-related downstream pathways and molecules of cisplatin resistance in lung adenocarcinoma.

BackgroundTo analyze the lncRNA UCA1‐related downstream pathways and molecules of cisplatin resistance in lung adenocarcinoma.MethodsWe constructed overexpression and siRNA vectors targeting UCA1 and TXNIP and then used next‐generation sequencing to compare the UCA1 overexpression and negative control from A549 cell.ResultsIt shown that 647 upregulated mRNAs and 633 downregulated differentially expressed mRNAs‐related UCA1, and the top ten upregulated mRNAs were CPD, AC007192.1, TGOLN2, LGR4, TFPI, CYP1B1, TOMM6, HLA‐B, SLC35F6, and TOP2A, and top ten downregulated mRNAs were TXNIP, SESN2, STC2, HSPA1A, MMP10, CHAC1, DNAJB1, AC004922.1, ATF3, and GABARAPL1. We found TXNIP mRNA expression level was the most significantly downexpressed mRNA. TXNIP mRNA expression level of LAD tissues was clearly lower than the adjacent tissues. UCA1 expression level of cisplatin insensitive group was markedly higher than that of cisplatin‐sensitive group, while TXNIP mRNA expression level of cisplatin insensitive group was clearly lower than that of cisplatin‐sensitive group. Compared to the BEAS‐2B, TXNIP mRNA expression level cut down in A549 and A549/DDP cell and that of A549/DDP cell was lower than A549 cell. After UCA1 overexpression, TXNIP mRNA obviously decreased, while proliferation ability and IC50 of A549 heightened. After knocking down UCA1, TXNIP mRNA was significantly increased, while proliferation ability and IC50 of A549/DDP lowered. PPI analysis result showed that TXNIP could interact with multiple proteins such as TXN, DDIT4, and NLRP3.ConclusionUCA1 promoted cisplatin resistance by downregulating TXNIP expression in LAD, and TXNIP could interact with multiple proteins. So, UCA1/TXNIP axis might affect cisplatin resistance in LAD.

MiR‑10a increases the cisplatin resistance of lung adenocarcinoma circulating tumor cells via targeting PIK3CA in the PI3K/Akt pathway.

Circulating tumor cells (CTCs) that are shed from the primary tumor invade the blood stream or surrounding parenchyma to form new tumors. The present study aimed to explore the underlying mechanism of cisplatin resistance in lung adenocarcinoma CTCs and provide clinical treatment guidance for lung cancer treatment. CTCs from the blood samples of 6 lung adenocarcinoma patients were treated with different concentrations of cisplatin along with A549 and H1299 cells. The sensitivity of CTCs to cisplatin was explored by detecting the inhibitory rate via CCK-8 assay. The related molecular mechanism was investigated by western blot analysis. miR-10a expression was detected using quantitative real-time PCR (RT-qPCR). The relationship between miR-10a and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α (PIK3CA) was verified and further confirmed by luciferase reporter assay, western blotting and RT-qPCR assay. The results revealed that CTCs exhibited lower cisplatin sensitivity than A549 and H1299 cells. Moreover, CTCs treated with cisplatin demonstrated higher miR-10a expression and lower PIK3CA expression than that in A549 and H1299 cells (P<0.01). Expression of phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt) phosphorylation were also decreased in A549 and H1299 cells compared with CTCs after cisplatin treatment. PIK3CA is a target of miR-10a, and both miR-10a overexpression and PIK3CA knockdown obviously decreased the sensitivity of A549 and H1299 cells to cisplatin as well as the expression of PI3K and phosphorylation of Akt. PIK3CA overexpression attenuated the cisplatin resistance of A549 and H1299 cells induced by miR-10a. In conclusion, miR-10a suppressed the PI3K/Akt pathway to strengthen the resistance of CTCs to cisplatin via targeting PIK3CA, providing a new therapeutic target for lung cancer treatment.

LncRNA-ATB Promotes Cisplatin Resistance in Lung Adenocarcinoma Cells by Targeting the miR-200a/β-Catenin Pathway.

IntroductionLung adenocarcinoma (LUAD), which is associated with high morbidity and mortality, is prone to cisplatin resistance, resulting in poor patient prognosis. Long non-coding RNAs (lncRNAs) have complex biological functions in a variety of tumors. Elucidating the underlying molecular mechanisms between lncRNA and cisplatin resistance in LUAD is expected to enable identification of new targets for drug development.MethodsCell proliferation was measured by CCK-8 assay and cell apoptosis was detected using flow cytometry analysis. Luciferase reporter assay was conducted to determine the interaction between lncRNA and MicroRNA. Gene expression was evaluated by Real-Time Quantitative Reverse Transcription Polymerase Chain Reaction and Western blot analysis.ResultsLong non-coding RNA activated by TGF-β (lncRNA-ATB) was shown to be significantly up-regulated in A549 cells resistant to cisplatin/cis-dichlorodiammineplatinum (II) (cis-DDP) (A549/CDDP cells), compared with corresponding levels in parental A549 cells. Overexpression of lncRNA-ATB significantly elevated cisplatin resistance in LUAD cell lines (A549 and H1975 cells), and this was associated with activation of apoptosis-related genes. Conversely, silencing of lncRNA-ATB decreased cisplatin resistance in LUAD cells. Mechanistically, lncRNA-ATB increased expression of β-catenin by directly binding to MicroRNA-200a (miR-200a), thereby promoting cell survival and cisplatin resistance. Transfection with a miR-200a mimic or treatment with the β-catenin downstream pathway inhibitor IWR-1 could reverse the phenotypes induced by lncRNA-ATB overexpression.ConclusionIn summary, this study revealed that lncRNA-ATB is dramatically up-regulated in cisplatin-resistant LUAD cell lines, and that lncRNA-ATB facilitates cell survival by targeting the miR-200a/β-catenin pathway in these cells.

MicroRNA-182-5p regulates hedgehog signaling pathway and chemosensitivity of cisplatin-resistant lung adenocarcinoma cells via targeting GLI2.

Lung cancer is one of the deadliest cancers worldwide. Late diagnosis at an advanced, inoperable stage makes chemotherapy a treatment of choice, yet, with low response rates. The hedgehog signaling pathway (HHSP) is often reactivated in cancer. We identified miR-182-5p as a regulator of GLI2, a transcriptional regulator of the HHSP, and explored the role of the miR-182-5p/GLI2 axis in carcinogenesis and cisplatin resistance of lung adenocarcinoma (LADC). Expression of miRNAs and target genes was analyzed by RT-qPCR, expression of the GLI-protein family in LADC and adjacent lung tissue (n = 27 pairs) by immunohistochemistry. MiR-182-5p was manipulated, and data were generated by immunoblotting, immunofluorescence, apoptosis, proliferation/viability, dual-luciferase-, and colony forming assays. MiR-182-5p was down-regulated in cisplatin-resistant LADC cells and directly targeted GLI2. Interference with miR-182-5p or GLI2 silencing resulted in modulation of cell proliferation, clonogenic potential, and cisplatin-sensitivity. HHSP was markedly reactivated in LADC tissue compared to adjacent non-malignant lung tissue. Our results indicate that the miR-182-5p/GLI2 axis modulates tumorigenesis and cisplatin-resistance in LADC cells, by influencing the HHSP. Therefore, this axis might be considered as a potential biomarker and future therapeutic target in LADC patients.

MDIG promotes cisplatin resistance of lung adenocarcinoma by regulating ABC transporter expression via activation of the WNT/β-catenin signaling pathway.

Mineral dust-induced gene (MDIG) is a proto- oncogene associated with lung cancer that serves a key role in the biological processes of tumorigenesis. The aim of the present study was to determine whether MDIG is involved in cisplatin (DDP) resistance in lung adenocarcinoma, and to investigate the associated molecular mechanism. In the present study, MDIG-knockdown and MDIG-overexpressing A549 cells and DDP-resistant A549/DDP cells were initially constructed, and then the mRNA and protein expression levels of MDIG and ATP-binding cassette (ABC) transporters (ABCB1, ABCC1, ABCG2), and the expression levels of the major associated proteins in the WNT/β-catenin pathway were determined by reverse transcription-quantitative PCR and Western blotting experiments. The results revealed that the mRNA and protein expression levels of MDIG in A549/DDP cells were significantly higher compared with those in A549 cells, and that the protein expression levels of MDIG increased in a dose-dependent manner with increasing DDP concentrations. Overexpression of MDIG in A549 and A549/DDP cells led to an increase in the IC50 value, whereas silencing of MDIG led to a clear reduction in the IC50 value. The overexpression of MDIG in the A549 and A549/DDP cells markedly upregulated the mRNA and protein expression levels of ABCB1, ABCC1, ABCG2, WNT family member 5A, WNT family member 3A and active β-catenin, and these were markedly decreased following MDIG silencing. Taken together, these results demonstrated that the DDP resistance of lung adenocarcinoma may be associated with an upregulation of MDIG expression, and that the expression levels of MDIG are positively associated with the degree of DDP resistance. Furthermore, MDIG promoted the expression of ABC transporters in tumor cells by activating the WNT/β-catenin signaling pathway, which may, in turn, lead to DDP resistance in lung adenocarcinoma.

An inverse interaction between HOXA11 and HOXA11-AS is associated with cisplatin resistance in lung adenocarcinoma

ABSTRACTHOXA11, which is a member of the homeobox (HOX) gene family, and its natural antisense transcript (NAT) HOXA11-AS have been reported to be closely related to the development of lung cancer. We aimed to investigate their specific roles in cisplatin (DDP) resistance in lung adenocarcinoma (LUAD). First, we found that HOXA11 is hypermethylated and significantly downregulated in a DDP-resistant A549 cell line (A549/DDP) and LUAD tissues, while the HOXA11-AS expression level is elevated. Although HOXA11 and HOXA11-AS mRNA overlap in the 5ʹ-untranslated region (5ʹ UTR) and share two CpG islands, DNA methylation only regulates the expression of HOXA11. Then, we found that HOXA11 and HOXA11-AS have an inverse interaction by transfecting their siRNAs and overexpression vectors into A549 and A549/DDP cells. A dual-luciferase reporter assay further confirmed that the overlapping 5ʹUTR is essential for the bidirectional regulation between HOXA11 and HOXA11-AS. Functional analysis showed that knockdown of HOXA11 expression in A549 cells induced DDP resistance and activated Akt/β-catenin signaling, while overexpression of HOXA11 in A549/DDP cells increased DDP sensitivity and inhibited Akt/β-catenin signaling. Moreover, HOXA11-AS knockdown in A549 cells increased DDP sensitivity and inhibited Akt/β-catenin signaling, while the overexpression of HOXA11-AS in A549/DDP cells induced DDP resistance and activated Akt/β-catenin signaling. In conclusion, our study demonstrates that the inverse interaction between HOXA11 and HOXA11-AS promotes DDP resistance in LUAD.

HOXA4-Dependent Transcriptional Activation of AXL Promotes Cisplatin- Resistance in Lung Adenocarcinoma Cells.

Lung cancer is one of the most leading causes of cancer-related deaths in adults worldwide. Non-Small Cell Lung Cancer (NSCLC), which comprises 80 to 85% of all lung cancers, is the most lethal subtype of lung cancer with a 5-year survival of less than 13%. In this study, we identified a poorly-studied kinase PDK4 as the most up-regulated kinase encoding gene in Cisplatin resistant lung adenocarcinoma. In vitro cell viability assay and in vivo tumor xenograft assay were used in the detection of cell proliferation. RNA isolation, quantitative Real-Time PCR, Western blot analysis, immunohistochemistry were used to investigate the expression of RNA and protein. Lentivirus infection was used to regulate gene expression. Luciferase assays were used to monitor EPAS1 promoter activity. In vivo PDK4 expression was elevated in a Cisplatin-resistant population of lung adenocarcinoma cells, PDK4-dependent Cisplatin-resistance promotes tumor growth of lung adenocarcinoma in vivo and in vitro, clinically PDK4 expression was associated with poor prognosis in lung adenocarcinoma patients, mechanically PDK4 promoted cell growth and Cisplatin-resistance of lung adenocarcinoma via transcriptional regulation of endothelial PAS domain-containing protein 1 (EPAS1). PDK4 is the most up-regulated kinase encoding gene in Cisplatin resistant lung adenocarcinoma and PDK4-dependent Cisplatin-resistance promotes tumor growth of lung adenocarcinoma mainly through transcriptional regulation of EPAS1. Enriched PDK4 expression was correlated with the poor prognosis of lung cancer patients, indicating that PDK4 could be a potential therapeutic target for Cisplatin-resistant lung adenocarcinoma.

Integrative PDGF/PDGFR and focal adhesion pathways are downregulated in ERCC1-defective non-small cell lung cancer undergoing sodium glycididazole-sensitized cisplatin treatment

BackgroundChemoresistance to cisplatin in lung cancer treatment remains prevalent. Since targeting excision repair cross-complementing 1 (ERCC1) may be a viable strategy to reestablish the therapeutic sensitivity to platinum-based agents in chemoresistant cases, and low ERCC1 level is beneficial to metastatic lung cancer patients undergoing platinum-based chemotherapy, we hypothesized that metastasis-associated process is involved in ERCC1-dependent cisplatin-resistance in lung adenocarcinoma. MethodsWe performed an RNA-Sequencing (RNA-Seq) analysis to identify differentially expressed genes in ERCC1-deficient cells co-treated with cisplatin and sodium glycididazole (CMNa). Differentially expressed genes and the hub genes in the cisplatin/CMNa-treated cells were identified by systematic network analysis. Oncomine expression analysis was also performed to evaluate the clinical implication of the identified hub gene. ResultsPlatelet-derived growth factor receptor (PDGF/PDGFR) and focal adhesion genes were downregulated in ERCC1-defective non-small cell lung cancer (NSCLC) cells undergoing combined cisplatin/CMNa treatment. Consistent with the finding, cell migration was reduced in these cells. PDGFRB was identified as the hub gene in the process by differential expressed gene network analysis. Importantly, elevated PDGFRB level was observed in advanced lung adenocarcinoma patients with metastases. ConclusionPDGF/PDGFR and focal adhesion signaling may serve as another mechanism in addition to ERCC1-mediated cisplatin-resistance in lung adenocarcinoma. Multiple pro-invasion/pro-migration/proliferation and DNA damage repair pathways may be integrated to confer growth advantages on tumor cells.

PDK2 induces cisplatin-resistance in lung adenocarcinoma via transcriptional regulation of CNNM3

Recurrence of lung adenocarcinoma has become one of the most frequent causes of major cancer incidence and mortality worldwide according to its frequently gained resistance to chemotherapies. In this study, we identified a poorly-studied kinase pyruvate dehydrogenase kinase isoform 2 (PDK2) as the most up-regulated kinase encoding gene in Cisplatin resistant lung adenocarcinoma. Additionally, PDK2-dependent Cisplatin-resistance promotes tumour growth of lung adenocarcinoma both in vitro and in vivo. Clinically, PDK2 expression was up-regulated in lung adenocarcinoma and was correlated to the poor prognosis of lung cancer patients. Mechanically, PDK2 promoted cell growth and Cisplatin-resistance of lung adenocarcinoma via transcriptional regulation of cyclin and CBS domain divalent metal cation transport mediator 3 (CNNM3), indicating that PDK2-CNNM3 signalling axis could be a potential therapeutic target for Cisplatin-resistant lung adenocarcinoma.

Highlights of This Issue

Cancer-associated fibroblasts (CAFs) promote cancer growth and metastasis. However, mechanistic understanding by which cancer cells promote activation of healthy fibroblasts into CAFs remains elusive. In the current issue, Goulet and colleagues demonstrate that exosomes released by bladder cancer cells are internalized by healthy fibroblasts (HFs) to promote CAF differentiation through the activation of the TGFβ/SMAD signaling pathway. In fact, exosomal TGFβ, shown to be localized inside the vesicle, contributed 53 to 86% of the total TGFβ present in the bladder cancer cell conditioned medium. In conclusion, this study highlights that TGFβ-derived cancer exosomes are important molecular modulators of tumor microenvironment and CAF differentiation.PARP inhibitors (PARPi) are synthetically lethal in tumors carrying BRCA1/2 mutations and with deficiencies in homologous recombination (HR)-mediated DNA repair. However, BRCA mutations are rare; thus, most tumors are resistant to PARPi. Sizemore and colleagues demonstrate that ionizing radiation (IR) induces BRCA1 sequestration to the cytoplasm and DNA repair deficiency, and subsequent PARPi synthetic lethality in multiple tumor model systems. Importantly, p53 status was discovered to be a significant determining factor of tumor cell sensitization to PARPi following IR. These results have the potential to significantly increase the number of patients who may clinically benefit from PARPi-based therapies.Cancer genomics has highlighted the prevalence of sequence variants of unknown significance. Singh and colleagues hypothesized that a fraction of these mutations reflect RNA-related selection processes, thereby impacting RNA metabolism and contributing to oncogenic processes. Analysis of whole-genome sequencing (WGS) data from multiple cancers uncovered frequent mutations in binding sites for RNA binding proteins and splicing regulators. Furthermore, RNA sequencing (RNA-seq) data from the same specimens validated a change in RNA processing in association to these mutations. The study describes new alterations in cancer that impact RNA processing and proposes a systematic method for the interpretation of non-coding variants in cancer genomes.Histone 2B monoubiquitination (H2Bub1) is commonly lost during carcinogenesis and is deubiquitinated by ubiquitin-specific peptidase 22 (USP22). Here, the impact of USP22 on stem cell characteristics and cisplatin resistance was investigated in cancer-initiating cells (CICs) derived from human lung adenocarcinomas. Elevated USP22 expression associated with stem-like characteristics and chemotherapy resistance. Furthermore, ALDH1A3 which has been implicated in cisplatin resistance in lung adenocarcinoma was down-regulated upon USP22 knockdown. These data demonstrate that USP22 plays a critical role in tumorgenicity and cisplatin resistance in lung adenocarcinoma and may be a useful target for therapy.

Abstract 147: Targeting USP22 suppresses tumorigenicity and enhances sensitivity to cisplatin in cancer-initiating cells from lung adenocarcinoma through downregulating ALDH1A3

Abstract We previously found that loss of monoubiquitination of histone H2B (H2Bub1) was associated with poor differentiation and enhanced malignancy of lung adenocarcinoma. Herein, we investigated the expression and roles of USP22, an H2Bub1 deubiquitinase, in cancer-initiating cells (CICs) with stem cell-like characteristics from primary lung adenocarcinoma. CICs from patient-derived cancer tissues were isolated and characterized, and the association of USP22 with CICs was investigated using flow cytometry, aldehyde dehydrogenase (ALDH) activity, Western blot, and fluorescence microscope assays. The impact of USP22 on stem cell-like characteristics and cisplatin resistance in CICs was examined by in vitro tumorsphere formation, in vivo transplantation, and apoptosis assays. We identified that USP22 is predominantly expressed in CICs, a subpopulation of cells with high expression of CD133 stem cell biomarker. The expression of USP22 in CICs is dramatically reduced upon serum-induced differentiation. Moreover, knockdown of USP22 significantly suppressed in vitro tumorsphere formation and in vivo xenograft growth in NOD-SCID mice. Notably, USP22 is dramatically elevated in tumorsphere cells that survived cisplatin treatment, while knockdown of USP22 significantly sensitizes tumorsphere cells to cisplatin. Interestingly, ALDH1A3, a dominant isoform of ALDH implicated in enhancing cisplatin resistance in lung adenocarcinoma, is significantly downregulated upon knockdown of USP22 in tumorsphere cells. Furthermore, knockdown of ALDH1A3 significantly sensitizes tumorsphere cells to cisplatin. Therefore, our data indicate that USP22 plays critical roles in tumorigenicity and cisplatin resistance in lung adenocarcinoma, and targeting USP22 may represent a potential therapeutic approach to eliminate CICs in lung adenocarcinoma through downregulation of ALDH1A3 expression. Citation Format: Keqiang Zhang, Xinwei Yun, Jinhui Wang, Melisa Bonner, Lu Yang, Jun Wu, Dan J. Raz. Targeting USP22 suppresses tumorigenicity and enhances sensitivity to cisplatin in cancer-initiating cells from lung adenocarcinoma through downregulating ALDH1A3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 147.

Targeting USP22 Suppresses Tumorigenicity and Enhances Cisplatin Sensitivity Through ALDH1A3 Downregulation in Cancer-Initiating Cells from Lung Adenocarcinoma.

Loss of monoubiquitination of histone H2B (H2Bub1) was found to be associated with poor-differentiation and enhanced malignancy of lung adenocarcinoma. This study investigated the association and impact of the ubiquitin-specific peptidase 22 (USP22), an H2Bub1 deubiquitinase, on stem cell-like characteristics and cisplatin resistance in cancer-initiating cells (CIC) from primary lung adenocarcinoma. CICs were isolated, enriched, and characterized from patient-derived cancer tissues using both in vitro tumorsphere formation and in vivo xenograft assays. USP22 was determined to be predominantly expressed in CICs, a subpopulation of cells with high expression of the stem cell biomarkers, CD133 and CD44. The expression of USP22 in CICs is markedly reduced upon FBS/retinoic acid-induced differentiation. Moreover, knockdown of USP22 significantly suppressed tumorsphere formation and xenograft growth in NOD-SCID gamma (NSG) mice. Notably, USP22 and aldehyde dehydrogenase (ALDH) activity were elevated in tumorsphere cells that survived cisplatin treatment, whereas knockdown of USP22 significantly sensitizes tumorsphere cells to cisplatin. Interestingly, ALDH1A3, a predominant ALDH isozyme implicated in enhancing cisplatin resistance in lung adenocarcinoma, is significantly downregulated upon knockdown of USP22 in tumorsphere cells. Furthermore, knockdown of ALDH1A3 significantly sensitizes tumorsphere cells to cisplatin. Combined, these data demonstrate that USP22, predominantly expressed in CD133+ CICs, plays a critical role in tumorigenicity and cisplatin resistance in lung adenocarcinoma.Implications: Targeting USP22 represents a potential therapeutic approach to suppress CICs in lung adenocarcinoma partially through downregulation of ALDH1A3 expression. Mol Cancer Res; 16(7); 1161-71. ©2018 AACR.

Glutamate-cysteine ligase catalytic subunit is associated with cisplatin resistance in lung adenocarcinoma.

Cisplatin is a key drug for treating lung adenocarcinoma, and its sensitivity to cisplatin is directly related to prognosis. We aimed to reveal the roles of genes related to glutathione synthesis (glutamate-cysteine ligase catalytic subunit, GCLC) and cystine uptake (cystine/glutamate transporter, xCT and CD44v8-10) in cisplatin resistance and prognosis in lung adenocarcinoma. We established cell lines stably expressing GCLC, xCT, standard isoform of CD44, and CD44v8-10, and investigated their sensitivities to cisplatin. We also measured mRNA expression levels of these genes in the tumor tissues from 92 lung adenocarcinoma patients. Patients were divided into high-expression (upper quartile, N = 23) and low-expression groups (remaining patients, N = 69). Recurrence-free survival, overall survival (N = 92), and post-recurrence survival (N = 22) were selected as endpoints. Compared with the control green fluorescent protein-expressing cell line (inhibitory concentration 50:6.9 μM), all the stable cell lines were more resistant to cisplatin (12.9 μM, P = 0.025; 13.9 μM, P = 0.028; 26.7 μM, P = 0.001; 17.7 μM, P = 0.008, respectively). In contrast, there was no significant difference in recurrence-free or overall survival between the high- and low-expression groups for any of the genes. However, high expression of GCLC was a risk factor for poorer post-recurrence survival (hazard ratio, 6.26; 95% confidence interval, 1.37-28.7; P = 0.018). High expression levels of genes related to glutathione synthesis and cystine uptake promote cisplatin resistance in lung adenocarcinoma cell lines. High expression of GCLC in tumor tissue may be a potential predictor of treatment failure.

USP22 Induces Cisplatin Resistance in Lung Adenocarcinoma by Regulating γH2AX-Mediated DNA Damage Repair and Ku70/Bax-Mediated Apoptosis.

Resistance to platinum-based chemotherapy is one of the most important reasons for treatment failure in advanced non-small cell lung cancer, but the underlying mechanism is extremely complex and unclear. The present study aimed to investigate the correlation of ubiquitin-specific peptidase 22 (USP22) with acquired resistance to cisplatin in lung adenocarcinoma. In this study, we found that overexpression of USP22 could lead to cisplatin resistance in A549 cells. USP22 and its downstream proteins γH2AX and Sirt1 levels are upregulated in the cisplatin- resistant A549/CDDP cell line. USP22 enhances DNA damage repair and induce cisplatin resistance by promoting the phosphorylation of histone H2AX via deubiquitinating histone H2A. In addition, USP22 decreases the acetylation of Ku70 by stabilizing Sirt1, thus inhibiting Bax-mediated apoptosis and inducing cisplatin resistance. The cisplatin sensitivity in cisplatin-resistant A549/CDDP cells was restored by USP22 inhibition in vivo and vitro. In summary, our findings reveal the dual mechanism of USP22 involvement in cisplatin resistance that USP22 can regulate γH2AX-mediated DNA damage repair and Ku70/Bax-mediated apoptosis. USP22 is a potential target in cisplatin-resistant lung adenocarcinoma and should be considered in future therapeutic practice.

CNTN-1 Enhances Chemoresistance in Human Lung Adenocarcinoma Through Induction of Epithelial-Mesenchymal Transition by Targeting the PI3K/Akt Pathway

Background/Aims: Chemoresistance has been a major obstacle to the effective treatment of lung cancer. Previously, we found that contactin-1 (CNTN-1) is related to cisplatin resistance in lung adenocarcinoma. Here, we aimed to investigate the underlying mechanism behind the role of CNTN-1 in cisplatin resistance in lung adenocarcinoma. Methods: EMT-associated phenotypes, including alterations in cellular morphology and marker (E-cadherin, N-cadherin and Vimentin) expression, were compared between A549 cells and A549/DDP cells (a cisplatin-resistant cell line of lung adenocarcinoma with abnormal CNTN-1 expression) by using real-time time PCR and Western blotting. Other methods, including CNTN-1 overexpression in A549 cells and CNTN-1 knockdown in A549/DDP cells, were also used to investigate the role of CNTN-1 in mediating the EMT phenotype and thr resulting cisplatin resistance and malignant progression of cancer cells in vitro and in vivo. Results: A549/DDP cells exhibited an EMT phenotype and aggravated malignant behaviors. CNTN-1 knockdown in A549/DDP cells partly reversed the EMT phenotype, increased drug sensitivity, and attenuated the malignant progression whereas CNTN-1 overexpression in A549 cells resulted in the opposite trend. Furthermore, the PI3K/Akt pathway was involved in the effects of CNTN-1 on EMT progression in A549/DDP cells, verified by the xenograft mouse model. Conclusion: CNTN-1 promotes cisplatin resistance in human cisplatin-resistant lung adenocarcinoma through inducing the EMT process by activating the PI3K/Akt signaling pathway. CNTN-1 may be a potential therapeutic target to reverse chemoresistance in cisplatin-resistant lung adenocarcinoma.

Prognostic Significance of microRNA-7 and its Roles in the Regulation of Cisplatin Resistance in Lung Adenocarcinoma

Background: Previously, microRNA (miR)-7 has been reported to function as a tumor suppressor in human cancers, but the correlations of miR-7 expression with prognosis and cisplatin (CDDP) resistance in lung adenocarcinoma (LA) are unclear. Here, our aim is to determine the prognostic significance of miR-7 and its roles in the regulation of CDDP resistance in LA. Methods: Quantitative real-time PCR (qRT-PCR) assay was performed to determine miR-7 expression in 108 paired of LA tissues and analyze its correlations with clinicopathological factors of patients. The patient survival data were collected retrospectively by Kaplan-Meier analyses, and multivariate analysis was performed using the Cox proportional hazards model to determine the prognostic significance of miR-7 expression. The effects of miR-7 expression on the chemosensitivity of LA cells to CDDP and its possible mechanisms were evaluated by MTT, flow cytometry, Western blot and luciferase assays. Results: It was observed that the relative expression level of miR-7 in LA tissues was significantly lower than that in the adjacent normal tissues and low miR-7 expression level was closely associated with poorer tumor differentiation, advanced pathological T-factor, higher incidence of lymph node metastasis and advanced p-TNM stage. Also, patients with low miR-7 expression showed a shorter overall survival than those with high miR-7 expression, and multivariate analysis indicated that status of miR-7 expression was an independent molecular biomarker for predicting the overall survival (OS) of LA patients. In addition, upregulation of miR-7 increases the sensitivity of LA cells to CDDP via induction of apoptosis by targeting Bcl-2. Conclusions: Our finding for the first time demonstrates that low miR-7 expression may be an independent poor prognostic factor and targeting miR-7 may be a potential strategy for the reversal of CDDP resistance in LA.

Aberrant Long Noncoding RNAs Expression Profiles Affect Cisplatin Resistance in Lung Adenocarcinoma.

Background Long noncoding RNAs (lncRNAs) have been shown to be involved in the mechanism of cisplatin resistance in lung adenocarcinoma (LAD). However, the roles of lncRNAs in cisplatin resistance in LAD are not well understood. Methods We used a high-throughput microarray to compare the lncRNA and mRNA expression profiles in cisplatin resistance cell A549/DDP and cisplatin sensitive cell A549. Several candidate cisplatin resistance-associated lncRNAs were verified by real-time quantitative reverse transcription polymerase chain reaction (PCR) analysis. Results We found that 1,543 lncRNAs and 1,713 mRNAs were differentially expressed in A549/DDP cell and A549 cell, hinting that many lncRNAs were irregular from cisplatin resistance in LAD. We also obtain the fact that 12 lncRNAs were aberrantly expressed in A549/DDP cell compared with A549 cell by quantitative PCR. Among these, UCA1 was the aberrantly expressed lncRNA and can significantly reduce the IC50 of cisplatin in A549/DDP cell after knockdown, while it can increase the IC50 of cisplatin after UCA1 was overexpressed in NCI-H1299. Conclusions We obtained patterns of irregular lncRNAs and they may play a key role in cisplatin resistance of LAD.

Autophagy facilitates lung adenocarcinoma resistance to cisplatin treatment by activation of AMPK/mTOR signaling pathway.

Resistance to cisplatin-based therapy is a major challenge in the control of lung cancer progression. However, the underlying mechanisms remain largely unclear. Autophagy is closely associated with resistance to lung cancer therapy, but the function of autophagy in cisplatin treatment is still controversial. Here, we investigated whether autophagy was involved in lung adenocarcinoma resistance to cisplatin and further elucidated the underlying molecular mechanisms. Cisplatin-refractory lung adenocarcinoma cells increased autophagic vacuole formation detected by monodansylcadaverine staining. When exposed to cisplatin, lung adeno-carcinoma cells demonstrated increased levels of autophagy detected by MAP1A/1B LC3B and mammalian homologue of yeast Atg6 (Beclin-1) expression using Western blot analysis. Activation of cisplatin-induced autophagic flux was increased by using chloroquine (CQ), which can accumulate LC3B-II protein and increase punctate distribution of LC3B localization. The combination of cisplatin with CQ was more potent than cisplatin alone in inhibiting lung adenocarcinoma cell growth, which also increased cisplatin-induced apoptosis. Compared to cisplatin treatment alone, the combination of cisplatin and CQ decreased p-AMPK and increased p-mTOR protein expressions, in addition, the AMPK inhibitor Compound C plus cisplatin downregulated p-AMPK and upregulated p-mTOR as well as depressed LC3B cleavage. These findings demonstrate that activation of autophagy is a hallmark of cisplatin exposure in human lung adenocarcinoma cells, and that there is a cisplatin-induced autophagic response via activation of the AMPK/mTOR signaling pathway. We speculate that autophagy can be used as a novel therapeutic target to overcome cisplatin-resistant lung adenocarcinoma.

MiR-15b regulates cisplatin resistance and metastasis by targeting PEBP4 in human lung adenocarcinoma cells.

MicroRNAs (miRNAs) have been identified as important posttranscriptional regulators involved in various biological and pathological processes of cells, but their association with tumor chemoresistance has not been fully understood. We detected miR-15b expression in two lung adenocarcinoma cell lines, A549 and A549/CDDP, and then investigated the effects of miR-15b on the metastasis and the chemosensitivity of cancer cells, using both gain- and loss-of-function studies. The correlation between miR-15b level and chemoresistance was further investigated in clinical lung adenocarcinoma specimens. miR-15b was significantly upregulated in cisplatin-resistant lung adenocarcinoma A549/CDDP cells compared with parental A549 cells. miR-15b regulates epithelial-mesenchymal transition (EMT) and cisplatin resistance in vitro and modulates response of lung adenocarcinoma cells to cisplatin in vivo. Further studies identified phosphatidylethanolamine-binding protein 4 (PEBP4) as a direct and functional target of miR-15b. Small-interfering RNA-mediated PEBP4 knockdown revealed similar effects as that of ectopic miR-15b expression, whereas overexpression of PEBP4 attenuated the function of miR-15b in lung adenocarcinoma cells. Increased miR-15b expression was also detected in tumor tissues sampled from lung adenocarcinoma patients treated with cisplatin-based chemotherapy and was proved to be correlated with low expression of PEBP4, decreased sensitivity to cisplatin and poor prognosis. Our results suggest that upregulation of miR-15b could suppress PEBP4 expression and in turn contribute to chemoresistance of lung adenocarcinoma cells to cisplatin.