Cisplatin-resistant Lung Cancer Research Articles

Peptide-Based Autophagic Gene and Cisplatin Co-delivery Systems Enable Improved Chemotherapy Resistance.

Cisplatin-based chemotherapy is a widely used first-line strategy for numerous cancers. However, drug resistances are often inevitable accompanied by the long-term use of cisplatin in vivo, significantly hampering its therapeutic efficacy and clinical outcomes. Among others, autophagy induction is one of the most common causes of tumor resistance to cisplatin. Herein, a self-assembled nanoprodrug platform was developed with the synergistic effect of cisplatin and RNAi to fight against cisplatin-resistant lung cancer. The nanoprodrug platform consists of three molecular modules, including prodrug complex of Pt(IV)-peptide-bis(pyrene), DSPE-PEG, and cRGD-modified DSPE-PEG. The Pt(IV) is immobilized with peptide via amide bonds, allowing the Pt(IV) to be loaded with a loading efficiency of >95% and rapid-release active platinum ions (Pt(II)) in the presence of glutathione (GSH). Meanwhile, the peptide of the prodrug complex could efficiently deliver Beclin1 siRNA ( Beclin1 is an autophagy initiation factor) to the cytoplasm, thereby leading to autophagy inhibition. In addition, incorporation of DSPE-PEG and cRGD-modified DSPE-PEG molecules improves the biocompatibility and cellular uptake of the nanoprodrug platform. In vivo results also indicate that the nanoprodrug platform significantly inhibits the growth of a cisplatin-resistant tumor on xenograft mice models with a remarkable inhibition rate, up to 84% after intravenous injection.

Versatile Pt NCs-based chemotherapeutic agents significantly induce the apoptosis of cisplatin-resistant non-small cell lung cancer

Recently, the incidence of lung cancer is generally rising along with air pollution and smoking, and non-small cell lung cancer (NSCLC) accounts for nearly 85% among all lung cancer diagnoses. With the development of chemotherapy, the drug resistance rate of common platinum-based chemotherapeutic drugs (like cisplatin) is gradually increased, which seriously affects the chemotherapy efficiency and survival rate of patients. In this study, polyethylenimine caged platinum nanoclusters (PEI-caged Pt NCs) were proposed as a new chemotherapeutic agent to apply in the treatment of NSCLC, choosing the classical cisplatin-resistant A549/DDP cells and normal A549 cells as targets. It was found that our Pt NCs-based chemotherapeutic drugs showed its preferable therapeutic effect in cisplatin-resistant NSCLC through the results of confocal microscopic images, cell counting kit-8 test, cell apoptosis assay and western blot. Most importantly, in the cisplatin-resistance A549/DDP cells, this kind of agents could enter the nucleus obviously, and emerged a superior inhibitory and apoptotic effects than A549 via activating p53 protein and the related signaling pathways. Comparing with the traditional chemotherapy drugs, these Pt NCs-based chemotherapeutic agents exhibit great potential and advantages in the treatment and diagnosis of NSCLC regardless of the therapeutic effect or toxic side effects, especially the drug resistance.

ТЕЙХОЄВА КИСЛОТА МОДУЛЮЄ ЕКСПРЕСІЮ ТОЛЛ-ПОДІБНИХ РЕЦЕПТОРІВ 4 У ЧУТЛИВИХ ТА РЕЗИСТЕНТНИХ ДО ДІЇ ЦИСПЛАТИНУ ЛІНІЯХ КЛІТИН ДРІБНОКЛІТИННОГО РАКУ ЛЕГЕНІ

The Toll-like receptor family plays crucial role in the innate immune system, recognizing the molecular structures associated with pathogens derived from different microbes. TLRs also recognize the molecular structures associated with damage associated with certain diseases, such as cancer. They can either promote tumorigenesis, or suppress it. Besides, the promotion of the tumor cells growth may be associated with the acquisition of drug resistance. The data on the TLR4 expression level changes during this pathological process are controversial. That is why the purpose of our study was to determine the expression level of TLR4 in cisplatin-sensitive and cisplatin-resistant lung cancer cells. Cells line NCI-H69 (human small cell lung carcinoma) and a drug resistant subline of NCI-H69/CPR were used to determine the expression level of TLR4.Incubation of cells with teichoic acid (1 μg / ml) was performed under standard conditions for two days. The level of TLR4 expression in the cell was determined with RT-PCR at 7500 Real-Time PCR Systems ("Applied Bіosystems", USA) and specific primers and asymmetric cyan cationic fluorochrom SYBRGreen (С32Н37N4S+) with spike of consumption at λmax = 488 nm and fluorescence at λmax = 522 nm. It was shown that TLR4 expression level was almost two times lower in WT H69 cells compared with H69 cells resistant to cisplatin. In contrast, teichoic acid oppositely influenced TLR4 expression level: increased by 1.3-times in WT H69 cells whereas decreased 4-times in H69 cells resistant to cisplatin compared with corresponding control samples without teichoic acid. In cisplatin-resistant lung cancer cells found high expression of TLR4 can be inhibited by addingteichoic acida ligand to TLRs.

NFκB and TNFα as individual key molecules associated with the cisplatin-resistance and radioresistance of lung cancer

Cisplatin-resistant (A549CisR and H292CisR) and radioresistant (A549R26 and H292R22) sub-line non-small cell lung cancer (NSCLC) cells were developed in our lab by long term treatment of parental cells with cisplatin or radiation. Our data showed no cross-resistance between these two sets of cell lines, indicating that molecular mechanisms of developing each resistance may be different. Using these sub-line cells, we sought to reveal the most significantly up-regulated molecules in cisplatin-resistant and radioresistant lung cancer cells, compared with parental cells. In qPCR analyses of screening DNA repair and cell survival-associated molecules, we identified NFκB and TNFα as the most significantly up-regulated molecules in cisplatin-resistant and radioresistant lung cancer cells, respectively, compared with parental cells. Western blot analysis of parental vs. resistant cells and the IHC staining of tumor tissues of A549P, A549CisR, and A549R26 cell-derived xenografts in mice confirmed such results. Next, studies using specific inhibitors of NFκB and TNFα and experiments using NFκB and TNFα-knocked down cells showed that inhibition or knockdown of NFκB overcame cisplatin-resistance, while inhibition or knockdown of TNFα increased radiosensitivity of radioresistant lung cancer cells. Therefore, these two molecules may be used as markers of the prognosis/diagnosis of individual resistance development during lung cancer treatment.

MA06.09 XRCC6BP1: A DNA Repair Gene in Cisplatin Resistant Lung Cancer Stem Cells That May Predict Survival Outcomes in Patients

MA06.09 XRCC6BP1: A DNA Repair Gene in Cisplatin Resistant Lung Cancer Stem Cells That May Predict Survival Outcomes in Patients

BCL9 promotes epithelial mesenchymal transition and invasion in cisplatin resistant NSCLC cells via β-catenin pathway

AimsBcell lymphoma 9 (BCL9)-Wnt/β-catenin pathway, a key signaling pathway related to epithelial-mesenchymal transition (EMT), is widely considered to be involved in invasion in various malignant tumors. However, the dysregulation of BCL9/β-catenin pathway in non-small cell lung cancer (NSCLC) has not been revealed. This study aimed to investigate the correlation between chemotherapy resistance and BCL9/Wnt/β-catenin signaling dysfunction. Main methodsWe performed BCL9 knockdown using a lentivirus-mediated sh-RNA interference in cisplatin-resistant (CR) lung cancer cells. Subsequently, the migration and invasion were determined by wound-healing and Transwell assays. Furthermore, EMT markers and β-catenin were examined by Western blot. Immunofluorescence was used to investigate the subcellular localization of β-catenin. The chemotherapeutic sensitivity to cisplatin in A549/DDP cell lines after treatment with BCL9 sh-RNA was estimated by MTT assay. Key findingsThe knockdown of BCL9 remarkably reduced the migration and invasion abilities of A549/DDP cells. Meanwhile, nuclear translocation of β-catenin was reduced after BCL9 was knocked down. BCL9 silencing also resulted in the downregulation of EMT-related proteins. Additionally, the Wnt/β-catenin agonist, CP21, significantly restored the expression of β-catenin and abilities of migration and invasion in BCL9-knockdown A549/DDP cell lines. Finally, we proved that the inhibition of BCL9 could partially attenuate the stemness of cancer cells and recover the chemotherapeutic sensitivity. SignificanceThese findings indicated BCL9 induced the occurrence of EMT and enhancement of stemness, which resulted in cisplatin-resistance and promoted migration in NSCLC cells. Mechanically, Wnt/β-catenin pathway is crucial in BCL9-induced migration, invasion, and chemotherapy resistance.

Abstract 5478: Targeting kynurenine pathway for the treatment of cisplatin-resistant lung cancer

Abstract We have found that increasing ROS (reactive oxygen species) level is a specific and yet common feature found in cisplatin resistant (CR) lung cancer cells. We also showed that manipulation of ROS levels can selectively killed CR cells. Here, we have further identified the underlying mechanism for increasing ROS and its relationship with metabolic reprogramming and immune evasion. CR cells no longer follow classic aerobic glycolysis (Warburg effect). They do not primarily utilize glucose, but rather consume amino acids such as glutamine and tryptophan for survival. CR cells take up twice as much L-[G-3H] glutamine (n=4, p<0.05) and tryptophan (TRP) (n=4, p<0.04) when compared to its parental counterpart. These fundamental understandings have led us to study another unique mechanism where we found that CR cells activate kynurenine pathway (TRP catabolism) when they encounter excessive oxidative stress in order to maintain a finite level of ROS for their growth and proliferation. Importantly, kynurenine (KYN) which is oxidized through indoleamine 2,3-dioxygenase (IDO) via kynurenine pathway, plays a key role in reprogramming naïve T-cells to immune suppressive regulatory T-cell (T-reg) phenotype. Inhibiting IDO using Epacadostat (Incyte Corp.), a known IDO inhibitor which is currently in phase 3 trial, led to elevated ROS and resulted in the demise of CR cells. ROS levels were increased (2-3X) more in resistant cells after Epacadostat treatment while no significant change occurred in parental cells. The ID50 dosage of parental cells was 2-4 fold more than their CR cell counterparts and no cytotoxicity was found in normal lung fibroblast (n=6; p<0.05). To further determine whether IDO correlated with ROS levels and sensitivity to Epacadostat, we inhibited IDO expressions in CR cell lines (ie. ALC and H460CR) using siRNA. Knocking down IDO enhanced ROS production and more importantly suppressed CR cells' growth which further implicates the important role of kynurenine pathway (KP) in proliferation of CR tumors. Moreover, the treatment of knocked down cells with Epacadostat did not result in further cell death, indicating the specificity of this compound for the IDO enzyme. FoxP3, a lineage-specific marker of T-reg cells, was higher in CR cells when compared to their parental cell counterparts. Treatment with Epacadostat significantly suppressed FoxP3 expression which further support the relationship between metabolic reprogramming and immune evasion. Overall, we believe that our work will have potential impact on (i) how one can effectively exploits the KP pathway to treat CR tumors, and (ii) improved understanding on how CR cells evade immune surveillance. Supported by Department of Veterans Affairs, CDA2 award (1K2BX001289). Citation Format: Medhi Wangpaichitr, Chunjing Wu, Dan JM Nguyen, Ying-Ying Li, Lynn G. Feun, Niramol Savaraj. Targeting kynurenine pathway for the treatment of cisplatin-resistant lung cancer [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 5478.

Metabolic vulnerability of cisplatin-resistant cancers.

Cisplatin is the most widely used chemotherapeutic agent, and resistance of neoplastic cells against this cytoxicant poses a major problem in clinical oncology. Here, we explored potential metabolic vulnerabilities of cisplatin-resistant non-small human cell lung cancer and ovarian cancer cell lines. Cisplatin-resistant clones were more sensitive to killing by nutrient deprivation invitro and invivo than their parental cisplatin-sensitive controls. The susceptibility of cisplatin-resistant cells to starvation could be explained by a particularly strong dependence on glutamine. Glutamine depletion was sufficient to restore cisplatin responses of initially cisplatin-resistant clones, and glutamine supplementation rescued cisplatin-resistant clones from starvation-induced death. Mass spectrometric metabolomics and specific interventions on glutamine metabolism revealed that, in cisplatin-resistant cells, glutamine is mostly required for nucleotide biosynthesis rather than for anaplerotic, bioenergetic or redox reactions. As a result, cisplatin-resistant cancers became exquisitely sensitive to treatment with antimetabolites that target nucleoside metabolism.

Targeting RNA polymerase I transcription machinery in cancer cells by a novel monofunctional platinum-based agent

Aberrant ribosome biogenesis and enlarged nucleoli have long been used by pathologists as a marker of aggressive tumors. Suppression of RNA polymerase I (Pol I) transcription machinery within the nucleolus could be a direct way to trigger the nucleolar stress and to inhibit the rapid proliferation of cancer cells. Here we modified cisplatin with an analogue of the selective inhibitor of RNA polymerase I-mediated transcription BMH-21 to develop a novel platinum-based Pol I selective inhibitor. We show that this novel monofunctional platinum-based agent, P1-B1, had enhanced antitumor activity of up to 17-fold greater than the clinical drug cisplatin in cisplatin-resistant non-small cell lung cancer cells. P1-B1 also had significantly lower cytotoxicity compared to cisplatin as well as the Pol I selective inhibitor BMH-21 in MRC-5 normal lung fibroblast cells, and the selectivity index (SI) greatly increases. Mechanistic investigations revealed that P1-B1 displayed significant nucleolar accumulation, selectively inhibited Pol I transcription, and induced nucleolar stress, leading to S-phase arrest and apoptosis. Our results suggest that the effects of P1-B1 are mechanistically distinct from those of conventional platinum agents and the recently described non-classical platinum compounds and that functionalizing platinum-based agents with directly Pol I transcription inhibition properties may represent an improved modality for cancer treatment.

Co-inhibition of Pol η and ATR sensitizes cisplatin-resistant non-small cell lung cancer cells to cisplatin by impeding DNA damage repair.

For the majority of patients with advanced non-small cell lung cancer (NSCLC), the standard of care remains platinum-based chemotherapy. However, cisplatin resistance is a big obstacle to the treatment, and elucidation of its mechanism is warranted. In this study, we showed that there was no difference in intracellular uptake of cisplatin or the removal of platinum-DNA adducts between a cisplatin-resistant NSCLC cell line (A549/DR) and a cisplatin-sensitive NSCLC cell line (A549). However, the capacity to repair DNA interstrand crosslinks (ICLs) and double-strand breaks (DSBs) was significantly enhanced in the A549/DR cell line compared to 3 cisplatin-sensitive cell lines. We found that the protein and mRNA expression levels of Pol η, a Y-family translesion synthesis (TLS) polymerase, were markedly increased upon cisplatin exposure in A549/DR cells compared with A549 cells. Furthermore, intracellular co-localization of Pol η and proliferation cell nuclear antigen (PCNA) induced by cisplatin or cisplatin plus gemcitabine treatment was inhibited by depleting ataxia telangiectasia mutated and Rad-3-related (ATR). Pol η depletion by siRNA sensitized A549/DR cells to cisplatin; co-depletion of Pol η and ATR further increased A549/DR cell death induced by cisplatin or cisplatin plus gemcitabine compared to depletion of Pol η or ATR alone, concomitant with inhibition of DNA ICL and DSB repair and accumulation of DNA damage. No additional sensitization effect of co-depleting Pol η and ATR was observed in A549 cells. These results demonstrate that co-inhibition of Pol η and ATR reverses the drug resistance of cisplatin-resistant NSCLC cells by blocking the repair of DNA ICLs and DSBs induced by cisplatin or cisplatin plus gemcitabine.

MiRNA 146a promotes chemotherapy resistance in lung cancer cells by targeting DNA damage inducible transcript 3 (CHOP)

The underlying molecular mechanism of lung cancer drug resistance is poorly understood. The mediator of endoplasmic reticulum stress CHOP (DNA damage inducible transcript 3) promotes stress-induced apoptosis and appears to function as a transcription factor in multiple diseases. However, its potential contributions to multidrug resistance in solid tumors is unknown. Here, we investigated CHOP expression in tumor tissues form 69 lung cancer patients, finding that deficient CHOP expression is associated with poor prognosis. Cisplatin-resistant lung cancer cells exhibited lower expression of CHOP compared to that in sensitive lung cancer cells, and silencing or augmenting CHOP expression enhanced or impaired cisplatin resistance, respectively. Mechanistic investigations revealed that CHOP is directly associated with the regulation of autophagy or apoptosis-regulatory genes including LC3-II, death receptor 5 (DR5), and telomere repeat-binding factor 3. Notably, CHOP was identified as a target of miR-146a, and increased miR-146a expression in lung cancer cells was suggested to be responsible for CHOP mRNA down-regulation. Further, animal models confirmed that abnormally expressed miR-146a in lung cancer cells does not affect growth, but rather alters chemotherapy sensitivity. Together, CHOP is a useful prognostic marker and miR-146a is a potential therapeutic target for multidrug-resistant lung cancer.

Miltirone-induced apoptosis in cisplatin-resistant lung cancer cells through upregulation of p53 signaling pathways.

The active ingredients of natural plants are important sources of antitumor agents. Miltirone is a major effective ingredient in traditional Chinese medicine and it is considered to have anti-infection and immunosuppressive activities. Clinically, it is often used for the treatment of arthritis and immune diseases. The effect of miltirone on cisplatin-resistant lung cancer cells has not been investigated to date. The present study aimed to examine the anticancer effect of miltirone in cisplatin-resistant lung cancer cells. Treatment with miltirone suppressed cell viability and induced apoptosis in HCC827 and A549 platinum-resistant lung cancer cells. It was also revealed that miltirone increased caspase-3/8 activity as well as B-cell lymphoma 2-associated X-protein, apoptosis-inducing factor (AIF), p53 and poly(ADP-ribose) polymerase (PARP) protein expression, whereas it inhibited mitochondrial reactive oxygen species (ROS) generation and matrix metalloproteinase (MMP)-2/9 protein expression in HCC827 and A549 platinum-resistant lung cancer cells. The results of the present study demonstrated that miltirone induces apoptosis in cisplatin-resistant lung cancer cells through ROS-p53, AIF, PARP and MMP2/9 signaling pathways.

LncRNA-MALAT1 contributes to the cisplatin-resistance of lung cancer by upregulating MRP1 and MDR1 via STAT3 activation

Multiple drug resistance is the main reason for chemotherapeutic failure in lung cancer patients with complex molecular mechanisms. LncRNA-MALAT1 plays functional roles in the progression of carcinomas and development of drug resistance. We aimed to identify the role of MALAT1 in DDP-resistant non-small cell lung cancer as well as potential mechanisms. Human lung cancer cell line A549 and the DDP-resistant cell line A549/DDP were used. Cell transfection was performed to establish A549/MALAT1 and A549/DDP/shMALAT1 cells. The qRT-PCR analysis was performed to detect lncRNA-MALAT1 level. Cell viability, colony formation assay, apoptosis analysis, western blot analysis, immunohistochemistry, and animal study were carried out. MALAT1 was upregulated in DDP-resistant A549 cell line. MALAT1 decreased DDP sensitivity in vitro and in vivo by upregulating MRP1 and MDR1 via STAT3 activation. Overexpression of MALAT1 contributed to the DDP resistance and might confer a potently poor prognosis.

Effects of HAD-B1 on the proliferation of A549 cisplatin-resistant lung cancer cells.

The present study investigated the toxicity of HangAmDan-B1 (HAD-B1) on A549-Cisplatin resistant (A549CR) cells. HAD‑B1 inhibited the growth of A549CR cells in a concentration‑dependent manner; HAD‑B1 was more effective at inhibiting A549CR cell viability compared with vehicle‑treated cells. The reduction in viability may be due to S‑phase cell cycle arrest and the induction of apoptosis in HAD‑B1‑treated cells. Cell cycle protein profile analysis of HAD‑B1‑treated A549CR cells using an InnoPharmaScreen (IPS) ProteoChip‑based antibody microarray chip indicated downregulation of signal transducer and activator of transcription 3. The activities of caspase‑3, ‑8 and ‑9 were significantly increased in HAD‑B1‑treated cells when compared with the vehicle‑treated control group. Furthermore, the HAD‑B1‑treated group exhibited similarly increased caspase levels when compared with the Afatinib‑treated group. Taken together, these observations suggest that HAD‑B1 may be a promising candidate for further research into the therapeutic management of cisplatin-resistant lung cancer.

The inhibitory effect of Cordycepin on the proliferation of cisplatin-resistant A549 lung cancer cells

The goal of this study is to determine the anti-cancer mechanism of Cordycepin in A549 Cisplatin-Resistance (CR) lung cancer cells. Cordycepin inhibited the viability of A549CR cells in a dose-dependent manner. The cell inhibition was due to induction of apoptosis in the cells treated with Cordycepin by activation of caspase −3, −8 and −9 activities. The cell cycle analysis showed that accumulation of Sub G1 was observed in Cordycepin-treated with A549CR lung cancer cells. Based on the data of expression profile analysis of cell signaling proteins using IPS-FPAA, H-Ras was down-regulated in Cordycepin-treated A549CR cells. Collectively, anti-proliferative function of Cordycepin was due to stimulation of the cell apoptosis and the cell cycle arrest via caspases activation and down-regulation of H-Ras.

Half-Sandwich Arene Ruthenium(II) and Osmium(II) Thiosemicarbazone Complexes: Solution Behavior and Antiproliferative Activity.

We report the synthesis, characterization, and antiproliferative activity of organo-osmium(II) and organo-ruthenium(II) half-sandwich complexes [(η6-p-cym)Os(L)Cl]Cl (1 and 2) and [(η6-p-cym)Ru(L)Cl]Cl (3 and 4), where L = N-(2-hydroxy)-3-methoxybenzylidenethiosemicarbazide (L1) or N-(2,3-dihydroxybenzylidene)-3-phenylthiosemicarbazide (L2), respectively. X-ray crystallography showed that all four complexes possess half-sandwich pseudo-octahedral “three-legged piano-stool” structures, with a neutral N,S-chelating thiosemicarbazone ligand and a terminal chloride occupying three coordination positions. In methanol, E/Z isomerization of the coordinated thiosemicarbazone ligand was observed, while in an aprotic solvent like acetone, partial dissociation of the ligand occurs, reaching complete displacement in a more coordinating solvent like DMSO. In general, the complexes exhibited good activity toward A2780 ovarian, A2780Cis cisplatin-resistant ovarian, A549 lung, HCT116 colon, and PC3 prostate cancer cells. In particular, ruthenium complex 3 does not present cross-resistance with the clinical drug cisplatin in the A2780 human ovarian cancer cell line. The complexes were more active than the free thiosemicarbazone ligands, especially in A549 and HCT116 cells with potency improvements of up to 20-fold between organic ligand L1 and ruthenium complex 1.

MiR-181 regulates cisplatin-resistant non-small cell lung cancer via downregulation of autophagy through the PTEN/PI3K/AKT pathway.

A number of miRNAs have been found to be abnormally expressed or mutated in numerous cancers and thus, are considered to act as oncogenes or tumor suppressor genes. The aim of the present study was to investigate the effect of miR-181 on cisplatin-resistant non-small cell lung cancer (NSCLC). In patients with cisplatin-resistant NSCLC, miR-181 expression was found to be markedly decreased. In addition, in the cisplatin-resistant human lung adenocarcinoma cell line A549/DDP, miR-181 downregulation promoted cell growth and metastasis and inhibited cell apoptosis, whereas miR-181 overexpression exerted the opposite effects. Furthermore, miR-181 downregulation suppressed LC3 and ATG5 protein expression in A549/DDP cells through suppression of the PTEN/PI3K/AKT/mTOR pathway, whereas miR-181 overexpression recovered LC3 and ATG5 protein expression by promoting PTEN/PI3K/AKT/mTOR signaling. In turn, PTEN inhibitors reduced the anticancer effects of miR-181 overexpression on A549/DDP cell growth via the regulation of autophagy through the PI3K/AKT/mTOR pathway. Therefore, miR-181 may be a novel and important regulator of cisplatin-resistant NSCLC by serving a role in the regulation of apoptosis, as an established rate-limiting miRNA target.

Upregulation of phosphatase and tensin homolog is essential for the effect of 4-aminopyridine on A549/CDDP cells

4-aminopyridine (4-AP), a voltage-gated potassium channel blocker, was revealed to possess pro‑apoptotic properties in various types of cancer cells. The present study aimed to explore the effect of 4‑AP on a cisplatin (DDP) resistant lung cancer cell line A549/CDDP and the underlying mechanism by which it had an effect. In the present study, an MTT assay and cell cycle analysis were used to determine that 4‑AP inhibited cell growth invitro and a tumorigenesis assay in nude mice determined that 4‑AP also inhibited cell growth invivo. 4‑AP induced cell apoptosis of A549/CDDP cells observed by electron microscopy and Annexin V‑APC/7‑ADD analysis. In addition, 4‑AP enhanced the sensitivity of A549/CDDP cells to DDP as revealed by an MTT assay. Mechanistically, 4‑AP upregulated the phosphatase and tensin homolog (PTEN) and modulated the phosphoinositide 3‑kinase/protein kinase B signaling pathway and its downstream cell cycle factors, including cyclin D1, cyclin‑dependent kinase 4 and p21, as well as apoptosis‑associated proteins B‑cell lymphoma 2, pro‑caspase 9, pro‑caspase 3, cleaved caspase 9 and cleaved caspase 3. The effects of 4‑AP on cell growth and apoptosis were reversed by PTEN silencing. In conclusion, the results indicated that 4‑AP inhibited cell growth, induced apoptosis and sensitized A549/CDDP cells to DDP via the upregulation of PTEN. 4‑AP may be a potential therapeutic agent for patients with DDP resistance.

Intracellular glutathione-depleting polymeric micelles for cisplatin prodrug delivery to overcome cisplatin resistance of cancers

The intrinsic or acquired cisplatin resistance of cancer cells frequently limits the final therapeutic efficacy. Detoxification by the high level of intracellular glutathione (GSH) plays critical roles in the majority of cisplatin-resistant cancers. In this report, we designed an amphiphilic diblock copolymer composed of poly(ethylene glycol) (PEG) and polymerized phenylboronic ester-functionalized methacrylate (PBEMA), PEG-b-PBEMA, which can self-assemble into micelles in aqueous solutions to load hydrophobic cisplatin prodrug (Pt(IV)). Pt(IV)-loaded PEG-b-PBEMA micelles (PtBE-Micelle) reverse cisplatin-resistance of cancer cells through improving cellular uptake efficiency and reducing intracellular GSH level. We found that the cellular uptake amount of platinum from PtBE-Micelle was 6.1 times higher than that of free cisplatin in cisplatin-resistant human lung cancer cells (A549R). Meanwhile, GSH concentration of A549R cells was decreased to 32% upon treatment by PEG-b-PBEMA micelle at the phenyl borate-equivalent concentration of 100μM. PtBE-Micelle displayed significantly higher cytotoxicity toward A549R cells with half maximal inhibitory concentration (IC50) of cisplatin-equivalent 0.20μM compared with free cisplatin of 33.15μM and Pt(IV)-loaded PEG-b-poly(ε-caprolactone) micelles of cisplatin-equivalent 0.75μM. PtBE-Micelle can inhibit the growth of A549R xenograft tumors effectively. Accordingly, PEG-b-PBEMA micelles show great potentials as drug delivery nanocarriers for platinum-based chemotherapy toward cisplatin-resistant cancers.

MiR-133b reverses cisplatin resistance by targeting GSTP1 in cisplatin-resistant lung cancer cells.

MicroRNAs play a critical role in chemoresistance and are implicated in various biological and pathological processes of cells. The objective of the present study was to explore the role of miR-133b and its mechanism in the regulation of cisplatin resistance and tumor progression in cisplatin-resistant non-small cell lung cancer (NSCLC) cells. Reverse transcription-quantitative polymerase chain reaction and western blot assays of the cisplatin-resistant cell lines A549/DPP and H1299/DDP displayed the reduced expression of miR-133b and increased expression of glutathione-S-transferase P1 (GSTP1) in the resistant cells compared with the respective parental cell lines A549 and H1299. Cell Counting kit-8, flow cytometry, colony formation and Transwell migration assays indicated that the overexpression of miR-133b increased the chemosensitivity to cisplatin and attenuated the proliferation and migration capacities of the cisplatin-resistant NSCLC cell lines in vitro. A dual-luciferase reporter assay demonstrated that miR-133b negatively regulated the expression of GSTP1 by targeting its 3′-untranslated region. In addition, the knockdown of GSTP1 by transfection with small interfering RNA exerted similar effects on cell chemosensitivity, proliferation and migration as did ectopic miR-133b expression, in addition to the upregulation of Bax and down-regulation of Bcl-2, survivin and matrix metalloproteinase expression. In conclusion, the present study findings provide the insights that miR-133b reduces cisplatin resistance and its overexpression contributes to the suppression of the malignant growth and aggressiveness of cisplatin-resistant NSCLC cells by targeting GSTP1. This could potentially be exploited as a novel therapeutic strategy for the reversal of cisplatin resistance.