NVP-BEZ235 overcomes gefitinib-acquired resistance by down-regulating PI3K/AKT/mTOR phosphorylation

CHKB-AS1 enhances proliferation and resistance to NVP-BEZ235 of renal cancer cells via regulating the phosphorylation of MAP4 and PI3K/AKT/mTOR signaling

Targeted therapy is pivotal in renal carcinoma treatment, and the dual-inhibitor NVP-BEZ235 has emerged as a promising candidate in preliminary studies. Its effectiveness against renal carcinoma and the mechanisms underlying potential resistance, however, warrant further exploration. This study aims to elucidate these aspects, enhancing our understanding of NVP-BEZ235's future clinical utility. To investigate resistance mechanisms, renal cancer cell lines were exposed to progressively increasing concentrations of NVP-BEZ235, leading to the development of stable resistance. These resistant cells underwent extensive RNA-sequencing analysis. We implemented gene interference techniques using plasmid vectors and lentivirus and conducted regular IC50 assessments. To pinpoint the role of LncRNAs, we utilized FISH and immunofluorescence staining assays, supplemented by RNA pull-down and RIP assays to delineate interactions between LncRNA and its RNA-binding protein (RBP). Further, Western blotting and qRT-PCR were employed to examine alterations in signaling pathways, with an animal model providing additional validation. Our results show a marked increase in the IC50 of NVP-BEZ235 in resistant cell lines compared to their parental counterparts. A significant revelation was the role of LncRNA-CHKB-AS1 in mediating drug resistance. We observed dysregulated expression of CHKB-AS1 in both clinical samples of clear cell renal cell carcinoma (ccRCC) and cell lines. In vivo experiments further substantiated our findings, showing that CHKB-AS1 overexpression significantly enhanced tumor growth and resistance to NVP-BEZ235 in a subcutaneous tumorigenesis model, as evidenced by increased tumor volume and weight, whereas CHKB-AS1 knockdown led to a marked reduction in these parameters. Critically, CHKB-AS1 was identified to interact with MAP4, a key regulator in the phosphorylation of the PI3k/Akt/mTOR pathway. This interaction contributes to a diminished antitumor effect of NVP-BEZ235, highlighting the intricate mechanism through which CHKB-AS1 modulates drug resistance pathways, potentially impacting therapeutic strategies against renal carcinoma.

Rapamycin enhanced the antitumor effects of doxorubicin in myelogenous leukemia K562 cells by downregulating the mTOR/p70S6K pathway

Chronic myelogenous leukemia (CML) is a common hematological malignancy. Some patients progressing to the blast phase develop chemotherapeutic drug resistance. In the authors' previous study, it was found that the mammalian target of rapamycin (mTOR) pathway was activated in CML and that rapamycin inhibited the proliferation of K562 cells. Targeting the mTOR pathway may be used in combination with chemotherapeutic drugs to enhance their efficacy and overcome multidrug resistance. The aim of the present study was to investigate the effects of rapamycin and doxorubicin on K562 cell proliferation following the combination treatment, and further focus on confirming whether rapamycin enhanced the antitumor effects of doxorubicin by downregulating the mTOR/ribosomal protein S6 kinase (p70S6K) pathway. It was found that rapamycin and doxorubicin significantly decreased the viability of K562 cells. The apoptotic cells were more frequently detected in rapamycin and doxorubicin treatment groups (25.50±1.25%). Both drugs decreased Bcl-2 and increased Bax expression in K562 cells. Rapamycin and doxorubicin also reduced the phosphorylation levels of mTOR and p70S6K. Meanwhile, p70S6K-targeting small interfering (si)RNA and doxorubicin inhibited cell proliferation and regulated key factors of the cell cycle. In addition, the exposure of cells to p70S6K siRNA and doxorubicin significantly increased cell apoptosis, as compared with single treatment. These results suggested that rapamycin could enhance the antitumor effects of doxorubicin on K562 cells by downregulating mTOR/p70S6K signaling. Targeting the mTOR/p70S6K pathway may be a new therapeutic approach for leukemia.

The dual PI3K/mTOR inhibitor BEZ235 restricts the growth of lung cancer tumors regardless of EGFR status, as a potent accompanist in combined therapeutic regimens

Background

Lung cancer is the most common cause of cancer-related mortality worldwide despite diagnostic improvements and the development of targeted therapies, notably including epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). The phosphoinositide 3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) signaling has been shown to contribute to tumorigenesis, tumor progression, and resistance to therapy in most human cancer types, including lung cancer. Here, we explored the therapeutic effects of co-inhibition of PI3K and mTOR in non-small-cell lung cancer (NSCLC) cells with different EGFR status.

Methods

The antiproliferative activity of a dual PI3K/mTOR inhibitor BEZ235 was examined by the WST-1 assay and the soft agar colony-formation assay in 2 normal cell lines and 12 NSCLC cell lines: 6 expressing wild-type EGFR and 6 expressing EGFR with activating mutations, including exon 19 deletions, and L858R and T790 M point mutations. The combination indexes of BEZ235 with cisplatin or an EGFR-TKI, BIBW2992 (afatinib), were calculated. The mechanisms triggered by BEZ235 were explored by western blotting analysis. The anti-tumor effect of BEZ235 alone or combined with cisplatin or BIBW2992 were also studied in vivo.

Results

BEZ235 suppressed tumor growth in vitro and in vivo by inducing cell-cycle arrest at G1 phase, but without causing cell death. It also reduced the expression of cyclin D1/D3 by regulating both its transcription and protein stability. Moreover, BEZ235 synergistically enhanced cisplatin-induced apoptosis in NSCLC cells by enhancing or prolonging DNA damage and BIBW2992-induced apoptosis in EGFR-TKI–resistant NSCLC cells containing a second TKI-resistant EGFR mutant.

Conclusions

The dual PI3K/mTOR inhibition by BEZ235 is an effective antitumor strategy for enhancing the efficacy of chemotherapy or targeted therapy, even as a monotherapy, to restrict tumor growth in lung cancer treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1282-0) contains supplementary material, which is available to authorized users.

Comprehensive analysis of circular RNA profiling in AZD9291-resistant non-small cell lung cancer cell lines

BACKGROUND

Osimertinib (AZD9291), a third-generation EGFR-tyrosine kinase inhibitor, can effectively prolong survival in non-small cell lung cancer (NSCLC) patients with EGFR mutations, particularly T790M mutations; however, acquired resistance to AZD9291 is inevitable, thus exploration of the targets of resistance is urgent.

METHODS

Considering the important role of circular RNAs (circRNAs) in cancers, we established AZD9291-resistant NSCLC cell lines (H1975/AZDR and HCC827/AZDR) and used microarray analysis to determine the circRNA expression profiles of the cells. The H1975/AZDR and HCC827/AZDR cell lines were induced by gradually increasing the drug concentration. CircRNA microarray expression profiles were obtained from H1975, HCC827, H1975/AZDR, and HCC827/AZDR cells and validated by quantitative reverse transcription PCR. Expression data were analyzed bioinformatically.

RESULTS

The H1975/AZDR and HCC827/AZDR cell lines were successfully established. The half-maximal inhibitory concentration and the invasion ability of H1975/AZDR and HCC827/AZDR cells were significantly enhanced. The proliferation rates of H1975/AZDR and HCC827/AZDR were much lower than H1975 and HCC827. Microarray analysis identified 15 504 circRNAs differentially expressed in H1975, HCC827, H1975/AZDR, and HCC827/AZDR cells. Among them, 7966 were upregulated and 7538 were downregulated more than two-fold. We predicted the possible miRNAs of the top dysregulated circRNAs. Furthermore, Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the most modulated circRNAs regulate several cancers and cancer-related pathways.

CONCLUSION

Our results reveal that circRNAs may play a role in NSCLC AZD9291 resistance and might be a promising molecular target candidate for gene therapy.

Drug candidate identification based on gene expression of treated cells using tensor decomposition-based unsupervised feature extraction for large-scale data

BACKGROUND

Although in silico drug discovery is necessary for drug development, two major strategies, a structure-based and ligand-based approach, have not been completely successful. Currently, the third approach, inference of drug candidates from gene expression profiles obtained from the cells treated with the compounds under study requires the use of a training dataset. Here, the purpose was to develop a new approach that does not require any pre-existing knowledge about the drug-protein interactions, but these interactions can be inferred by means of an integrated approach using gene expression profiles obtained from the cells treated with the analysed compounds and the existing data describing gene-gene interactions.

RESULTS

In the present study, using tensor decomposition-based unsupervised feature extraction, which represents an extension of the recently proposed principal-component analysis-based feature extraction, gene sets and compounds with a significant dose-dependent activity were screened without any training datasets. Next, after these results were combined with the data showing perturbations in single-gene expression profiles, genes targeted by the analysed compounds were inferred. The set of target genes thus identified was shown to significantly overlap with known target genes of the compounds under study.

CONCLUSIONS

The method is specifically designed for large-scale datasets (including hundreds of treatments with compounds), not for conventional small-scale datasets. The obtained results indicate that two compounds that have not been extensively studied, WZ-3105 and CGP-60474, represent promising drug candidates targeting multiple cancers, including melanoma, adenocarcinoma, liver carcinoma, and breast, colon, and prostate cancers, which were analysed in this in silico study.

Mechanism of Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors and a Potential Treatment Strategy

Treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) improves the overall survival of patients with EGFR-mutated non-small-cell lung cancer (NSCLC). First-generation EGFR-TKIs (e.g., gefitinib and erlotinib) or second-generation EGFR-TKIs (e.g., afatinib and dacomitinib) are effective for the treatment of EGFR-mutated NSCLC, especially in patients with EGFR exon 19 deletions or an exon 21 L858R mutation. However, almost all cases experience disease recurrence after 1 to 2 years due to acquired resistance. The EGFR T790M mutation in exon 20 is the most frequent alteration associated with the development of acquired resistance. Osimertinib-a third-generation EGFR-TKI-targets the T790M mutation and has demonstrated high efficacy against EGFR-mutated lung cancer. However, the development of acquired resistance to third-generation EGFR-TKI, involving the cysteine residue at codon 797 mutation, has been observed. Other mechanisms of acquired resistance include the activation of alternative pathways or downstream targets and histological transformation (i.e., epithelial⁻mesenchymal transition or conversion to small-cell lung cancer). Furthermore, the development of primary resistance through overexpression of the hepatocyte growth factor and suppression of Bcl-2-like protein 11 expression may lead to problems. In this report, we review these mechanisms and discuss therapeutic strategies to overcome resistance to EGFR-TKIs.

Preclinical evaluation of novel PI3K/mTOR dual inhibitor SN202 as potential anti-renal cancer agent

ABSTRACT The PI3K/mTOR pathway is one of the most frequently aberrantly activated pathways in human malignancies, such as renal cell carcinoma (RCC), and contributes to resistance to antitumor therapies. Thus, PI3K/mTOR is an attractive target for the development of antitumor agents. In this study, we evaluated the preclinical effects of a novel inhibitor SN202. We examined Akt/mTOR activities in renal cancer cells after SN202 treatment. The preclinical effects of SN202 on tumor growth were evaluated in renal cancer cells in vitro and in murine xenografts in vivo. SN202 inhibits PI3Kα, PI3Kγ, and mTOR, the corresponding IC₅₀ values were 3.2, 3.3, and 1.2 nM, respectively. In A498, 786-0, and ACHN renal cancer cell lines, SN202 inhibits cell proliferation in a dose-dependent manner and significantly inhibits 786-0 cell growth. Western blot analysis revealed that SN202 decreases the phosphorylation of PI3K downstream signaling molecules, Akt and S6K, in 786-0 renal cancer cells. Furthermore, oral administration of SN202 results in significant inhibition in human renal carcinoma xenografts in nude mice and favourable pharmacokinetic properties in rats. These results suggest that SN202 might be a promising therapeutic agent against RCC as a dual PI3K/mTOR inhibitor.

Study on Biological Characteristics and Mechanism of Paclitaxel Induced Drug Resistance in Endometrial Carcinoma Cells

Objective

To study the biological characteristics of paclitaxel resistant endometrial carcinoma cells and its mechanism of drug resistance.

Method

The paclitaxel resistant cell lines were established by high-dose paclitaxel (TAX) injection. The IC50 of paclitaxel was determined by CCK-8 assay in Ishikawa and Ishikawa-TAX. The cell cycle and apoptosis rate were detected by flow cytometry. Western blot was used to detect the expression of p-AKT and p-p70S6K. The expression of drug resistance-related genes Pgp and MDR1 was determined by RT-PCR. Cell viability was determined by soft agarose assay and invasive ability in vitro by transwell assay.

Results

Paclitaxel and NVP-BEZ235 cotreatment group can further inhibit the clonogenicity and invasion of Ishikawa and Ishikawa-TAX cells compared with paclitaxel alone and NVP-BEZ235 treatment group. Paclitaxel and NVP-BEZ235 cotreated groups increased the apoptosis rate of Ishikawa and increased G0/G1 phase arrest in both cells. Paclitaxel alone significantly inhibited p-AK and p-p70 S6K protein expression in Ishikawa and Ishikawa-TAX cells and the inhibition was enhanced by NVP-BEZ235 when cotreated with paclitaxel.

Conclusion

Paclitaxel can inhibit Ishikawa and Ishikawa-TAX cell via PI3K/Akt/mTOR signaling pathway. Paclitaxel and NVP-BEZ235 cotreatment can enhance the inhibitory effect.

Rare Mechanism of Acquired Resistance to Osimertinib in Korean Patients with EGFR-mutated Non-small Cell Lung Cancer

Epidermal growth factor receptor (EGFR)‒tyrosine kinase inhibitors (TKIs) are effective clinical therapeutics for EGFR-mutant non-small cell lung cancer (NSCLC). Osimertinib, a thirdgeneration EGFR TKI, has proven effective against T790M mutations. However, the vast majority of patients acquire resistance following successful treatment. A 59-year-old female patient with metastatic NSCLC developed resistance after 43 weeks of osimertinib. CancerSCAN of the metastatic liver lesion revealed a EGFR C797G mutation at an allele frequency of 72%, a preexisting T790M mutation (73%) in cis and an exon 19 deletion (87%). Another 53-year-old female patient developed systemic progression after 10 months of osimertinib. CancerSCAN of the lung biopsy identified an EGFR L718Q mutation at an allele frequency of 7%, concomitant PIK3CA E545K (12.90%) and preexisting EGFR L858R (38%), but loss of the T790M mutation. The heterogeneity of osimertinib resistance mechanisms warrants further investigation into novel or combination agents to overcome the rare acquired resistances.

Endoplasmic reticulum stress promotes autophagy and apoptosis and reverses chemoresistance in human ovarian cancer cells

Ovarian cancer presents the highest mortality rate among gynecological tumors. Here, we measured cell viability, proliferation, apoptosis, autophagy, and expression of endoplasmic reticulum stress (ERS)-related proteins, PI3K/AKT/mTOR pathway-related proteins, and apoptosis- and autophagy-related proteins in SKOV3 and SKOV3/CDDP cells treated with combinations of CDDP, tunicamycin, and BEZ235 (blank control, CDDP, CDDP + tunicamycin, CDDP + BEZ235, and CDDP + tunicamycin + BEZ235). Increasing concentrations of tunicamycin and CDDP activated ERS in SKOV3 cells, reduced cell viability and proliferation, increased apoptosis and autophagy, enhanced expression of ERS-related proteins, and inhibited expression of PI3K/AKT/mTOR pathway-related proteins. CDDP, tunicamycin, and BEZ235 acted synergistically to enhance these effects. We also detected lower expression of the ERS-related proteins caspase-3, LC3 II and Beclin 1 in ovarian cancer tissues than adjacent normal tissues. By contrast, expression of Bcl-2 and PI3K/AKT/mTOR pathway-related proteins was higher in ovarian cancer tissues than adjacent normal tissues. Lastly, expression of the ERS-related proteins Beclin 1, caspase-3 and LC3 II was higher in the sensitive group than the resistant group, while expression of Bcl-2, LC3 I, P62 and PI3K/AKT/mTOR pathway-related proteins was decreased. These results show that ERS promotes cell autophagy and apoptosis while reversing chemoresistance in ovarian cancer cells by inhibiting activation of the PI3K/AKT/mTOR signaling pathway.

Activation of endoplasmic reticulum stress promotes autophagy and apoptosis and reverses chemoresistance of human small cell lung cancer cells by inhibiting the PI3K/AKT/mTOR signaling pathway

OBJECTIVE

This study aims to investigate the effects of endoplasmic reticulum stress (ERS) on autophagy, apoptosis and chemoresistance of human small cell lung cancer (SCLC) cells via the PI3K/AKT/mTOR signaling pathway.

RESULTS

The expressions of ERS-related proteins (PEAK, eIF2α and CHOP) up-regulated, autophagy-related proteins (LC3, LC3-II and Beclin1) and apoptosis-related proteins (Bax and procaspase-3) down-regulated in NCI-H446 and H69 cells after tunicamycin treatment for 24 h. Compared with the blank group, the tunicamycin, BEZ235 and tunicamycin + BEZ235 groups exhibited decreased expressions of p-PI3K, p-AKT and p-mTOR, and increased expressions of autophagy-related proteins (LC3, LC3-II and Beclin1) and apoptosis proteins (Bax and procaspase-3), and the most obvious changes were observed in the tunicamycin + BEZ235 group.

MATERIALS AND METHODS

CCK-8 assay was applied to select the best cell line from five SCLC cell lines (NCI-H446, H69, H526, H146 and H209). Finally, NCI-H446 and H69 cells were selected for further experiments. NCI-H446/CDDP and H69/CDDP were selected and divided into the blank group, tunicamycin (an ESR inducer) group, BEZ235 (inhibitors of PI3K/AKT/mTOR pathway) group and tunicamycin + BEZ235 group. Cell apoptosis was detected by flow cytometry. Autophagy was observed by fluorescence microscopy and flow cytometry. Western blotting was used to detect the expressions of ERS-related proteins, autophagy-related proteins, apoptosis-related proteins and PI3K/AKT/mTOR pathway-related proteins.

CONCLUSIONS

Our findings provide evidence that the activation of ERS could promote autophagy and apoptosis and reverse chemoresistance of human SCLC cells by inhibiting the PI3K/AKT/mTOR pathway.

Knockdown of SALL4 overcomes cisplatin-resistance through AKT/mTOR signaling in lung cancer cells

Drug resistance is an important factor for the poor prognosis of non-small cell lung cancer (NSCLC). Sal-like protein 4 (Sall4) is a stem cell marker, and plays a role in maintaining self-renewal. Previous studies have demonstrated that Sall4 may be a candidate for use as support in the diagnosis of lung cancer, and may also represent a therapeutic target. However, the role of Sall4 on drug resistance of lung cancer cells and the mechanism by which Sall4 regulates the sensitivity of lung cancer cells to cisplatin (DDP) remains unknown. In this study, we aim to investigate whether knockdown of Sall4 by siRNA can enhance the apoptosis induced by cisplatin in lung cancer cells. We here reported that the expression of Sall4 was dramatically upregulated in cisplatin-resistant A549 cells compared with the parental cells. Knockdown of Sall4 by siRNA in cisplatin-resistant A549 cells reduced the IC₅₀ compared with the parental cells. In addition, knockdown of Sall4 significantly inhibited cell proliferation, induced apoptosis and invasion cisplatin-resistant A549 cells through AKT/mTOR signaling. Our findings demonstrate that Sall4 is an essential regulator in cisplatin-induced apoptosis, and knockdown of Sall4 may restore cisplatin sensitivity in acquired resistant cells. Thus, our study provides an effective therapeutic strategy for NSCLC treatment.

Acquired resistance to PI3K/mTOR inhibition is associated with mitochondrial DNA mutation and glycolysis

Acquired resistance (AQR) to drug treatment occurs frequently in cancer patients and remains an impediment to successful therapy. The aim of this study was to gain insight into how AQR arises following the application of PI3K/mTOR inhibitors. H1975 lung cancer cells with EGFR T790M mutations that confer resistance to EGFR inhibitors underwent prolonged treatment with the PI3K/mTOR inhibitor, BEZ235. Monoclonal cells with stable and increased resistance to BEZ235 were obtained after 8 months treatment. These AQR clones showed class-specific resistance to PI3K/mTOR inhibitors, reduced G1 cell cycle arrest and impedance of migration following PI3K/mTOR inhibition, reduced PTEN expression and increased Akt and S6RP phosphorylation. Transcriptome analysis revealed the AQR clones had increased expression of the metabolite transporters SLC16A9 and SLC16A7, suggestive of altered cell metabolism. Subsequent experiments revealed that AQR clones possess features consistent with elevated glycolysis, including increased levels of glucose, lactate, glutamine, glucose dependence, GLUT1 expression, and rates of post-glucose extracellular acidification, and decreased levels of reactive oxygen species and rates of oxygen consumption. Combination treatment of BEZ235 with the glycolysis inhibitor 3-bromopyruvate was synergistic in AQR clones, but only additive in parental cells. DNA sequencing revealed the presence of a mitochondrial DNA (mtDNA) MT-C01 variant in AQR but not parental cells. Depletion of mitochondrial DNA in parental cells induced resistance to BEZ235 and other PI3K/mTOR inhibitors, and was accompanied by increased glycolysis. The results of this study provide the first evidence that a metabolic switch associated with mtDNA mutation can be an underlying mechanism for AQR.

Clinical management of epidermal growth factor receptor mutation-positive non-small cell lung cancer patients after progression on previous epidermal growth factor receptor tyrosine kinase inhibitors: the necessity of repeated molecular analysis

One of the most important advances in the treatment of non-small cell lung cancer (NSCLC) has been the identification of molecular alterations vulnerable to targeted inhibition, such as mutations in the epidermal growth factor receptor (EGFR) gene. EGFR tyrosine kinase inhibitors (EGFR-TKIs) are targeted agents used to treat EGFR mutation-positive advanced NSCLC showing significant improvements in terms of response rate (RR) and progression-free survival (PFS) compared to conventional chemotherapy. However, all patients eventually develop resistance to first-line EGFR-TKIs. The most common mechanism of acquired resistance is the secondary acquisition of a single missense mutation within exon 20 in the EGFR gene, known as the T790M mutation (49-60%). New agents targeting the T790M mutation have undergone clinical development, and among these, osimertinib has shown significant activity in relapsing EGFR mutation positive patients harbouring the T790M mutation. Although precision medicine is a reality for NSCLC, obtaining relevant tissue for repeated molecular analysis from these patients remains a challenge. In this article, a group of experts from the Spanish Society of Medical Oncology (SEOM) and the Spanish Lung Cancer Group (GECP) evaluated the role of rebiopsy and the potential application of plasma-testing methodologies in advanced EGFR mutation patients progressing after EGFR-TKI.

Efficacy of the dual PI3K and mTOR inhibitor NVP-BEZ235 in combination with imatinib mesylate against chronic myelogenous leukemia cell lines

BACKGROUND

Phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is a therapy target of cancer. We aimed to confirm the effect of dual PI3K/mTOR inhibitor NVP-BEZ235 on proliferation, apoptosis, and autophagy of chronic myelogenous leukemia (CML) cells and sensitivity of tyrosine kinase inhibitor in vitro.

METHODS

Two human CML cell lines, K562 and KBM7R (T315I mutant strain), were used. The proliferation of CML cells was detected by MTS (Owen's reagent) assay. Cell cycle and apoptosis assay were examined by flow cytometric analysis. The phosphorylation levels and the expression levels were both evaluated by Western blot analysis. NVP-BEZ235 in combination with imatinib was also used to reveal the effect on proliferation and apoptosis.

RESULTS

NVP-BEZ235 significantly inhibited the proliferation in a time- and dose-dependent manner, and the half-maximal inhibitory concentration values of NVP-BEZ235 inhibiting the proliferation of K562 and KBM7R were 0.37±0.21 and 0.43±0.27 μmol/L, respectively, after 48 h. Cell apoptosis assay showed that NVP-BEZ235 significantly increased the late apoptotic cells. Cell cycle analysis indicated that the cells were mostly arrested in G1/G0 phase after treatment by NVP-BEZ235. In addition, results also found that, after treatment by NVP-BEZ235, phosphorylation levels of Akt kinase and S6K kinase significantly reduced, and the expression levels of cleaved caspase-3 significantly increased; meanwhile, the expression levels of caspase-3, B-cell lymphoma-2, cyclin D1, and cyclin D2 significantly decreased, and the ratio of LC3II/LC3I was significantly increased with increased LC3II expression level. Moreover, imatinib in combination with NVP-BEZ235 induced a more pronounced colony growth inhibition than imatinib alone.

CONCLUSION

NVP-BEZ235 effectively inhibited cell proliferation by G0/G1 cell cycle arrest and induced apoptosis through deregulating PI3K/Akt/mTOR pathway in CML cells; in addition, NVP-BEZ235 can enhance cell autophagy, and is conducive to raising CML cell sensitivity to imatinib to inhibit the growth of imatinib-resistant cells.

Intrinsic resistance to EGFR tyrosine kinase inhibitors in advanced non-small-cell lung cancer with activating EGFR mutations

Identifying activating EGFR mutations is a useful predictive strategy that helps select a population of advanced non-small-cell lung cancer (NSCLC) patients for treatment with EGFR tyrosine kinase inhibitors (TKIs). Patients with sensitizing EGFR mutations (predominantly an in-frame deletion in exon 19 and an L858R substitution) are highly responsive to first-generation EGFR TKIs, such as gefitinib and erlotinib, and show improved progression-free survival without serious side effects. However, all patients with activating EGFR mutations who are initially responsive to EGFR TKIs eventually develop acquired resistance after a median progression-free survival of 10-16 months, followed by disease progression. Moreover, ~20%-30% of NSCLC patients have no objective tumor regression on initial EGFR TKI treatment, although they harbor an activating EGFR mutation. These patients represent an NSCLC subgroup that is defined as having intrinsic or primary resistance to EGFR TKIs. Different mechanisms of acquired EGFR TKI resistance have been identified, and several novel compounds have been developed to reverse acquired resistance, but little is known about EGFR TKI intrinsic resistance. In this review, we summarize the latest findings involving mechanisms of intrinsic resistance to EGFR TKIs in advanced NSCLC with activating EGFR mutations and present possible therapeutic strategies to overcome this resistance.

Implications of MicroRNAs in the Treatment of Gefitinib-Resistant Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) represents about 85% of the reported cases of lung cancer. Acquired resistance to targeted therapy with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib, is not uncommon. It is thus vital to explore novel strategies to restore sensitivity to gefitinib. Provided that microRNAs (miRNAs) negatively regulate their gene targets at the transcriptional level, it is speculated that miRNA mimetics may reduce the expression, activity and signal transduction of EGFR so that sensitization of tumour sites to gefitinib-induced cytotoxicity can be achieved. Indeed, a growing body of evidence has shown that the manipulation of endogenous levels of miRNA not only attenuates the EGFR/PI3K/Akt phosphorylation cascade, but also restores apoptotic cell death in in vitro models of experimentally-induced gefitinib resistance and provoked tumour regression/shrinkage in xenograft models. These data are in concordant with the clinical data showing that the differential expression profiles of miRNA in tumour tissues and blood associate strongly with drug response and overall survival. Furthermore, another line of studies indicate that the chemopreventive effects of a variety of natural compounds may involve miRNAs. The present review aims to discuss the therapeutic capacity of miRNAs in relation to recent discoveries on EGFR-TKI resistance, including chronic drug exposure and mutations.