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Paclitaxel is a first-line chemotherapeutic agent for gastric cancer; however, resistance limits its effectiveness. Investigation into the underlying mechanisms of paclitaxel resistance is urgently required. In the present study, a paclitaxel-resistant gastric cancer cell line (MGC-803R) was generated with a morphological phenotype of epithelial-to-mesenchymal transition (EMT) and increased expression levels of microRNA (miR)-155-5p. MGC-803R cell-derived exosomes were effectively taken up by paclitaxel-sensitive MGC-803S cells, which exhibited EMT and chemoresistance phenotypes. miR-155-5p was enriched in MGC-803R-exosomes and could be delivered into MGC-803S cells. miR-155-5p overexpression in MGC-803S cells via transfection with mimics resulted in similar phenotypic effects as treatment with MGC-803R exosome and increased miR-155-5p content in MGC-803S exosomes, which then capable of inducing the malignant phenotype in the sensitive cells. GATA binding protein 3 (GATA3) and tumor protein p53-inducible nuclear protein 1 (TP53INP1) were identified as targets of miR-155-5p. Exosomal miR-155-5p inhibited these targets by directly targeting their 3′ untranslated regions. Knockdown of miR-155-5p was observed to reverse the EMT and chemoresistant phenotypes of MGC-803R cells, potentially via GATA3 and TP53INP1 upregulation, which inhibited MGC-803R-exosomes from inducing the malignant phenotype. These results demonstrated that exosomal delivery of miR-155-5p may induce EMT and chemoresistant phenotypes from paclitaxel-resistant gastric cancer cells to the sensitive cells, which may be mediated by GATA3 and TP53INP1 suppression. Targeting miR-155-5p may thus be a promising strategy to overcome paclitaxel resistance in gastric cancer.

Exosomes derived from lung cancer cells confer cisplatin (DDP) resistance to other cancer cells. However, the underlying mechanism is still unknown. A549 resistance to DDP (A549/DDP) was established. Microarray was used to analyze microRNA (miRNA) expression profiles of A549 cells, A549/DDP cells, A549 exosomes, and A549/DDP exosomes. There was a strong correlation of miRNA profiles between exosomes and their maternal cells. A total of 11 miRNAs were significantly upregulated both in A549/DDP cells compared with A549 cells and in exosomes derived from A549/DDP cells in contrast to exosomes from A549 cells. A total of 31 downregulated miRNAs were also observed. miR-100-5p was the most prominent decreased miRNA in DDP-resistant exosomes compared with the corresponding sensitive ones. Downregulated miR-100-5p was proved to be involved in DDP resistance in A549 cells, and mammalian target of rapamycin (mTOR) expression was reverse regulated by miR-100-5p. Exosomes confer recipient cells' resistance to DDP in an exosomal miR-100-5p-dependent manner with mTOR as its potential target both in vitro and in vivo. Exosomes from DDP-resistant lung cancer cells A549 can alter other lung cancer cells' sensitivity to DDP in exosomal miR-100-5p-dependent manner. Our study provides new insights into the molecular mechanism of DDP resistance in lung cancer.

Background. Based on PACIFIC trial, durvalumab as consolidation therapy following concurrent chemoradiotherapy (cCRT) has been a new standard treatment for unresectable stage III non-small cell lung cancer (NSCLC). In clinical applications, there are heterogeneous adjustments or novel strategies following specialized discussions in experienced multidisciplinary teams. This study retrospectively compared the efficacy and safety of different first-line treatments for unresectable stage III NSCLC. Methods. We retrospectively analyzed 397 patients who received first-line treatment for unresectable stage III NSCLC. Comparisons and statistical analyses of treatment were made in terms of efficacy and safety. Adverse events and responses were assessed using CTCAE v5.0 and RECIST v1.1. The progression-free survival (PFS) was estimated using the Kaplan–Meier method or the Cox survival regression model and compared using the log-rank test. Results. In wild-type driver genes group, the objective response rate (ORR), disease control rate (DCR), and median PFS (mPFS) were prolonged in the radiotherapy group compared to those in the nonradiotherapy group (ORR: 50.94% vs. 30.06%, p < 0.001; DCR: 98.11% vs. 80.37%, p < 0.001; and mPFS: 21.00 vs. 8.20 months, p < 0.001). The incidence of pneumonia at any grade in the radiotherapy group was higher than that in the nonradiotherapy group (9.43% vs. 2.45%, p = 0.008). In the radiotherapy group, the chemoradiotherapy (CRT) plus immunotherapy subgroup had longer mPFS than the CRT subgroup, with increased toxicity at any grade (24.60 vs. 17.90 months, p = 0.025, and 83.17% vs. 65.52%, p = 0.011). In the nonradiotherapy group, the DCR and mPFS were higher in the chemotherapy plus immunotherapy subgroup than in the chemotherapy subgroup, with increased toxicity at any grade (DCR: 93.67% vs. 67.86%, p < 0.001; mPFS: 13.53 vs. 5.07 months, p < 0.001; and 68.35% vs. 41.67%, p = 0.001). In the mutant driver genes group, the efficacy did not significantly differ among the radiotherapy subgroup, targeted therapy subgroup, and radiotherapy plus targeted therapy subgroup (ORR: p = 0.633; mPFS: p = 0.450). Conclusions. For unresectable stage III NSCLC patients with wild-type driver genes, the combination of radiotherapy and immunotherapy in the initial treatment was essential to significantly improve the efficacy. For patients with mutant driver genes, radiotherapy, targeted therapy, and the combination of radiotherapy and targeted therapy showed similar short-term efficacy.

Breast cancer is the leading cause of cancer-related mortality in women worldwide. Long non-coding RNAs (lncRNAs) are of critical importance in tumor drug resistance. Herein, this study aims to determine the roles of lncRNA ZEB1-AS1 in drug resistance of breast cancer involving microRNA-129-5p (miR-129-5p) and ZEB1. Microarray-based gene expression profiling of breast cancer was conducted to identify the differentially expressed lncRNAs. ZEB1 expression was measured in adjacent and cancerous tissues. Next, MCF-7 and MDA-MB-231 cells were treated with a series of inhibitor, mimic or siRNA to clarify the roles of lncRNA ZEB1-AS1 and miR-129-5p in drug resistance of breast cancer. Then the target relationship of miR-129-5p with lncRNA ZEB1-AS1 and ZEB1 was verified. The expression patterns of miR-129-5p, lncRNA ZEB1-AS1, - , - , ZEB1 and corresponding proteins were evaluated. Moreover, the apoptosis and drug resistance of MCF-7 cell were detected by CCK-8 and flow cytometry respectively. LncRNA ZEB1-AS1 was observed to be an upregulated lncRNA in breast cancer, and ZEB1 overexpression was noted in breast cancerous tissues. MiR-129-5p was revealed to specifically bind to both ZEB1 and lncRNA ZEB1-AS1. Moreover, the expression levels of ZEB1-AS1, ZEB1, - , - , and corresponding proteins were decreased, but the expression of miR-129-5p was increased with transfection of miR-129-5p mimic and lncRNA ZEB1-AS1 siRNA. Besides, drug resistance to cisplatin was inhibited, and cell apoptosis was promoted in breast cancer after transfection of miR-129-5p mimic, lncRNA ZEB1-AS1 siRNA, and ZEB1 siRNA. In conclusion, the study provides evidence that lncRNA ZEB1-AS1 silencing protects against drug resistance in breast cancer by promoting miR-129-5p-dependent ZEB1 downregulation. It may serve as a novel therapeutic target in breast cancer treatment.

Objective As monotherapy such as topotecan has reached a plateau of effectiveness, new second-line treatments based on experience have been used in clinical application. This study compared the efficacy and safety of different second-line treatments for advanced small-cell lung cancer (SCLC). Methods A total of 380 patients with advanced SCLC were screened selectively in the retrospective study. Adverse events and patient responses were assessed using Common Terminology Criteria for Adverse Events v5.0 and Response Evaluation Criteria for Solid Tumors v1.1. The progression-free survival (PFS) was estimated using the Kaplan-Meier method or Cox survival regression model and compared using the log-rank test. Results In the platinum-resistant group, disease control rate (DCR) and median PFS (mPFS) were prolonged in the combination group versus single-agent group (DCR: 49.24% vs 24.39%, P = .004; mPFS: 3.73 vs 1.90 months, P < .001). Grade 3/4 toxicity was similar between the 2 groups (P = .683). The mPFS did not differ among single-agent groups (P = .380). No significant difference was observed in mPFS of different combination therapy groups (P = .170). In terms of platinum-based chemotherapy, the DCR and mPFS were prolonged in irinotecan-platinum group versus taxol-platinum group (DCR: 56.14% vs 9.09%, P = .004; mPFS: 3.87 vs 1.93 months, P = .012). Grade 3/4 toxicity was similar between the 2 groups (P = .614). The mPFS was prolonged in the chemotherapy plus immunotherapy group versus single-agent chemotherapy group (P = .003). In the platinum-sensitive group, the mPFS did not differ between the combination group and single-agent group (P = .200). The mPFS did not differ among different single-agent groups (P = .260) or combination groups (P = .150). There was no difference in mPFS among different platinum-based chemotherapy groups (P = .830). Conclusions For patients with platinum-resistant SCLC, combination therapy has shown better efficacy and acceptable toxicity profile than monotherapy. Among combination therapies, irinotecan–platinum has shown better efficacy than taxol–platinum. For patients with platinum-sensitive SCLC, the efficacy of different single-agent or combination therapies was similar.

Exosomes are small extracellular membrane vesicles of endocytic origin released by many cells that could be found in most body fluids. The main functions of exosomes are cellular communication and cellular waste clean-up. This study was conducted to determine the involvement of exosomes in the regulation of sensitivity of the lung cancer cell line A549 to cisplatin (DDP). When DDP was added to A549 cells, exosomes secretion was strengthened. Addition of the secreted exosomes to other A549 cells increased the resistance of these A549 cells to DDP. Upon exposure of A549 to DDP, the expression levels of several miRNAs and mRNAs reportedly associated with DDP sensitivity changed significantly in exosomes; these changes may mediate the resistance of A549 cells to DDP. Exosomes released by A549 cells during DDP exposure decreased the sensitivity of other A549 cells to DDP, which may be mediated by miRNAs and mRNAs exchange by exosomes via cell-to-cell communication. Although the detailed mechanism of resistance remains unclear, we believed that inhibition of exosomes formation and release might present a novel strategy for lung cancer treatment in the future.

This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1186/s12935-021-01759-5.

Epidermal growth factor receptor monoclonal antibody was approved for treatment of metastatic colorectal cancer patients carrying KRAS wild type DNA. However, recent studies showed that patients with KRAS G13D mutation may benefit from EGFR antibody therapy. In this study we tried to explore whether the abundance of KRAS mutation could affect the efficacy of EGFR antibody therapy. We firstly established a PNA-PCR method which could calculate the percentage of KRAS mutation in total DNA and proved its ability on 47 colorectal cancer samples bearing KRAS mutations. Then we analyzed the correlation between the abundance of KRAS mutations and efficacy of EGFR antibody therapy in another 35 metastatic colorectal cancer patients. We proved that PNA-PCR assay could calculate the abundance of KRAS mutation and the percentage of mutant DNA in tumor cells varied a lot (10.8%∼98.3%) on the 47 colorectal cancer patients. The efficacy of EGFR antibody correlated with the abundance of KRAS mutations: in the KRAS mutation less than 30% group, the disease control rate was 44.4% (4/9); the disease control rate of 30∼80% group was 5.6% (1/18) and the >80% group was 12.5% (1/8) (P = 0.038). In summary, our study showed that PNA-PCR method could easily detect the percentage of KRAS mutation in tumor cells and colorectal cancer patients with low abundance of KRAS mutation might benefit from EGFR antibody therapy.

To understand the mechanism involved in gefitinib resistance, we established gefitinib-resistant human HCC827/GR-8-1 cell line from the parental HCC827 cell line. We compared the micro-RNA expression profiles of the HCC827 cells HCC827/GR-8-1 using Agilent micro-RNA microarrays. The micro-RNAs, such as the miR-149-5p, were up- or downregulated and associated with acquired gefitinib resistance. Quantitative real-time polymerase chain reaction was then performed to verify the expression patterns of different micro-RNAs. The result showed that miR-149-5p was upregulated in the HCC827/GR-8-1 cell line. To investigate the biological function of miR-149-5p in non–small cell lung cancer cells acquired gefitinib resistance, we examined cell proliferation using a cell counting kit-8 assay. Cell viability was evaluated after the miR-149-5p mimics, inhibitors, and negative control were separately transfected into the non–small cell lung cancer cells. The results showed that the non–small cell lung cancer cells transfected with miR-149-5p mimics exhibited reduced cell motility. The drug-sensitivity assay results revealed that the overexpression of miR-149-5p effectively evaluates the half maximal inhibitory concentration values of the cell in response to gefitinib, and the downregulation of miR-149-5p can attenuate the half maximal inhibitory concentration values of the cell lines in response to gefitinib. Furthermore, the levels of miR-149-5p in the HCC827 and HCC827/GR-8-1 cells were inversely correlated with caspase-3 expression. In conclusion, this study revealed that miR-149-5p is upregulated in the HCC827/GR-8-1 cells and involved in the acquired gefitinib resistance.

EGFR-mutant lung cancer (LC) patients display a poor response to PD-1/PD-L1 blockade. In the absence of independent genetic validation, whether EGFR mutation distorts host antitumor immunity is unknown. Here, we showed that in the clinic, LC with the E746-A750 deletion mutation (EGFR-19del) displayed a temporal association with the loss of intratumoral CD8+ T cells. In a xenograft model, EGFR-19del-expressing Lewis lung cancer (LLC) tumors had a low T cell density at the early stage of tumor development, along with dendritic cells (DCs) exhibiting variant phenotypes in the tumors and draining lymph nodes (LNs). Importantly, EGFR-19del DCs were observed in the LNs of tumor-bearing mice and LC patients. The proliferative activity of T cells within the LN was significantly dampened. In vitro experiments indicated that the function of DCs was repressed by EGFR-19del LLC cells through exosome uptake in which exosomes derived from the EGFR-19del LLC cells could efficiently transfer active EGFR-19del to the surface of the DCs. Injection of EGFR-19del tumor-derived exosomes promoted LLC tumor progression and induced immunosuppression. The combination of gefitinib and GM-CSF treatment recovered tumor T cell infiltration in EGFR-19del tumors by rescuing the function of DCs and increasing the efficacy of anti-PD-L1 treatment. Together, these results indicated that LC with the EGFR E746-A750 deletion mutation induced anergic DCs to repress antitumor immunity through exosomes.