miR-145-5p Targets Sp1 in Non-Small Cell Lung Cancer Cells and Links to BMI1 Induced Pemetrexed Resistance and Epithelial–Mesenchymal Transition

Abstract

Pemetrexed is a folic acid inhibitor used as a second-line chemotherapeutic agent for the treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC), which accounts for 85% of lung cancers. However, prolonged treatment with pemetrexed may cause cancer cells to develop resistance. In this study, we found increased expressions of BMI1 (B Lymphoma Mo-MLV insertion region 1 homolog) and Sp1 and a decreased expression of miR-145-5p was found in pemetrexed-resistant A400 cells than in A549 cells. Direct Sp1 targeting activity of miR-145-5p was demonstrated by a luciferase based Sp1 3’-UTR reporter. Changed expression of miR-145-5p in A400 or A549 cells by transfection of miR-145-5p mimic or inhibitor affected the sensitivity of the cells to pemetrexed. On the other hand, the overexpression of Sp1 in A549 cells caused the decreased sensitivity to pemetrexed, induced cell migratory capability, and epithelial–mesenchymal transition (EMT) related transcription factors such as Snail Family Transcriptional Repressor 1 and Zinc Finger E-Box Binding Homeobox 1. In addition, the overexpression of BMI1 in the A549 cells resulted in an increase in Sp1 and a decrease in miR-145-5p accompanied by the elevations of cell proliferation and EMT transcription factors, which could be reduced by the overexpression of miR-145-5p or by treatment with the Sp1 inhibitor of mithramycin A. In conclusion, the results of this study suggest that the downregulation of miR-145-5p by BMI1 overexpression could lead to the enhanced expression of Sp1 to induce the EMT process in pemetrexed-resistant NSCLC cells. These results suggest that increasing miR-145-5p expression by delivering RNA drugs may serve as a sensitizing agent for pemetrexed-resistant NSCLC patients.

A dynamic Boolean network reveals that the BMI1 and MALAT1 axis is associated with drug resistance by limiting miR-145-5p in non-small cell lung cancer

“…For example, the targets of miR-145 such as Cyclin-dependent kinases 4 and 6 complexes/CyclinD1 (CDK4/6-Cyclin D) [ 4 ], Mdm2 [ 24 ], Sirt1 [ 25 ], Myc [ 4 ], Sp1 [ 2 ], KLF4 [ 1 ], and BCL2 [ 5 ], have been studied extensively. Whereas, MALAT1 targets miR-145 [ 2 ] and p53 [ 26 ]. We employed public datasets for this, such as TARGET SCAN HUMAN 7.2 ( http://www.targetscan.org/vert_72/ ) [ 27 ].…”

“…It is well known that p53 promotes miR-145 expression [ 30 ]. When miR-145 is activated, it targets Myc [ 4 ], Cyclin D [ 4 ], Bcl2 [ 5 ], Sirt1 [ 25 ], Sp1 [ 2 ], KLF4 [ 1 ], and MDM2 [ 24 ]. Myc directly activates BMI1 expression [ 31 ] and upregulated BMI1 directly inhibits miR-145 [ 2 ] and forms a positive circuit between miR-145 (miR-145/Myc/BMI1), additionally, it triggers Sp1 [ 2 ] and KLF4 expression [ 1 ].…”

“…In this setting, Cui et al [ 1 ] revealed that MALAT1 overexpression directly targets miR-145 and controls KLF4 expression, which is implicated in drug resistance in NSCLC cells. More evidence comes from an investigation by Chang et colleagues [ 2 ], who showed that when BMI1 is overexpressed, miR-145 is downregulated, which boosts Sp1 expression and triggers EMT in pemetrexed-resistant NSCLC cells [ 2 ]. Interestingly, the expression of MALAT1 is induced by Sp1 in NSCLC [ 3 ].…”

LncRNA PTOV1-AS2 Promotes Colon Cancer Progression through the miR-145-5p/FSCN1 Axis

“…The miR-145-5p mimics (sense: 5′-GUCCAGUUUUCCCAGGAAUCCCU-3′, antisense: 5′-GGAUUCCUGGGAAAACUGGACUU-3′) and miR-145-5p inhibitors (5 5′-AGGGAUUCCUGGGAAAACUGGAC-3′) [ 19 ] were purchased from BGI Genomics Co., Ltd. (Shenzhen, China). The PTOV1-AS2 overexpression plasmid was constructed as follows: the PTOV1-AS2 gene sequence was obtained from the NCBI website, and then the linear cDNA sequence was synthesized manually, subcloned into the pcDNA3.1 vector and verified by one-generation DNA sequencing.…”

Identification of Key Genes and Related Drugs of Adrenocortical Carcinoma by Integrated Bioinformatics Analysis

“…Floxuridine is a nucleoside analog, and studies have demonstrated that Floxuridine-based chemotherapy regimens preserve fertility in patients with trophoblastic tumors during pregnancy [77]. Pemetrexed is a novel anti-folate drug that is used frequently in the clinic for the treatment of advanced non-small cell lung cancer [78]. Tegafur-uracil is a fluoropyrimidine antitumor agent, which significantly improves the overall survival rate of patients with advanced oral cancer [79].…”