• Asian Pacific Journal of Cancer Prevention
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• v.14 no.1
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• pp.387-392
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• 2013

Objective: The aim of the present study was to explore mechanisms by which let-7c suppresses NSCLC cell proliferation. Methods: The expression level of let-7c was quantified by qRT-PCR. A549 and H1299 cells were transfected with let-7c mimics to restore the expression of let-7c. The effects of let-7c were then assessed by cell proliferation, colony formation and cell cycle assay. Mouse experiments were used to confirm the effect of let-7c on tumorigenicity in vivo. Luciferase reporter assays and Western blotting were performed to identify target genes for let-7c. Results: HOXA1 was identified as a novel target of let-7c. MTS, colony formation and flow cytometry assays demonstrated that forced expression of let-7c inhibited NSCLC cell proliferation by inducing G1 arrest in vitro, consistent with inhibitory effects induced by knockdown of HOXA1. Mouse experiments demonstrated that let-7c expression suppressed tumorigenesis. Furthermore, we found that let-7c could regulate the expression of HOXA1 downstream effectors CCND1, CDC25A and CDK2. Conclusions: Collectively, these results demonstrate let-7c inhibits NSCLC cell proliferation and tumorigenesis by partial direct targeting of the HOXA1 pathway, which suggests that restoration of let-7c expression may thus offer a potential therapeutic intervention strategy for NSCLC.

• Molecules and Cells
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• v.38 no.4
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• pp.304-311
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• 2015

Most follicles in the mammalian ovary undergo atresia. Granulosa cell apoptosis is a hallmark of follicle atresia. Our previous study using a microRNA (miRNA) microarray showed that the let-7 microRNA family was differentially expressed during follicular atresia. However, whether the let-7 miRNA family members are related to porcine (Sus scrofa) ovary follicular apoptosis is unclear. In the current study, real-time quantitative polymerase chain reaction showed that the expression levels of let-7 family members in follicles and granulosa cells were similar to our microarray data, in which miRNAs let-7a, let-7b, let-7c, and let-7i were significantly decreased in early atretic and progressively atretic porcine ovary follicles compared with healthy follicles, while let-7g was highly expressed during follicle atresia. Furthermore, flow cytometric analysis and Hoechst33342 staining demonstrated that let-7g increased the apoptotic rate of cultured granulosa cells. In addition, let-7 target genes were predicted and annotated by TargetScan, PicTar, gene ontology and Kyoto encyclopedia of genes and genomes pathways. Our data provide new insight into the association between the let-7 miRNA family in granulosa cell programmed death.

• BMB Reports
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• v.45 no.8
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• pp.464-469
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• 2012

Endothelial cells (ECs) apoptosis induced by oxidized low-density lipoprotein (ox-LDL) is thought to play a critical role in atherosclerosis. MicroRNAs (miRNAs) are a class of noncoding RNAs that posttranscriptionally regulate the expression of genes involved in diverse cell functions, including differentiation, growth, proliferation, and apoptosis. MiRNA let-7 family is known to be involved in the regulation of cell apoptosis. However, the function of let-7 in ox-LDL induced ECs apoptosis and atherosclerosis is still unknown. Here, we show that let-7c expression was markedly up-regulated in ox-LDL induced apoptotic human umbilical cord vein endothelial cells (HUVECs). Let-7c over-expression enhanced apoptosis in ECs whereas inhibition of let-7c could partly alleviate apoptotic cell death mediated by ox-LDL. Searching for how let-7c affected apoptosis, we discovered that antiapoptotic protein Bcl-xl was a direct target of let-7c in ECs. Our data suggest that let-7c contributes to endothelial apoptosis through suppression of Bcl-xl.

• Nutrition Research and Practice
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• v.10 no.4
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• pp.377-384
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• 2016

BACKGROUND/OBJECTIVES: Resveratrol, a natural polyphenol, has multiple functions in cellular responses including apoptosis, survival, and differentiation. It also participates in the regulation of inflammatory response and oxidative stress. MicroRNA-Let-7A (miR-Let7A), known as a tumor suppressor miRNA, was recently reported to play a crucial role in both inflammation and apoptosis. Therefore, we examined involvement of miR-Let7A in the modulation of inflammation and cell survival/apoptosis regulated by resveratrol. MATERIALS/METHODS: mRNA expression of pro-/anti-inflammatory cytokines and sirtuin 1 (SIRT1), and protein expression of apoptosis signal-regulating kinase 1 (ASK1), p-ASK1, and caspase-3 and cleaved caspase-3 were measured, and cell viability and Hoechst/PI staining for apoptosis were observed in Lipopolysaccharide (LPS)-stimulated human THP-1 macrophages with the treatment of resveratrol and/or miR-Let7A overexpression. RESULTS: Pre-treatment with resveratrol ($25-200{\mu}M$) resulted in significant recovery of the reduced cell viabilities under LPS-induced inflammatory condition and in markedly increased expression of miR-Let7A in non-stimulated or LPS-stimulated cells. Increased mRNA levels of tumor necrosis $factor-{\alpha}$ and interleukin (IL)-6 induced by LPS were significantly attenuated, and decreased levels of IL-10 and brain-derived neurotrophic factor were significantly restored by resveratrol and miR-Let7A overexpression, respectively, or in combination. Decreased expression of IL-4 mRNA by LPS stimulation was also significantly increased by miR-Let7A overexpression co-treated with resveratrol. In addition, decreased SIRT1 mRNA levels, and increased p-ASK1 levels and PI-positive cells by LPS stimulation were significantly restored by resveratrol and miR-Let7A overexpression, respectively, or in combination. CONCLUSIONS: miR-Let7A may be involved in the inflammatory response and cell survival/apoptosis modulated by resveratrol in human THP-1 macrophages.

• Molecules and Cells
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• v.39 no.4
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• pp.345-351
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• 2016

Wound healing is a complex physiological process necessitating the coordinated action of various cell types, signals and microRNAs (miRNAs). However, little is known regarding the role of miRNAs in mediating this process. In the present study, we show that let-7c miRNA is decreased in heat-denatured fibroblasts and that inhibiting let-7c expression leads to the increased proliferation and migration of dermal fibroblasts, whereas the overexpression of let-7c exerts an opposite effect. Further investigation has identified heat shock protein 70 as a direct target of let-7c and has demonstrated that the expression of HSP70 in fibroblasts is negatively correlated with let-7c levels. Moreover, down-regulation of let-7c expression is accompanied by up-regulation of Bcl-2 expression and down-regulation of Bax expression, both of which are the downstream genes of HSP70. Notably, the knockdown of HSP70 by HSP70 siRNA apparently abrogates the stimulatory effect of let-7c inhibitor on heat-denatured fibroblasts proliferation and migration. Overall, we have identified let-7c as a key regulator that inhibits fibroblasts proliferation and migration during wound healing.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.1
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• pp.23-30
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• 2019

Objective: Recent studies have demonstrated that lin-28 homolog B (LIN28B)/miRNA let-7 (let-7) plays a role in the regulation of pubertal onset in mammals. However, the role of LIN28B/let-7 in the onset of ovine puberty remains unknown. We cloned the Duolang sheep Lin28B cDNA sequence, detected the expression change of LIN28B, let-7a and let-7g in hypothalamus, pituitary and ovary tissues at three different pubertal stages. Methods: The reverse transcriptase polymerase chain reaction (RT-PCR) was used to clone the cDNA sequence of LIN28B gene from Duolang sheep and the bioinformatics methods were applied to analyze the amino acid sequence of LIN28B protein. The mRNA expression levels of the LIN28B gene at different pubertal stages were examined by real time RT-PCR. Results: LIN28B cDNA of Duolang sheep was cloned, and two transcripts were obtained. The amino acid sequence of transcript 1 shares 99.60%, 98.78%, and 94.80% identity with those of goat, wild yak and pig, respectively. Strong LIN28B mRNA expression was detected in the hypothalamus, pituitary, ovary, oviduct and uterus, while moderate expression was found in the liver, kidney, spleen and heart, weak expression was observed in the heart. No expression was found in the lungs. Quantitative real-time PCR (QPCR) and western-blot analysis revealed that the LIN28B was highly expressed in the hypothalamus and ovary at prepuberty stages, and this expression significantly decreased from the prepuberty to puberty stages (p<0.05). Markedly increased levels of mRNA expression were detected in the pituitary from prepuberty to puberty (p<0.05) and then significantly decreased from puberty to post-puberty (p<0.05). The expression levels of let-7a and let-7g showed no significant changes among different pubertal stages (p>0.05). Conclusion: These results provided a foundation for determining the functions of LIN28B/let-7 and their role in the onset of sheep puberty.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1887-1890
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• 2016

Breast cancer is the most common cause of cancer-related death among women in the whole world. MiR- 34a and let-7a are well known tumor suppressors that participate in the regulation of apoptosis, invasion and other cellular functions. In this study, expression of miR-34a, let-7a and apoptosis pathway genes such as Bcl-2, Caspase-3 and P53 were evaluated using quantitative real-time PCR in 45 paired samples of normal margin and tumor tissue collected from breast cancer patient at advanced stage (3-4). MiR-34a, let-7a, caspase-3 and P53 expression are reduced and Bcl-2 expression is increased within tumoral tissues in comparison with normal margin tissues. P53 expression directly or indirectly was correlated with miR-34a, let-7a, Bcl-2 and caspase-3 expression. In This study we found that MiR-34a and let-7a expression are reduced in the tumoral tissues. Down-regulation of these two molecules correlated with expression of genes associated with apoptosis. These results suggest that due to the correlation of miR-34a and let-7a with apoptotic and anti-apoptotic pathways these molecules could participate as regulators in advanced clinical stages of breast cancer and should be considered as markers for diagnosis, prognostic assessment and targeted therapy.

• BMB Reports
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• v.52 no.3
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• pp.214-219
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• 2019

The role of tumor-proximal factors in tumor plasticity during chemoresistance and metastasis following chemotherapy is well studied. However, the role of endothelial cell (EC) derived paracrine factors in tumor plasticity, their effect on chemotherapeutic outcome, and the mechanism by which these paracrine factors modulate the tumor microenvironment are not well understood. In this study, we report a novel mechanism by which endothelial miR-125a and let-7e-mediated regulation of interleukin-6 (IL-6) signaling can manipulate vasculogenic mimicry (VM) formation of MDA-MB-231 breast cancer cells. We found that endothelial IL-6 levels were significantly higher in response to cisplatin treatment, whereas levels of IL-6 upon cisplatin exposure remained unchanged in MDA-MB-231 breast cancer cells. We additionally found an inverse correlation between IL-6 and miR-125a/let-7e expression levels in cisplatin treated ECs. Interestingly, IL-6, IL-6 receptor (IL-6R), and signal transducer and activator of transcription 3 (STAT3) genes in the IL-6 pathway are closely regulated by miR-125a and let-7e, which directly target its 3' untranslated region. Functional analyses revealed that endothelial miR-125a and let-7e inhibit IL-6-induced adhesion of monocytes to ECs. Furthermore, conditioned medium from cisplatin treated ECs induced a significantly higher formation of VM in MDA-MB-231 breast cancer cells as compared to that from intact ECs; this effect of cisplatin treatment was abrogated by concurrent overexpression of miR-125a and let-7e. Overall, this study reveals a novel EC-tumor cell crosstalk mediated by the endothelial miR-125a/let-7e-IL-6 signaling axis, which might improve chemosensitivity and provide potential therapeutic targets for the treatment of cancer.

• Korean Journal of Mathematics
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• v.7 no.1
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• pp.85-101
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• 1999

Let $p$ be analytic in the unit disc U and let $q$ be univalent in U. In addition, let ${\Omega}$ be a set in C and let ${\psi}:c^3{\times}U{\rightarrow}C$. The author determines conditions on ${\psi}$ so that $$\{{\psi}(p(z),zp^{\prime}(z),z^2p^{{\prime}{\prime}}(z);z){\mid}z{\in}U\}{\subset}{\Omega}{\Rightarrow}p(U){\subset}q(U)$$. Applications of this result to differential inequalities, differential subordinations and integral inequalities are presented.

• Genomics & Informatics
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• v.21 no.3
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• pp.38.1-38.8
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• 2023

Non-small cell lung cancer (NSCLC) is an important cause of cancer-associated deaths worldwide. Therefore, the exact molecular mechanisms of NSCLC are unidentified. The present investigation aims to identify the miRNAs with predictive value in NSCLC. The two datasets were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed miRNAs (DEmiRNA) and mRNAs (DEmRNA) were selected from the normalized data. Next, miRNA-mRNA interactions were determined. Then, co-expression network analysis was completed using the WGCNA package in R software. The co-expression network between DEmiRNAs and DEmRNAs was calculated to prioritize the miRNAs. Next, the enrichment analysis was performed for DEmiRNA and DEmRNA. Finally, the drug-gene interaction network was constructed by importing the gene list to dgidb database. A total of 3,033 differentially expressed genes and 58 DEmiRNA were recognized from two datasets. The co-expression network analysis was utilized to build a gene co- expression network. Next, four modules were selected based on the Z_summary score. In the next step, a bipartite miRNA-gene network was constructed and hub miRNAs (let-7a-2-3p, let-7d-5p, let-7b-5p, let-7a-5p, and let-7b-3p) were selected. Finally, a drug-gene network was constructed while SUNITINIB, MEDROXYPROGESTERONE ACETATE, DOFETILIDE, HALOPERIDOL, and CALCITRIOL drugs were recognized as a beneficial drug in NSCLC. The hub miRNAs and repurposed drugs may act a vital role in NSCLC progression and treatment, respectively; however, these results must validate in further clinical and experimental assessments.