CN116327944A

CN116327944A - Application of miR-27a-3p inhibitor in preparation of medicine for treating breast cancer

Info

Publication number: CN116327944A
Application number: CN202310121709.6A
Authority: CN
Inventors: 陈婷梅; 陈泓菱
Original assignee: International Institute Of In Vitro Diagnostics Chongqing Medical University
Current assignee: International Institute Of In Vitro Diagnostics Chongqing Medical University
Priority date: 2023-02-16
Filing date: 2023-02-16
Publication date: 2023-06-27

Abstract

The invention belongs to the technical field of biological medicines, and discloses application of a miR-27a-3p inhibitor in at least one of the following: (1) preparing a product for inhibiting proliferation of breast cancer cells; (2) preparing a product for inhibiting invasion of breast cancer cells; (3) preparing a product for inhibiting migration of breast cancer cells; (4) preparing a product for inhibiting breast cancer growth; (5) preparing a product for inhibiting breast cancer metastasis; (6) preparing a medicament for treating breast cancer. The invention discloses a mechanism how miRNA recognizes a gene target to control transcription, provides scientific basis for developing a new breast cancer treatment target and a treatment medicine, and is expected to provide a new breast cancer treatment medicine.

Description

Application of miR-27a-3p inhibitor in preparation of medicine for treating breast cancer

Technical Field

The invention relates to the technical field of biomedicine, in particular to application of a miR-27a-3p inhibitor in preparation of a medicament for treating breast cancer.

Background

Breast cancer is one of the most common cancers in women, with the prevalence of female malignancies being highest. With recent intensive research into the pathogenesis of breast cancer, hypoxia has become an important component of the development of breast cancer. The hypoxic region was found to exist at an early stage of tumor formation and to expand as the tumor grows. Hypoxia is associated with tumor invasion, metastasis and therapeutic resistance of breast cancer. HIF-1 (hypoxia inducible factor-1) is a key regulator in hypoxic environments, and the main pathway for HIF-1 regulation is transcription and posttranscriptional regulation. During tumor development, both angiogenic and oxygen-independent metabolic pathways are dependent on the HIF-1 family.

MicroRNAs (miRNAs) is involved in almost all essential cellular functions including cell proliferation, differentiation, migration, apoptosis and stem maintenance. Furthermore, the role of deregulated miRNAs in cancer has been demonstrated. mirnas are small endogenous RNAs of 18-24 nucleotides, which can act as regulators of cancer progression. Previous studies have shown that mature mirnas can bind to the 3' -untranslated region (UTR) of mRNA and regulate gene expression in the post-transcriptional stage by inhibiting mRNA translation or promoting mRNA degradation. However, with the improvement of scientific research technology, various miRNA action mechanisms are discovered successively. For example, mirnas can interact with the 5' -UTR region to enhance translation. With the development of current technologies such as microarrays and RNA-seq, a great deal of enrichment of miRNA targets within the gene promoter region has been discovered. Many mature mirnas are concentrated in the nucleus, indicating that mirnas with nuclear localization are more common than previously thought.

Furthermore, the mechanism of action of mirnas in the nucleus is extremely complex. In the transcriptional gene silencing model, overexpression of miRNA reduced occupancy of RNA polymerase ii (RNAPol ii) and increased promoter region histone H3 lysine 9 dimethyl (H3K 9me 2), resulting in silencing of chromatin levels. However, in the transcriptional gene activation model, when the gene promoter region is in an open transcribed state, miRNA and Ago2 proteins form a mature miRNA complex, targeting directly to the TATA box motif or transcription factor binding site, resulting in recruitment of some transcription factors and/or epigenetic modifiers to the promoter region, further facilitating RNAPol ii recruitment and epigenetic modification. Through this recruitment, the miRNA complexes promote target gene transcription and induce mRNA elongation. Furthermore, the Ago2 protein may play an important role in the recruitment of RNAPol ii. Importin 8 (IPO 8, input protein 8) is critical for the transfer of mature mirnas to the nucleus. IPO8 is a member of the nuclear transport protein family, mediating the transport of mature mirnas from the cytoplasm to the nucleus. Specifically, IPO8 recognizes nuclear localization sequences, which subsequently facilitate their passage through the nuclear pore complex. In other words, the introduction of the Ago2-miRNA complex into the nucleus is accomplished by binding to the introduction protein. miRNA expression in the nucleus decreased following IPO8 knockdown. However, the mechanism by which mirnas recognize their gene targets to control transcription remains a controversial issue.

Disclosure of Invention

The research of the invention finds that: hypoxia causes increased expression of miR-27a-3p in breast cancer, hypoxia causes translocation of miR-27a-3p to the nucleus through improtin8, miR-27a-3p in the nucleus binds to the promoter region of HIF1A and recruits RNA polymerase II through the Ago2 protein to activate HIF1A transcription, thereby activating the downstream signaling pathway of HIF1A, enhancing invasion, metastasis and proliferation of breast cancer. Based on the research results of the invention, the invention provides the following technical scheme:

use of a miR-27a-3p inhibitor in at least one of the following (1) - (6):

(1) Preparing a product for inhibiting proliferation of breast cancer cells;

(2) Preparing a product for inhibiting invasion of breast cancer cells;

(3) Preparing a product for inhibiting migration of breast cancer cells;

(4) Preparing a product for inhibiting breast cancer growth;

(5) Preparing a product for inhibiting breast cancer metastasis;

(6) Preparing the medicine for treating breast cancer.

The miR-27a-3p inhibitor comprises a nucleic acid molecule, a protein molecule or a compound.

The nucleic acid molecule is a nucleic acid molecule which is combined with the stem loop structure of miR-27a-3p and forms a mature complex with Ago2 in a competition manner, and the sequence is as follows:

5'-GCGGAACUUAGCCACUGUGAA-3'。

the sequence of the miR-27a-3p is as follows: 5'-UUCACAGUGGCUAAGUUCCGC-3'.

The miR-27a-3p inhibitor inhibits translocation of miR-27a-3p to the nucleus through improtin8, so that miR-27a-3p in the nucleus is inhibited from combining with a promoter region of HIF1A, thereby inhibiting the action of Ago2 protein recruitment RNA polymerase II to activate HIF1A transcription, further inhibiting a downstream signal pathway of HIF1A, and inhibiting invasion, metastasis and proliferation of breast cancer.

The invention also provides application of the reagent for detecting miR-27a-3p expression in preparation of a kit for diagnosing breast cancer prognosis.

In the application technical scheme, the high expression of miR-27a-3p indicates that the prognosis of a breast cancer patient is poor.

The beneficial effects of the invention are as follows: the mechanism of how miRNA recognizes its gene target to control transcription is revealed, and the action mechanism of increasing the expression of miR-27a-3p in breast cancer caused by hypoxia, leading to translocation of miR-27a-3p to the nucleus through improtin8, binding of miR-27a-3p in the nucleus to the promoter region of HIF1A and recruiting RNA polymerase II through Ago2 protein to activate HIF1A transcription is revealed, thereby activating the downstream signal pathway of HIF1A and enhancing invasion, metastasis and proliferation of breast cancer. Experiments prove that the miR-27a-3p inhibitor can inhibit proliferation, invasion and migration of breast cancer cells, and in animal experiments, the miR-27a-3p inhibitor can inhibit tumor size and volume and lung metastasis of breast cancer, so that scientific basis is provided for developing new breast cancer treatment targets and treatment medicines, and a new breast cancer treatment medicine is hopefully provided.

Drawings

FIG. 1 shows the results of research on the expression of miR-27a-3p in breast cancer cells.

FIG. 2 is the experimental results of research on the promotion of the migration, proliferation and metastasis of breast cancer cells by the overexpression of miR-27a-3 p.

FIG. 3 is the experimental results of the study of the effect of miR-27a-3p knockdown on proliferation, migration and invasion of breast cancer cells.

FIG. 4 is a result of a study of the correlation of HIF1A expression and miR-27a-3p expression in a breast cancer sample.

FIG. 5 is a study result of translocation of miR-27a-3p in a case of sublocalization in cells under normal oxygen environment and in a case of hypoxia.

FIG. 6 is a result of a study of the mechanism by which miR-27a-3p triggers HIF1A transcription.

FIG. 7 is the results of a study of the effects of a xenograft tumor model of BALB/C nude mice constructed MDA-MB-231 (231) on breast cancer growth by exploring inhibition of miR-27a-3 p.

Detailed Description

The invention is further illustrated, but is not limited, by the following examples.

The experimental methods in the following examples are conventional methods unless otherwise specified.

Example 1

1 Material method

1.1 cell lines and cultures

Human breast cancer cells MDA-MB-231 cells were purchased from Kunming animal institute, national academy of sciences. The human ductal breast cancer cell line BT-549 was obtained from China Center for Type Culture Collection (CCTCC). All cells were validated at the time of purchase using Short Tandem Repeat (STR) analysis. MDA-MB-231 cells were cultured in DMEM/F12 (1:1) medium (BasalMedia, china) (FBS; gibco, USA) supplemented with 10% fetal bovine serum and 1% penicillin-streptomycin (100 IU/ml). BT-549 cells were cultured in 1640 medium supplemented with 10% FBS, 0.023U/ml insulin, and 1% penicillin-streptomycin (100 IU/ml). Human normal mammary epithelial cells MCF-10A cells were cultured in MCF-10A dedicated medium (Woheprunorace life technologies Co., ltd., china). All cells were incubated at 37℃with 5% CO ₂ Culturing under the condition of 95% relative humidity.

1.2 RNA extraction and RT-PCR

Total RNA was extracted using Trizol reagent (Takara, japan) according to the instructions of the product manufacturer. OD260/280 values were analyzed in a spectrophotometer (NanoDrop Technology, wilmington, DE) to determine the quality and quantity of total RNA. cDNA was generated from 1,000ng total RNA using PrimeScript RT kit (Takara) with gDNAEras. Using

Premix ex taq (tm ii) (Takara, japan), RNA expression was examined in triplicate using quantitative real-time Polymerase Chain Reaction (PCR).

1.3 anoxic treatment

MDA-MB-231 cells and BT-549 cells in the presence of cobalt chloride (CoCl) ₂ The method comprises the steps of carrying out a first treatment on the surface of the SigmaAldrich, darmstadt, germany) in 5% CO ₂ Culturing at 37℃and a relative humidity of 95% to create an anoxic model. All media were changed every three days.

1.4 CCK8

The viability of the cells mentioned was assessed using the Cell Counting Kit-8 (CCK-8) (MCE, china) assay. Briefly, after transfection of a cell group with the appropriate reagents, a Negative Control (NC) was used as a control. After 48 hours of treatment, the cell suspension was treated at 5X 10 ³ The density of individual cells/wells was seeded in 96-well plates. After incubation for 24 hours, 48 hours and 72 hours, respectively, the cells were treated with 10%Cell Counting Kit-8 (CCK-8) for 1.5 hours at 37 ℃. Optical Density (OD) values at 450nm were read using a digital spectrophotometer. Each experiment was performed in triplicate.

1.5 invasion assay

Matrigel (1:8 dilution; BD Bioscience) was diluted with serum-free medium, and each chamber containing 100ul of diluted Matrigel was incubated at 37℃for 1.5 hours to separate the upper and lower chambers. Lentiviral infected and transfected MDA-MB-231 and BT-549 cells (1X 10 per group) ⁵ Individual cells) were planted in triplicate in the upper chamber. The chemotactic agent in the lower compartment is a growth medium containing 10% fbs. After growth at 37℃for 16-24 hours, the invading cells were fixed and stained with crystal violet. Cells that did not invade the cells were cleared using a cotton swab. Finally, a photograph of the fixed cells was taken using a microscope.

1.6 wound healing test

Lentiviral infected and transfected MDA-MB-231 cells and BT-549 cells were seeded in 6-well plates and the cells were incubated overnight to 60% -80% confluency of cell monolayers. A wound was cut at the central region of the confluence region with a 200. Mu.L pipette tip, and the dish was washed 3 times with PBS to remove detached cells. Serum-free medium was added and images were taken using a phase contrast microscope (Olympus, japan) at0 hours, 12 hours, 24 hours, 36 hours, and 48 hours.

1.7 RNA isolation and miRNA detection

RNA was extracted from cells 72 hours after transfection using Trizol reagent (Takara, japan). Complementary DNA was generated from 1. Mu.g total RNA in a 20. Mu.l reaction using PrimeScript RT kit and gDNAEraser (Takara) and RT primers for miR-27-3p or U6. For quantitative analysis of mature miR-27a-3p, stem-loop qRT-PCR experiments were performed using primers based on miRNA sequences. The expression of miR-27a-3p adopts a 2-delta CT method, and U6 is used as an internal reference. The primer sequences are shown in Table 1.

TABLE 1 sequence

The qRT-PCR amplification procedure was: after mixing, 3min at 95 ℃, 10s at 95 ℃, 30s at 72 ℃ after 30s at 58 ℃ and 40 cycles.

1.8 fluorescence in situ hybridization

The localization of miR-27a-3p (hsa-miR-27 a-3p MIMAT0000084:5'-UUCACAGUGGCUAAGUUCCGC-3', SEQ ID NO. 45) in the nucleus and cytoplasm of breast cancer cells was identified using a FISH kit (GenePharma, china). The probe of miR-27a-3p is 5'-GCGGAACTTAGCCACTGTGAA-3' (SEQ ID NO. 46).

Will be 4×10 ⁴ The individual cells were seeded in the center of a petri dish (Cellvis, canada) and incubated overnight in an incubator. Cells were washed with PBS and fixed with 4% paraformaldehyde for 15 min. Briefly, after fixation, 0.1% buffera was added for 10min to permeabilize the cells. Blocking solution was added and incubated at 37℃for 30 minutes. After removing the blocking solution, probe working solution was added and incubated overnight at 37℃in the absence of light. After the probe working solution is washed the next day, DAPI working solution is added for dyeing for 10-20 minutes. DAPI working solution was aspirated and discarded, and cells were then washed twice with PBS for 5 minutes each. Then drop-wise applying the anti-blocking agentThe chemicals were exploded and the samples were examined using a fluorescence microscope (Leica TCS SP8, germany).

1.9 miRNA transfection

Control miRNA inhibitors and miR-27a-3p inhibitors were purchased from GenePharma (Shanghai, china). The miRNA sequences used in this study were as follows: the sequence of the miR-27a-3p inhibitor is as follows: 5'-GCGGAACUUAGCCACUGUGAA-3' (SEQ ID NO. 43); the sequence of the miRNA inhibitor negative control is: 5'-CAGUACUUUUGUGUAGUACAA-3' (SEQ ID NO. 44). When the number of cells per dish reached 60-80%, cells were seeded with Lipofectamine 2000 (Invitrogen, usa) as inhibitor control or miR-27a-3p inhibitor according to the manufacturer's recommendations.

1.10 siRNA transfection

Cells were transfected with siRNA (clear biotechnology, beijing, china) or scrambled according to the manufacturer's protocol. The siRNA sequence is shown in SEQ ID NO.42 in Table 1.

1.11 shRNA mediated Improtin8 knockdown

MDA-MB-231 cells and BT-549 cells were transfected with pSIH vector control or pSIH vector expressing IPO8 inhibitor using Lipofectamine 2000 (Invitrogen, USA) to inhibit IPO8 expression. 48 hours after transfection, cells were selected and cultured for one week in the presence of puromycin (8 μg/ml) to confirm stable integration of cells with control scrambling sequences or IPO8 inhibitors. RNA and protein levels were measured to determine IPO8 expression. The shRNA sequences are shown in SEQ ID NO.40 and 41 in Table 1.

1.12 RNA immunoprecipitation

RNA immunoprecipitation assay (RIP) was performed using a MagnaRIPTM RNA binding protein immunoprecipitation kit (Millipore Sigma, U.S.) according to the instructions of the reagent manufacturer. Lysates were incubated with antibodies conjugated to Dynabeads ProteinA/G (Thermofisher) overnight at 4 ℃. To degrade the proteins, the immobilized immunoprecipitated complexes were treated with proteinase K for 30 min at 55deg.C. The co-precipitated RNA and input were eluted and purified using Trizol reagent prior to qRT-PCR analysis. The proportion of co-precipitated RNA is given in fold enriched form. The primers are listed in Table 1.

1.13 Western blot

RIPA solutions (including protease inhibitors) are used to lyse designated cells; protein concentration was assessed using the bicinchoninic acid (BCA) protein assay kit (Beyotime, china); proteins were separated on 8% -12% SDS-PAGE gels and transferred to PVDF membrane (Bio-Rad, canada). After incubation with primary antibody overnight at 4 ℃. The next day, membranes were washed, probed and analyzed after one hour exposure to secondary anti-mouse or anti-rabbit IgG (bio world) at room temperature. Antibodies are shown in table 2:

TABLE 2

Antibodies to	Source	Goods number
			Glut1	Cell Signaling Technology	Cat#12939；1:1000
Snail	Cell Signaling Technology	Cat#3895；1:1000
			Importin 8	Novus Biologicals	Cat#NBP2-24751；1:1000
Alpha Tubulin	proteintech	Cat#66031-1-Ig；1:2000
			HIF1A	proteintech	Cat#20960-1-AP；1:1000
VEGF	Santa Cruz Biotechnology	Cat#sc-7269；1:500
			RNA POL Ⅱ	Santa Cruz Biotechnology	Cat#sc-56767；1:1000
CyclinD1	Wanleibio	Cat#WL01435a；1:1000
			LDH	Wanleibio	Cat#03217；1:1000

1.14 luciferase reporter detection

24 hours prior to transfection, 2X 10 ⁴ The individual MDA-MB-231 cells were seeded into 96-well plates. Lipofectamine 2000 (Invitrogen, USA) was used to co-transfect Wild Type (WT) or mutant HIF1A promoters and miRNA negative control plasmids or over-express miR-27a plasmids, respectively. Luc-Pair Duo-Luciferase HS Assay Kit (GeneCopoeia, USA) was used to quantify Renilla luciferase activity 48 hours after transfection and to adjust the results according to firefly luciferase activity. miR-27a-3p reporter activity is normalized to empty vector.

1.15 Co-immunoprecipitation

For immunoprecipitation, lysates were spin pre-cleared with protein A/G beads (Thermo Fischer Scientific) at 4℃for 1 hour, then incubated with IPO8 and control IgG antibodies (Santa Cruz Biotechnology, U.S.) coupled to the proteins overnight at 4 ℃. The samples were then washed with lysis buffer and spin-treated with 20. Mu.g/mL RNaseA (Thermo Scientific) for 15 minutes at room temperature. Subsequently, the protein antibodies bound to the beads and the proteins were eluted in 2x SDS sample buffer (BioRad) for 10 minutes at 95 ℃.

1.16 chromatin immunoprecipitation

ChIP experiments were performed according to the protocol of SimpleChlP enzymatic chromatin immunoprecipitation kit (9003,Cell Signaling Technologies, usa). MDA-MB-231 cells and MDA-MB-231 cells overexpressing miR-27a-3p were crosslinked with 37% formaldehyde at a final concentration of 1% at room temperature for 10 minutes, and then glycine solution was added to terminate the crosslinking process. The fragmented chromatin is treated with nucleases and sonicated. Chromatin immunoprecipitation was performed overnight at 4 ℃ using mouse anti-RNAPol ii antibody (1:50,Santa Cruz Biotechnology, usa) and normal mouse IgG (1:250,Cell Signaling Technologies) as negative controls. Protein G was added to the beads at 4 ℃ for an additional two hours. Chromatin was then washed and eluted from the protein G magnetic beads using the kit buffer and DNA was assessed using quantitative PCR. The primers are listed in Table 1.

1.17 xenograft mouse model

Animal experiments strictly meet the requirements of the animal management committee of the university of medical university of Chongqing animal protection standard guidelines. Preparation of MDA-MB-231 breast cancer cells (1X 10) ⁶ ) Subcutaneously injected into 3-4 week old BALB/c nude mice. One week later, antagomiR-27a-3p and antagomiR control were injected, respectively. The dosage of AntagomiR is 15ug each, and the injection is carried out every three days. Five mice were used for each group. The volume was measured every three days with calipers and calculated according to the following formula: tumor volume (mm) ³ ) At the end of the animal experiment, mice were sacrificed =pi lw2/6. Tumor tissue and lung tissue were isolated, weighed, photographed, and used for further Immunohistochemical (IHC) staining to detect expression of the relevant proteins.

2 experimental results

2.1 Upregulation of miR-27a-3p expression in breast cancer cells

Previous studies have shown that miR-27a-3p as a pro-oncogene is involved in the development of tumor cells, such as cell proliferation, migration and invasion. To confirm the findings, we analyzed the GEO database to find that miR-27a-3p was contained in tumor samples much higher than in normal tissues (fig. 1A). Not coincidentally, we also found that miR-27a-3p was abundantly expressed in breast cancer by analysis of the TCGA database (FIG. 1B). Quantitative RT-PCR (qRT-PCR) analysis showed elevated expression of miR-27a-3p in MDA-MB-231, hs578T and BT-549 cells compared to normal mammary epithelial cells MCF-10A (FIG. 1C). Finally, the KM-plotter was used to observe the overall survival of breast cancer patients with different miR-27a-3p expression levels from the METABIIC database. The result shows that the expression quantity of miR-27a-3p is inversely related to the prognosis of the breast cancer patient. Namely, the prognosis of the patient with the breast cancer tissue high-expression miR-27a-3p is poor, and the prognosis of the patient with the breast cancer tissue low-expression miR-27a-3p is good (figure 1D).

2.2miR-27a-3p overexpression promotes migration, proliferation and metastasis of breast cancer cells

MDA-MB-231 and BT-549 cell lines were infected with lentiviruses to increase expression of miR-27a-3p in the cell lines (FIG. 2A). CCK8 experiments were used to test the cell proliferation potential of each group, with the average cell proliferation rate of the miR-27a-3p over-expressed group being significantly higher than that of the control group. This suggests that overexpression of miR-27a-3p can increase proliferation of breast cancer cells (figure 2B). In wound healing assays, overexpression of miR-27a-3p increased the ability of cells to migrate and repair (FIG. 2C). In addition, transwell invasion assays were used to assess the effect of miR-27a-3p on breast cancer cell invasion. According to the results of the Transwell invasion assay, when miR-27a-3p expression was elevated, the invasion capacity of MDA-MB-231 cells and BT-549 cells was significantly enhanced (FIG. 2D). Westernblot results indicate elevated protein levels of cyclin D1, snail and Bcl2 following overexpression of miR-27a-3p (FIG. 2E). In conclusion, the increase of miR-27a-3p in breast cancer cells can promote proliferation, migration and invasion of the breast cancer cells.

2.3 reduction of miR-27a-3p expression reduces migration, proliferation and metastasis of breast cancer

Expression of miR-27a-3p was reduced by transfection of MDA-MB-231 and BT-549 cell lines with miR-27a-3p inhibitors (FIG. 3A). CCK8 testing showed that the average cell proliferation rate of miR-27a-3p knockdown cells was much lower than that of the control. This suggests that inhibition of miR-27a-3p may limit breast cancer cell proliferation (fig. 3C). In wound healing studies, inhibition of miR-27a-3p impaired the ability of cells to migrate and repair (figure 3B). In addition, transwell experiments showed that MDA-MB-231 cells and BT-549 cells were less invasive when miR-27a-3p expression was decreased (FIG. 3D). When miR-27a-3p was inhibited, protein levels of cyclin D1, snail and Bcl2 were reduced as indicated by Western blotting (FIG. 3E). In conclusion, decreasing expression of miR-27a-3p in breast cancer cells can decrease proliferation, migration and invasion of breast cancer cells.

2.4HIF1A promotes expression of miR-27a-3p

Since hypoxia is a hallmark event of the occurrence and progression of breast cancer, it promotes the progression of breast cancer through a variety of molecular mechanisms. Through the TCGA database, we found that HIF1A expression was positively correlated with miR-27a-3p expression in breast cancer samples (fig. 4). Meanwhile, the interaction between HIF1A and miR-27a-3p is found by cancer gene network analysis. mRNA levels of miR-27a-3p were found to be elevated in HIF1A overexpressing cell lines using qRT-PCR detection. Whereas knocking down HIF1A with siRNA resulted in a gradual decrease in the expression level of miR-27a-3 p. A similar change in miR-27a-3p expression level was observed in MDA-MB-231 cells. Therefore, HIF1A increases expression of miR-27a-3 p.

2.5 hypoxia leads to increased translocation of miR-27a-3p to the nucleus

Since more and more evidence in recent years indicates that mirnas have nuclear localization, the first step in this study requires a clear determination of the subdocalization of miR-27a-3p within the cell. Through a series of biological processes, pre-miRNAs produce mature miRNAs. Thus, mature miRNAs are mainly present in the cytoplasm and affect post-transcriptional levels of genes through the RISC complex formed. Findings of nuclear isolation and stem-loop qRT-PCR specifically designed to identify mature mirnas indicate that most of the mature miR-27a-3p is present in the cytoplasm under normal oxygen environment (fig. 5A-B). After hypoxia treatment of MDA-MB-231 cells and BT-549 cells, nuclear RNA isolation and qRT-PCR detection showed that miR-27a-3p was expressed in the nucleus much higher than in the cytoplasm (FIG. 5A-B). In addition, fluorescence in situ hybridization results showed that the subcellular localization of miR-27a-3p was altered after hypoxia treatment (FIGS. 5C-D). These results indicate that hypoxia promotes miR-27a-3p entry into the nucleus. As a nuclear transport protein, it has previously been found that impatin 8 can transport mature mirnas into the nucleus. To confirm the hypothesis that miR-27-3p is transported to the nucleus by this conventional pathway, RNA immunoprecision experiments indicated that IPO8 and miR-27a-3p were significantly bound during hypoxia (FIG. 5E). Furthermore, miR-27a-3p is produced primarily in the cytoplasm after shRNA knockdown of IPO8 protein, even after hypoxia treatment of the cells. Taken together, miR-27a-3p is primarily found in the nucleus under hypoxic conditions.

2.6 miR-27a-3p enhances HIF1A transcription in the nucleus

What is miR-27a-3p plays a role in the development and pathogenesis of breast cancer in the nucleus? Analysis based on the Gene Ontology Cell Composition (GOCC) showed that miR-27a-3p was closely related to RNAPol II transcriptional regulatory complexes and transcriptional regulatory complexes (FIG. 6A). This result suggests that miR-27a-3p may be involved in transcriptional regulation after nuclear import. qRT-PCR results showed that overexpression of miR-27a-3p in MDA-MB-231 cells and BT-549 cells increased mRNA levels of HIF1A and genes downstream of HIF1A (FIG. 6B). After knocking down miR-27a-3p, HIF1A and HIF 1A-dependent genes decreased mRNA levels (FIG. 6C). Notably, the level of miR-27a-3p expression in the nucleus was much higher than that in the cytoplasm after lentivirus over-expressed miR-27a-3p (FIG. 6D). The western blot results show that protein levels are increased by over-expressing miR-27a-3p, HIF1A and HIF1A downstream genes. However, protein levels of HIF1A and genes downstream of HIF1A decreased following miR-27a-3p knockdown (FIG. 6E). The nuclear import transporter IPO8 was then knocked down based on stabilization of the miR-27a-3 p-overexpressing cell line. The results indicate that protein levels of HIF1A and genes downstream thereof were inhibited after knocking down IPO8 (fig. 6F). To confirm that miR-27a-3p increases HIF1A transcription, chIP experiments were performed using RNAPolII antibodies to determine if miR-27a-3p enhances formation of a HIF1A promoter region transcriptional complex. As can be seen from the results, miR-27a-3p significantly increased RNAPolII occupancy at the HIF1A promoter (FIG. 6G). RNAhyrid predicts three sites in the HIF1A promoter region that bind to miR-27a-3p (FIG. 6H). The results show that the promoter activity of HIF1A is enhanced after transfection of 293T cells with plasmids overexpressing miR-27a-3 p. After mutation of these three sites, miR-27a-3 p-induced promoter activity was significantly reduced (FIG. 6I). Co-immunoprecipitation experiments showed that Ago2 was able to recruit more RNAPolII when miR-27a-3p was overexpressed in MDA-MB-231 cells (FIG. 6J). The results for BT-549 cells were similar. In contrast, RNAPolII attracts more Ago2 in cells that overexpress miR-27-3p (FIG. 6K). This study shows that miR-27a-3p in the nucleus may recruit RNAPolII via Ago2, triggering transcription of HIF 1A.

2.7 inhibition of miR-27a-3p reduces proliferation and metastasis of breast cancer cells in vivo

Next we constructed xenograft tumor models of MDA-MB-231 (231) with BALB/C nude mice to explore the effects of inhibiting miR-27a-3p on breast cancer growth. First BALB/C nude mice were subcutaneously injected with MDA-MB-231 breast cancer cells (2X 10) ⁶ cells/animal), intratumoral injection of antagomiR-27a-3p or control antagomiR after one week, once every three days, and mice were sacrificed after three weeks. The tumor size and volume were significantly inhibited after inhibition of miR-27A-3p (FIG. 7A). FISH experiments show that the expression level of miR-27a-3p is reduced by antagomiR-27a-3 p. Based on this, the result of immunohistochemistry shows that the inhibition of miR-27a-3p leads to the reduction of the expression level of HIF1A, and the expression levels of Ki-67 and Snail also decrease along with the reduction of miR-27a-3 p. HE staining and histochemical results of lung tissue demonstrated that decreasing the expression level of miR-27a-3p inhibited lung metastasis in breast cancer cells (FIG. 7B).

3 analysis

Overall, this study demonstrates that hypoxia treatment regulates the occurrence and progression of breast cancer by altering intracellular subdominance of miR-27-3 p. In the nucleus, mature miR-27a-3p promotes the transcriptional level of HIF1A, leading to activation of the HIF1A pathway, which in turn increases proliferation, migration and invasion of breast cancer cells.

Claims

Use of a mir-27a-3p inhibitor in at least one of the following (1) - (6):

(1) Preparing a product for inhibiting proliferation of breast cancer cells;

(2) Preparing a product for inhibiting invasion of breast cancer cells;

(3) Preparing a product for inhibiting migration of breast cancer cells;

(4) Preparing a product for inhibiting breast cancer growth;

(5) Preparing a product for inhibiting breast cancer metastasis;

(6) Preparing the medicine for treating breast cancer.
2. The use according to claim 1, characterized in that: the miR-27a-3p inhibitor comprises a nucleic acid molecule, a protein molecule or a compound.
3. The use according to claim 2, characterized in that: the nucleic acid molecule is a nucleic acid molecule which is combined with the stem loop structure of miR-27a-3p and forms a mature complex with Ago2 in a competition manner, and the sequence is as follows:

5'-GCGGAACUUAGCCACUGUGAA-3'。
4. the use according to claim 1, characterized in that: the sequence of the miR-27a-3p is as follows: 5'-UUCACAGUGGCUAAGUUCCGC-3'.
5. The use according to claim 1, characterized in that: the miR-27a-3p inhibitor inhibits translocation of miR-27a-3p to the nucleus through improtin8, so that miR-27a-3p in the nucleus is inhibited from combining with a promoter region of HIF1A, thereby inhibiting the action of Ago2 protein recruitment RNA polymerase II to activate HIF1A transcription, further inhibiting a downstream signal pathway of HIF1A, and inhibiting invasion, metastasis and proliferation of breast cancer.
6. Use of a reagent for detecting miR-27a-3p expression in preparation of a kit for diagnosing breast cancer prognosis.
7. Use according to claim 6, characterized in that: high expression of miR-27a-3p is indicative of poor prognosis in breast cancer patients.