CN112442500A

CN112442500A - siRNA for inhibiting MCM7, composition and application thereof

Info

Publication number: CN112442500A
Application number: CN201910818294.1A
Authority: CN
Inventors: 梁纯; 王俊; 张文熙
Original assignee: Enkang Pharmaceutical Technology Guangzhou Co ltd; Foshan Yingte Pharmaceutical Technology Co ltd; Guangzhou Intelgen Technology Co ltd; Enzhi Guangzhou Pharmaceutical Technology Co ltd
Current assignee: Enkang Pharmaceutical Technology Guangzhou Co ltd; Foshan Intelgen Pharmaceuticals Co ltd
Priority date: 2019-08-30
Filing date: 2019-08-30
Publication date: 2021-03-05
Also published as: WO2021037264A1

Abstract

The siRNA designed and verified by the invention can efficiently inhibit MCM7 gene expression, thereby inhibiting DNA synthesis, cell proliferation and cell clone generation of cancer cells and achieving the purposes of preventing and treating tumors. The invention provides a new target and a candidate drug for preventing or treating cancer.

Description

siRNA for inhibiting MCM7, composition and application thereof

Technical Field

The invention belongs to the field of biomedicine, and particularly relates to siRNA for inhibiting MCM7, a composition and application thereof.

Background

The MCM complex consists of MCM 2-7 subunits, has helicase activity in cells, opens a DNA double strand before DNA replication, and participates in DNA replication initiation (Bik type, Annual Review of Biochemistry, 1999). Moreover, the MCM complex plays an important role in regulating and controlling cell proliferation, DNA damage repair and cell cycle.

Small interfering RNA (siRNA) is a double-stranded RNA with a length of 20-25 nucleotides, and is first found in post-transcriptional gene silencing in plants, and it has been reported that synthetic siRNA can silence specific gene expression in mammalian cells (Thomas Tuschl et al, Nature, 2001; Thomas Tuschl et al, Science, 2001; Thomas Tuschl et al, Cell, 2002). Since siRNA can target interference at the gene level, there is no need to rely on the crystal structure of the target protein. Thus, scientists have studied a series of methods for inhibiting the expression of target genes by RNA interference (RNAi) using siRNA, thereby performing gene function studies and disease treatment.

Since different sites on the target gene have different secondary structures and different thermodynamic properties due to their different sequences, the probability and degree of interference of different sites by siRNA varies greatly. In addition, the activity of the same siRNA may vary in different cell types. Thus, the design, testing and acquisition of highly active siRNA is a process of the inventive invention for any target gene in any one cell.

At present, reports on siRNA of MCM7 gene for inhibiting cancer cells such as liver cancer, stomach cancer, prostate cancer and the like are not found.

Disclosure of Invention

The primary object of the present invention is to provide an siRNA that inhibits MCM 7.

Another object of the present invention is to provide the use of the above siRNA.

Still another object of the present invention is to provide a method for preventing or treating tumor/cancer by specifically targeting MCM7 gene by siRNA.

The inventor designs and tests a plurality of RNA interference fragments aiming at MCM7 gene, but most siRNAs have low interference efficiency and cannot effectively perform the research of late tumor treatment. The inventor inventively invents a plurality of efficient siRNA sequences for interfering MCM7 gene through research and study. This is important for the application of RNA interference, i.e., different effects of siRNA at different sites of the target gene are very different, and may be related to factors such as the secondary (meta) structure and thermodynamic properties of siRNA, base distribution, etc.

The inventors further explored the discovery that by altering one or more bases of the sense strand of siRNA, such that the sense and antisense strands form an incomplete complementary pair, thereby altering the thermodynamic properties of the entire double-stranded RNA, the efficiency of the antisense strand entering the RNA interference complex protein is increased, thereby increasing the efficiency of siRNA inhibition of the target MCM7 gene.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the inventors designed siRNA with MCM7 protein as target. The siRNA inhibits the synthesis of MCM7 protein by inhibiting the expression of human MCM7 gene, thereby preventing the formation of the whole MCM complex (MCM2-MCM7), and inhibiting DNA replication and cell proliferation to achieve the purpose of preventing or treating tumors/cancers.

The expression inhibition of any subunit of the MCM complex by siRNA can inhibit the formation of the whole complex, and further inhibit the cell proliferation to generate an anti-tumor effect.

In one aspect of the present invention, siRNA is provided, which can inhibit MCM7 gene expression, and consists of a sense strand and an antisense strand, wherein the siRNA is selected from the group consisting of:

siRNA-1: sense strand: 5'-GGACUUAAUUUGUGAGAAU-3', respectively;

antisense strand: 5'-AUUCUCACAAAUUGAGUCC-3', respectively;

or

siRNA-2: sense strand: 5'-GGAAGUGGUAAAUAAAGAU-3', respectively;

antisense strand: 5'-AUCUUUAUUUACCACUUCC-3', respectively;

or has more than 80% homology, or better more than 90% homology, with the sense strand or antisense strand sequence of the siRNA-1 or siRNA-2, or the base of the siRNA-1 or siRNA-2 can be modified into a derivative of nucleic acid and has the same function.

Furthermore, two deoxyribonucleotides dT or dN in a single-stranded suspension structure are required to be added at the 3' ends of the sense strand and the antisense strand of the siRNA.

Further, the siRNA prevents or treats tumor/cancer by inhibiting MCM7 gene expression.

Further, the tumor/cancer is selected from liver cancer, stomach cancer, prostate cancer, breast cancer, lung cancer, pancreatic cancer, cervical cancer, endometrial cancer, colorectal cancer, lung cancer, nasopharyngeal carcinoma, ovarian cancer, skin cancer, esophageal cancer or brain tumor.

Further, the tumor may slow or stop growing, shrink or disappear due to the suppression of MCM7 gene expression.

Further, the MCM7 gene is selected from a human MCM7 gene.

Further, the sequence of the siRNA can be locally modified at partial sites as long as the binding and inhibition of the siRNA to a target are not affected.

Further, the base of the siRNA sequence and its local modified sequence can be modified into a derivative of nucleic acid as long as the binding and inhibition to the target are not affected.

In still another aspect of the present invention, the application of siRNA in preparing medicine or composition for preventing or treating tumor/cancer is provided.

Further, the tumor/cancer may slow or stop growing, shrink or disappear due to the suppression of MCM7 gene expression.

Further, the concentration of siRNA is 5-150 nM, preferably 10-100 nM, more preferably 15-60 nM, and most preferably 20-40 nM.

The following additional technical features may also be provided:

the siRNA can inhibit MCM7 gene expression and consists of a sense strand and an antisense strand,

wherein the siRNA is selected from the group consisting of:

siRNA-1: sense strand: 5'-GGACUUAAUUUGUGAGAAU-3', respectively;

antisense strand: 5'-AUUCUCACAAAUUGAGUCC-3', respectively;

or

siRNA-2: sense strand: 5'-GGAAGUGGUAAAUAAAGAU-3', respectively;

antisense strand: 5'-AUCUUUAUUUACCACUUCC-3', respectively;

Further, the MCM7 gene is selected from the group consisting of the human MCM7 gene.

Further, the siRNA may be modified locally at a portion of the site, as long as its binding to and inhibition of the target is not affected.

Further, the base of the siRNA sequence and its locally modified sequence may be modified to be a derivative of nucleic acid, as long as it does not affect its binding to and inhibition of the target.

In yet another aspect of the present invention, a medicament or composition for preventing or treating tumor/cancer is provided, the medicament or composition comprising:

the siRNA of any one of the above;

or an expression system capable of expressing any of the above siRNAs.

The concentration of the siRNA is 5-150 nM, preferably 10-100 nM, more preferably 15-60 nM, and most preferably 20-40 nM.

Further, the above mentioned drug or composition further comprises:

a pharmaceutically acceptable carrier;

other active ingredients for preventing or treating tumors.

Further, pharmaceutically acceptable carriers and/or adjuvants include, but are not limited to, buffers, emulsifiers, suspending agents, stabilizers, preservatives, physiological salts, excipients, fillers, coagulants and conditioners, surfactants, dispersing agents, antifoaming agents.

Further, the other active ingredients for preventing or treating tumors comprise: chemotherapeutic agents, radiotherapeutic agents or antibody drugs.

Further, the form of the medicament or composition is suitable for: direct naked RNA injection, liposome-encapsulated RNA direct injection, protein-or polypeptide-encapsulated RNA direct injection, gold-encapsulated RNA gene gun bombardment, bacteria-carried plasmid expression RNA, or virus expression RNA.

Further, the siRNA drug or composition may be selected from any form of solid, liquid, gel, semifluid, aerosol.

The siRNA can effectively inhibit MCM7 gene expression and protein synthesis, and can treat tumors/cancers.

The invention has the beneficial effects that:

the invention changes the 6 th base of the 5' end cis number of the sense strand of the siRNA-1 sequence to ensure that the sense strand and the antisense strand form incomplete complementary pairing, thereby changing the thermodynamic property of the whole double-stranded RNA, improving the efficiency of the antisense strand entering RNA interference complex protein and further improving the efficiency of the siRNA-1 inhibiting target MCM7 gene.

Compared with the conventional gene knockout technology, the siRNA targeting the MCM7 gene provided by the invention is simple and convenient to operate and short in test period; on the levels of mRNA and protein, the inhibition effect of the siRNA on MCM7 is as high as more than 90%, the inhibition efficiency is extremely high, and the specificity is good; meanwhile, the DNA replication, proliferation and clone forming capability of cancer cells can be effectively inhibited, and the method has important significance for developing new anti-cancer gene drugs and improving the treatment effect of cancers and has obvious clinical application prospect and economic value.

Drawings

FIG. 1 shows the silencing effect of MCM7 specific siRNA-1 on MCM7mRNA level in HepG2 and Hep3B hepatoma cells.

FIGS. 2A-C show the silencing effect of MCM7 specific siRNA-1 in HepG2 and Hep3B liver cancer cells and the silencing effect of siRNA-2 in MCM7 protein level in HepG2 liver cancer cells, wherein beta-actin is an internal reference protein.

FIG. 3 is a fluorescence microscope photograph of EdU positive cells with siRNA-1 inhibiting DNA replication of HepG2 hepatoma cells, wherein FIGS. 3A, C and E are overlapping photographs of fluorescence microscope photograph of EdU positive cells, cell nucleus DNA photograph of Hochst staining, cell fluorescence microscope photograph of EdU positive cells and cell nucleus DNA photograph of Hochst staining after NC transfection of HepG2 hepatoma cells into negative control cells, respectively; wherein FIGS. 3B, D and F are overlapping images of the EdU-positive cytofluorescence microscopy image, the Hochst-staining nuclear DNA image, the EdU-positive cytofluorescence microscopy image and the Hochst-staining nuclear DNA image, respectively, after siRNA-1 transfection of HepG2 hepatoma cells.

FIG. 4 is a statistical plot of the proportion of HepG2 cells that were positive for EdU incorporation.

FIGS. 5A-E are growth curves of siRNA-1 inhibiting proliferation of HepG2 liver cancer cell, Hep3B liver cancer cell, SGC-7907 stomach cancer cell, PC3 prostate cancer cell and MCF7 breast cancer cell, respectively.

FIG. 6 is a graph showing the results of siRNA inhibition on the cloning of various cancer cells, and FIGS. A to E are graphs comparing the numbers of the cloning of cancer cells after transfection of HepG2 liver cancer cell, Hep3B liver cancer cell, SGC-7907 stomach cancer cell, PC3 prostate cancer cell and MCF7 breast cancer cell with siRNA-1 or negative control NC, respectively.

FIG. 7 shows the ability of siRNA to inhibit the cloning of various cancer cells, and FIGS. A-E show the ratio of the total cloning area of cancer cells to the total area of wells after transfection of HepG2 liver cancer cell, Hep3B liver cancer cell, SGC-7907 stomach cancer cell, PC3 prostate cancer cell and MCF7 breast cancer cell with siRNA-1 or negative control NC, respectively.

Detailed Description

The technical solution of the present invention is clearly and completely illustrated below with reference to the following examples, but is not limited thereto.

Example 1 siRNA design

According to the basic principle of siRNA target sequence, siRNA sequences (1 nucleotide 21) expressed by human MCM7 gene transcript (NM-001278595.1), namely sense strand and antisense strand of siRNA, are designed and synthesized, and the base sequences are as follows:

siRNA-1 sense strand: 5 '-GGACUUAUUGAGAAUdTdT-3'; (SEQ ID NO.1)

siRNA-1 antisense strand: 5 '-AUUCACAAUUGAGUCCTdT-3' (SEQ ID NO. 2).

Or

siRNA-2 sense strand: 5'-GGAAGUGGUAAAUAAAGAUdTdT-3' (SEQ ID NO. 3);

siRNA-2 antisense strand: 5 '-AUCUUUAUUACCACUUCCDTdT-3' (SEQ ID NO. 4).

The base sequence of the negative control RNA (NC) is:

sense strand: 5'-CUCUUAGCCAAUAUUCGCUdTdT-3' (SEQ ID NO. 5);

antisense strand: 5 '-AGCGAAUAUUGGCCUAAGAGdTdT-3' (SEQ ID NO. 6).

The siRNA sequence and the 3' end of the sense strand and the antisense strand of the control RNA are added with two deoxyribonucleotides (dT or dN) in a single-stranded suspension structure so as to enhance the stability of the siRNA in vivo and in vitro and prevent the siRNA from being degraded by nuclease.

The siRNA sequence of the invention can be locally modified at partial sites as long as the binding and inhibition of the siRNA sequence on a target are not influenced.

The base of the siRNA sequence and the local modified sequence thereof can be modified into a derivative of nucleic acid as long as the binding and inhibition of the siRNA sequence to a target are not influenced.

Example 2 transfection of siRNA into cells

Liposome Lipofectamine RNAiMax was used as a transfection reagent, following the protocol of Thermo Fisher Scientific. The cell lines used were HepG2 and Hep3B liver cancer cell line, SGC-7907 stomach cancer cell line, PC3 prostate cancer cell line and MCF7 breast cancer cell line.

The experimental procedures of the present invention, which do not specify specific conditions, are generally carried out according to conventional conditions such as Sambrook et al molecular cloning: the conditions described in the Laboratory Manual (New York: Cold Spring Harbor Laboratory Press, 1989), or according to the manufacturer's recommendations.

The transfection procedure was as follows: the different cell lines are respectively inoculated into a 12-hole plate, and cultured overnight at 37 ℃ and 5% CO2, so that the cell growth density reaches 40-50%. The siRNA and negative control RNA (NC) prepared according to the invention were transfected into different cell lines, respectively, according to the Lipofectamine RNAiMax (Thermo Fisher Scientific) protocol. After transfection, cells were collected and further examined for interfering effect of siRNA by qRT-PCR and Western blotting.

Example 3 siRNA inhibition of MCM7mRNA expression assay

The method comprises the following steps: and (3) collecting cells after transfection, extracting total RNA, performing real-time fluorescent quantitative PCR after reverse transcription, and detecting the expression quantity of MCM7mRNA after cancer cells are treated by siRNA.

The siRNA and the negative control RNA (NC) prepared by the invention are respectively transfected into a liver cancer cell line HepG2, are also transfected into a liver cancer cell line Hep3B by the same method, are transfected for 24 hours, are collected, are taken to be re-inoculated into a 6-well plate, and are collected after 72 hours to extract total RNA. Reverse transcription and real-time fluorescent quantitative PCR are carried out to detect MCM7 mRNA.

1. Total RNA extraction

(1) Respectively collecting tumor cells to a centrifuge tube, centrifuging at 800rpm for 3min, discarding supernatant, adding PBS (phosphate buffer solution) for washing once and transferring to an EP (EP) tube;

(2) centrifuging at 800rpm again for 3min, removing the supernatant, adding 0.5ml of TRIzol, repeatedly blowing to dissolve tumor cells, and standing at room temperature for 5-10 min;

(3) adding 0.2ml chloroform/ml TRIzol, vigorously shaking and mixing for 15sec, and standing at room temperature for 10 min;

(4) centrifuging at 12000rpm and 4 ℃ for 15 min;

(5) after centrifugation, the liquid is divided into three layers, namely a phenol/chloroform layer, an intermediate protein layer and an upper colorless water phase in sequence from bottom to top, and RNA is stored in the upper water phase;

(6) sucking the upper aqueous phase into a new EP tube, taking care to avoid sucking out the intermediate protein;

(7) adding 0.5ml/ml of precooled isopropanol into the solution of TRIzol, reversing and uniformly mixing the solution, and standing the mixture for 10min at room temperature;

(8) centrifuging at 12000rpm and 4 ℃ for 10 min;

(9) discarding the supernatant, washing the RNA precipitate with 75% ethanol (750. mu.l absolute ethanol, 250. mu.l DEPC water), centrifuging at 12,000rpm for 5min at 4 ℃;

(10) discarding the supernatant, and drying in an air blast manner in an ultra-clean bench for about 3 minutes to obtain semitransparent RNA;

(11) adding 15-20 mul of 1 per mill DEPC water to dissolve the RNA precipitate, measuring the concentration and OD value by an ultraviolet spectrophotometer, and storing at-70 ℃ or directly using for reverse transcription reaction.

2. Reverse transcription into cDNA

Pre-deforming at high temperature for 5min, quickly freezing on ice, and performing reverse transcription reaction:

reaction conditions are as follows: 15min at 37 ℃, 5min at 50 ℃, 5min at 95 ℃ and keeping at 4 ℃. The synthesized cDNA was immediately used for downstream experiments or stored in a freezer at-20 ℃.

3. Fluorescent quantitative real-time PCR

After diluting the reverse transcribed cDNA samples in the appropriate ratio, the following PCR reaction system was configured using THUNDERRID SYBR qPCR Mix:

wherein:

the sequence of the upstream primer is 5'-GTGAAGGATCCTGCGACACA-3' (SEQ ID NO. 7);

the sequence of the downstream primer is 5'-ACACGCGTTCTTTTGTTCCG-3' (SEQ ID NO. 8);

the sequence of the internal reference upstream primer is 5'-ACACGCGTTCTTTTGTTCCG-3' (SEQ ID NO. 9);

the sequence of the internal reference downstream primer is 5'-GGACTCCATGCCCAGGAAGGAA-3' (SEQ ID NO. 10).

As a result: FIGS. 1A and B show that, compared with the control group NC, after the cancer cells are transfected by siRNA-1, the expression level of MCM7mRNA in HepG2 and Hep3B liver cancer cells is effectively inhibited respectively, and the silencing effect reaches more than 90%.

Example 4 siRNA inhibition of MCM7 protein expression assay

The method comprises the following steps: the siRNA and the negative control RNA (NC) prepared by the invention are respectively transfected into a liver cancer cell line HepG2, are also transfected into a liver cancer cell line Hep3B by the same method, are transfected for 24 hours, are collected, are taken to be re-inoculated into a 12-well plate, and are collected for a western blot experiment after 72 hours.

1. Absorbing the culture medium, adding a proper amount of 2 × laemmli buffer solution, slightly shaking a 12-pore plate to crack cells, collecting the cells in a PE tube, rubbing the PE tube with the holes of a PE tube frame to shatter DNA, and boiling for 2min at 95 ℃;

2. performing polyacrylamide gel electrophoresis and Western blotting on the boiled and denatured sample, and then sealing the PVDF membrane at room temperature for 0.5 hour by using 5% skimmed milk;

3. the appropriate primary antibody (mouse anti-human MCM7 monoclonal antibody, Santa Cruz Biotechnology) was selected and incubated with PVDF membrane at 4 ℃ overnight at the appropriate dilution ratio;

4. the next day, TBST washing 3 times, 10min each time;

5. selecting an anti-mouse IgG secondary antibody marked by HRP corresponding to the primary anti-host species, and incubating the secondary antibody and the PVDF membrane for 1 hour at room temperature according to a proper dilution ratio;

6. TBST washing for 3 times, each time for 10 min;

7. and (4) developing by ECL solution, and detecting the expression condition of the MCM7 protein in the tumor cells.

As a result: FIGS. 2A, B and C show that, relative to control NC, transfection of cancer cells with siRNA-1 effectively inhibited expression of MCM7 protein in HepG2 and Hep3B cells; after the siRNA-2 is used for transfecting cancer cells, the expression of MCM7 protein in HepG2 cells can be effectively inhibited; the silencing effect of both siRNA-1 and siRNA-2 can reach over 90 percent.

Example 5 siRNA inhibits cancer cell DNA replication

The method comprises the following steps: the siRNA and the negative control RNA (NC) prepared by the invention are respectively transfected into a liver cancer cell line HepG2 and also transfected into a liver cancer cell line Hep3B by the same method, after 24 hours of transfection, the cells are collected, and a proper amount of cells are taken and re-inoculated into a 96-well plate. After 12 hours, the mimosine reagent was added to the cells and incubated for 24 hours to synchronize the cells at the junction of G1 phase and S phase.

Cells were washed three times with fresh medium, three minutes apart each time, releasing the cells from the inhibition of mimosine. The cells were cultured with fresh medium for 3.5 hours, and then 50mmol/L EdU (5-ethyl-2' -deoxyuridine, a thymidine analog) was added and the culture was continued for 0.5 hours. Cells were fixed and stained, observed under a fluorescent microscope and counted for the proportion of EdU incorporated into cells that were positive.

As a result: FIGS. 3 and 4 show that after siRNA-1 transfects cancer cells, the proportion of EdU incorporated into cells that were positive compared to negative control NC is significantly reduced, indicating that siRNA-1 significantly inhibited DNA replication in cancer cells.

The fresh medium was Gibco RPMI 1640.

Example 6 siRNA inhibition of cancer cell proliferation

The method comprises the following steps: the siRNA prepared by the invention and negative control RNA (NC) are respectively transfected into different cancer cell lines, and the cells are collected after 24 hours of transfection. Dividing a proper amount of cells into five equal parts, re-inoculating the cells into a 12-well plate, continuously counting for five days, and selecting cells in one well every day for counting. Cell growth curves were plotted after transfection.

As a result: as shown in the results of figure 5, the siRNA-1 can effectively inhibit the proliferation of HepG2 liver cancer cells, Hep3B liver cancer cells, SGC-7907 stomach cancer cells, PC3 prostate cancer cells and MCF7 breast cancer cells.

Similarly, siRNA-2 is also effective in inhibiting the proliferation of the cancer cells.

Example 7 inhibition of cancer cell clonogenicity by siRNA

The method comprises the following steps: the siRNA prepared by the invention and negative control RNA (NC) are respectively transfected into different cancer cell lines, and the cells are collected after 24 hours of transfection. Will be provided withCells were seeded in 6-well plates at a cell density of 0.4X 10³Per well. After 14 days of culture, fixation with methanol and staining with crystal violet was performed.

As a result: as shown in fig. 6 and 7, it can be seen in fig. 6A to E that the number of cancer cell clones was significantly reduced after siRNA-1 transfection of cancer cells compared to negative control NC; as shown in FIGS. 7A-E, the ratio of the total cloning area to the total pore area was decreased after transfection of cancer cells with siRNA-1, as compared with negative control NC, which indicates that siRNA can effectively inhibit the cloning ability of HepG2 liver cancer cells, Hep3B liver cancer cells, SGC-7907 stomach cancer cells, PC3 prostate cancer cells and MCF7 breast cancer cells.

Example 8 MCM7siRNA application

The MCM7siRNA is applied to the preparation of medicines for preventing or treating tumors/cancers, wherein the cancers are selected from liver cancer, stomach cancer, prostatic cancer, breast cancer, lung cancer, pancreatic cancer, cervical cancer, endometrial cancer, colorectal cancer, lung cancer, nasopharyngeal cancer, ovarian cancer, skin cancer, esophageal cancer or brain tumor.

In conclusion, the siRNA effectively inhibits the MCM7 gene expression, thereby reducing the synthesis of MCM7 protein, and the siRNA has the inhibition effect of more than 90 percent, extremely high inhibition efficiency and good specificity; meanwhile, the DNA replication, proliferation and clone forming capability of cancer cells can be effectively inhibited, and the method has important significance for developing new anti-cancer gene drugs and improving the treatment effect of cancers and has obvious clinical application prospect and economic value.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

SEQUENCE LISTING

<110> Enzhi (Guangzhou) medical science and technology Limited Enkang pharmaceutical technology (Guangzhou) Limited

Guangzhou Intel Gene technology, Inc., Yingte medical science, Inc., Foshan mountain

<120> siRNA inhibiting MCM7, composition and use thereof

<130>

<160> 10

<170> PatentIn version 3.5

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Claims

1. An siRNA that inhibits MCM7 gene expression, comprising a sense strand and an antisense strand, wherein said siRNA is selected from the group consisting of:

siRNA-1: sense strand: 5'-GGACUUAAUUUGUGAGAAU-3', respectively;

antisense strand: 5'-AUUCUCACAAAUUGAGUCC-3', respectively;

or

siRNA-2: sense strand: 5'-GGAAGUGGUAAAUAAAGAU-3', respectively;

antisense strand: 5'-AUCUUUAUUUACCACUUCC-3', respectively;

or has homology of more than 80% with the sequence of the sense strand or the antisense strand of the siRNA-1 or the siRNA-2, or the base of the siRNA can be modified into a derivative of nucleic acid and has the same function.

2. The siRNA of claim 1, wherein two deoxyribonucleotides dT or dN in a single-stranded overhang structure are added to the 3' ends of the sense strand and the antisense strand of the siRNA.

3. Use of siRNA according to claim 1 or 2 for the preparation of a medicament or composition for the prevention or treatment of a tumor/cancer.

4. Use according to claim 3, wherein the tumor/cancer is selected from liver cancer, stomach cancer, prostate cancer, breast cancer, lung cancer, pancreatic cancer, cervical cancer, endometrial cancer, colorectal cancer, lung cancer, nasopharyngeal cancer, ovarian cancer, skin cancer, esophageal cancer or brain tumor.

5. A medicament or composition for the prevention or treatment of tumors/cancers, comprising:

the siRNA of claim 1 or 2;

or an expression system capable of expressing the siRNA of any one of claims 1 or 2.

6. The medicament or composition of claim 5, wherein the tumor/cancer is selected from liver cancer, stomach cancer, prostate cancer, breast cancer, lung cancer, pancreatic cancer, cervical cancer, endometrial cancer, colorectal cancer, lung cancer, nasopharyngeal cancer, ovarian cancer, skin cancer, esophageal cancer, or brain tumor.

7. The drug or composition of claim 5, further comprising:

a pharmaceutically acceptable carrier and/or adjuvant;

other active ingredients for preventing or treating tumors.

8. The medicament or composition of claim 7, wherein the pharmaceutically acceptable carrier and/or adjuvant comprises, but is not limited to, buffers, emulsifiers, suspending agents, stabilizers, preservatives, salts, excipients, fillers, coagulants and conditioners, surfactants, dispersing agents, antifoaming agents.

9. The drug or composition of claim 7, wherein the other active ingredients for preventing or treating tumors comprise: chemotherapeutic agents, radiotherapeutic agents or antibody drugs.

10. A medicament or composition according to any one of claims 5 to 9, wherein the medicament or composition is in any form selected from the group consisting of solid, liquid, gel, semifluid and aerosol.