1. A composition comprising primers for amplifying a BCR-ABL fusion gene, the primers having the sequence set forth in SEQ ID NO: 1 and SEQ ID NO: 2, respectively.

2. The composition of claim 1, further comprising a probe having a sequence set forth in SEQ ID NO: 3.

3. the composition of claim 2, further comprising primers and probes for amplifying an internal reference gene.

4. The composition of claim 3, wherein the primers for amplifying the reference gene have the sequences as set forth in SEQ ID NO: 4 and SEQ ID NO: 5, respectively.

5. The composition of claim 4, wherein the probe for amplifying the reference gene has a sequence as set forth in SEQ ID NO: and 6.

6. The composition of any one of claims 2 to 5, wherein the probe is labeled with a fluorophore.

7. The composition of claim 6, wherein the fluorescent group is selected from the group consisting of FAM, BHQ-MGB, TAMRA, TET, HEX, ROX.

8. A fluorescent quantitative PCR reaction system, which is characterized by comprising: the primer sequence is shown as SEQ ID NO: 1. SEQ ID NO: 2. SEQ ID NO: 4. SEQ ID NO: 5, the probe sequence is shown as SEQ ID NO: 3. SEQ ID NO: 6, the probe is marked with a fluorescent group.

9. Use of a composition according to any one of claims 1 to 7 and a reactive system according to claim 8 for the preparation of a reagent for the detection of minimal residual disease.

10. A kit for detecting minimal residual disease, comprising the composition of any one of claims 1 to 7, a negative quality control, and a positive quality control.

Background

Leukemia is a common malignant blood disease, the incidence rate of leukemia is on the rise in recent years, the human health is seriously harmed, more than 3 million patients dying from leukemia every year in China are treated, in recent years, the treatment effect of acute and chronic leukemia is obviously improved due to the progress of chemoradiotherapy and increasingly wide clinical application of hematopoietic stem cell transplantation, most patients can be relieved, more and more cases exist for long-term survival, the key of the long-term remission and even cure of leukemia is the problem of how to control relapse after remission, and the detection of the minimal residual disease (nIimardsialdsiease, MRD) has very important significance for the curative effect evaluation prognosis judgment, relapse monitoring and the like of leukemia when entering the acute stage after remission of most leukemia is the result of clone proliferation of original leukemia cells.

MRD refers to the state of small residual leukemic cells in the body after a leukemia patient has been treated to complete remission (including bone marrow transplant therapy). Clinically, if the total number of leukemia cells is controlled below 105, that is, the number of primary or immature tumor cells in bone marrow is below 5%, the disease condition of a patient can be completely controlled to achieve a clinical complete remission state (called CR), but the potential of malignant clonal proliferation can exist in the leukemia cells below 5%, and there is no fixed limit between minimal residual leukemia and clinical leukemia, which mainly depends on the sensitivity of the detection method. Thus, the presence of MRD is a major factor leading to acute exacerbation of relapse after remission of leukemia and affecting long-term survival of patients. The important significance of improving the level of residual leukemia cell detection technology lies in: (1) guiding leukemia chemotherapy, and determining whether to continue or stop treatment according to the load of leukemia cells in vivo; (2) selecting the most appropriate treatment at the new level; (3) drug resistance was earlier found; ) Earlier prediction of leukemia recurrence; (5) evaluating the purification effect of the bone marrow transplantation; (6) therefore, in order to objectively evaluate the treatment effect of leukemia, determine prognosis, adjust post-remission treatment, improve curative effect, and prevent relapse, the research of MRD (acute leukemia and chronic leukemia) becomes an important problem in recent years.

Chronic Myelogenous Leukemia (CML) is a malignant clonal hematological disease that originates in hematopoietic stem cells. The marker feature is that t (9; 22) (q 34; q11) easy position, namely Ph chromosome, is formed, and then BCR-ABL fusion gene is generated. Due to differences in the BCR gene cleavage sites, three different types of BCR/ABL fusion gene transcripts are typically produced: M-BCR (e1a2), M-BCR (e13a2/e14a2) and μ -BCR (e19a2), encoding fusion proteins of 190-kDa, 210-kDa and 230-kDa, respectively. P210 is mainly present in Chronic Myelogenous Leukemia (CML) patients and in 30% of Ph + ALL patients, P190 is mainly present in Ph + ALL patients, and P230 is commonly found in chronic neutrophilic myelogenous leukemia (CNL). Previous research reports show that P190 and P210 can be expressed separately or exist together in Ph + B-ALL. It was found that P190 and P210 differ in activation and signal transduction, suggesting that the biological characteristics and clinical significance of the different BCR/ABL transcripts may differ. However, the clinical characteristics, as well as the prognostic significance, with respect to the distribution of BCR/ABL different transcripts, particularly P190 and P210 co-expressing patients, remain unknown. Currently, Real-time fluorescent quantitative PCR (RT-qPCR) is widely used clinically for molecular monitoring of BCR/ABL (P210). It was experimentally confirmed that the RT-qPCR results of the patients treated by TKI in the first 3 months were directly related to their prognosis. However, the results of BCR/ABL (P210) transcripts in various laboratories are not comparable due to different influencing factors such as laboratory instruments, reagents, reference genes and the like. To solve this problem, the molecular biological response (MR) of the patient was first assessed internationally using the reduced levels of BCR/ABL (P210) transcript corresponding to the initial diagnosis. In 2005, The National Institutes of Health (NIH) proposed The use of International Standards (IS) to convert The BCR-ABL/ABL detection values of each laboratory into international standard values (BCR-ABL/ABLIS) by a coefficient, i.e., each laboratory conversion Coefficient (CF). If the transformed value is reduced by 3 log values, i.e., 1000-fold, relative to the patient's initial level, it is an indication that the CML patient has achieved Major Molecular biology Remission (MMR). In 2012, europe proposed a deep-level of molecular biological responses: MR4.0, MR4.5 and MR 5.0.

Isav (the Imatinib resuscitation and evaluation study) has reported that 108 CML patients who were treated with Imatinib (IM) for more than 24 months, maintained Complete cellular remission (CMR) for at least 18 months, experienced 48.1% relapse after IM withdrawal and 73.1% experienced molecular biological relapse within 9 months after withdrawal. It is shown that even though the RT-qPCR cannot detect the Minimal residual leukemia cells (MRD), the leukemia cells may still exist due to the limitation of the sensitivity of the current detection method. This puts higher demands on the sensitivity of the detection method.

Disclosure of Invention

The invention aims to solve the problems that in the prior art, an RT-PCR method for detecting a tiny residual focus is low in sensitivity and detection accuracy, and a primer and a probe for detecting BCR/ABL (P210) are sought to be designed, so that a novel tiny residual disease detection kit with super-sensitivity and good detection repeatability is established.

In order to solve the technical problems, the invention adopts the following technical scheme.

The invention provides a composition, which comprises a primer for amplifying a BCR-ABL fusion gene, wherein the sequence of the primer is shown as SEQ ID NO: 1 and SEQ ID NO: 2, respectively.

Preferably, the composition further comprises a probe, and the sequence of the probe is shown in SEQ ID NO: 3.

preferably, the composition further comprises primers and probes for amplifying the reference gene.

Preferably, the sequence of the primer for amplifying the reference gene is shown as SEQ ID NO: 4 and SEQ ID NO: 5, respectively.

Preferably, the sequence of the probe for amplifying the reference gene is shown as SEQ ID NO: and 6.

Preferably, the probe is labeled with a fluorophore.

Preferably, the fluorescent group is selected from FAM, BHQ-MGB, TAMRA, TET, HEX, ROX.

The invention provides a fluorescent quantitative PCR reaction system, which comprises: the primer sequence is shown as SEQ ID NO: 1. SEQ ID NO: 2. SEQ ID NO: 4. SEQ ID NO: 5, the probe sequence is shown as SEQ ID NO: 3. SEQ ID NO: 6, the probe is marked with a fluorescent group.

Wherein, the SEQ ID NO: 1 is tgaaactcc agaccgtcca.

Wherein, the SEQ ID NO: 2 is ttagagtgttatctccactg.

Wherein, the SEQ ID NO: 3 is cttggagttccaacgagcggcttca.

Wherein, the SEQ ID NO: 1 is cagtagcat ctgactttga.

Wherein, the SEQ ID NO: 1 is gcttagagtgttatctcca.

Wherein, the SEQ ID NO: 1 is attttcactgggtccagcgagaag.

The invention claims the application of the composition and the reaction system in preparing a reagent for detecting the micro residual focus.

The invention requests to protect a kit for detecting tiny residual lesions, which comprises the composition, negative quality control and positive quality control.

By designing primers and probe sequences aiming at the specificity of the BCR-ABL fusion gene and amplifying K562 positive cells, the detection sensitivity can reach 10^-6Has extremely high sensitivity, and detects compared with the existing detection kitThe sensitivity is low, or the detected target is only a corresponding positive plasmid, the reliability is not enough, and the kit has higher operability. And the copy number of the fusion gene BCR-ABL of the patient diagnosed with CML in different treatment periods is detected, and the detected copy number of the fusion gene is consistent with the treatment trend and the detection of an imported kit in different treatment periods CR1, CR2 and CR 3. The detection process is simple and convenient, and the precision, accuracy and specificity are high, so that the correctness of the detection result can be ensured.

Drawings

FIG. 1 shows the sensitivity of fluorescent quantitative detection of BCR-ABL gene.

FIG. 2 fluorescent quantitative detection sensitivity of housekeeping gene ABL.

FIG. 3 detection of BCR-ABL genes at different treatment periods for patients with CML

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

EXAMPLE 1 culture of K562 cells

Preparing: sterilizing articles (centrifuge tubes, culture bottles, pipettes, gun heads, etc.); 1640/calf serum medium (9: 1);

taking out the K562 cell freezing tube from the liquid nitrogen tank, placing in a 42 deg.C water bath to rapidly melt cells, transferring into a 15ml centrifugal tube containing 3ml 1640 culture solution containing 10% Fetal Bovine Serum (FBS), centrifuging at 1000rpm for 5min, discarding supernatant, suspending cells with 1ml 1640 culture solution containing 10% FBS, transferring into a 25T culture bottle containing 5ml 1640 culture solution containing 10% FBS, placing at 37 deg.C, and 5% CO₂Culturing in an incubator, and subculturing every 2-3 days.

Freezing and storing: collecting cells in logarithmic growth phase, changing liquid once 24 hr before collecting cells, centrifuging at 1000rpm for 5min, and discarding supernatant about every 10min⁶Adding 1ml of the frozen stock solution (fetal bovine serum: DMSO: 95: 5) into each cell, uniformly mixing, and subpackaging 1ml of the frozen stock solution into 1.5ml of each frozen stock tube, wherein the date and the name are indicated. Temperature reduction processThe sequence is 1h 40min at 4 ℃, and overnight at-80 ℃, and the mixture is transferred into liquid nitrogen for long-term storage.

EXAMPLE 2 extraction of mononuclear cells (Density gradient centrifugation)

(1) Equal amounts of normal human peripheral blood were mixed with PBS and layered.

(2) A centrifuge tube was taken and an equal amount of the separation medium from the peripheral blood sample was added.

(3) The blood sample was carefully pipetted onto the surface of the separation medium and centrifuged at 2500rpm for 15 min.

(4) After centrifugation, the centrifuge tube is divided into four layers from top to bottom. Wherein the first layer is a plasma layer; the second layer is a ring-shaped milky white lymphocyte layer; the third layer is a transparent separation liquid layer; the fourth layer is a layer of red blood cells.

(5) The second layer of circular opalescent lymphocytes was carefully pipetted into another centrifuge tube, 10ml of 1 XPBS was added to the tube and the cells were mixed. After centrifugation at 2000rpm for 8min, the supernatant was discarded.

(6) The cells were resuspended in 2ml of 1 XPBS using a pipette, centrifuged at 1800rpm for 6min, and the supernatant was discarded.

(7) Repeat step 6 for 2-3 times, discard the supernatant and resuspend the cells in 1ml of 1 XPBS, store at 4 ℃ until use.

Example 3 cell counting and gradient dilution of cells

(1) Cleaning the cell counting plate and the cover glass with alcohol, wiping the cell counting plate and the cover glass with special cleaning cloth, and placing the cover glass at a proper position of the counting plate.

(2) 10ul of cell suspension was aspirated into the gap between the counting plate and the cover glass, and observed under a 10-fold electron microscope.

(3) Four large grids are counted respectively, and if the cells are positioned on the line, only the upper line and the left line are counted (counting up and counting down, counting left and counting right).

(4) The total number of cells was calculated according to the following formula: cell number/ml 4 total large grid × dilution factor × 10⁴/4。

(5) Equal-concentration equal-volume K562 cell and human Peripheral Blood Mononuclear Cell (PBMC) suspension is taken and mixed evenly to obtain K562 to PBMC 1 to 1 cell suspension.

(6) 100ul of 1: 1 cell suspension was added to 900ul of PBMC suspension and mixed well to obtain K562: PBMC 1: 10 cell suspension.

(7) 100ul of 1: 10 cell suspension was added to 900ul of PBMC suspension, and mixed well with K562: PBMC 1: 10²A suspension of cells.

(8) Then sequentially diluting the mixture in a gradient manner to 1: 10³、1∶10⁴、1∶10⁵、1∶10⁶A suspension of cells.

(9) The cell suspension diluted in the above gradient was stored at 4 ℃.

Example 4 extraction of Total RNA (gradient dilution of cell suspension and patient peripheral blood) and reverse transcription

(1) And centrifuging the cell suspension after gradient dilution at 1000rpm for 5min, discarding the culture medium, washing by 5ml of 1 XPBS at 1000rpm, centrifuging for 5min, discarding the supernatant, repeating the previous step, and leaving the cell precipitate. Adding 300ul of collected CML patient peripheral blood into 900ul of the red breaking liquid, mixing uniformly, standing for 10min, 12000rpm, centrifuging for 1min, discarding supernatant, and leaving cell precipitate.

(2) Adding 100ul DEPC water into the cell sediment, respectively, blowing, stirring uniformly, adding 350ul MRC solution, mixing uniformly, adding 350ul 70% ethanol, and mixing uniformly.

(3) The sample is added into a prepared binding column-collecting column, and centrifuged for 1min at 14000rpm, and waste liquid is discarded and added into 300ul RNA wash buffer at 14000rpm, and centrifuged for 1 min.

(4) Discard the waste liquid, add 700ul RNAwash buffer, 14000rpm, centrifuge for 1 min.

(5) Discard the waste liquid, add 500ul RNAwash buffer, 14000rpm, centrifuge for 1 min.

(6) Discarding the waste liquid, adding 500ul RNAwash buffer at 14000rpm, centrifuging for 1min, discarding the waste liquid, and centrifuging for 2min in an empty tube.

(7) The collection column was placed in a new EP tube, 25ul DEPC water was added, and after standing for 2min at 12000rpm, centrifugation was carried out for 2 min. Storing at-80 deg.C for use.

(8) A total RNA sample (200 ng) was taken and reverse transcribed to form cDNA. Firstly, adding 0.5 mu l of random primer, carrying out reverse transcription to form a cDNA sample, supplementing 11.1 mu l of DEPC water, carrying out hot bath at 70 ℃ for 5min, and immediately carrying out ice bath on a product after the completion; adding reverse transcriptase 1 μ l and prepared RT-Buffer 8 μ l into the reaction tube; the reaction conditions are as follows: 10min at 25 ℃, 60min at 42 ℃ and 10min at 70 ℃, and storing the product at-20 ℃ for later use after the reaction is finished. .

EXAMPLE 5 establishment of fluorescent quantitative PCR reaction System and sensitivity measurement

Fluorescent quantitative PCR experiment: taking 6. mu.l of cDNA to perform PCR reaction, wherein the system is as follows: premix Ex Taq (TaKaRa) 12.5. mu.l, DEPC water 4.5. mu.l, BCR/ABL (P210) upstream and downstream primers 0.5. mu.l (10. mu.M), TaqMan Probe (Probe) 1. mu.l (10. mu.M), primer Probe SEQ ID NO: 1-3. Total 25 μ l volume. And carrying out detection reaction of ABL internal reference in the same system, wherein a primer probe is SEQ ID NO: 4-6. The reaction conditions were 45 cycles of pre-denaturation at 95 ℃ for 10s, followed by repeated denaturation at 95 ℃ for 15s, and annealing at 62 ℃ for 30 s.

RT-qPCR detection of cell suspensions of K562 cells and PBMC diluted in sequential gradients showed: the minimum detection concentration of RT-qPCR is 10^-6. The results are shown in FIG. 1, which is a BCR-ABL (P210) fusion gene amplification curve (curves are 1 and 10 from left to right in sequence)^-1、10^-2、10^-3、10^-4、10^-5、10^-6Gradient dilution of cell suspension); FIG. 2 shows the amplification curve of the housekeeping gene ABL (curves from left to right are 1 and 10 in sequence)^-1、10^-2、10^-3、10^-4、10^-5、10^-6Gradient dilution of cell suspension).

Shows that the lowest detection concentration of the primer probe can reach 10^-6And has high detection sensitivity.

Example 6 accuracy of fluorescent quantitative PCR method for detecting minute residual lesions

Peripheral blood of patients diagnosed with CML at different treatment periods (30 days of treatment at CR1, 30 days of treatment at CR2 and 30 days of treatment at CR 3) was extracted, corresponding cDNA amplification templates were prepared according to the methods of examples 2-5, and the presence of minimal residual foci in vivo after treatment was examined, with the amplification results shown in FIG. 3. As can be seen from FIG. 3, after treatment, the copy number of the BCR-ABL fusion gene in the patient body is obviously reduced, which indicates that the minimal residual focus is obviously reduced and the symptoms of the patient are relieved, and the result is further verified by importing a kit, and the obtained result is consistent with the method of the present invention.

The present invention is illustrated by the above examples, but the present invention is not limited to the above process steps, i.e., it is not meant to imply that the present invention must rely on the above process steps to be practiced. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected materials for the invention and addition of auxiliary components, selection of specific modes and the like, are within the scope of the invention and the disclosure.