Detailed Description
The present invention will be described more fully hereinafter in order to facilitate an understanding of the present invention. This invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
The experimental procedure, which does not address the specific conditions in the examples below, is generally followed by routine conditions, such as, for example, sambrook et al, molecular cloning: conditions described in the laboratory Manual (New York: cold Spring Harbor Laboratory Press, 1989) or as recommended by the manufacturer. The various chemicals commonly used in the examples are commercially available.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In one aspect, the invention relates to a real-time fluorescent quantitative RT-PCR detection kit for PCA3 and PSA RNA, wherein the kit is introduced with a double polymerase amplification method of Stofel fragments and Tfl DNA polymerase except MMLV DNA polymerase. Wherein the Stoffel fragment is Taq DNA polymerase with the 5'-3' exonuclease activity domain removed, and the correction activity of a small amount of 3'-5' exonuclease is recovered while the 5'-3' exonuclease activity is removed, so that the defect of insufficient specificity of Tfl DNA polymerase is overcome. Whereas Tfl DNA polymerase provides 5'-3' exonuclease activity that cleaves the taqman probe. The detection specificity is improved, and more templates can be tolerated. On the other hand, the Stoffel fragments and Tfl DNA polymerase have strong inhibitor resistance, so that more templates can be added into the fluorescent RT-PCR kit constructed according to the invention, thereby being capable of improving sensitivity. Meanwhile, a primer and a probe for the PCA3 and PSA genes are designed, the primer for the PCA3 gene is shown as SEQ ID NO.1 and SEQ ID NO.2, and the probe is shown as SEQ ID NO. 3; the primers for the PSA gene are shown as SEQ ID NO.10 and SEQ ID NO.11, and the probes are shown as SEQ ID NO. 12. Thus, a high-sensitivity and high-specificity detection amplification system is formed.
The detection introduces the optimized Tris-MOPS-sodium citrate buffer solution which is more suitable for RNA amplification, so that the sensitivity and the specificity of the detection are greatly improved.
In the detection of PCA3 and PSA genes, a qualitative method can be performed, PCA3 score=1000/2(PCA3 Ctvalue-PSA Ct value The expression quantity of PCA3RNA can be accurately quantified. PCA3 score is positively correlated with the likelihood of prostate cancer. A PCA3 score < 35 is less likely to be positive for prostate puncture, and if a PCA3 score > 35 is more likely to be positive for prostate puncture. Therefore, by noninvasively detecting PCA3 through urine, unnecessary prostate puncture of partial patients can be reduced, and pain of the patients can be relieved.
The effectiveness of extraction, purification and PCR amplification of exosome RNA is indicated by adding an internal reference gene ACTB into each reaction system. The RNA of a gene is detected through two different fluorescent channels, and the single-tube double quantification avoids the operation error when the single tube is used for single quantification.
The real-time fluorescence quantitative RT-PCR detection method and the kit for the PCA3 and the PSA RNA in the urine exosomes can realize rapid detection of target RNA in the urine exosomes, and are extremely convenient to apply.
The invention optimizes the real-time fluorescent quantitative RT-PCR detection and amplification system based on the existing kit. The primer and the probe with better detection effect are designed on the sequence on the exon 3 of the PCA3 gene selection, meanwhile, the optimized Tris-MOPS-sodium citrate buffer solution which is more suitable for RNA amplification is introduced into the reaction solution, the Stofel fragment or Tfl DNA polymerase is introduced, the detection specificity is improved, and more templates can be tolerated. The detection sensitivity of the optimized amplification system can reach 93 percent, and the specificity can reach 85 percent.
The present invention is further illustrated below in conjunction with specific examples, but is not intended to limit the scope of the present invention.
Example 1: PCA3 and PSA gene detection kit
Design of specific primers and probes:
(1) Primer groups and probes for detecting PCA3RNA designed for the RNA sequence on the PCA3 genome exon 3 have the following sequences:
forward primer Y21:5'-TTCCCCACAAGAATTTCAACGA-3' SEQ ID NO:1;
reverse primer Y22:5'-TCATCTAAAGCAATATAGCCCAT-3' SEQ ID NO:2;
fluorescent probe Y27:5'FAM-ACTAACCTGAATGCCTAGACCC-BHQ1-3' SEQ ID NO:3;
for the RNA sequence on exon 4 of the PCA3 genome, a primer set and a probe for detecting PCA3RNA are designed, and the sequences are as follows:
forward primer Y21-1:5'-GGAAGCACAGAGATCCCTGCGA-3' SEQ ID NO:4;
reverse primer Y22-1:5'-TAAAGCACAGGGCGAGGCTCAT-3' SEQ ID NO:5;
fluorescent probe Y27-1:5'FAM-ACT AGAAATGCCCGGCCGCCATC-BHQ1-3' SEQ ID NO:6;
(2) For the RNA sequence of the internal reference ACTB genome, a primer group and a probe for detecting the internal reference gene are designed, and the sequences are as follows:
forward primer Y25:5'-CAAATGCTTCTAGGCGGAC-3' SEQ ID NO:7;
reverse primer Y26:5'-AAACAAATAAAGCCATGCCAA-3' SEQ ID NO:8;
fluorescent probe Y28:5'JOE-ATGACTTAGTTGCGTTACACCCTT-BHQ1-3' SEQ ID NO:9;
(2) For PSA genomic RNA sequences, primer sets and probes for detecting PSA RNA were designed, the sequences of which are as follows:
forward primer Y23:5'-CTCAGGCCAGGTGATGACTCC-3' SEQ ID NO:10;
reverse primer Y24:5'-CATGACCTTCACAGCATCCGT-3' SEQ ID NO:11;
fluorescent probe Y29:5'FAM-CCTCATGCTGCTCCGCCTGTCAGA-BHQ1-3' SEQ ID NO:12.
Specimen collection and pretreatment:
the detection method and the kit are suitable for specimen types including urine samples, and the samples are collected from three courts in Guangzhou city.
Urine was collected after regular prostate massage. The urine collecting pipe is used for collecting not less than 10mL of urine according to the proposal of the manufacturer, and the urine sample can be immediately used for detection or stored at the temperature of 2-8 ℃ for not more than 24 hours; the food is not preserved at-20deg.C; the sample can be stored for six months at a temperature lower than-70deg.C, and repeated freezing and thawing is avoided.
And (3) placing the urine tube into a centrifugal machine for centrifugation, wherein the rotating speed is 1350+/-150 rcf, centrifuging for 10 minutes, taking the urine tube out of the centrifugal machine, transferring the supernatant urine into a 15mL centrifuge tube made of polypropylene material by using a new disposable pipette, and marking a sample number.
Extraction of urine exosomes and RNA:
nucleic acid extraction or purification kit using Guangzhou Ruibaobio-technology Co-Ltd, containing exosome separation reagent (Yue ear mechanical preparation 20181281)
Preparation of a cationic quality control product:
and synthesizing the amplified target fragment into a plasmid serving as a negative and positive quality control product.
ACTB gene fragment:
5’-CAAATGCTTCTAGGCGGACTATGACTTAGTTGCGTTACACCCTTTCTTGACAAAACCTAACTTGCGCAGAAAACAAGATGAGA-3’(SEQ ID NO.13)
PCA3 gene exon 3 fragment:
5’-CTTCCCCACAAGAATTTCAACGACTCTCAAGTCTTTTCTTCCATCCCCACCACTAACCTGAATGCCTAGACCCTTATTTTTATTAATTTCCAATAGATGCTGCCT-3(SEQ ID NO.14)
PCA3 gene exon 4 fragment:
5’-GGAAGCACAGAGATCCCTGCGAGGACTAGAAATGCCCGGCCGCCATCTTGGGTCATCGATGAGCCTCGCCCTGTGCTTTA-3(SEQ ID NO.15)
PSA gene RNA fragment:
5’-CTCAGGCCAGGTGATGACTCCAGCCACGACCTCATGCTGCTCCGCCTGTCAGAGCCTGCC--3(SEQIDNO.16)
example 2:
fluorescent quantitative PCR amplification:
each test reaction system was formulated as follows, 50 μl system: 2.5. Mu.L of the enzyme mixture (set up experimental group and control group) and 17.5. Mu.L of PCR Mix (set up experimental group and control group) were subjected to instantaneous centrifugation, and 30. Mu.L of RNA to be detected was then added; positive and negative controls were also set up according to the above system, and 30 μl of positive or negative quality control was added for amplification.
The PCA3 PCR (experimental group) Mix was:
| solution (Solution) | Working |
| 1M Tris-SO4 (pH9@25℃) | 66mM |
| 1M MOPS(pH7@25℃) | 18mM |
| Sodium citrate | 3mM |
| 2M(NH4)2 SO4 | 20mM |
| 1M MgSO4 | 7mM |
| Brij-35 | 0.10% |
| 30mg/mL acetylated BSA (3%) | 0.1mg/mL |
| Y21(20μM) | 0.1μl |
| Y22(20μM) | 0.1μl |
| Y27(100μM) | 0.1μl |
| Y25(100μM) | 0.1μl |
| Y26(100μM) | 0.1μl |
| Y28(100μM) | 0.1μl |
| dNTP(10mM) | 1μl |
The PSA PCR (experimental group) Mix is:
the enzyme mixture also comprises an experimental group and a control group
The PCA3 PCR (control group) Mix was:
the PSA PCR (control) Mix was:
| Solution | Working |
| 1M Tris-Cl(pH9@25℃) | 66mM |
| 2M(NH4)2 SO4 | 20mM |
| 1M MgSO4 | 7mM |
| Brij-35 | 0.10% |
| 30mg/mL acetylated BSA (3%) | 0.1mg/mL |
| Y23(20μM) | 0.1μl |
| Y24(20μM) | 0.1μl |
| Y29(100μM) | 0.1μl |
| Y25(100μM) | 0.1μl |
| Y26(100μM) | 0.1μl |
| Y28(100μM) | 0.1μl |
| dNTP(10mM) | 1μl |
Each reaction tube was placed in a reaction tank of a quantitative PCR instrument (ABI 7500), the name and the type of fluorescent group of each detection were set (PCA 3 and PSA reporter group were set as FAM, internal reference group was JOE, and quencher group was none), and the circulation conditions were set:
result analysis and determination:
1. and (3) setting result analysis conditions: automatically storing the result after the reaction is finished, automatically analyzing the result by using instrument matched software, adjusting the Start value and End value of Baseline according to the analyzed image to be Threshold value (the user can adjust the Start value to be 2-8 and the End value to be 10-20 according to the actual situation,fluorescence Threshold (Threshold) setting principle is that a Threshold line just exceeds the highest point of a negative quality control amplification curve (irregular noise line), ct value is displayed as undet, analysis results are automatically obtained by clicking Analysis, result values are arranged and analyzed, and PCA3 score = 1000/2 is calculated(PCA3Ct value-PSA Ct value PCA3 score was determined.
2. Quality control
A PCR reaction was verified to be effective if both negative and positive quality controls met the criteria set forth in the following table, and the patient sample was measured along with both negative and positive quality controls in the same PCR reaction. If either or both of the negative or positive quality control samples are not effective, the results of the patient samples cannot be analyzed, and the test is repeated for all patient samples.
Quality control product for verifying validity of PCR reaction
3. And (3) result judgment: on the premise that the numerical values of the negative quality control product and the positive quality control product are normal, the sample result is judged as follows:
if the Ct value of the internal standard channel of the sample to be detected is more than 38 or the Ct value of the PSA channel is more than 34, the sample is extracted again or the sample is extracted again and then is detected.
In the case where both PCR reaction solutions were effective and PSA was positive, ct values of PCA3 and PSA were substituted into the following formula to calculate
PCA3 score. PCA3 score = 1000/2 (PCA 3 Ct value-PSA Ct value)
4. Interpretation of results:
| PCA3 scoring | Interpretation of | Result prompt |
| <35 | Negative of | Less likelihood of positive prostate puncture |
| ≥35 | Positive and negative | The probability of positive prostate puncture is high |
Test results:
10 urine specimens collected are extracted, and the pathological diagnosis is 2 healthy human samples and 8 prostate cancer samples. The extraction and quantification were performed as described above. Internal standard JOE channel Ct values>34, PSA FAM channel Ct values<38, the numerical results are valid. Ct values of prostate cancer patient samples>30, ct values of healthy human samples are all<30. The sample detection result meets the experimental requirements. Wherein the amplification effect of the primer probe set at the 3 position of the exon is better than that at the 4 position of the exon, which is selected by the PCA3 reaction system: the average difference is 1.5 Ct values, i.e., the amplification efficiency on exon 3 of the PCA3 gene is 2-4 times higher than on exon 4. PCR mix in which PSA reaction solution was compared with conventional Tris-HCl as buffer pair, optimized Tris-SO was used4 Buffer solution composed of MOPS and sodium citrate, and has higher sensitivity: the Ct phase difference after optimization is about 1, namely the amplification efficiency is increased by 1-2 times.
Example 2: gene fragments were selected as positive references and diluted as shown in the following table.
The test groups and results are as follows:
as can be seen from the above table analysis, when the sample size was 5. Mu.L, normal amplification was possible using Taq DNA polymerase and mmlv DNA polymerase (group 5);
when the sample size was increased to 30. Mu.L, amplification was not possible using Taq DNA polymerase and MMLV DNA polymerase alone (groups 2 and 4), whereas normal amplification was possible using Stoffel fragment, tfl DNA polymerase and MMLV DNA polymerase (groups 1 and 3); the kit is introduced with a double-polymerase amplification method of Stoffel fragments and Tfl DNA polymerase except MMLV DNA polymerase, so that a sample taking RNA as a template can be amplified more effectively.
Therefore, the primer probe on the exon 3 is matched with an optimized enzyme system and reaction liquid, and is more suitable for RNA amplification with different concentrations.
Example 3:
the synthesized RNA fragment mixture was diluted to a certain ratio according to the following table and used as a sample to be tested, and the sensitivity and precision of the PCA3 reaction solution and the PSA reaction solution were searched.
Detection results of precision reference:
detection results of precision reference: the precision reference prepared above is used for carrying out PCR reaction with the PCA3 reaction liquid and the PSA reaction liquid respectively, and the two tubes of the reaction liquid are respectively repeated for 10 holes, so that as shown in the figures 1 and 2, the Ct value of a detection channel (FAM) of the PCA3 reaction liquid is in the range of 31.10-31.46, the coefficient of variation (CV value) is 0.38 percent and within 5 percent, the repeatability is good, the Ct value of the detection channel (FAM) of the PSA reaction liquid is in the range of 31.12-31.63, the coefficient of variation (CV value) is 0.54 percent and within 5 percent, and the repeatability is good.
Detection results of sensitivity reference:
results of sensitivity: the sensitivity reference is used for respectively carrying out PCR reaction with the PCA3 reaction liquid and the PSA reaction liquid, 20 holes are repeated, the result is shown in the figures 3 and 4, the Ct value of a detection channel (FAM) of the PCA3 reaction liquid is in the range of 33.60-35.39, the Ct value of a reference channel (JOE) is in the range of 27.79-28.63, the Ct value of the detection channel (FAM) of the PSA reaction liquid is in the range of 33.11-34.25, and the Ct value of the reference channel (JOE) is in the range of 28.12-28.71. The variation coefficients (CV values) of the FAM channel and the JOE channel of the reaction solution are within 5%, and the amplification repeatability is good.
Example 4: determination of PCA3 score positive judgment and sensitivity specificity comparison on exons 3 and 4
The ROC curve is a curve obtained by dividing a diagnosis experiment result into a plurality of critical points, taking sensitivity corresponding to each critical point as an ordinate and 1-specificity as an abscissa, and drawing the curve, wherein the optimal threshold value of detection is determined by selecting a point which is as close to the upper left of the curve as possible and combining with professional actual conditions, so that the ROC curve is an effective tool for comprehensively and accurately evaluating the diagnosis experiment.
In this embodiment, 200 clinical samples are detected in total, wherein 100 cases of positive samples and 100 cases of negative samples of prostate cancer are detected, FAM channel Ct values of PCA3 and PSA corresponding to 200 cases of clinical samples are substituted into a formula, PCA3 scores are calculated, possible PCA3 score tangential points are used as thresholds to calculate sensitivity and specificity, sensitivity is used as ordinate, 1-specificity is used as abscissa, a ROC curve is obtained by drawing, and a positive judgment value of PCA3 scores is found out through the ROC curve.
PCA3 score = 1000/2(PCA 3 Ct value-PSA Ct value) The expression quantity of PCA3RNA can be accurately quantified. PCA3 score is positively correlated with the likelihood of prostate cancer.
Amplification results corresponding to exon 3: a PCA3 score < 35 is less likely to be positive for prostate puncture, and if a PCA3 score > 35 is more likely to be positive for prostate puncture.
Sensitivity and specificity of amplified sample PCA3 scoring at exon 3 for different thresholds
Referring to the above table and FIG. 5, the amplification result on exon 3 should be based on ROC principle, the point closest to the upper left corner should be taken as the critical point, the PCA3 score of the corresponding point of the ROC curve is 35, the detection sensitivity is 93%, the specificity is 85% and the about dengue index is the maximum when the PCA3 score is 35.
Sensitivity and specificity of amplified sample PCA3 scoring at exon 4 for different thresholds
As a result of amplification on exon 4, the point closest to the upper left corner should be taken as the critical point according to the ROC principle, the PCA3 score at the point corresponding to this ROC curve is 40, and when the PCA3 score is 40, the detection sensitivity is 88%, the specificity is 80%, and the about dengue index is the maximum.
Therefore, the primer/probe on the selected exon 3 of the kit is matched with the corresponding enzyme system and reaction liquid, so that the kit has better amplification efficiency, and the interpretation requirements are as follows: and judging that the PCA3 score is less than 35 and is negative, and judging that the PCA3 score is more than or equal to 35 and is positive. The amplification sensitivity was 93% and the specificity was 85%.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
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