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PCR in Cancer detection

  1. Nov 6, 2018 #1
    How is PCR able to detect chromosomal translocations causing cancer?

    I understand it is possible through FISH but how PCR?
     
  2. jcsd
  3. Nov 6, 2018 #2

    Andrew Mason

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    Hi SanjuktaGhosh.

    I think they are referring to RT-PCR. Both PCR and RT-PCR involve making copies of DNA but in RT-PCR one first uses reverse transcriptase to reverse transcribe a subject RNA strand into its DNA complement (cDNA). One then uses PCR to amplify the cDNA.

    AM
     
  4. Nov 6, 2018 #3

    Ygggdrasil

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    PCR is able to detect specific chromosomal translocations, such as the "Philadelphia chromosome" that produces the BCR-ABL1 fusion in many leukemias. Basically, since the genes for BCR and ABL1 are normally on different chromosomes, a PCR reaction using one primer against BCR and one primer against ABL1 will normally not produce a product. However, if a translocation has occured which creates the BCR-ABL1 fusion, the PCR reaction will then amplify the BCR-ABL1 gene, enabling detection of the fusion. PCR methods are very sensitive, allowing researchers to detect minute amounts of fused DNA in a mixed population of normal and cancerous cells.

    https://www.lls.org/leukemia/chronic-myeloid-leukemia/diagnosis
    https://www.cancer.org/cancer/chron...etection-diagnosis-staging/how-diagnosed.html

    No, these tests are normally done by conventional PCR, looking for chromosomal translocations at the DNA level.
     
    Last edited: Nov 6, 2018
  5. Nov 6, 2018 #4

    Andrew Mason

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    Would finding the BCR-ABL mRNA be easier than finding the fused DNA? This is not my area, but RT-PCR does seem to be used for this purpose: See for example: https://www.ncbi.nlm.nih.gov/pubmed/17705578

    AM
     
  6. Nov 6, 2018 #5

    Ygggdrasil

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    Typically, DNA is more stable than RNA, so I would have thought that it would be preferable to check DNA by qPCR. Upon further investigation, it does appear that you are correct and diagnosis is typically done by RT-qPCR to look for BCR-ABL1 mRNA (e.g. see http://www.bloodjournal.org/content/114/5/937.long?sso-checked=true).
     
  7. Nov 9, 2018 #6
    Thank you both of you. So basically to detect BCR-ABL1 fusion gene, a forward primer that anneals to the starting portion of BCR and a reverse primer that anneals to the ending portion of ABL1 are used?
     
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