Polymerase Chain Reaction and AML

PCR is currently the most sensitive approach to determining the presence of leukemic cells when the genetic alterations are known and a suitable molecular probe is available. Usually a reverse transcriptase method (RT-PCR) is used for determining MRD.^[4]

M2, myeloblastic with significant maturation. While M2 is shown, in 10% of cases, the morphology is that of M1 with the characteristic Auer rod and the presence of the (8;21) translocation.^[4]

Translocation (8;21). Partial karyotype showing the t(8;21)(q22;q22) usually seen in M2. Arrows point to the breakpoints on the derivative chromosomes resulting from this translocation.[4] This is generally a favorable prognostic factor.[16]

PCR showing t(8;21). PCR amplification of the translocation (8;21)(q22;q22)(227 bp) seen in AML (M2) detecting the junction of the fusion gene (AML1-ETO) resulting from this translocation in three patients (pX1-3). The cell line (Kasumi-1) is known to have this translocation and was used as a positive control. Transcripts of this fusion gene are evident for the three patients studied. No fusion product was seen in normal lymphocytes. PCR, courtesy of Dr Nicoletta Sacchi.[4]

M3, APL. The abnormal promyelocytes have many granules, some intensely basophilic.[4] This morphology, along with t(15;17), comprises a favorable prognosis.[16]

Translocation (15;17)(q22;q12). t(15;17)(q22;q12) characterizes M3, leading to the genesis of an abnormal fusion gene between the PML and RAR-alpha genes (PML-RAR-alpha). The breakpoints on this partial karyotype are indicated by arrows.[4]

PCR analyses of gene involvement.
A. A schematic diagram of PML-RAR-alpha fusion mRNA, depicting RT-PCR primer pairs of the two common nucleic acid junctions, with the vertical arrows pointing to the position in the PML exonic sequences of the breakpoints. The horizontal arrows point to the location of the oligonucleotide primer pairs used for nested PCR amplification.[4]

B. Shown is the amplification of RNA prepared from the marrow cells of two APL patients expressing fusion mRNAs with two different breakpoints in the gene shown in A. cDNA was amplified by nested PCR, size-separated by electrophoresis on an agarose gel, and visualized by staining with ethidium bromide. Molecular weight base pair size standards appear as numbers at the left of the figure. PCR, courtesy of Dr Wilson H. Miller, Jr.[4]

M2, myeloblastic with significant maturation. Myeloblasts (and a more mature neutrophilic cell) with minor granulation and evident nucleoli in a case of Ph(+) AML.[4]

The Philadelphia translocation, (9;22). The breakpoints on this partial karyotype are indicated by arrows.[4]

PCR analyses. A PCR amplification of the translocation (9;22) detecting the junction of the fusion gene BCR-ABL in a case of M1. In column 1, the transcript of the fusion gene, indicative of the Ph-translocation, and in column 2, that of the normal ABL gene. The column marked M is a molecular weight ladder serving to identify the molecular weights of the transcripts.[4]

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