Hematological Malignancies MLL Partial Tandem Duplication (Acute Myeloid Leukemia)

A partial tandem duplication (PTD) of the mixed lineage leukemia (MLL) gene on chromosome 11q23 occurs in approximately 10% of cytogenetically normal acute myeloid leukemias (CN-AML) and in the majority of AMLs with trisomy 11.   The partial tandem duplication occurs in an internal portion of the MLL gene that spans multiple exons, and results in an in-frame fusion transcript and protein with a duplicated DNA-binding domain.  Leukemia cell RNA with the MLL PTD can be detected with RT-PCR using primers that flank the duplication repeat.  This RT-PCR method has a greater sensitivity compared to genomic DNA amplification and Southern blotting.

Clinical Utility:
In adult AML, the presence of an MLL-PTD mutation is an adverse prognostic indicator for relapse-free and overall survival.  In addition, the detection of MLL-PTD post-treatment, for minimal residual disease monitoring, has been shown to be effective in detecting relapse prior to overt clinical manifestations.

RNA extracted from blood or bone marrow cells  is subjected to RT-PCR specific for the MLL gene partial tandem duplication by using forward primers upstream of the breakpoint cluster region (exon 9) and reverse primers within the (normally) upstream region (exon 4).   A reference gene RNA is concomitantly amplified to control for RNA integrity.  The RT-PCR products are detected by capillary electrophoresis, and range in size from 153 bp to 616 bp depending on the breakpoints of the partial tandem duplication.   No RT-PCR products are visible in the absence of the MLL-PTD.

Sensitivity:
MLL-PTD RNA can be detected down to a dilution limit of approximately 5% leukemia cells (variable, depending on the initial leukemic clone).

• Blood or Bone Marrow: 5-10 mL  purple (EDTA) or yellow (ADC) tube (unspun)
• If sample is to be shipped overnight, pour blood/bone marrow into RPMI media at a 1:1 ratio (1 mL of RPMI to 1 mL of blood/bone marrow) and mix thoroughly.
• 2-5mL Blood or bone marrow in a Paxgene tube is also acceptable.
• Deliver to lab at shipping address above within 24 hours of collection, if sample cannot arrive within 24 hours, refrigerate until sample can be transported, then transport on ice packs; do not freeze.

A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES. Please provide detailed clinical information.

Weekly

7-10 days

• Maintain specimen at refrigerator temperature - do not freeze. 
• Blood must arrive in lab within 36 hours of collection. 
• Ship via overnight express, using the cold pack provided to keep the specimen cool, not frozen. 
• Contact Client Services at (855) 535-1522 for shipping kits and instructions.

1. Patel JP, Gonen M, Figueroa ME, et al. Prognostic Relevance of Integrated Genetic Profiling in Acute Myeloid Leukemia. N Engl J Med 2012;366(12):1079-1089.
2. Whitman SP, Shujun L, Vukosavljevic T. The MLL Partial Tandem Duplication: Evidence for Recessive Gain-Of-Function in acute myeloid leukemia identifies a novel patient subgroup for molecular-targeted therapy. Blood. 2005;106(1):345-352.
3. Schnittger S, Wormann B, Hiddermann W, Griesinger F. Partial Tandem Duplications of the MLL Gene Are Detectable in Peripheral Blood and Bone Marrow of Nearly All Healthy Donors. Blood. 1998;92(5):1728-1734.