The UIHC Molecular Pathology Laboratory will begin testing for mutations in the CCAAT/enhancer binding protein-alpha gene (CEBPA) starting on July 19th, 2012. Somatic mutations of CEBPA are among the most common in acute myelogenous leukemia ranging from 5-14% of cases particularly in the former FAB M1 and M2 subtypes.  Along with having a normal karyotype, the majority of CEBPA-mutated cases have two distinct CEPBA mutations affecting different functional domains of the protein.  In the absence of other unfavorable mutations that mitigate CEBPA double-mutations, there is an associated favorable prognosis as measured by overall and disease-free survival.

 

Specimen type: Peripheral blood or non-decalcified bone marrow aspirate that contains a minimum of 20% suspected AML cells. 

 

Method: The CEBPA test was developed by the Molecular Pathology Laboratory, and is based upon an initial amplification of CEBPA-specific gene fragments by PCR, followed by traditional Sanger cycle sequencing with dye terminator dideoxy nucleotide triphosphates, as CEBPA mutations are scattered across the CEBPA coding sequence. The test has a turn-around-time of 7 days. Importantly, this assay cannot discriminate the cis-trans phase of multiple CEBPA mutations; the finding of two (or more) distinct pathogenic mutations is assumed to represent a biallelic mutation in CEBPA.

 

The CEBPA Sequencing test result will be reported as primary and secondary findings.  The presence of one or more pathogenic, or probably pathogenic mutations will be indicated for both the coding sequence and protein sequence changes according to standard nomenclature designation.  A NEGATIVE result indicates that no pathogenic mutations were identified, although previously reported single nucleotide polymorphisms (SNPs) and novel benign variants will be listed separately under secondary findings.  An INDETERMINATE result indicates that the analysis was technically valid, but the result is not interpretable.  The most likely event in this category would be the isolated finding of a potentially pathologic mutation on only one strand.  For these cases, repeat amplification and/or resequencing may be required.  Finally, the category of "VARIANT of UNKNOWN SIGNIFICANCE (VUS)" may be assigned to a primary finding in the event that a novel missense or potential splice-site sequence variant has been identified on both strands, but our variant impact analysis failed to assign the new variant as pathogenic, probably pathogenic, benign or likely benign.  Such cases may require additional testing, including testing of germline DNA and related family members, to clarify the VUS status.

 

For more information about CEBPA mutation analysis, please contact Jon Heusel (6-8616; jon-heusel@uiowa.edu), Deqin Ma, MD, Ph.D (ext. 4-5700), or Aaron Bossler, MD, PhD (ext. 4-9566).