Fusion of ETV6 to the Caudal-Related Homeobox Gene CDX2 in Acute Myeloid Leukemia With the t(12;13)(p13;q12)

Abstract

The t(12;13)(p13;q12) is a rare, recurrent translocation reported in a range of hematological malignancies. We have analyzed the molecular basis of this lesion in three patients with acute myeloid leukemia (AML), two of whom were known to have chromosome 12 breakpoints within the ETV6 gene. Fluorescence in situ hybridization (FISH) with ETV6 cosmids indicated that this gene was also disrupted in the third patient, while the normal ETV6 allele was retained. 3′ rapid amplification of cDNA ends (RACE) polymerase chain reaction (PCR) from bone marrow mRNA of this individual identified a novel sequence fused to ETV6 that was homologous to a region just upstream of the mouse CDX2 homeobox gene, the human homologue of which has previously been mapped to chromosome 13q12. PCR primers designed to amplify an ETV6-CDX2 fusion identified two major transcripts from this patient. First, a direct in-frame fusion between exon 2 of ETV6 and exon 2 of CDX2, and second, a transcript that had an additional sequence of unknown origin spliced between these same exons. Surprisingly, apparently normal CDX2 transcripts, usually expressed only in intestinal epithelium, were also detectable in cDNA from this patient. Neither normal nor fusion CDX2 mRNA was detectable in the two other patients with a t(12;13), indicating that this translocation is heterogeneous at the molecular level. Reverse transcription-PCR analysis showed that CDX2 mRNA, but not ETV6-CDX2 mRNA, was strongly expressed in 1 of 10 patients with chronic myeloid leukemia in transformation, suggesting that deregulation of this gene may be more widespread in leukemia. CDX2 is known to regulate class I homeobox genes and its expression in hematopoietic cells may critically alter the balance between differentiation and proliferation.

The Cdx‐Hox Pathway in Hematopoietic Stem Cell Formation from Embryonic Stem Cells

“…These findings suggest that regulated expression of Cdx4 is important for the homeostasis of adult hematopoietic cells, and argue for a role for Cdx genes in the adult hematopoietic system. 32,33 ESC-derived hematopoietic progenitors modified with ectopic Cdx4 and HoxB4 are enriched in multilineage progenitor activity in vitro, yet their ability to produce multilineage engraftment in vivo is strikingly inferior to that of adult bone marrow. This disparity could be explained either by a reduced proliferative capacity of ESC-derived progenitors or by an impaired ability to engraft adult bone marrow.…”

GENETIC PROFILEOF ACUTE MYELOID LEUKEMIA

“…One type of fusion results from two different translocations – the t(3; 12) (q26; p13) and the t(12; 13) (p13; q12) – and ETV6 drives the expression of the partner genes, i.e. MDS1/EVI1 in the t(3; 12), and CDX2 in the t(12; 13) (59, 60).…”

Myeloid- and lymphoid-specific breakpoint cluster regions in chromosome band 13q14 in acute leukemia

“…Whether these breakpoints in fact deregulate the same gene is not yet known. In some of the t(12;13) cases, it is likely that the consequence of these breakpoints was the production of an ETV6-13q14 fusion mRNA, as has been observed with other ETV6 translocations Wlodarska et al, 1996;Peeters et al, 1997a;1997b;Knezevich et al, 1998;Tosi et al, 1998;Chase et al, 1998).…”

“…Finally, the case of HD/MDS with t(12;13)(p12; q12) exhibited a break in the YAC that contains BRCA2, but apparently outside the PAC clone 214k23, containing BRCA2 itself, suggesting that a gene other than BRCA2 was the target for this translocation (unpublished observations). The lack of material in this case did not allow us to test the potential involvement of CDX2 at 13q12, a homeobox gene recently shown to be involved in a t(12;13)(p13;q12) (Chase et al, 1998).…”