Acute Myeloblastic Leukemia (AML) with Inv (16)(P13; Q22) and the Rare I Type CBF Β-MYH11 Transcript: Report of Two New Cases

Acute myeloblastic leukemia (AML) with inv (16)(p13;q22) and the rare I type CBF␤- MYH11 transcript: report of two new cases

TO THE EDITOR

Inv(16)(p13;q22) or t(16;16)(p13;q22) is one of the most frequent recurring chromosomal rearrangements detected in AML, generally observed in cases showing myelo-monocytic differentiation and hav- ing abnormalbone marrow eosinophils(M4 Eo AML in the French– American–British (FAB) classification1). This rearrangement results in the disruption of the myosin heavy chain (MYH) gene at 16p13 and the core binding factor ␤ (CBF␤) gene at 16q22.2 Untilnow, 10 differ- ent CBF␤-MYH11 transcripts have been reported3–6 (A to J), but the frequency of each transcript is variable: 85% for the A type, 5% for each of the D and E types, other rearrangements being rare. Recently, a standardized RT-PCR technique, considered to be able to identify all CBF␤-MYH11 transcripts, has been reported.6 From 1993 to 2001, we analyzed 40 cases of inv(16) by RT-PCR. All 40 cases showed CBF␤-MYH11 rearrangement, which was A type in 36 cases and D type in two cases. In this report, we present the remaining two cases of CBF␤-MYH11 rearrangement, with I type fusion transcript, corresponding to a breakpoint nt 399 (exon 4) of the CBF␤ gene and at nt 2134 (exon 13) of the MYH11gene. To date, to our knowledge, only one case of I type transcript had been reported.7 Patient 1 was a 53-year-old woman, with a 2 year history of breast cancer treated by localized radiotherapy and chemotherapy with six courses of 5 fluoro-uracile (5FU), epirubicin and cyclophosphamide. She was admitted in January 2001 for anemia and thrombocytopenia. She had no organomegaly. The hemoglobin (Hb) level was 6.2 g/dl, platelet count 28 × 109/l and white blood cells (WBC) count 5.5 × 109/l with 11% neutrophils, 44% lymphocytes, 35% monocytes, 4% myelemia and 6% blast cells. The bone marrow aspiration was normocellular with 34% blast cells, 14% monocytes, and 5% eosinophils without abnormality (Figure 1a, b). The myeloperoxidase (MPO) reaction was positive in 100% of blast cells. Prominent hypogranulation and hyposegmentation of the neutrophils was seen. Auer rods were observed in some of the blast cells (Figure 1a). The bone marrow karyotype showed 46, XX, inv(16)(p13;q22) in 15/20 metaphases examined (Figure 1c). A diagnosis of M2 AML with inv(16) was made. The patient reached complete remission with an anthracycline-Ara-C regimen and remained in complete remission at July 2001. Figure 1 Patient 1 (a, b, c, d) and patient 2 (e, f, g, h). Bone mar- Patient 2 was a 36-year-old man who presented in July 2000 with row stained by May–Gru¨nwald-Giensa. (a, b) Major myelodysplastic anemia and thrombocytopenia. He had no organomegaly. The Hb features and Auer rods (arrow) were seen for patient 1. (e) Major level was 4.2 g/dl, platelet count 20 × 109/land WBC 7.5 × 109/lwith dyseosinopoiesis (bold arrow) and (f) Auer rods (arrow) in neutrophils 18% neutrophils, 17% monocytes and 35% blast cells. The bone mar- for patient 2. Conventionalcytogenetic. (c) inv(16)(p13;q22) in patient 1. (g) inv(16)(p13;q22) and + 8 inv (16) in patient 2. Arrow shows the row aspiration was normocellular with 31% blast cells, 6% monocytes ␤ and 10% dystrophic eosinophils (Figure 1e). Many Auer rods were derivative chromosome 16. FISH analysis using CBF dual-color observed in blast cells but also in neutrophils (Figure 1f). Prominent probes. (d, h) In both patients a normalchromosome 16 detected by hypogranulation of neutrophils and dyserythropoiesis were found. yellow fusion signal and a derivative chromosome 16 (arrow) harbor- The MPO reaction was positive in 100% of blast cells. The bone ing a green signalon the longarm and a red signalon the short arm marrow karyotype showed 46, XY, inv(16)(p13;q22) in 9/20 meta- can be seen. phases and 47, XY, +8, inv(16)(p13;q22) in 6/20 metaphases examined (Figure 1g). A diagnosis of M2 AML with abnormaleosinophils CBF␤-MYH11 transcripts but positive for the ubiquitous Abelson and inv(16) was made. Complete remission was obtained with an controlgene. 8 anthracycline–Ara-C regimen and the patient remained in complete Because a new CBF␤-MYH11 transcript (I type) had been reported remission in July 2001. 7 ␤ by Dissing et al in a case of therapy-related AML with inv(16), we In both patients, inv(16) was confirmed by FISH using CBF dual- designed a new reverse primer on exon 13 of MYH11 gene (MYH13: color probes (Vysis, Downers Grove, IL, USA) (Figure 1d, h). Prelimi- 5′ gTT-CgT-TTC-gCT-CgT-CTT-CCA-gT-3′) in order to use the same nary study by RT-PCR using the technique described and rec- ␤ 6 forward primer (CBF A located on exon 4 of CBF ) and the otherwise ommended by the Biomed-1 concerted action was negative for the classical RT-PCR protocol recommended by the Biomed-1 concerted action.6 In both patients we obtained, using CBFA and MYH13 primers, a specific PCR product of 169 bp (Figure 2a) which after sequencing Correspondence: C Preudhomme, Laboratoire d’He´matologie A, CHU showed a breakpoint at nt 399 (exon 4) of the CBF␤ gene and at nt Lille, Hopital Calmette, Boulevard du Pr Leclercq, 59037 Lille France; 2134 (exon 13) of MYH11 gene (Figure 2b), as found by Dissing et Fax: 33-3 20.44.55.10 al7 in the I form transcript. Received 16 July 2001; accepted 7 September 2001 Interestingly, using these primers, amplification of the A type tran- Correspondence 151 recommended by the Biomed-1 concerted action for detection of CBF␤-MYH11 transcripts when this rearrangement is suspected.

Acknowledgements

We are indebted to D Talandier, R Coudenis, M Crepin and the Institut Fe´de´ratif de Recherche No. 22 (Lille, France) for their excellent techni- cal assistance and support in molecular biology. This work was sup- ported by CHU of Lille (PHRC 1997) The Ligue nationale contre le cancer (Comite´ du Nord et de l’Aisne) and the Fondation of France (Comite´ des leuce´mies)

N Grardel1,2 1Laboratoire d’He´matologie A, CHU C Roumier1,2 Lille, France; 2Inserm U524, IRCL, Lille, V Soenen1,2 France; 3Service de Ge´ne´tique me´dicale, JL Lai2,3 CHU Lille, France; 4Service I Plantier4 d’He´matologie Clinique, Hoˆpital de C Gheveart5 Roubaix, France; 5Laboratoire A Cosson1,2 d’He´matologie, Hoˆpital de Roubaix, P Fenaux2,6 France; 6Service des Maladies du sang, C Preudhomme1,2 CHU Lille, France

References

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Leukemia