TAL1 gene deregulation is frequent in T‐cell acute lymphoblastic leukemia (T‐ALL) and can result from translocations involving 1p32 or, more frequently, from a cytogenetically undetectable interstitial deletion of chromosome 1. This study presents a case of T‐ALL with a t(1;5)(p32;q31) involving TAL1, in which the breakpoint occurs approximately 10 kbp 5′ to the gene and leads to transcriptional activation and synthesis of a TAL1 protein, and extends the spectrum of recognized TAL1 gene translocations associated with T‐ALL. Genes Chromosomes Cancer 23:36–43, 1998. © 1998 Wiley‐Liss, Inc.

The colony-forming unit-granulocyte-macrophage (CFU-GM) assay, an essential test in evaluation of the quality of autologous grafts of hematopoietic stem cells, has yet to be standardized. With this aim in view, we carried out a multicenter study of five commercially available culture kits for CFU-GM evaluation. Four kits were methylcellulose-based (H4431, H4434, H4435, StemBio1d) and one was collagen-based (EasyClone-Multi). Using fresh and frozen samples of PBSC grafts, we compared CFU-GM and burst-forming unit-erythrocytes (BFU-E) growth using the EasyClone kit to each of the methylcellulose kits. BFU-E and CFU-GM clonogenicity of both fresh and frozen PBSC was clearly inferior with the H4431 kit, which provides conditioned medium only. CFU-GM numbers obtained with fresh and frozen PBSC samples were significantly higher with the EasyClone kit than with the H4434 and StemBio kits. BFU-E numbers were also higher with the EasyClone kit, but only when colonies were scored after May-Grünwald-Giemsa (MGG) staining. Finally, although the H4435 kit provides higher doses of recombinant cytokines than the EasyClone kit, CFU-GM and BFU-E numbers obtained for fresh or frozen PBSC with both kits were similar. In addition, CFU-GM and BFU-E numbers correlated well with CD34+ cell numbers for all five kits for both fresh and frozen PBSC. In summary, our study shows that the EasyClone-Multi and H4435 kits provide the best CFU-GM growth. The collagen-based EasyClone kit has the additional advantage of allowing gel staining and storage, which facilitates colony identification and, more importantly, makes gel exchange possible for standardization of the CFU-GM assay.

We report a case of chronic myelomonocytic leukaemia (CMML), which transformed first into acute myeloblastic leukaemia (AML) and then into acute lymphoblastic leukaemia (ALL). In the AML and ALL phases, chromosome analysis showed a classic Philadelphia chromosome (Ph) t(9;22)(q34;q11). Molecular studies showed breakpoint cluster region rearrangement between exons e1 and a2 compatible with a p190bcr/abl breakpoint as observed in Ph‐positive lymphoblastic acute leukaemia. The minor (m‐bcr) rearrangement was also detected during complete remission. This observation supports a multistep pathogenesis of leukaemias, and that the p190bcr/abl breakpoint may influence the course of the disease.

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