Double t(1;7)(p36;p11) in a megakaryocytic crisis of chronic myelogenous leukemia with variant t(5;9;22)

Defining the sister rat mammary tumor cell lines HH-16 cl.2/1 and HH-16.cl.4 as an in vitro cell model for Erbb2

Cancer cell lines have been shown to be reliable tools in genetic studies of breast cancer, and the characterization of these lines indicates that they are good models for studying the biological mechanisms underlying this disease. Here, we describe the molecular cytogenetic/genetic characterization of two sister rat mammary tumor cell lines, HH-16 cl.2/1 and HH-16.cl.4, for the first time. Molecular cytogenetic analysis using rat and mouse chromosome paint probes and BAC/PAC clones allowed the characterization of clonal chromosome rearrangements; moreover, this strategy assisted in revealing detected breakpoint regions and complex chromosome rearrangements. This comprehensive cytogenetic analysis revealed an increase in the number of copies of the Mycn and Erbb2 genes in the investigated cell lines. To analyze its possible correlation with expression changes, relative RNA expression was assessed by real-time reverse transcription quantitative PCR and RNA FISH. Erbb2 was found to be overexpressed in HH-16.cl.4, but not in the sister cell line HH-16 cl.2/1, even though these lines share the same initial genetic environment. Moreover, the relative expression of Erbb2 decreased after global genome demethylation in the HH-16.cl.4 cell line. As these cell lines are commercially available and have been used in previous studies, the present detailed characterization improves their value as an in vitro cell model. We believe that the development of appropriate in vitro cell models for breast cancer is of crucial importance for revealing the genetic and cellular pathways underlying this neoplasy and for employing them as experimental tools to assist in the generation of new biotherapies.

t(3;9;22) 3-way chromosome translocation in chronic myeloid leukemia is associated with poor prognosis

Chronic myelogenous leukemia (CML) is genetically characterized by the reciprocal translocation of chromosome 9 and 22. Around 5-8% of CML develop complex variant Ph translocations involving one or more chromosomal regions besides 9 and 22. Chromosome 3 is not frequently involved in complex translocations in CML. We report in this study a case of CML displaying a t(3;9;22) 3-way translocation. A review of the literature appears to indicate that CML patients with this translocation tend to have an aggressive course and poor outcome. Additional 3-way chromosome translocations associated with CML are also reviewed.

The unexplored 5q13 locus: a role in hematopoietic malignancies

Deletions and translocations at 5q13 point out a locus involved in the development of acute myeloblastic leukemia (AML) and myelodysplastic syndromes (MDS) as well as other neoplasms. The chromosomal rearrangements of 5q13 are well documented, but have not been a primary focus of research. In this report, we provide evidence for a novel critical locus at 5q13.3, encoding gene(s) which may be disrupted by chromosomal translocations or deletions. Rare cases of myeloid neoplasms with t(5q13) as the sole chromosomal anomaly argue for a gene which gives rise to fusion proteins. Our preliminary studies have localized one of the critical genes to a <3 Mb. interval between the polymorphic markers AFMB347yf9 and GATAP18104 at the band 5q13.3. Other results also suggest that the 5q 13.3 locus may span a fragile site which undergoes unbalanced translocations and interstitial deletions accompanied by loss of significant segments of chromosome 5. Molecular reagents generated by the human genome mapping and sequencing initiative will allow us to characterize the critical genes at 5q13.3 and facilitate genotypic analysis of AML and MDS.