Deletion 6q in Lymphatic Neoplasms

Among the most frequent aberrations in both acute lymphoblastic leukemia and aggressive as well as indolent lymphoma are deletions involving the long arm of chromosome 6 (90). In B-CLL, 6q deletions were found in 6% of the evaluable cases by means of chromosome banding, whereby bands 6q15 and 6q23 were most often affected (21). In an extensive analysis of various types of lymphoma, at least two independent deletion regions were identified, one in bands 6q21-q23 and

Fig. 4. Matrix CGH in B-CLL. Hybridization of DNA derived from a patient with a 13q14 deletion (labeled in green) vs human control DNA (labeled in red). Inset: PAC clone localized in band 13q14 exhibits a dominant red fluorescence signal after hybridization, indicating the deletion of this region (arrow) (89).

Fig. 4. Matrix CGH in B-CLL. Hybridization of DNA derived from a patient with a 13q14 deletion (labeled in green) vs human control DNA (labeled in red). Inset: PAC clone localized in band 13q14 exhibits a dominant red fluorescence signal after hybridization, indicating the deletion of this region (arrow) (89).

another in bands 6q25-q27 (91). Deletion 6q21-q23 was associated with the subgroup of lymphomas with lymphocytic differentiation, which may be considered as nonleukemic correlates to B-CLL (92).

Deletions in band 6q21 in B-CLL were also described in several more recent molecular genetic studies. Merup et al. (93) found 6q deletions in 6% of B-CLL cases, with a minimal deletion region in band 6q21. Gaidano et al. (94) observed 6q deletions in only 4 of100 B-CLL cases in band 6q27. In another extensive series, 285 B-CLL cases were examined with probes from bands 6q21 and 6q27 (95). The incidence of deletion 6q was 6%, and all deletions affected band 6q21, whereas band 6q27 was deleted in only one-third of the cases, and isolated 6q27 deletion was not observed in any case. In agreement with this, Zhang et al. (96) described a 4-5-Mb large minimal deleted region in band 6q21 in a series of various subtypes of lymphomas and leukemias. Although several candidate genes are located in the critical 6q21 region, it has not yet been possible to demonstrate a pathogenic role for one of these genes.

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