CDNA Microarray and Comparative Genomic Hybridization

Other new molecular techniques also hold promise for the future. Expression profiling, both DNA microarray (167) and protein expression profiles (proteomics) (168) has yielded some interesting results for a limited number of CLL patients. In a pilot study, Voss et al. (168) determined that a patient population with a decreased survival time showed changed levels of redox enzymes, heat shock protein 27, and protein disulfide isomerase. Stratowa et al. (167) showed that low expression levels of IL-1ß and IL-8 correlated with poor survival, higher Rai clinical stage, and 11q deletions.

Comparative genomic hybridization studies of CLL have been reported from three laboratories. Bentz et al. (169) note that 13q14 deletions in CLL can sometimes be too small to be detected with present diagnostic thresholds. Karhu et al. (170) confirmed the consistent loss of the 11q14-24 region in a subset of CLL patients. Odero et al. (171) compared comparative genomic hybridization with amplotyping using arbitrarily primed PCR (AP-PCR) and found that AP-PCR was more sensitive in the detection of small 13q14 deletions.

Using genomic-scale gene expression profiling, Rosenwald et al. (172) have shown that CLL patients share a characteristic gene expression signature in their leukemic cells. Although they were unable to find two separate and distinct subgroups, they did confirm the relationship between unmutated and mutated Ig genes and clinical course. They were able to show that patients with germline, unmutated Ig genes compared with patients with mutated Ig genes, had a median time to treatment of 28 and 95 mo, respectively (Fig. 45). They interpret this to mean that CLL consists of a single disorder rather than two distinct diseases and suggest that their data support a common cell of origin and or a common mechanism of neoplastic transformation. Interestingly, they were able to show that the unmutated subtype genes were associated with B-cell activation

Fig. 42. Probability of survival from the date of diagnosis among the patients in the five genetic categories. The median survival times for the groups with 17p deletion, 11q deletion, 12q trisomy, normal karyotype, and 13q deletion as the sole abnormality were 32, 79, 114, 111, and 133 mo, respectively. Twenty-five patients with various other chromosomal abnormalities were not included in the analysis. (From ref. 144, Dohner et al., 2000, Fig. 1. Copyright © 2000 Massachusetts Medical Society. All rights reserved.)

Fig. 42. Probability of survival from the date of diagnosis among the patients in the five genetic categories. The median survival times for the groups with 17p deletion, 11q deletion, 12q trisomy, normal karyotype, and 13q deletion as the sole abnormality were 32, 79, 114, 111, and 133 mo, respectively. Twenty-five patients with various other chromosomal abnormalities were not included in the analysis. (From ref. 144, Dohner et al., 2000, Fig. 1. Copyright © 2000 Massachusetts Medical Society. All rights reserved.)

(Fig. 46). They interpret this finding to suggest that Ig-unmutated CLL cells may be continuously stimulated in vivo via antigen through the BCR. Alternatively, the malignant transformation activates the same B-cell activation signaling process independently in the absence of antigen stimulation. Finally, for the molecular differential diagnosis of CLL, i.e., the two Ig gene variants of unmutated and mutated CLL, they offer a simpler diagnostic test (PT-PCR) for one to three genes rather than the DNA sequence analysis of Ig gene variable regions. One of these genes, ZAP70, is being tested.

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