AIM. Expression changes of D-type cyclins are thought to be an early event in the genesis of Multiple Myeloma and are associated with distinct cytogenetic aberrations. These aberrations appear with different percentages (“clonal” or “subclonal”) in a given patient. We assessed whether the height of CCND expression assessed by gene expression profiling and quantitative RT-PCR (qRT-PCR) correlates with the presence of clonal or subclonal aberrations of 11q13, t(11;14) and t(4;14).

PATIENTS AND METHODS. 128 newly diagnosed MM-patients (65 training (TG)/63 independent validation group (VG)) and 14 normal donors (ND) were included. Bone marrow aspirates were CD138-purified by activated magnetic cell sorting. RNA was in-vitro transcribed and hybridised to Affymetrix HG U133 A+B GeneChip (TG) and HG U133 2.0 plus array (VG). CCND1 and CCND2 expression was verified by real time RT-PCR and western blotting. iFISH was performed on purified MM-cells using probesets for chromosomes 1q21, 9q34, 11q23, 11q13, 13q14, 15q22, 17p13, 19q13, 22q11 and the translocations t(4;14) and t(11;14). Clonal aberrations were defined as being present in >60%, subclonal aberrations in 20 to 60% of MMC in a given patient. Expression data were gcrma normalised and a Kruskal-Wallis rank sum test used (Bioconductor).

RESULTS. 11q13+. CCND1 (208711_s_at, 208712_at) is significantly higher (p<0.0001), CCND2 (200953_s_at, 200951_s_at) significantly lower (p<0.0001) expressed in MMC harbouring clonal, compared to subclonal, or no gain of 11q13. t(11;14). CCND1 is significantly higher (p<0.0001), CCND2 significantly lower (p<0.0001) expressed in MMC harbouring clonal, compared to subclonal, or no t(11;14). t(4;14). CCND1 is significantly lower (p<0.0001), CCND2 significantly higher (p<0.0001) expressed in MMC harbouring clonal compared to subclonal, or no t(4;14). The expression of CCND3 (201700_at) is not significantly different between the 3 groups for all aberrations investigated. CCND2 and CCND3, but not CCND1 are expressed by normal plasma cells. Results have been verified by qRT-PCR (n=40) for CCND1 and CCND2. Expression of CCND1, CCND2 and CCND3 has been verified by western blotting on selected samples. The expression of CCND2 correlates with short EFS, but not if patients with t(4;14) are excluded. There is no significant difference in EFS for patients harbouring the respective aberrations in a clonal or subclonal pattern.

CONCLUSION.

  1. An additional copy of 11q13 or t(11;14) correlates with increased CCND1 and decreased CCND2 expression, a t(4;14) is associated with an increase of CCND2 and a decrease of CCND1 expression.

  2. In each case, the height of the CCND-expression is significantly different whether the respective aberration is clonal or subclonal.

  3. Thus, when interpreting expression data in the context of cytogenetic aberrations, it is important to consider if plasma cells carry a respective aberration in a subclonal/clonal pattern.

Topics:
chromosome abnormality, cyclins, multiple myeloma, cyclin d1, polymerase chain reaction, western blotting, bone marrow aspiration, cell separation, gene expression profiling, quantitative real-time polymerase chain reaction

Disclosure: No relevant conflicts of interest to declare.

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2006, The American Society of Hematology
2006
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