Clinical implication of centrosome amplification and expression of centrosomal functional genes in multiple myeloma

Abstract

Background: Multiple myeloma (MM) is a low proliferative tumor of postgerminal center plasma cell (PC). Centrosome amplification (CA) is supposed to be one of the mechanisms leading to chromosomal instability. Also, CA is associated with deregulation of cell cycle, mitosis, DNA repair and proliferation. The aim of our study was to evaluate the prognostic significance and possible role of CA in pathogenesis and analysis of mitotic genes as mitotic disruption markers.

Design and methods: A total of 173 patients were evaluated for this study. CD138+ cells were separated by MACS. Immunofluorescent labeling of centrin was used for evaluation of centrosome amplification in PCs. Interphase FISH with cytoplasmic immunoglobulin light chain staining (cIg FISH) and qRT-PCR were performed on PCs.

Results: Based on the immunofluorescent staining results, all patients were divided into two groups: CA positive (38.2%) and CA negative (61.8%). Among the newly diagnosed patients, worse overall survival was indicated in the CA negative group (44/74) in comparison to the CA positive group (30/74) (P = 0.019). Gene expression was significantly down-regulated in the CA positive group in comparison to CA negative in the following genes: AURKB, PLK4, TUBG1 (P < 0.05). Gene expression was significantly down-regulated in newly diagnosed in comparison to relapsed patients in the following genes: AURKA, AURKB, CCNB1, CCNB2, CETN2, HMMR, PLK4, PCNT, and TACC3 (P < 0.05).

Conclusions: Our findings indicate better prognosis for CA positive newly diagnosed patients. Considering revealed clinical and gene expression heterogeneity between CA negative and CA positive patients, there is a possibility to characterize centrosome amplification as a notable event in multiple myeloma pathogenesis.

Figure 1

Different pattern of centrin staining. The isotypic PCs were identified by cytoplasmic or light chain antibody conjugated with AMCA (cIg, blue), and centrin was stained with anticentrin1/2 conjugated with TR. The cells were visualized using Olympus BX-61 fluorescent microscope with Vosskuhler 1300D digital camera and LUCIA-KARYO/FISH/CGH digital analysis system (Laboratory Imaging, s.r.o, Prague, Czech Republic). (For interpretation of the references to color in this figure (A) Two signals – cells with 1–4 signals were considered to have normal centrosome. (B) Abnormal PCs with centrosome amplification (>4 fluorescence signals of centrin).

Figure 2

Overall survival of CA groups of newly diagnosed MM patients. Kaplan-Meier curves for OS of newly diagnosed MM patients (n = 74). CA positive patients (n = 30) had significantly better survival when compared to CA negative patients (n = 44) subgroups (P = 0.019).

Figure 3

Gene expressions in CA groups of newly diagnosed MM patients. The expression levels of selected genes were compared in CA positive and CA negative groups of newly diagnosed MM patients. Significant differences (P < 0.05) in relative quantification coefficient R (abscissa axis) are marked with an asterisk.

Figure 4

Gene expressions in newly diagnosed and relapsed MM patients. The expression levels of selected genes were compared in newly diagnosed and relapsed MM patients. Significant differences (P < 0.05) in relative quantification coefficient R (abscissa axis) are marked with an asterisk.

Figure 5

Gene expressions in hyperdiploid and non-hyperploid MM patients. The expression levels of selected genes were compared in hyperdiploid and non-hyperploid MM patients. Significant differences (P < 0.05) in relative quantification coefficient R (abscissa axis) are marked with an asterisk.