Expression of Cyclin D1 as prognostic factor at different stages of multiple mieloma

The aim of the study was to find out is there any correlation between expression of Cyclin D1 protein in plasma cells and clinical stage by Salmon – Durie (S-D) and β-2 microglobulin level (B2MG) in cases of multiple myeloma (MM).

Materials and methods.
70 patients with primary diagnosed MM from 2011 to 2014 in Riga Eastern Clinical University Hospital’s Hematology center were enrolled in this study. Bone marrow biopsies were routinely stained with haematoxylin-eosin, Gordon-Sweet's reticulin silver and immunostained with Cyclin D1. Statistical analyses were performed using Graph Pad Prism 5 software.

Results.
MM clinical stages according to S-D clinical staging system were: I A, B (20%, n =14) : II A, B (43%, n =30), III A, B (73%, n =26). Patients mean age was (Mean ±SD) 63.61 ± 10.81 years.
A positive correlation by Spearman test was found between Cyclin D1 expression and S-D clinical staging system (rs = +0.363; p = 0.002) and B2MG level (rs = +0.2623; p = +0.0487).
Cyclin D1 positive patients group had statistically significant higher B2MG level (5.174 ± 4.599 mg / dl) than those of the Cyclin D1 negative group (3.204 ± 1.909 mg / dl) (p = 0.0462, unpaired t-test).
Cyclin D1 positive patients group showed late stages of multiple myeloma by S-D clinical staging system than those of the Cyclin D1 negative patient group (p = 0.0026, Mann Whitney U test). Cyclin D1 positive patients group accordingly S-D staging ratio was: I A (5%, n = 2); II A, B (46%, n = 17) ; III A, B (49%, n = 18) but Cyclin D1 negative patients groups staging ratio was: I A, B (36.5%, n = 12); II A, B (39.5%, n = 13); III A, B (24%, n = 8).

Conclusions.
Our study demonstrated that expression of Cyclin D1 correlated with late stages of MM and this marker is indicator of poorer prognosis for patients. Cyclin D1 positive cases showed higher levels of serum B2MG, this could prove expression of Cyclin D1 as negative predictive factor.