Prognostic factors in multiple myeloma

Introduction: Multiple myeloma is a malignant neoplasm originating in plasma cells. It is frequently associated with poor prognosis and characterized by the production of a monoclonal immunoglobulin called the M component. Multiple myeloma (MM) is connected to a numer of chromosomal abnormalities, in most cases IgH translocation with FGFR3, CCND1, CCND2, CCND3, c-MAF in early stages. Further chromosomal changes appear with the progression of the disease the most frequent of which are monoallelic deletion or monosomy of chromosome 13, trisomies of chromosome 8, 9, 15 and many others. It has also been revealed that some proteins controlling cell the cycle and apoptosis (p53, p16, FGFR3, cyclin D 1, 2, 3, Bcl-2, caspase 3, 8, 9) seem to play an important role during MM pathogenesis and progression. However, there are no reliable data on their prognostic significance in the various stages of disease (monoclonal gammapathy of uncertain significance – MGUS, smouldering MM and advanced MM). Therefore the aim of this pilot study was analysis of expression of these proteins in various stages of MM and potentially extend the panel of prognostic markers which allows differentiation of the abovementioned disease stages.

Materials and methods: Bone marrow from 35 patients treated by the same chemotherapy protocol (VAD) and autologous transplantation were used. Standard indirect immunohistochemistry on formalin fixed, paraffin-embedded sections was used for the detection of p53, p16, FGFR3, cyclin D 1, 2, 3, Bcl-2, caspase 3, 8, 9 using a high temperature epitope retrieval technique. Immunohistochemical staining was evaluated by a semi-quantitative method using a histoscore which is the multiplication of positivity by intensity of staining. Intensity of staining was scored as weak (1), moderate (2) or strong (3) while positivity of staining was assessed as percentage of tumour cells.

Results: Bone marrow samples of patients in advanced stages of MM showed high expression of Bcl-2 in tumor cells, in contrast to those in remission which showed weak or no positivity for Bcl-2. p53 and p16 were completely negative. Caspase 8 was negative in most cases. However, we detected a few caspase 8 positive cells in patients in remission. Caspase 9 was negative in biopsies taken before treatment but we detected several caspase 9 positive cells in patients after treatment.

Conclusions: Based on decreased BCl-2 expression in patients in remission, these preliminary data suggest that detection of low BCl-2 expression in bioptic samples of MM might be used as positive prognostic factor. Negativity of p16 can be explained by hypermethylation which leads to p16 deactivation. Mutation of p53 is probably infrequent in multiple myeloma but the mechanism of its impaired function needs further study.