Multiple myeloma and bone marrow microenvironment - immunohistochemical study

Objective: Neoplastic milieu is an integral part of all malignant diseases including mul­tiple myeloma and plays variable role in their development, retention/adhesivity, resistency or sensitivity to a therapeutic approach, homing and also paraneoplastic manifestations. Relatively genetical stabile milieu may play more important role in a new specific molecular therapeutic approaches and therefore should be contextually studied with neoplastic cells as complex neoplastic tissues. The expressions of 11 proteins were analysed in consecutives multiple myeloma specimens.

Methods: Bone marrow trephine biopsy specimens with multiple myeloma were included in our prospective study. FFPE tissues were processed in app. 5microm sections and placed on charged slides. The indirect immunohistochemical staining was applicated after antigen retrieval and commercial primary antibodies were used for a detection of observed proteins. Standard secondary antibody and ABC method were included in visualisation. The expression of MIP1alfa, Annexin A2, TRAP, DKK-1, RANK, RANKL, OPG, Sclerotisin, Activin A, NFkappaB proteins (p50, p52, p65), p62 (sequestosome 1), and MMP9 was analysed.

Results: Bone marrow multiple myeloma specimens showed variable positivity of MIP1alfa in 61 % (cut-off point 20 %), Annexin A2 in 28 % (myeloma cells, cut-off point 30 %) and in 40 % (stromal cells, cut-off point 5 %), TRAP in 64 % (cut-off point 5 %), DKK-1 in 20 % (cut-off point 30 %), RANK in 44 % (cut-off point 30 %), RANKL in 66 %, OPG in 3,6 % (cut-off point 5 %), Sclerotisin in 100 % (cut-off point 90 %), Activin A in 36 % (cut-off point 30 %), cytoplasmic positivity of p50 in 24 %, p52 in 84 % (cut-off point 10 %), p62 in 100 % (cut-off point 10 %), p65 in 76 % (cut-off point 10 %) and positivity of MMP9 in 56 % (cut-off point 30 %).

Conclusion: Our preliminary study showed variable expression of observed proteins in mul­tiple myeloma and its bone marrow microenvironment that implicate different biological „stage", development and/or stromal plasticity in this complex hemato-oncological disease including myeloma cells itself and myeloma bone disease. The knowledge of engaged signaling pathways may suggest more specific or tailored therapeutic approches in a particular patient and also in his stabile or progressive multiple myeloma disease.

Supported by NT 14393.