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Updated: Jun 22, 2026
Interphase Fluorescence in situ Hybridization of Bone Marrow Smears of Multiple Myeloma
Published on: April 15, 2022
IGFBP-1 protease activity and IGFBP-1 fragments in a patient with multiple myeloma
Katrin Brandt1, Jing Wang, Kerstin Lundell
1Department of Molecular Medicine and Surgery, Karolinska Institutet, L1:01 Karolinska University Hospital Solna, SE-171 76 Stockholm, Sweden.
Objective:
Cleavage of IGFBPs by proteases results in IGFBP fragments that have altered IGF-binding affinity, and IGF-independent roles. We have previously purified a specific IGFBP-1 protease activity from the urine of an individual with multiple myeloma and dermatitis. The aim of this study was to determine whether IGFBP-1 protease activity and/or IGFBP-1 fragments were present in the circulation of this patient.
Methods:
The size of immunoreactive IGFBP-1 in serum samples was determined after Superose 12 chromatography. Intact IGFBP-1 and IGFBP-1 fragments were characterized in four RIAs and after SDS-PAGE.
Results:
Specific proteolysis of IGFBP-1 generated an N-terminal fragment (IGFBP-1(1-130)) with a predicted molecular mass of 13kDa but an apparent mass of 21kDa on SDS-PAGE. A C-terminal fragment (IGFBP-1(131-234)) produced in vitro migrated at 11.4kDa, close to its predicted size. However a C-terminal fragment of cleaved IGFBP-1 (IGFBP-1(142-234)) migrated at 14kDa on SDS-PAGE. Serum from the patient inhibited IGFBP-1 protease activity. Immunoreactive IGFBP-1 in patient serum was present at molecular masses consistent with IGFBP-1 fragments, in addition to intact IGFBP-1.
Conclusions:
Specific cleavage of IGFBP-1 occurs at the tissue level and not in the circulation in a patient with multiple myeloma and dermatitis. The fragments that are generated may have endocrine roles.
