RT-PCR amplicons in the plasma of multiple myeloma patients--clinical relevance and molecular pathology.

The occurrence of RNA (RT-PCR amplicons) in the plasma of 70 patients was quantified: 65 patients with multiple myeloma (MM), 3 with Waldenstrom's macroglobulinemia (WM), 2 with monoclonal gammopathy of undetermined significance (MGUS), and 50 from healthy controls. A 713nt amplicon occurred in 16/18 MM patients in relapse, 5/8 untreated patients, 2,3 WM patients and 1,2 MGUS plasmas. None of the initial specimens from 37 patients in remission nor the 50 healthy controls was positive. Homology between 4 sequenced 713nt amplicons was > 99.7% and matched (99.6%) a 704nt sequence of the flanking region of the peroxisome proliferator activator receptor gene, located on chromosome 22q11.2. A 255mer within the 713nt amplicon had a 90.2% homology with an AluSc consensus sequence. The occurrence of RNA amplicons seemed to serve as accurate surrogate markers for active disease in MM that provide new insights to the molecular pathogenesis of the disease.