Biclonal and hypodiploid multiple myeloma

Plasma cell DNA and RNA content was measured by flow cytometry of acridine orange-stained bone marrow cells from 72 untreated patients with multiple myeloma. Biclonal or hypodiploid DNA stemlines were identified in 10 patients, nine of whom had a low RNA content and did not have response to chemotherapy. Biclonal tumors often showed atypical myeloma protein changes with chemotherapy, suggesting that one clone was reduced whereas the other remained unchanged. These findings suggest a genetic basis for the resistance of low RNA tumors to chemotherapy.