Adriamycin-inducible proteins associated with drug sensitivity in resistant immunoblastic B lymphoma cells

We have previously established an immunoblastic B lymphoma cell line, designated HOB1. This cell line is hypersensitive to a wide spectrum of chemotherapeutic agents. Two co-regulated polypeptides around 64 kDa (termed p64) were induced 10-30-fold in response to adriamycin and some other drugs at the IC₅₀ (the concentration inhibiting cell growth by 50%). These inducible proteins are localized as monomeric forms in the cytosolic fraction, with isoelectric points of pH = 6.2 (major protein) and pH = 7.0 (minor protein). An adriamycin-resistant cell line was established from HOB1 cells. The p64 inducibility was dramatically reduced in resistant HOB1 cells or unrelated cell lines which show phenotypic resistant to adriamycin toxicity. The loss of p64 inducibility in resistance cells is not due to a failure of cells to take up adriamycin since drug accumulation kinetics remained the same as in the parental cells.