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Effects of Phytohemagglutinin and Isoproterenol on DNA Synthesis in Lymphocytes from Normal Donors and Patients with Chronic Lymphocytic Leukemia¹

Department of Biochemistry, University of Oklahoma, School of Medicine, and Biochemistry Section, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104

DNA synthesis was studied in both normal and leukemic lymphocytes as a function of stimulation with phytohemagglutinin (PHA). In normal lymphocytes the onset of DNA synthesis occurred at approximately 24 hr and maximum DNA synthesis was observed 3 to 4 days after stimulation. Within 6 days, the extent of DNA synthesis was reduced to approximately 10% of that observed after 3 to 4 days. In PHA-stimulated lymphocytes obtained from patients with chronic lymphocytic leukemia, the extent of DNA synthesis was comparable to that observed in stimulated normal lymphocytes; however, in contrast, the time of maximum DNA synthesis was later than in normal cells. Depending upon the white blood cell count of the patient, maximum activity occurred from 5 to 7 days after stimulation. Lymphocytes from patients with low to medium white blood cell counts (10,000 to 65,000/cu mm) exhibited maximum DNA synthesis from 5 to 6 days after PHA stimulation, while lymphocytes from patients with high white blood cell counts (>65,000/cu mm) reached a peak at 7 days.

Treatment of cultured cells with isoproterenol (8.0 x 10^-5 M) inhibited PHA-stimulated DNA synthesis in chronic lymphocytic leukemia lymphocytes, but not in normal lymphocytes. Furthermore, the fraction of lymphocytes from a leukemic patient which was insensitive to isoproterenol responded to PHA addition in the same manner as the lymphocytes from normal donors. These results suggest that the peripheral leukocytes obtained from chronic lymphocytic leukemia patients consist of populations of both normal and leukemic lymphocytes.

¹ This work was supported by Grant CA-10683 from the National Cancer Institute, NIH, USPHS, and by Institutional Grant IN-50 from the American Cancer Society. A preliminary account of this work has appeared (1).

Received 5/ 5/69. Accepted 8/11/69.