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Terminal Deoxynucleotidyl Transferase Activity in Blastic Phase of Chronic Myelogenous Leukemia¹

Department of Experimental Therapeutics and Grace Cancer Drug Center [B. I. S. S., S. A. K.], and Departments of Immunology [J. M.], Medicine B [G. A. G.], and Medicine A [I. R.], Roswell Park Memorial Institute, New York Department of Health, Buffalo, New York 14263

Twenty-four Philadelphia chromosome-positive, chronic myelogenous leukemia patients were examined for DNA polymerase activity, terminal deoxynucleotidyl transferase (terminal transferase) activity, cell surface markers, morphology of peripheral blood blast cells, and response to therapy. All patients had high DNA polymerase ( and ß) activity which was comparable to that observed in blasts from acute leukemia patients. Twenty patients had low terminal transferase activity of 0.1 to 1.2 units/mg DNA [where 1 unit = 1 nmole Mn²⁺-deoxyguanosine triphosphate/hr on (dA)_12–18 initiator], one had "intermediate" activity of 2.4 units/mg DNA, and three had high activity of 11, 55, and 151 units/mg DNA. Blasts from the last three patients did not have morphological or cytochemical characteristics of lymphoblasts but had, instead, "myeloblastic" morphology and lacked B- and T-cell surface markers and thymus leukemia antigens; one of the patients examined for Greaves' non-T/non-B acute lymphoblastic leukemia antigens was negative. Although the patient with intermediate terminal transferase had a cell population consisting of "myeloblasts" and some cells suggestive of lymphoid origin, such a mixed population was also seen in many of the other 20 patients who had low terminal transferase activity. Moreover, one patient with a majority of lymphoblast-like cells and a hypodiploid karyotype not only had low terminal transferase activity but also did not respond to vincristine-prednisone therapy. Similarly, patients with high terminal transferase activity of 11 and 151 units showed no improvement with vincristine alone or in combination with other drugs, and one with an activity of 55 units did not respond to vincristine-prednisone. These results indicate that high terminal transferase activity or "lymphoid" appearance of cells in blastic phase of chronic myelogenous leukemia should not necessarily be considered as indicators of lymphoblasts or of therapy with agents useful in acute lymphoblastic leukemia.

¹ This work was supported by USPHS Grants CA-17140, CA-5834, and CA-14413 from the National Cancer Institute.

² To whom requests for reprints should be addressed.

Received 2/24/77. Accepted 7/13/77.