Multiparameter flow cytometry may be used to detect minimal residual disease in acute leukemia because leukemic cells often display aberrant phenotypes when compared to normal cells. One limitation of this approach in B-precursor ALL is that leukemic phenotypes are often qualitatively similar to normal marrow B progenitors, though it has long been recognized that the latter show a predictable pattern of antigen expression with differentiation. In this study we used four-color flow cytometry to define precisely the patterns of normal antigen expression on a series of normal bone marrows using two different four-color combinations of antibodies: CD19-APC/CD45-perCP/CD20-PE/CD10-FITC; and CD19-APC/CD45-perCP/CD9-PE/CD34-FITC. A series of dual parameter displays were created in which normal B precursors occupied predictable regions. We then tested these antibody combinations on a series of 82 cases of B-precursor ALL and found that in 76/82 cases (93%) the first combination demonstrated an abnormal population on at least one of the dual parameter displays, and that 72/77 cases tested (94%) showed an abnormality with the second combination. When taken together, 81/82 cases (99%) showed an abnormality. When purified blasts were serially diluted into normal marrows we found a sensitivity of detection of 1 cell in 10 4 normal marrow cells provided sufficient CD19 + cells were acquired to visualize the abnormal population as a discrete cluster. Because the pattern of antigen expression in normals is very reproducible, it is possible to create a fixed set of geometrical regions to define the normal; this makes analysis of an unknown sample very straightforward. We conclude that our approach could be employed as a simple method for the detection of minimal residual disease in B-precursor ALL, and unlike many other methods should prove applicable to virtually all cases of this malignancy.

Acute promyelocytic leukemia (APL) is a relatively common form of acute myeloid leukemia (AML) that has an excellent prognosis. In contrast, secondary acute myeloid leukemias, including therapy-related AML and AML with myelodysplasia-related changes, have a relatively poor prognosis. We identified 9 cases of APL at our institution in which there was a history of chemotherapy, radiotherapy, chronic immunosuppression, or antecedent myelodysplastic syndrome. The clinical and pathologic findings in these cases of secondary APL were compared with the clinical and pathologic findings in cases of de novo APL. We found that secondary and de novo APL had abnormal promyelocytes with similar morphologic and immunophenotypic features, comparable cytogenetic findings, comparable rates of FMS-like tyrosine kinase mutations, and similar rates of recurrent disease and death. These data suggest that secondary APL is similar to de novo APL and, thus, should be considered distinct from other secondary acute myeloid neoplasms.

The topoisomerase (topo) II-directed agents etoposide, daunorubicin (DNR), and amsacrine (m-AMSA) are widely used in the treatment of acute myelogenous leukemia (AML). In the present study, multiple aspects of topo II-mediated drug action were examined in marrows from adult AML patients. Colony-forming assays revealed that the dose of etoposide, DNR, or m-AMSA required to diminish leukemic colony formation by 90% (LD90) varied over a greater than 20-fold range between different pretreatment marrows. Measurement of nuclear DNR accumulation in the absence and presence of quinidine revealed evidence of P-glycoprotein (Pgp) function in 8 of 82 samples at diagnosis and 5 of 36 samples at first relapse, but the largest quinidine-induced increment in DNR accumulation (< 2-fold) was too small to explain the variations in drug sensitivity. Restriction enzyme-based assays and sequencing of partial topo II alpha and topo II beta cDNAs from the most highly resistant specimens failed to demonstrate topo II gene mutations that could account for resistance. Western blotting of marrow samples containing greater than 80% blasts revealed that the content of the two topo II isoenzymes varied over a greater than 20-fold range, but did not correlate with drug sensitivity in vitro or in vivo. In addition, levels of topo II alpha and topo II beta in 46 of 47 clinical samples were lower than in human AML cell lines. Immunoperoxidase staining showed that these low topo II levels were accompanied by marked cell-to- cell heterogeneity, with topo II alpha being abundant in some blasts and diminished or absent from others. There was a trend toward increasing percentages of topo II alpha-positive cells in pretreatment marrows that contained more S-phase cells. Consistent with this observation, treatment of patients with granulocyte-macrophage colony- stimulating factor for 3 days before chemotherapy resulted in increases in topo II alpha-positive cells concomitant with increases in the number of cells traversing the cell cycle. These observations have implications for the regulation of topo II in AML, for the use of topo II-directed chemotherapy, and for future attempts to relate drug sensitivity to topo II levels in clinical material.

The topoisomerase (topo) II-directed agents etoposide, daunorubicin (DNR), and amsacrine (m-AMSA) are widely used in the treatment of acute myelogenous leukemia (AML). In the present study, multiple aspects of topo II-mediated drug action were examined in marrows from adult AML patients. Colony-forming assays revealed that the dose of etoposide, DNR, or m-AMSA required to diminish leukemic colony formation by 90% (LD90) varied over a greater than 20-fold range between different pretreatment marrows. Measurement of nuclear DNR accumulation in the absence and presence of quinidine revealed evidence of P-glycoprotein (Pgp) function in 8 of 82 samples at diagnosis and 5 of 36 samples at first relapse, but the largest quinidine-induced increment in DNR accumulation (< 2-fold) was too small to explain the variations in drug sensitivity. Restriction enzyme-based assays and sequencing of partial topo II alpha and topo II beta cDNAs from the most highly resistant specimens failed to demonstrate topo II gene mutations that could account for resistance. Western blotting of marrow samples containing greater than 80% blasts revealed that the content of the two topo II isoenzymes varied over a greater than 20-fold range, but did not correlate with drug sensitivity in vitro or in vivo. In addition, levels of topo II alpha and topo II beta in 46 of 47 clinical samples were lower than in human AML cell lines. Immunoperoxidase staining showed that these low topo II levels were accompanied by marked cell-to- cell heterogeneity, with topo II alpha being abundant in some blasts and diminished or absent from others. There was a trend toward increasing percentages of topo II alpha-positive cells in pretreatment marrows that contained more S-phase cells. Consistent with this observation, treatment of patients with granulocyte-macrophage colony- stimulating factor for 3 days before chemotherapy resulted in increases in topo II alpha-positive cells concomitant with increases in the number of cells traversing the cell cycle. These observations have implications for the regulation of topo II in AML, for the use of topo II-directed chemotherapy, and for future attempts to relate drug sensitivity to topo II levels in clinical material.

No abstract