Cellular biology of acute myelogenous leukemia.

The acute myelogenous leukemias (AMLs) are a heterogeneous group of disorders with diverse morphologic, histochemical, and antigenic characteristics. In this article, we discuss the heterogeneous nature of AML with regard to its cellular level of origin, cell surface antigen expression, and hematopoietic growth factor responsiveness.

Further evidence for the existence of a clonal Ph-negative stage in some cases of Ph-positive chronic myelocytic leukemia.

The Ph chromosome abnormality is involved in the pathogenesis of almost all patients with chronic myelocytic leukemia (CML). Previous studies on the B-lymphoid cell lineage in two patients with Ph-positive CML suggest that there may also be a clonal Ph-negative stage in CML and that the Ph-positive stage arises by subclonal expansion. To determine whether this is a frequent or a rare occurrence, 14 additional glucose-6-phosphate dehydrogenase (G6PD)-heterozygous patients with CML were studied. In five of these patients there was a statistically significant excess of Ph-negative B-lymphoid cell lines expressing the same G6PD type expressed in the corresponding CML clone. In no case was an excess of B-lymphoid lines expressing the opposite G6PD type recovered. These data provide further evidence that in some patients the Ph chromosome arises in a pluripotent stem cell from a pre-existing Ph-negative clone that enjoys a growth advantage.

Intrafamilial phenotypic expression of autosomal dominant polycystic kidney disease.

It has been suggested that the clinical expression of autosomal dominant polycystic kidney disease (ADPKD) is uniform among individuals of a given family. To test this hypothesis, intrafamilial variations in ages at onset of first symptoms, types of first symptoms, serum creatinine concentrations, and renal sizes were evaluated in 131 patients with ADPKD from 36 unrelated families. These parameters were compared in younger and older affected relatives in the same family at a single time, due to difficulties of following them longitudinally. Because the natural course of the disease is to progress with age, it was presumed that disease progression in a given family was nonuniform if older individuals had lower serum creatinine concentrations, and/or smaller kidneys than their affected younger relatives, or if relatives of similar ages had different serum creatinine concentrations and/or kidney sizes. Nonuniform progression was suggested in 38% of affected relatives by serum creatinine concentrations and in 53% by kidney sizes. Ages at onset of first symptoms and types of first symptoms were also different in patients from the same families. These data indicate that phenotypic expression of ADPKD may differ considerably among patients who belong to the same families.

Evidence for clonal development of Wilms' tumor.

To assess the clonality of Wilms' tumor, glucose-6-phosphate dehydrogenase (G6PD) enzymes were studied in normal and tumor tissue from 11 black girls who were heterozygous for G6PD. Normal tissues expressed both A and B type G6PD, whereas only a single G6PD enzyme was found in all tumor specimens. These data support the clonal nature of Wilms' tumor. In the one patient with bilateral disease, type B G6PD was found in both a recurrence and a subsequent tumor in the contralateral kidney. This finding is consistent with either the chance occurrence of the same G6PD in independent tumors or persistence of the original malignant clone. Another patient, who presented with the nephroblastomatosis complex (a precursor of Wilms' tumor), also had only type B enzyme detected. Further studies in patients with bilateral disease or the nephroblastomatosis complex, including the use of molecular biologic probes, are needed to test the hypothesis that Wilms' tumor in these cases arises from a somatic mutation as a second event in persons with an underlying genetic alteration.

Evidence that weak promotion of carcinogen-initiated cells prevents their progression to malignancy.

Repeated promotion of 7,12-dimethylbenz[alpha]anthracene-initiated cells in mouse skin with 12-O-tetradecanoylphorbol-13-acetate (TPA) induces them to grow as premalignant skin papillomas and some of these subsequently progress to carcinomas. In this study, we demonstrate that this TPA-induced progression of initiated cells to papillomas and carcinomas could be prevented by exposing them previously to weak promoting regimens or to agents that mimic TPA activity.

Increased sensitivity to two-stage skin carcinogenesis of mice heterozygous for the repeated epilation mutation (Er).

Mice heterozygous for repeated epilation mutation (Er) have cutaneous abnormalities that result in repeated loss of hair. Skin papillomas and carcinomas occur spontaneously in such Er/+ mice. BALB/c mice are generally resistant to induced skin cancers. We investigated whether Er/+ heterozygous mice of BALB/c genetic background exhibit increased susceptibility to spontaneous and induced skin tumors. Although none of the Er/+ CXB(N5) mice spontaneously developed skin tumors, they exhibited increased sensitivity to the development of skin papillomas induced by an initiation-promotion regimen. Er/+ mice developed papillomas after 20 micrograms DMBA initiation in the absence of TPA promotion, but the same dose of DMBA was subtumorigenic in +/+ (sibling) mice. Although 15 weeks of TPA promotion resulted in similar tumor susceptibilities, tumor latencies and tumor frequencies in the 2 groups of initiated mice, the papillomas were qualitatively different. Er/+ mice developed more papillomas of the delayed promoter-independent type, which occur after termination of promotion. In contrast, +/+ mice developed more promoter-dependent papillomas, which regress after termination of promotion. Therefore Er/+ mice had a significantly higher number of papillomas than +/+ mice at the termination of the experiment. These results suggest that Er-mutation-induced skin defects not only lead to the repeated loss of hair, but also influence the mode of development of skin papillomas from carcinogen-initiated cells.

Clinical manifestations of autosomal dominant polycystic kidney disease in patients older than 50 years.

The purpose of this study was to define manifestations of autosomal dominant polycystic kidney disease (ADPKD) in older patients with the disease. Fifty-seven subjects age 50 years or more, who were at risk for having inherited the gene for ADPKD, were evaluated for renal size, hypertension, back and abdominal pain, symptoms consistent with urinary tract infection (UTI), hematuria, end-stage renal failure, and liver cysts. The diagnosis of ADPKD was made in 32 of the 57 at-risk subjects (56%). At the time of study, only one patient with the disease was asymptomatic and normotensive and denied any previous symptoms suggestive of the disease. Clinical manifestations of ADPKD in the 31 symptomatic patients were hypertension (69%), a history of back and abdominal pain (47%), symptoms consistent with UTI (41%), hematuria (31%), and end-stage renal failure (47%). Liver cysts were found in 44% of patients. No statistically significant differences in the frequency of any manifestations of ADPKD between men and women were found, although the frequency of symptoms consistent with UTI tended to be higher in women (53%) than in men (27%). Most patients developed symptoms after the age of 40 years. Notably, 31% of the older patients with ADPKD had normal serum creatinine levels. Thus, older subjects with kidney cysts who are at risk to have inherited the gene for ADPKD, should be considered to have the disease even in the presence of well-preserved kidney function. This observation may play an important role in assessing the prognosis of older subjects at risk who have bilateral renal cysts and in genetic counseling of their relatives.

Stem cell origin of human myeloid blood cell neoplasms.

Studies with G6PD and molecular probes indicate that the myeloid leukemias and the chronic myeloproliferative disorders are clonal diseases. The G6PD data indicate that chronic myelogenous leukemia, polycythemia vera and essential thrombocythemia involve stem cells pluripotent for granulocytes, erythrocytes, megakaryocytes and lymphocytes. Agnogenic myeloid metaplasia is also a clonal disease that involves multipotent hematopoietic stem cells. However, myelofibrosis, the predominant clinical manifestation, occurs secondarily and is not a component of the abnormal clonal proliferation. Acute nonlymphocytic leukemia is a clonal disease, but G6PD studies suggest that there are at least two forms of this leukemia. In one type of ANL, the involved stem cells exhibit pluripotent differentiative expression. In another type of ANL, differentiative expression is largely restricted to the granulocytic pathway. The heterogeneity of ANL has both clinical and pathogenetic implications.

The Use of Genetic Markers in Studies of Myeloid Neoplasia.

We have focused this review on some aspects of the use of genetic markers in analyses of cell lineage relationships in myeloid leukemia relying predominantly on studies of women heterozygous for G6PD. We have emphasized the advantages of using markers which are extrinsic to the clonal process and if possible, combining them with markers intrinsic to the neoplastic clone. It is likely that additional intrinsic markers will become available as the multiple genetic defects leading to neoplastic transformation are elucidated. However, it is probable that these will prove to be markers of subclonal evolution and only by relying on cell markers that antedate the occurrence of neoplasia will it be possible to fully appreciate its multistep nature.

Clonal analysis of childhood acute lymphoblastic leukemia with "cytogenetically independent" cell populations.

Acute lymphoblastic leukemia (ALL) is generally regarded as a clonal disease in which a single abnormal progenitor cell gives rise to neoplastic progeny. Five of 463 cases of childhood ALL with adequately banded leukemic cells were found to have two cytogenetically independent cell populations. In addition, two of the four cases tested had more than two rearranged immunoglobulin genes and (or) T cell receptor genes. To investigate the clonality of these unusual leukemias, we examined the neoplastic cells for X-linked markers extrinsic to the disease. Leukemic cells from each of the three patients heterozygous for an X-linked, restriction fragment length polymorphism showed a single active parental allele, suggesting that both apparently independent cell populations developed from a common progenitor. These cases provide evidence that leukemogenesis involves a multistep process of mutation and suggest that karyotypic abnormalities may be a late event of malignant transformation.

Host origin of marrow stromal cells obtained from marrow transplant recipients and transformed in vitro by simian virus-40.

We evaluated the karyotypes of marrow-derived stromal cell lines established by simian virus-40 (SV-40) transformation of long-term cultures from four men who received marrow transplants from women donors. In all cases a normal female karyotype was found in marrow cells. In contrast, a Y chromosome was identified in metaphase cells from the stromal lines, suggesting that following successful marrow transplantation, cells in the marrow microenvironment susceptible to SV-40 transformation remain host in origin.

Evidence for clonal development and stem cell origin of M7 megakaryocytic leukemia.

Previous studies have shown that acute nonlymphocytic leukemias are clonal diseases in which there is heterogeneity in the pattern of stem cell differentiative expression. To determine whether M7 megakaryocytic leukemia is a clonal disease and to evaluate the differentiative expression of the cells involved by the leukemia we studied a patient with megakaryocytic leukemia who was heterozygous for the X-chromosome-linked glucose-6-phosphate dehydrogenase (G6PD). The diagnosis of megakaryocytic leukemia was based on results obtained with the immunogold method and ultrastructural studies with the monoclonal anti-Gplla/IIIb antibody, 10E5. Direct testing of blood and marrow mononuclear cells and blood platelets demonstrated only A-type G6PD, whereas skin exhibited both B and A enzymes. The results indicate that the megakaryocytic leukemia in this patient was clonal at the time of study. To determine the differentiative expression of the stem cells, granulocyte/macrophage colony forming units and erythroid burst forming units were cultured and the resultant colonies were tested for G6PD. The results indicate that the stem cells involved by the leukemia exhibited differentiative expression multipotent for the megakaryocytic and granulocytic pathways, but no definitive conclusion could be made regarding the erythroid lineage.

Influence of dose of initiator on two-stage skin carcinogenesis in BALB/c mice with cellular mosaicism.

We examined the effects of initiation with different doses of 7,12-dimethylbenz[a]anthracene (DMBA) on two-stage skin carcinogenesis in BALB/c mice. The induction of skin papillomas and their sequential tumor progression were followed by determination of locations of the tumors on the back of each mouse, by histological evaluation and by determining the phosphoglycerate kinase (PGK) phenotypes of neoplasms. Three doses of DMBA were tested, 20.0, 2.0 and 0.2 micrograms. Lowering the dose of DMBA initiation prolonged tumor latency and reduced tumor susceptibility and frequency. All of the papillomas that developed with the lowest dose of DMBA initiation were found to be clonal by PGK analysis and each of them was promoter dependent; termination of TPA promotion led to its regression. The 0.2-micrograms DMBA initiation dose also reduced to zero the delayed promoter-independent papillomas and the frequency of papillomas changing their PGK phenotype during tumor progression. Thus, these studies provide evidence that the carcinogen not only causes initiation in mouse skin epidermal cells but also that the dose of carcinogen strongly influences the mode of growth of the initiated cells to papillomas and the progression of these tumors.

The effect of long-term marrow culture on the origin of colony-forming cells in acute myeloblastic leukemia: studies of two patients heterozygous for glucose-6-phosphate dehydrogenase.

Long-term marrow cultures (LTMCs) provide a selective growth advantage for cytogenetically normal cells in patients with acute and chronic myeloid leukemias. In the present study, LTMCs were established from two patients with newly diagnosed acute myeloid leukemia (AML) who were heterozygous for the X-linked enzyme glucose-6-phosphate dehydrogenase (G6PD). Initially only leukemic clusters grew from cells plated in semisolid medium, but after 1 or more weeks in LTMC, morphologically normal granulocyte-macrophage colonies were detected. Nonetheless, in one of the patients, more than 80% of these colonies expressed the G6PD type observed in the leukemic blast cells, indicating a probable neoplastic derivation for many of them. In the second patient, colonies cultured during the first 3 weeks of the LTMC were predominantly derived from clonal progenitors, whereas after week 4 the colonies were derived from normal stem cells. Colonies derived from clonal or normal stem cells were not morphologically distinguishable. These data support the conclusion that LTMC has a selective anti-leukemic effect on marrow cells from some patients. However, normalization of colony growth is by itself not a sufficient criterion for determination of whether committed progenitor cells from patients with AML are derived from normal or leukemic stem cells.

Sequential studies of skin tumorigenesis in PGK mosaic mice: the effect of repeated exposure to a carcinogen on regressed mouse skin papillomas.

Most mouse skin papillomas developing after 7,12-dimethylbenz[a]anthracene (DMBA) initiation followed by repeated 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion are promoter-dependent; termination of promotion results in their regression. Previous evidence, from mapping the locations of papillomas and using the X-chromosome-linked phosphoglycerate kinase cell markers, shows that regression of promoter-dependent papillomas is permanent. Exposure to another course of TPA promotion was found not to induce regeneration in the regressed papillomas. To determine whether repeated exposure to a carcinogen causes regeneration of regressed papillomas, the effects of weekly applications of low doses of DMBA were tested. The results reported here indicate that regressed promoter-dependent papillomas do not regenerate when exposed repeatedly to DMBA. However, the treatment with DMBA induced many new tumors most of which were promoter-independent papillomas or malignant carcinomas. These findings provide further support for the conclusion that termination of promotion leads to permanent regression of most promoter-dependent mouse skin papillomas.