Epidemiology of Huntington disease: first post-HTT gene analysis of prevalence in Italy.

Huntington disease (HD) prevalence shows geographic variability and has been recently updated by taking into account the mutation diagnostic test. In Italy, the last epidemiological estimation was reported well before the HTT gene discovery and the availability of the corresponding genetic test. It reported a prevalence of affected subjects ranging between 2.3 and 4.8/100,000 in some restricted areas of Northern Italy. We have performed a service-based epidemiological analysis in a very restricted geographic area named Molise, where our institutions currently operate and represent the only point of reference for rare neuropsychiatric diseases. The estimated prevalence rate found was 10.85/100,000 (95% confidence interval (CI): 7.20-14.50), remarkably higher than that previously described before the gene test analysis was available, and expected to an increase of an additional 17% by 2030, because of Italian population aging. According to our analysis, we estimate that about 6500 subjects are currently affected by HD in Italy, and that this number will further increase in the next decades because of population aging, variable phenotype penetrance and improved life expectancy.

The p85 regulatory subunit of PI3K mediates cAMP-PKA and insulin biological effects on MCF-7 cell growth and motility.

Recent studies have shown that hyperinsulinemia may increase the cancer risk. Moreover, many tumors demonstrate an increased activation of IR signaling pathways. Phosphatidylinositol 3-kinase (PI3K) is necessary for insulin action. In epithelial cells, which do not express GLUT4 and gluconeogenic enzymes, insulin-mediated PI3K activation regulates cell survival, growth, and motility. Although the involvement of the regulatory subunit of PI3K (p85α (PI3K)) in insulin signal transduction has been extensively studied, the function of its N-terminus remains elusive. It has been identified as a serine (S83) in the p85α (PI3K) that is phosphorylated by protein kinase A (PKA). To determine the molecular mechanism linking PKA to insulin-mediated PI3K activation, we used p85α (PI3K) mutated forms to prevent phosphorylation (p85A) or to mimic the phosphorylated residue (p85D). We demonstrated that phosphorylation of p85α (PI3K)S83 modulates the formation of the p85α (PI3K)/IRS-1 complex and its subcellular localization influencing the kinetics of the insulin signaling both on MAPK-ERK and AKT pathways. Furthermore, the p85α (PI3K)S83 phosphorylation plays a central role in the control of insulin-mediated cell proliferation, cell migration, and adhesion. This study highlights the p85α (PI3K)S83 role as a key regulator of cell proliferation and motility induced by insulin in MCF-7 cells breast cancer model.

Requirement for cAMP-PKA pathway activation by M phase-promoting factor in the transition from mitosis to interphase.

Cell cycle progression in cycling Xenopus egg extracts is accompanied by fluctuations in the concentration of adenosine 3',5'-monophosphate (cAMP) and in the activity of the cAMP-dependent protein kinase (PKA). The concentration of cAMP and the activity of PKA decrease at the onset of mitosis and increase at the transition between mitosis and interphase. Blocking the activation of PKA at metaphase prevented the transition into interphase; the activity of M phase-promoting factor (MPF; the cyclin B-p34cdc2 complex) remained high, and mitotic cyclins were not degraded. The arrest in mitosis was reversed by the reactivation of PKA. The inhibition of protein synthesis prevented the accumulation of cyclin and the oscillations of MPF, PKA, and cAMP. Addition of recombinant nondegradable cyclin B activated p34cdc2 and PKA and induced the degradation of full-length cyclin B. Addition of cyclin A activated p34cdc2 but not PKA, nor did it induce the degradation of full-length cyclin B. These findings suggest that cyclin degradation and exit from mitosis require MPF-dependent activation of the cAMP-PKA pathway.

p85 regulatory subunit of PI3K mediates cAMP-PKA and estrogens biological effects on growth and survival.

Cyclic adenosine 3'5' monophosphate (cAMP) and protein kinase A (PKA) cooperate with phosphatidylinositol 3' kinase (PI3K) signals in the control of growth and survival. To determine the molecular mechanism(s) involved, we identified and mutagenized a specific serine (residue 83) in p85alpha(PI3K), which is phosphorylated in vivo and in vitro by PKA. Expression of p85alpha(PI3K) mutants (alanine or aspartic substitutions) significantly altered the biological responses of the cells to cAMP. cAMP protection from anoikis was reduced in cells expressing the alanine version p85alpha(PI3K). These cells did not arrest in G1 in the presence of cAMP, whereas cells expressing the aspartic mutant p85D accumulated in G1 even in the absence of cAMP. S phase was still efficiently inhibited by cAMP in cells expressing both mutants. The binding of PI3K to Ras p21 was greatly reduced in cells expressing p85A in the presence or absence of cAMP. Conversely, expression of the aspartic mutant stimulated robustly the binding of PI3K to p21 Ras in the presence of cAMP. Mutation in the Ser 83 inhibited cAMP, but not PDGF stimulation of PI3K. Conversely, the p85D aspartic mutant amplified cAMP stimulation of PI3K activity. Phosphorylation of Ser 83 by cAMP-PKA in p85alpha(PI3K) was also necessary for estrogen signaling as expression of p85A or p85D mutants inhibited or amplified, respectively, the binding of estrogen receptor to p85alpha and AKT phosphorylation induced by estrogens. The data presented indicate that: (1) phosphorylation of Ser 83 in p85alpha(PI3K) is critical for cAMP-PKA induced G1 arrest and survival in mouse 3T3 fibroblasts; (2) this site is necessary for amplification of estrogen signals by cAMP-PKA and related receptors. Finally, these data suggest a general mechanism of PI3K regulation by cAMP, operating in various cell types and under different conditions.

The p85 regulatory subunit of PI3K mediates TSH-cAMP-PKA growth and survival signals.

Phosphatidylinositol 3-kinase (PI3K) is necessary for thyroid stimulating hormone (TSH)-induced cell cycle progression. To determine the molecular mechanism linking PI3K to TSH, we have identified a serine residue in p85alpha(PI3K) phosphorylated by protein kinase A (PKA) in vitro and in vivo. Expression of an alanine mutant (p85A) abolished cyclic AMP/TSH-induced cell cycle progression and was lethal in thyroid cells (FRTL-5). The aspartic version of the p85alpha(PI3K) (p85D) inhibited apoptosis following TSH withdrawal. The p85alpha(PI3K) wild type not the p85A bound PKA regulatory subunit RIIbeta in cells stimulated with cAMP or TSH. The binding of the aspartic version of p85alpha(PI3K) to RIIbeta was independent of cAMP or TSH stimulation. Similarly, binding of PI3K to p21Ras and activation of AKT, a downstream PI3K target, were severely impaired in cells expressing the p85A mutant. Finally, we found that the catalytic activity of PI3K was stimulated by TSH in cells expressing the wild-type p85alpha(PI3K) but not in cells expressing p85A. This latter mutant did not affect the epidermal growth factor-stimulated PI3K activity. We suggest that (1) TSH-cAMP-induced PKA phosphorylates p85alpha(PI3K) at serine 83, (2) phosphorylated p85alpha(PI3K) binds RIIbeta-PKA and targets PKAII to the membrane, and (3) PI3K activity and p21Ras binding to PI3K increase and activate PI3K downstream targets. This pathway is essential for the transmission of TSH-cAMP growth signals.

p53 genes mutated in the DNA binding site or at a specific COOH-terminal site exert divergent effects on thyroid cell growth and differentiation.

Expression of mutated versions of the p53 gene deranged the differentiation program of thyroid cells and resulted in deregulated growth. Specifically, p53 mutants in several residues of the DNA-binding region induced thyrotropin (TSH) -independent growth and inhibition of the expression of thyroid-specific genes. The loss of the differentiated phenotype invariably correlated with the blockage of the expression of the genes coding for the thyroid transcriptional factors PAX-8 and TTF2. Conversely, thyroid cells transfected with a p53 gene mutated at codon 392, located outside the DNA-binding region, stimulated the expression of differentiation genes in the absence of the TSH, and induced TSH-independent growth. cAMP intracellular levels were higher in thyroid cells transfected with the p53 gene mutated at the 392 site than in the untransfected thyroid cells, but lower in the cells transfected with the other mutated p53 genes. Fra-1 and c-jun were induced by p53, resulting in increased AP-1 levels. The results of this study suggest that p53 exerts effects on cAMP transduction pathway in thyroid cells, which are exquisitely sensitive to cAMP.

Somatic mutations in the VI transmembrane segment of the thyrotropin receptor constitutively activate cAMP signalling in thyroid hyperfunctioning adenomas.

We have discovered two somatic mutations in the VI transmembrane domain of the thyrotropin receptor gene in thyroid hyperfunctioning adenomas. The mutated amino acid residues are phenylalanine 631 (to cysteine) and threonine 632 (to isoleucine). Cloning and expression of the mutated versions of the receptor in COS cells increased significantly the basal and the TSH-induced cAMP levels compared to the wild type receptor. Moreover, the expression of a reporter gene under the control of the cAMP-inducible promoter, was likewise constitutively activated in cells expressing the 631 and 632 TSH receptor mutants relative to the wild type. These data indicate that the VI transmembrane segment in the TSH receptor and presumably in the other G-protein coupled receptors is a critical domain for the activation of G-protein signalling and that the mutations described here may be the cause of the thyroid hyperfunctioning adenoma.

Mutations of thyrotropin receptor isolated from thyroid autonomous functioning adenomas confer TSH-independent growth to thyroid cells.

TSH receptor mutants in the VI transmembrane segment, found in thyroid autonomously functioning adeonomas, have been expressed in differentiated thyroid cells. All mutant receptors constitutively stimulated adenylyl cyclase. The biological activity, measured as cAMP production relative to the wild type receptor, was specific for each mutant in transient and stable transfection assays. Cells expressing these mutants proliferated in the absence of TSH. The rate of growth in the absence of TSH paralleled basal cAMP production for each mutant receptor. Low TSH concentrations stimulated the growth of mutant receptor-expressing cells, and not of the cells expressing the wild type receptor. Also, the entry in the cell cycle and the plating efficiency were markedly stimulated by the expression of the mutant receptors. These data provide a molecular link between the occurrence of TSH receptor mutations and thyroid autonomously functioning adenomas.

MACOP-B versus ProMACE-MOPP in the treatment of advanced diffuse non-Hodgkin's lymphoma: results of a prospective randomized trial by the non-Hodgkin's Lymphoma Cooperative Study Group.

PURPOSE: The aim of our study was to compare in a multicentric randomized trial two regimens widely used in the treatment of advanced-stage intermediate- to high-grade non-Hodgkin's lymphoma and to assess whether a third-generation regimen (methotrexate with leucovorin, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin [MACOP-B]) was superior to a second-generation regimen (procarbazine, methotrexate with leucovorin, doxorubicin, cyclophosphamide, and etoposide [ProMACE-MOPP]). PATIENTS AND METHODS: Between January 1987 and August 1991, 221 patients with diffuse intermediate- to high-grade non-Hodgkin's lymphoma (Working Formulation groups F, G, H, and K), stage II bulky (> 10 cm), III, or IV, were randomized by the Non-Hodgkin's Lymphoma Cooperative Study Group (NHLCSG) to receive ProMACE-MOPP for six cycles or MACOP-B for 12 weeks. Survival, progression-free survival, and disease-free survival were determined, and multivariate analysis of prognostic factors was performed. RESULTS: In the two groups of patients, there was no significant difference in terms of complete remission (CR) rate (49.1% with ProMACE-MOPP and 52.3% with MACOP-B), 3-year overall survival rate (45.2% with PROMACE-MOPP and 52.3% with MACOP-B), and 3-year progression-free survival rate (36.4% with ProMACE-MOPP and 36.1% with MACOP-B). In terms of toxicity, no significantly greater toxicity occurred in either arm. Overall toxicity was acceptable. The most frequent side effects were grade II through IV leukopenia, infection, mucositis, and anemia. Treatment-related deaths were equally distributed. CONCLUSION: No significant differences in terms of efficacy and/or toxicity between ProMACE-MOPP and MACOP-B are evident. These results are consistent with recent randomized trials showing that the new-generation aggressive regimens are no better than previous ones.

VACOP-B versus VACOP-B plus autologous bone marrow transplantation for advanced diffuse non-Hodgkin's lymphoma: results of a prospective randomized trial by the non-Hodgkin's Lymphoma Cooperative Study Group.

PURPOSE: The aim of this multicenter randomized study was to compare conventional therapy with conventional plus high-dose therapy (HDT) and autologous bone marrow transplantation (ABMT) as front-line treatment for poor-prognosis non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS: Between October 1991 and June 1995, 124 patients, aged 15 to 60 years, with diffuse intermediate- to high-grade NHL (Working Formulation criteria), stages II bulky (> or = 10 cm), III, or IV were enrolled. Sixty-one patients were randomized to receive etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin (VACOP-B) for 12 weeks and cisplatin, cytarabine, and dexamethasone (DHAP) as a salvage regimen (arm A), and 63 to receive VACOP-B for 12 weeks plus HDT and ABMT (Arm B). RESULTS: There was no significant difference in terms of complete remissions (CRS) in the two groups: 75% in arm A, and 73% in arm B. The median follow-up observation time was 42 months. The 6-year survival probability was 65% in both arms. There was no difference in disease-free survival (DFS) or progression-free survival (PFS) between the two groups. DFS was 60% and 80% (P = .1) and PFS was 48% and 60% (P = .4) for arms A and B, respectively. Procedure feasibility was the major problem. In arm B, 29% of enrolled patients did not undergo HDT and ABMT. A statistical improvement in terms of DFS (P = .008) and a favorable trend in terms of PFS (P = .08) for intermediate-/high- plus high-risk group patients assigned to HDT and ABMT was observed. CONCLUSION: In this study, conventional chemotherapy followed by HDT and ABMT as front-line therapy seems no more successful than conventional treatment in terms of overall results. However, our results suggest that controlled studies of HDT plus ABMT should be proposed for higher risk patients.

NIDDM associated with mutation in tyrosine kinase domain of insulin receptor gene.

A population of 103 patients with non-insulin-dependent diabetes mellitus (NIDDM) was screened for mutations in the tyrosine kinase domain of the insulin receptor gene. Patient genomic DNAs corresponding to exons 17-21 of the insulin receptor gene have been amplified by polymerase chain reaction and analyzed by denaturing gradient gel electrophoresis (DGGE). One patient was identified with an altered pattern of mobility of exon 20 in the DGGE assay. Direct sequence of amplified DNA showed a single nucleotide substitution in the codon 1152 (CGG-- greater than CAG), resulting in the replacement of Arg with Gln. Two bands appeared in the sequence of exon 20 of the insulin receptor (nucleotide position 3584), indicating that this patient was heterozygous for the mutation. Insulin binding to intact erythrocytes from the patient was in the normal range. Although autophosphorylation of the purified insulin receptor also seemed normal, its kinase activity toward the exogenous substrate poly Glu:Tyr (4:1) was undetectable. This mutation may impair insulin receptor kinase and contribute to insulin resistance in this patient.

Autologous bone marrow transplantation for adult advanced stage lymphoblastic lymphoma in first CR. A study of the NHLCSG.

Fourty successive adult patients with lymphoblastic lymphoma entered a study of sequential chemotherapy consisting of an intensive LSA-L2-type protocol to induce first complete remission. Twenty-one patients in first CR (median age 24 years, range 15-43), after receiving a conditioning regimen consisting of cyclophosphamide and total body irradiation, underwent autologous bone marrow transplantation. At this time fourteen patients are alive and well 5-72 months post-transplant (median follow-up 58 months) with an actuarial disease free survival of 66%. These early results suggest that high-dose chemoradiotherapy followed by autologous bone marrow transplantation may improve long-term disease free survival in advanced stage adult lymphoblastic lymphoma.

ProMACE-MOPP vs MACOP-B in high grade non-Hodgkin's lymphomas: a randomised study in a multicenter cooperative study group (NHLCSG).

From January '85 to April '87, 81 patients (pts) with diffuse intermediate and high-grade non-Hodgkin's lymphomas were treated with the ProMace/MOPP protocol in a large Italian Cooperative Study Group (NHLCSG). Criteria for entry into the study included: no prior therapy, stage III-IV or stage II with bulky disease and/or B-symptoms, age below 65. 79 pts were evaluable for response. Almost all pts received six courses of chemotherapy, plus radiotherapy on bulky disease. 53 pts (67%) achieved complete remission (CR), 7 (9%) partial remission (PR), 4 (5%) were considered stable disease (SD) and 15 (19%) progression disease (PD) with 5 of them died early during treatment. The actuarial overall survival (OS) and disease free survival (DFS) are respectively 54% at 61 mos and 62% at 41 mos. The median follow-up from the end of therapy is 56 mos (range 40-68). Until now 20 pts (38%) relapsed on a median time of 8 mos (range 2-21) from CR. These data allowed to us to consider this regimen as effective as the third generation protocols also taking into account the multicenter basis of this study. With the aim to evaluate the impact of the third generation regimen on the outcome of these pts, a randomized study has been performed comparing ProMACE-MOPP with the third generation regimens MACOP-B. Therefore, from 1988 up to now, 206 pts with similar clinical and histological characteristics, have been enrolled in the two arms. No differences in terms of CR and DFS have been registered between the two treatments, with roughly the same toxicity. An analysis of prognostic factors in the larger series of pts treated with ProMACE-MOPP in the first and in the second study (167 pts) was performed. On these basis it seems reasonable that our next step would be to candidate these poor prognosis pts to a new therapeutic strategy which included the use of ABMT and/or PBSC transplantation as first line.

The role of anthracyclines in adult acute lymphoblastic leukaemia.

The role of anthracyclines (ANT) in the treatment of adult acute lymphoblastic leukaemia (ALL) is poorly defined as regards drug dosage, schedule, preferable compound, and indications for use in specific treatment phases or disease subset. We therefore reviewed ANT treatment results in adult ALL. Altogether, an early and intensive use of ANT would improve both initial response rate and long-term disease-free survival; idarubicin (IDR) exhibits a considerable antileukaemic activity deserving further evaluation as possible reference drug; and the prognosis of CD10+ t(9;22)/BCR-ABL- ALL can be particularly good following an early dose-intensive ANT consolidation program.

The early growth response gene EGR-1 behaves as a suppressor gene that is down-regulated independent of ARF/Mdm2 but not p53 alterations in fresh human gliomas.

PURPOSE: EGR-1 is an immediate early gene with diverse functions that include the suppression of growth. EGR-1 is down-regulated many cancer cell types, suggesting a tumor suppressor role, and may critically involve the p53 pathway. The aim of this work was to measure the expression of EGR-1 and the p16/INK4a/ARF-Mdm2-p53 pathway status in fresh human gliomas. EXPERIMENTAL DESIGN: Thirty-one human gliomas with different grades of malignancy were investigated for Egr-1 mRNA and the protein expression, frequency, and spectrum of p53 gene mutations, mdm2 gene amplification, and p16/INK4a/ARF allele loss. RESULTS: The amplification of Mdm2 and the deletion of the p16/INK4a gene was found in 3 and 5 cases, respectively, whereas mutations of p53, including two novel mutations, were observed in 10 other cases. The three types of changes occurred strictly mutually exclusively, emphasizing that these genes operate in a common pathway critical to glioma progression. EGR-1 mRNA was significantly down-regulated in astrocytomas (14.7 +/- 5.1%) and in glioblastomas (33.6 +/- 10.0%) versus normal brain. Overall, EGR-1 mRNA was strongly suppressed (average, 15.2 +/- 13.9%) in 27 of 31 cases (87%), independent of changes in p16/INK4a/ARF and Mdm2; whereas 4 of 31 cases with residual EGR-1 expression as well as the highest EGR-1 variance segregated with p53 mutations. Immunohistochemical analyses confirmed the suppression of EGR-1 protein. CONCLUSIONS: These results indicate that EGR-1 is commonly suppressed in gliomas independent of p16/INK4a/ARF and Mdm2 and that suppression is less crucial in tumors bearing p53 mutations, and these results implicate an EGR-1 growth regulatory mechanism as a target of inactivation during tumor progression.

Mutations of thyrotropin receptor gene.

Thyrotropin is the primary pituitary hormone which stimulates the growth and differentiation of thyroid cells. TSH binds a specific receptor present in the plasma membrane of thyroid cells and signals the G protein transducers, which activate different effectors, mainly adenyl cyclase and phospholipase C. The TSH receptor belongs to a broad class of receptors known as seven-loop receptors because they contain a long stretch of amino acids which cross the plasma membrane seven times. Mutations in the TSH receptor gene have been found in hyperfunctioning thyroid adenomas. These mutations are: (a) somatic (present only in the tumor), (b) dominant (only one copy of the gene is affected), and (c) lead to the constitutive activation of the cAMP signaling cascade. Most mutations which have been identified occur in the intracellular loop III and in the transmembrane domain VI. Germline mutations in the same regions of the receptor have been found in congenital nonautoimmune hyperthyroidism. In addition, germ line mutations have been described in the extracellular domain of the receptor leading to increased TSH levels. The clinical implications of these findings are discussed.

Electron microscopy of human fetal erythroid cells before and after cryopreservation.

Fetal erythropoiesis was studied in human livers at 10 to 12 weeks of gestation. The most primitive blood cells were often observed in large indentations of the surface of hepatocytes and the plasma membranes of the two cell types were adherent at sites of attachment. Erythroid cell maturation occurred predominantly in the lumen of the sinusoids. Cell suspensions obtained from fetal livers were centrifuged, frozen at -196 degrees C, thawed and studied by electron microscopy. The primitive cells were morphologically altered by these procedures. Changes included damage to mitochondria and cell membranes and vacuole formation. Erythroblasts, by comparison, were virtually intact and even displayed some indications of reestablished functions within 10 minutes after thawing.

Limiting dilution analysis of a novel tripeptide anticancer agent Ambamustine (PTT-119): effect on K-562, CCRF-SB and multidrug resistant LoVo-Dk cell lines.

Cell suspensions of normal human bone marrow were mixed with human acute lymphoblastic or myelogenous leukemic cells of the CCRF-SB or K-562 lines. After incubating the cell mixtures in vitro with different dose levels of Ambamustine (PTT-119), a quantity of 10(4) treated cells were dispensed into microculture plates, and graded cell numbers of the lines used to contaminate the normal marrow were added. Limiting dilution analysis (LDA) was used to estimate the frequency of leukemic cells persisting after treatment. Incubation with 50 micrograms/mL of PTT-119 produced a total elimination of K-562 acute myelogenous blasts, whereas nearly 0.17 and 0.27 leukemic cells were still present in the cell mixtures after treatment with 5 and 25 micrograms/mL, respectively. When normal bone marrow was contaminated with CCRF-SB lymphoblastic cells, incubation with either 50 or 25 micrograms/mL of PTT-119 produced a complete clearing of leukemic cells, whereas with 5 micrograms/mL the leukemic cells in each well were 0.18. When PTT-119 was incubated with LoVo-DX, a colon cancer cell line which expresses the pleiotropic drug resistance MDR phenotype, virtually complete inhibition of clonogenic colonies was observed with as little as 5 micrograms/mL. This suggests that PTT-119 could be used in clinical trials as a non-cross-resistant agent in multidrug protocol.

Allogeneic marrow transplantation for thalassemia.

Thirteen patients with homozygous beta thalassemia underwent allogeneic marrow transplantation from sibling donors, 12 of whom were heterozygous for beta thalassemia. Six patients were transplanted in an advanced stage of their disease while seven were transplanted early in their disease course. Donors and recipients were genotypically identical for the HLA-A, -B and -D loci in 11 cases and mismatched for the D locus in two. A variety of preparative regimens was utilized involving high doses of busulphan (Bu) and/or cyclophosphamide (CY) and/or total body irradiation (TBI). Failure of engraftment or autologous hematologic recovery after transient engraftment was seen after intensive preparative regimens including: CY 200 mg/kg and 800 rad of TBI; Bu 8 mg/kg and CY 200 mg/kg; and Bu 8 mg/kg, CY 200 mg/kg, and 300 rad of TBI. A regimen of Bu 16 mg/kg, CY 200 mg/kg, and 400 rad of TBI resulted in deaths from transplant-related causes in the three patients treated with this regimen. Seven of the 13 patients are surviving 363-665 days after transplant. Five of the seven failed to achieve engraftment or had autologous reconstitution after transient engraftment. Five of the six deaths were transplant related, and one patient died of cardiac failure one year after an unsuccessful transplant attempt. Two patients are surviving with engraftment and without thalassemia major 363 and 491 days after transplantation. Both of these patients were transplanted early in their disease course.

Effect of two cyclophosphamide derivatives on hemopoietic progenitor cells and pluripotential stem cells.

The studies described herein were undertaken to help define the effects of certain cyclophosphamide derivatives that have been used for selective removal of leukemic cells from marrow samples used for autologous transplantation. We have tested the effect of 4-HC and another cyclophosphamide congener, ASTA-Z 7557, on pluripotent stem cells (CFU-S) and committed progenitor cells (CFU-GM) in mice. The CFU-S were evaluated by the spleen colony assay at eight days and 12 days after transplant. The eight-day colonies are transient in nature, rapidly growing, mainly erythroid, and lack pluripotential precursors. The 12-day colonies are believed to provide a measure of hemopoietic stem cells as they slowly grow and do contain primitive precursors. Our data show that at the maximum dose levels tested, both drugs caused a 100% loss of CFU-GM and about 80%-95% inhibition of early transient CFU-S. In contrast, about 70% of the pluripotent 12-day CFU-S were spared. These data appear to explain the hemopoietic recovery seen in man after transplantation with marrow cells treated with 4-HC despite their relative absence of hemopoietic progenitor cells.