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Biomedical subjects

M Danova

Publications and source records attributed to M Danova.

At least 19 recordsLinked to original sources
PubMed1998

Bivariate flow cytometric analysis of DNA content versus immunopositivity for ribonucleotide reductase M1 subunit in the cell cycle.

Ribonucleotide reductase (RR) is a cytoplasmatic enzyme catalyzing the reduction of all four ribonucleotides to their corresponding deoxyribonucleotides. Its activity strongly correlates to the rate of DNA synthesis. By using a specific monoclonal antibody against the large M1 subunit of RR, we assessed the expression of M1-RR versus DNA content by dual-parameter flow cytometry. The aim of this paper was to compare the variations in the immunopositivity for M1-RR during the cell cycle to the positivity for other cell cycle markers identifying either proliferating cells (Ki-67 and PCNA) or quiescent cells (statin). To do this, normal human embryonic fibroblasts in different growth conditions as well as several other mammalian cell lines (rat C6 glioma cells; mouse 3T3 fibroblasts and B16 melanoma cells; human epithelial EUE cells and mammary carcinoma MCF-7 cells) were used. The expression of M1-RR antigen was found to correlate positively with the expression of Ki-67 and PCNA, and negatively with the expression of statin. During early G1 phase, M1-RR becomes detectable by specific antibodies relatively later compared to PCNA and Ki-67; therefore, the lack of immunopositivity for M1-RR cannot be taken as an absolute indication of cell quiescence in G0.

3T3 Cells↗
PubMed1998

5-Fluorouracil plus interferon alpha-2a compared to 5-fluorouracil alone in the treatment of advanced colon carcinoma: a multicentric randomized study.

Biochemical modulation is one of the most interesting fields in cancer chemotherapy. Interferon-alpha (IFNalpha) is a cytokine that is able to influence the pharmacodynamics of 5-fluorouracil (5FU) through a number of mechanisms. With the aim of confirming some data emerging from the literature, we initiated a multicentric randomized study comparing the combination of 5FU and IFNalpha-2a with 5FU alone in the treatment of advanced or metastatic colon cancer. A group of 205 colon cancer patients (104 in the 5FU arm and 101 in the 5FU + IFNapha-2a arm) were included in the final intention-to-treat analysis. Rectal cancers were not considered eligible. All patients had measurable disease, were aged 75 years or less, had a Karnofsky index of at least 60 and had good bone marrow, renal, liver and cardiac functions. No previous chemo-immunotherapy was allowed. The treatment was 750 mg/m2 5FU (4 h i.v. infusion) on days 1 5 and then i.v. bolus weekly, starting from day 12, with or without IFNalpha-2a given s.c. three times weekly (starting dose 3 x 10(6) IU rising to 9 x 10(6) IU, if tolerated). Patients were treated until progression or, if responsive, for a maximum of 48 weeks and then observed for a period of 2 years. The primary end-point of the study was objective clinical response (OR); secondary parameters were time to progression, overall survival, and time to death after progression. WHO criteria were used for both clinical response and toxicity measurements. Dose reduction was planned a priori in the event of significant toxicity due to 5FU, IFNalpha-2a or both. Association between primary and secondary end-points and treatment was studied by univariate and multivariate analysis. Altogether, 47 patients achieved a documented response. A 25% OR was observed in the combination arm while a 21% OR was seen in the 5FU arm; this difference is not statistically significant (P = 0.6). Patients with a small tumour burden (below 5 cm2) showed a higher probability of response in both arms. Patients in the experimental arm had a higher but not statistically significant cumulative progression-free probability. Median survival was 47.1 weeks overall, while it was 43.7 and 48.5 weeks in the control and experimental arms, respectively. The combination was clearly more toxic than 5FU alone, leukopenia being the most frequent side-effect in the experimental arm and nausea and vomiting in the control arm. In conclusion these results are quite disappointing and 5FU + IFNalpha-2a can not be considered a standard treatment for advanced colon cancer.

Aged↗
PubMed1998

All-trans retinoic acid (ATRA)-induced apoptosis is preceded by G1 arrest in human MCF-7 breast cancer cells.

In this study the effects of all-trans retinoic acid (ATRA) on cell cycle and apoptosis of MCF-7 human breast cancer cells were investigated to elucidate the mechanisms underlying the antineoplastic potential of this retinoid in breast cancer. The antiproliferative effect of ATRA was evaluated by DNA content measurements and dual-parameter flow cytometry of bromodeoxyuridine (BrdU) incorporation and of the expression of cell cycle-related proteins (Ki-67 as proliferation marker and statin as quiescence marker) vs DNA content. Apoptosis was also studied by flow cytometry of either DNA content or Annexin V labelling. After 10(-6) M ATRA treatment, the fraction of S-phase cells decreased significantly, and cells accumulated in the G0/G1 range of DNA contents. Dual-parameter flow cytograms showed a decrease in the percentage of Ki-67-labelled cells (after 10 days, only 20% of the cells were still positive for Ki-67 compared with 95% in controls), while the fraction of statin-positive cells increased slightly. From 3 days of treatment onwards, apoptosis was found to occur. These results show that ATRA-induced inhibition of MCF-7 cell growth is related to two mechanisms, i.e. the block of cell proliferation, mostly in a pre-S phase, and the induction of apoptosis. These results should be taken into account when attempting to design treatment programmes that associate ATRA with antineoplastic compounds of different cell cycle specificity.

Annexin A5↗
PubMed1998

5-Fluorouracil dose intensification and granulocyte-macrophage colony-stimulating factor in cisplatin-based chemotherapy for relapsed squamous cell carcinoma of the head and neck: a phase II study.

A previous phase I study showed that in a 5-day combination of cisplatin (CDDP) 20 mg/m2/day and 5-fluorouracil (5-FU) intravenous bolus, the maximum tolerable dose of 5-FU is 200 mg/m2/day without the use of growth factors and 300 mg/m2/day with recombinant human granulocyte-monocyte colony-stimulating factor (rhGM-CSF) support. In the present phase II study, 26 patients with relapsed and/or metastatic squamous cell carcinoma of the head and neck (SCCHN) were treated with CDDP, 20 mg/m2/day, and 5-FU, 300 mg/m2/day intravenous bolus, for 5 consecutive days every 3 weeks. Granulocyte-macrophage colony-stimulating factor, 5 mg/kg/day subcutaneously, was administered from days 8 to 19. All patients had previously undergone surgery and/or radiation treatment. None had previously received chemotherapy. Mucositis (19% of the patients) and thrombocytopenia (42%) were the most frequent, but generally mild, toxicities. Relevant, GM-CSF-related side effects were detected in 12% of the patients. The median number of cycles delivered was four. Three complete and five partial responses were recorded (31% overall response rate). Further investigation of this regimen is unwarranted because of both its lack of improvement in antitumoral activity and the high costs incurred with the use of growth factors.

Adolescent↗
PubMed1998

The predictive role of flow cytometry-derived tumor potential doubling time (Tpot) in radiotherapy: open questions and future perspectives.

Measurement of tumor-cell kinetic parameters, following in vivo administration of thymidine analogues and bivariate flow cytometry, allows quantitative cell kinetic determinations in a clinically relevant time-scale, potentially useful for selection of individual radiotherapy schedules. Among the dynamic cell kinetic parameters that can be measured using the in vivo method, the tumor potential doubling time (Tpot), defined as the time to double the number of proliferating tumor cells in the absence of cell loss, has been postulated to be a predictor of a tumor's proliferative capability, thus representing a potential predictive factor of local control after irradiation. So far, published data have shown the safety and feasibility of the technique, even in multicenter studies, and demonstrated a wide range of parameter values in many tumor sites. With only a few exceptions the hypothesis that Tpot is an independent prognostic indicator cannot be considered proven yet. We review the major controversial issues and open questions, mainly in the area of data production and analysis, that must be resolved before the predictive role of Tpot is unequivocally defined. The future of radiotherapy predictive assays lies in the development of multiparametric studies, accounting for multiple factors of radiation response, which may prove of greater prognostic significance than any single parameter approach based only on cell kinetics.

Bromodeoxyuridine↗
PubMed1996

Accelerated radiation therapy for locally advanced squamous cell carcinomas of the oral cavity and oropharynx selected according to tumor cell kinetics--a phase II multicenter study.

PURPOSE: A Phase II multicenter trial testing an accelerated regimen of radiotherapy in locally advanced and inoperable cancers of the head and neck, in patients selected on the basis of 5-bromo-2-deoxyuridine/DNA flow cytometry-derived tumor potential doubling time (Tpot). METHODS AND MATERIALS: From September 1992 to September 1993, 23 patients consecutively diagnosed to have locally advanced, inoperable carcinomas of the oral cavity and the oropharynx, with Tpot of < or = 5 days, received an accelerated radiotherapy regimen (AF) based on a modification of the concomitant boost technique: 2 Gy/fraction once a day, delivered 5 days a week up to 26 Gy, followed by 2 Gy/fraction twice a day, with a 6-h interval, one of the two fractions being delivered as a concomitant boost to reduced fields, up to 66 Gy total dose (off-cord reduction at 46 Gy), shortening the overall treatment time to 4.5 weeks. A contemporary control group of 46 patients with Tpot of >5 days or unknown was treated with conventional fractionation (CF): 2 Gy/fraction once a day, 5 days a week, up to 66 Gy in 6.5 weeks, with fields shrinkage after 46 Gy. RESULTS: All patients completed the accelerated regimen according to protocol and in the prescribed overall treatment time. Immediate tolerance was fairly good: 65% of the patients in the AF group experienced Grade 3 mucositis vs. 45% in the CF group (p = n.s.). Symptoms related to mucosal reactions seemed to persist longer in AF than in CF patients. The crude proportion of mild (Grades 1 and 2) late effects on skin (p < 0.01) and salivary glands (p < 0.05) was higher in AF than in CF patients, although these reactions did not exceed the limits of tolerance. Three patients in the AF and 1 in the CF arm experienced a late Grade 4 bone complication. Actuarial estimates of severe (Grades 3 and 4) late complications showed a 2-year hazard of 33.3% in the AF arm and 49.7% in CF (p = NS). The actuarial 2-year local control rate of the AF patients was 49.4%, while actuarial 2-year overall survival for the same patients was 43.5%. CONCLUSION: The results suggested that this accelerated regimen is worth testing in a controlled randomized trial to compare different accelerated schedules. Our findings also confirmed the 5-bromo-2-deoxyuridine/DNA flow cytometry technique as a suitable method of evaluating tumor cell kinetics in multicenter clinical studies, on condition that all measurements are carried out by one most experienced laboratory.

Adult↗
PubMed1996

Erythropoietin and granulocyte-macrophage colony-stimulating factor allow acceleration and dose escalation of cyclophosphamide/epidoxorubicin/5-fluorouracil chemotherapy: a dose-finding study in patients with advanced breast cancer.

To verify whether the association of granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (EPO) would allow both the acceleration and the dose escalation of the cyclophosphamide/epidoxorubicin/5-fluorouracil (CEF) regimen as first-line therapy in advanced breast cancer patients, we conducted a dose-finding study. Cohorts of three consecutive patients received cyclophosphamide (Ctx, dose range 800-1400 mg/m2), epidoxorubicin (Epidx, dose range 70-100 mg/m2), and 5-fluorouracil (5-Fu, 600 mg/m2, fixed dose) given as an intravenous bolus on day 1 every 14 days; GM-CSF at 5 micrograms/kg given as a subcutaneous injection from day 4 to day 11; and EPO at 150 IU/kg given as a subcutaneous injection three times a week. In no single patient was any dose escalation allowed. A total of 14 patients entered the study. At the 4th dose level (Ctx 1400 mg/m2, Epidx 100 mg/m2, 5-Fu 600 mg/m2), two patients had dose-limiting mucositis and one patient developed dose-limiting neutropenia. Therefore, the 3rd cohort received the maximum tolerated dose, i.e. Ctx at 1200 mg/m2, Epidx at 90 mg/m2, and 5-Fu at 600 mg/m2, given every 18.5 (+/-2.5) days. Toxicity was moderate and manageable in an outpatient setting. Only 1 admission at the 4th dose level was required. Throughout the 4 dose levels there was no toxicity-related death; grade IV leukopenia ranged from 24% to 75% of cycles and grade IV thrombocytopenia ranged from 6% to 8%. No grade IV anemia was recorded. Increasing the doses of Ctx and Epidx while maintaining a fixed dose of 5-Fu with the support of both EPO and GM-CSF allows safe acceleration and dose escalation of CEF chemotherapy. Further controlled studies will evaluate the activity and efficacy of this strategy.

Adult↗
PubMed1996

Phase I study of simultaneous dose escalation and schedule acceleration of cyclophosphamide-doxorubicin-etoposide using granulocyte colony-stimulating factor with or without antimicrobial prophylaxis in patients with small-cell lung cancer.

A phase I study was designed to assess whether dose intensity of an 'accelerated' cyclophosphamide-doxorubicin-etoposide (CDE) regimen plus granulocyte colony-stimulating factor (G-CSF) could be increased further, in an outpatient setting, by escalating the dose of each single drug of the regimen. Patients with previously untreated small-cell lung cancer (SCLC) received escalating doses of cyclophosphamide (C) 1100-1300 mg m-2 intravenously (i.v.) on day 1, doxorubicin (D) 50-60 mg m-2 i.v. on day 1, etoposide (E) 110-130 mg m-2 i.v. on days 1, 2, 3 and every 14 days for at least three courses. Along with chemotherapy, G-CSF (filgastrim) 5 micrograms kg-1 from day 5 to day 11 was administered subcutaneously (s.c.) to all patients. Twenty-five patients were enrolled into the study. All patients at the first dose level (C 1100, D 50, E 110 x 3) completed three or more cycles at the dose and schedule planned by the protocol and no 'dose-limiting toxicity' (DLT) was seen. At the second dose level (C 1200, D 55, E 120 x 3) three out of five patients had a DLT consisting of 'granulocytopenic fever' (GCPF). Another six patients were treated at this dose level with the addition of ciprofloxacin 500 mg twice a day and only two patients had a DLT [one episode of documented oral candidiasis and one of 'fever of unknown origin' (FUO) with generalised mucositis]. Accrual of patients proceeded to the third dose level (C 1300, D 60, E 130 x 3) with the prophylactic use of ciprofloxacin. Four out of six patients experienced a DLT consisting of GCPF or documented non-bacterial infection. Accrual of patients at the third dose level was then resumed adding to ciprofloxacin anti-fungal prophylaxis (fluconazole 100 mg daily) and anti-viral prophylaxis (acyclovir 800 mg twice a day) from day 5 to 11. Out of five patients treated three experienced a DLT consisting of severe leucopenia and fever or infection. With a simultaneous dose escalation and schedule acceleration it is indeed possible to take maximum advantage of G-CSF activity and to increase CDE dose intensity by a factor 1.65-1.80 for a maximum of 3-4 courses. The role of antimicrobial prophylaxis in this setting deserves to be investigated further.

Antibiotic Prophylaxis↗
PubMed1996

Saporin, a ribosome-inactivating protein used to prepare immunotoxins, induces cell death via apoptosis.

The plant toxin saporin is a ribosome-inactivating protein which inhibits protein synthesis and growth of both normal and tumour cells. Its cytotoxic activity can be increased by coupling with antibodies recognizing cell surface antigens. In this work we performed experiments to test the hypothesis that saporin induces cell death via apoptosis. Exposure to saporin induced apoptosis in different cellular models, such as human peripheral blood B lymphocytes and neutrophils, in the Daudi B-cell line, and in the haemopoietic cell lines HL-60 and TF-1. This was indicated by: (a) the appearance of typical morphological features such as chromatin condensation, nuclear fragmentation and blebbing of plasma membranes: (b) DNA degradation into oligonucleosomal fragments: (c) the appearance of apoptotic cells on DNA flow cytometry as a cell population with reduced DNA content (A0 region). The fraction of cells showing features of apoptosis ranged from 19 +/- 5% for TF-1 cells to 35 +/- 8% for neutrophils. In experiments with normal peripheral blood B lymphocytes or with Daudi cells, we compared the activity of native saporin with that of an immunotoxin hybrid molecule obtained by binding the toxin to two bispecific antibodies recognizing both saporin and the B lymphocyte-specific antigen CD22 (Sap/BsAb complexes). Saporin bound to the antibodies was 2-3 logs more effective than native saporin in inducing apoptosis, with maximal inhibitions being observed at concentrations of 10(-6) M for native saporin and 10(-9)-10(-8) M for the hybrid molecules. These findings indicate that treatment with saporin results in apoptosis of target cells and suggest that this may be relevant to the therapeutic use of saporin-containing immunotoxins. In fact, if used in vivo as an immunotoxin, its cytotoxic activity could be devoid of more extensive and non-specific tissue damaging effects as would be the case if saporin induced necrosis of target cells.

Antibodies, Monoclonal↗
PubMed1996

Cell proliferation and ploidy of human solid tumours: methodological experience with in vivo bromodeoxyuridine and DNA flow cytometry.

A sequential procedure for single and multiparameter flow cytometry (FCM) that allows detailed cell proliferation and DNA ploidy studies of human solid tumours is reported here. This description includes time collection and storage, tissue disaggregation and staining as well as FCM analysis of samples. The overall feasibility, together with some critical aspects of the DNA/bromodeoxyuridine (BrdU) in vivo assay for cell kinetic studies in human solid tumours, are reported, based on our experience in recent years. We found that the BrdU in vivo method, coupled with bivariate FCM for measurements, is a valuable approach for a 'dynamic' assessment of tumour cell proliferation in the clinical setting. Routine measurements can be achieved providing that well standardised tissue disaggregation and immunolabelling procedures are performed. In different solid tumours, cytokinetic results were satisfactory in 85% of cases as far as the BrdU-labelling index is concerned while 70% were acceptable for DNA synthesis time and tumour potential doubling time. Causes of failure are also considered and discussed. In order to guarantee the finest detection of aneuploidy, routine high resolution single-parameter DNA analysis is suggested. Our experience with further improvements in cell kinetic studies based on the possibility of gating the BrdU/DNA analysis for a subpopulation of interest (i.e. cytokeratin-positive cells in epithelial tumours) is also reported.

Bromodeoxyuridine↗
PubMed1996

In vivo bromodeoxyuridine labelling index, AgNOR protein expression and DNA content in human tumours.

The correlation between AgNOR (silver stained nucleolar organizer region) protein quantity and the percentage of S-phase cells was determined in 45 human tumours of different origin (28 from endometrium, 8 from cervix, 4 from ovary, 3 from larynx, 1 from rhinopharynx and 1 from tongue). AgNOR protein quantity was evaluated by image analysis on histological sections stained by the one-step silver staining method. S-phase cells were detected in histological sections with anti-bromo-deoxyuridine (BrdU) antibodies after in vivo BrdU infusion. The relationship between AgNOR protein and BrdU labelling index (LI) values was tested by linear regression analysis. A highly significant association of the two parameters was found (r = 0.78; p < 0.001), independent of the tumour type. DNA content of the 45 tumours was also determined by flow cytometry, and the DNA quantity was correlated with the kinetics data. Euploid tumours had a mean AgNOR protein area of 3.33 +/- 1.34 microns2 and a mean BrdU-LI of 10.78 +/- 8.94%, while in aneuploid tumours the mean AgNOR protein area was 4.78 +/- 1.78 microns2 and the mean BrdU-LI 17.37 +/- 8.79%. Both AgNOR protein quantity and BrdU-LI were significantly higher in aneuploid than in euploid tumours (Student-t Test: p < 0.05 and p < 0.02 for AgNOR and BrdU values, respectively). However, despite this significant difference, a relevant overlap of AgNOR protein and BrdU-LI scores was found within both the aneuploid and euploid groups.

Aneuploidy↗
PubMed1996

[High-dose carboplatin superselective intraarterial chemotherapy in advanced head and neck cancer].

Advances in vascular radiology techniques for superselective transfemoral arterial infusion prompted us to evaluate the effects of high-dose rapid regional carboplatin infusion for patients with advanced head and neck squamous cell carcinomas. Twenty untreated patients received three infusions of carboplatin (300-350 mg/m2) every 2 weeks with this method. All the infusions were performed without any complication. Treatment was well tolerated, with moderate (Grade 1-3 WHO) local toxicity (stomatitis, dermatitis and alopecia) and minimal (Grade 1-2 WHO) myelosuppression. The total response index (complete response plus partial response) was 94% for primary tumors and 50% for neck metastases. Neoadjuvant chemotherapy employing superselective rapid infusion of high-dose carboplatin is a feasible, relatively nontoxic, effective technique and may have important applications in multimodality therapy of untreated patients with advanced head and neck cancer.

Adult↗
PubMed1995

Identification of resting cells by dual-parameter flow cytometry of statin expression and DNA content.

Statin, a 57-kDa nuclear protein, has been recognized as a unique marker of quiescent (G0) cells; specific monoclonal antibodies (MoAb) against statin have been produced and used to label resting cells in tissue sections and in cultured cells. We present an improved method for the identification of G0 cells by dual-parameter flow cytometry of statin expression and DNA content. The appropriate technical conditions were set up by using resting and cycling human fibroblasts as a model cell system. Several fixatives proved to be suitable for the immunocytochemical detection of statin; among them, 70% ethanol was selected because this fixation procedure is suitable for DNA staining with intercalating dyes and is routinely used for the immunolabeling of proliferation markers (such as proliferating cell nuclear antigen [PCNA] and Ki-67) and of bromodeoxyuridine (BrdUrd) incorporation. Following cell permeabilization with detergent, exposure to the antistatin antibody (S-44), and indirect fluorescein isothiocyanate immunolabeling, cells were counterstained for DNA with propidium iodide and analyzed by dual-parameter flow cytometry. In cells from several animal sources (rat thymocytes and C6 glioma cells, mouse 3T3 cells, and human MCF-7 cells), under different experimental conditions, the expression of statin was found to correlate inversely with that of PCNA and Ki-67, and with the BrdUrd labeling index. In dual-parameter flow scattergrams, G0 (statin positive) cells can be discriminated from the potentially cycling (statin negative) G1 cells, i.e., within a cell fraction having the same DNA content. This approach can be envisaged as a powerful tool both for monitoring changes in the resting cell fraction and for investigating the process of G0-G1 transition in unperturbed and drug-treated cell populations.

3T3 Cells↗
PubMed1995

Cell kinetics of CD34-positive hematopoietic cells following chemotherapy plus colony-stimulating factors in advanced breast cancer.

Bone-marrow (BM) hematopoietic precursors are recruited into proliferative activity when colony-stimulating factors (CSF) are sequenced with chemotherapy (CT). Previous studies suggested that further CT can be safely administered only when the increased proliferative activity of these cells has subsided, because most cytostatic drugs selectively damage cycling cells. The safest interval between CSF discontinuation and the start of the next CT course needs to be ascertained in vivo. Thirty patients with advanced breast cancer were treated with an intensified FEC regimen, planned at 21-day intervals, sequenced with granulocyte-macrophage (GM)-CSF (15 patients) or granulocyte (G)-CSF (15 patients). Using flow cytometry (FCM) we evaluated the proliferation kinetics of CD34+ BM hematopoietic progenitors before CT+CSF and at different times after CSF administration was stopped. FEC+GM- and FEC+G-CSF sequences both induced a rapid and sustained increase in the percentage of BM myeloid precursors (BMMP%) and in the cycling status of CD34+BM cells. However, while the BMMP% remained elevated in both cases after CSF were stopped, the enhanced proliferative activity of CD34+ cells decreased more rapidly after GM- than after G-CSF. Using FCM, CD34+ BM-derived hematopoietic presursor cell kinetics is readily evaluated in the clinical setting. The administration of CSF following CT increases both the proliferative activity of CD34+ BM cells and the BMMP%. After CSF were discontinued a kinetic refractoriness of hematopoietic progenitors was more evident after GM-CSF than after G-CSF. These data may be of value in designing clinical trials to avoid cytostatic damage to the BM hematopoietic stem-cell compartment.

Aged↗
PubMed1995

Oligodeoxynucleotides antisense to c-abl specifically inhibit entry into S-phase of CD34+ hematopoietic cells and their differentiation to granulocyte-macrophage progenitors.

A number of experimental observations suggest that the proto-oncogene c-abl participates in the regulation of hematopoietic cell growth. We used an antisense strategy to study the relationship between c-abl expression and hematopoietic cell proliferation and differentiation. Purified normal human bone marrow-derived CD34+ cells were obtained by immunomagnetic selection and incubated with 18-base-unmodified antisense oligodeoxynucleotides complementary to the first six codons of the two alternative first exons of c-abl, la and lb. At the end of incubation, an aliquot of cells was assayed for clonogenic growth and the remainder was used for flow cytometric analyses. Cell kinetics were evaluated by means of both single parameter DNA and bivariate DNA/bromodeoxyuridine (BrdU) flow cytometry. Apoptosis was routinely studied by DNA flow cytometric analysis and, in some cases, also through DNA agarose gel electrophoresis for detection of oligonucleosomal DNA fragments. Expression of differentiation markers was studied by flow cytometry. Exposure to antisense oligonucleotides specifically inhibited the accumulation of c-abl mRNA in CD34+ cells. Preincubation with the c-abl antisense oligomers reduced the proportion of cells in S-phase from 19% +/- 5% (mean +/- SD) to 7% +/- 4% (P < .05), and BrdU labeling from 13% +/- 6% to 6% +/- 3% (P < .05). Flow cytometry and DNA agarose gel electrophoresis showed that treated CD34+ cells accumulated in the G0/G1 region of the DNA histogram with no evidence of either differentiation or apoptosis. By contrast, both growth factor deprivation and exposure of CD34+ cells to the tyrosine kinase inhibitor tyrphostin AG82 clearly induced apoptosis. When cells were preincubated with antisense oligonucleotides and then plated for evaluation of colony formation, this resulted in a significant inhibition of colony forming unit granulocyte-macrophage growth (from 44 +/- 15 to 22 +/- 9; P < .01) but had no effect on burst-forming unit erythroid growth (24 +/- 11 v 21 +/- 11; P < .05). These results suggest that c-abl expression is critical for entry of human CD34+ hematopoietic cells into S-phase and for their differentiation to granulocyte-macrophage progenitors. They also indicate that other tyrosine kinases besides p145c-alb are active in the prevention of apoptosis, so that inhibition of c-abl RNA accumulation arrests CD34+ cells in G0/G1 without activating programmed death.

Antigens, CD34↗