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S A Gregory

Publications and source records attributed to S A Gregory.

At least 19 recordsLinked to original sources
PubMed2005

Chemotherapy dose intensity in non-Hodgkin's lymphoma: is dose intensity an emerging paradigm for better outcomes?

BACKGROUND: Higher chemotherapy dose intensity has been studied as a way of improving the clinical outcomes in various malignancies, including non-Hodgkin's lymphoma (NHL). METHODS: We reviewed clinical trials that have studied the relation between dose and response in cancer chemotherapy, the theory behind dose-intense chemotherapy, and the clinical results with dose-escalated and dose-dense therapy in aggressive NHL. RESULTS: Myeloablative high-dose chemotherapy with stem cell transplantation produces higher 5-year survival rates than standard salvage chemotherapy in relapsed aggressive lymphoma, but its role as initial therapy is not yet clear. Nonmyeloablative dose-escalated chemotherapy is feasible with granulocyte colony-stimulating factor (G-CSF) support, but this approach does not improve outcomes. Dose-dense (14-day) CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) with G-CSF support produces better results than 21-day CHOP in patients with previously untreated aggressive lymphoma, without additional toxicity. The addition of etoposide to dose-dense CHOP may provide further benefits in younger patients. The addition of rituximab to G-CSF-supported dose-dense CHOP is feasible. Preliminary data suggest the feasibility of dose-dense chemotherapy for NHL with the once-per-cycle G-CSF, pegfilgrastim. CONCLUSION: Dose-dense chemotherapy with G-CSF support produced better clinical outcomes in both younger and older patients. Phase 3 trials of dose-dense CHOP plus rituximab with CSF support are warranted.

Aged↗
PubMed2005

The evolving role of alemtuzumab in management of patients with CLL.

New insights into prognostic markers and the pathophysiology of chronic lymphocytic leukemia (CLL) are beginning to change the concept of CLL treatment. Alemtuzumab has evolved as a potent and effective therapeutic option for patients with CLL. Specifically, alemtuzumab has demonstrated substantial efficacy in fludarabine-refractory patients and has shown impressive responses when administered subcutaneously in first-line therapy. A group of experts gathered to discuss new data related to the use of alemtuzumab in CLL and to assess its place in the rapidly changing approach to treating patients with this disease. The main goals of this program were to update the management guidelines that were previously developed for alemtuzumab-treated patients and to provide community oncologists with guidance on the most effective way to integrate alemtuzumab into a CLL treatment plan.

Alemtuzumab↗
PubMed2001

Mitoxantrone and fludarabine in the treatment of patients with non-Hodgkin's lymphoma failing primary therapy with a doxorubicinor mitoxantrone-containing regimen.

Patients with recurrent lymphoma of any grade were treated with mitoxantrone (12 mg/m2 given intravenously (IV) over 15-30 minutes on day 1) followed by fludarabine at a dose of (25 mg/m 2 given IV over 30 minutes on days 1-3) every 28 days fludarabine at a dose of (25 mg/m2 given IV over 30 minutes on days 1-3) every 28 days. All patients had failed one prior chemotherapy regimen that contained either doxorubicin or mitoxantrone, total dose not exceeding 350 mg/m2 doxorubicin or 80 mg/m2 mitoxantrone. mitoxantrone. Thirty one patients (22 with intermediate- or high-grade and 9 with low-grade NHL) were enrolled. Median age was 63 years (range: 21 to 87). The objective response rate for patients with intermediate/high-grade NHL was 55% (27% with CR) and 89% (56% with CR) for patients with low-grade NHL. Median time to disease progression was 5.1 months for patients with intermediate/high-grade NHL and 10.8 months for patients with low-grade NHL. Median time to death for patients with intermediate/high-grade disease was 11.4 months. Median time to death for patients with low-grade NHL was not calculable as only one death (due to respiratory failure) occurred in this group 6.5 months after study start. The regimen was well tolerated. Grade 3/4 neutropenia was reported in 80% (24 of 30) of patients and Grade 3/4 thrombocytopenia in 19% (6 of 31) of patients. Nine hospitalizations for adverse events (primarily fever and neutropenia) occurred among eight patients, all with intermediate/high-grade NHL, during a total of 118 cycles of therapy. Further studies of this combination regimen in patients with intermediate/high-grade NHL and studies combined with monoclonal antibodies in low-grade NHL are warranted.

Adult↗
PubMed2001

Effectiveness of interferon-alfa and mid-cycle chemotherapy added to an anthracycline-based regimen in the treatment of aggressive non-Hodgkin's lymphoma.

Interferon-alfa in combination with cytotoxic chemotherapy has been shown to be effective in treating certain types of non-Hodgkin's lymphoma (NHL) (1). However, there is no published data on upfront induction treatment of aggressive NHL with IFN-alfa containing regimens. Studies have also shown that one can overcome regrowth resistance by administering mid-cycle agents which slow tumor proliferation between courses of cytotoxic therapy (2). Based on this, we treated 32 consecutive patients between 1/93 and 9/96 with a regimen containing cyclophosphamide 750 mg/m2, mitoxantrone 12 mg/m2, and teniposide 60 mg/m2 IV on day 1 with prednisone 100 mg PO given on days 1-5. On day 15, patients received vincristine 1.4 mg/m2 (2 mg max.) and bleomycin 10 units/m2 IV. Interferon-alfa-2b 5x10(6) units/m2 SQ was administered on days 22-26. The median age was 55 (range 26-83), M:F ratio was 2.5:1, and the median International Prognostic Index was 2. 38% of patients had stages I-II and 62% had stages III-IV disease. Fifty-nine percent of the patients achieved a complete response, 22% a partial response, and 19% had progressive disease. The overall survival (OS) was 81% and the progression free survival (PFS) was 56% at 4.3 years. There were no severe (grade IV) hematologic, flu-like, GI and infectious toxicities from IFN-alpha. Leukopenia was the main severe toxicity related to the chemotherapy regimen (days 1-15), but not IFN-alpha. Severe infection secondary to the chemotherapy regimen occurred in one patient. Interferon-alfa-2b and mid-cycle chemotherapy added to an anthracycline based regimen is effective induction treatment for patients with aggressive NHL. The OS and PFS using this regimen, based on regrowth resistance, appears to be at least as or more effective than CHOP therapy for this group of patients. Severe toxicities were rare.

Adult↗
PubMed2001

High remission rate in acute myeloblastic leukemia with only two days of chemotherapy.

Twenty five patients with AML who had neither a history of toxic exposure or myelodysplasia were treated with a remission induction regimen consisting of two pulses of chemotherapy separated by 96 hrs. Each pulse consisted of cytarabine 2gm/m(2) (at t=0 and t=12 hrs) with mitoxantrone [30mg/m(2) ] administered immediately after the second cytarabine administration. Amifostine was administered three times a week [on Monday, Wednesday, and Friday] until the outcome of therapy was known. This regimen induced complete remissions in 15 of 17 patients less than 70 years of age and in 5 of 8 patients older than 70 years.

Adult↗
PubMed2000

Tumor necrosis factor modulates CD 20 expression on cells from chronic lymphocytic leukemia: a new role for TNF alpha?

Tumor necrosis factor alpha (TNF alpha) is a pleiotropic cytokine that is constitutively produced by leukemic cells in B Chronic Lymphocytic Leukemia (B-CLL). It has been shown to have autocrine and paracrine functions in normal B cells and in B lymphoproliferative diseases. This study was conducted to determine the effect of TNF alpha (in vitro) on CD20 expression on cells from patients with B-CLL. Currently, anti-CD20 monoclonal antibody therapy is becoming a second line treatment in the management of B cell disorders like low-grade non-Hodgkin's lymphoma (NHL) and B-CLL. Our results demonstrate amply that very low doses of TNF alpha (0. 0125 ng/ml) can be used to significantly increase CD20 expression on cells from patients of B-CLL as evidenced by increases in both percentage positivity and mean fluorescence intensity. The upregulation is evident as early as 24 hours and is maintained for up to 72 hours. We propose that the upregulation is a direct result of in vitro differentiation stimulated by TNF alpha. The results presented can be exploited in the designing of priming protocols prior to antibody therapy and this is discussed.

Antibodies, Monoclonal↗
PubMed2000

Poor prognosis acute myelogenous leukemia: 1 - response to treatment with high dose cytarabine/mitoxantrone/ethyol @ (Amifostine).

Twenty patients with poor prognosis AML and four patients in the blastic phase of a myeloproliferative disorder were treated with two 'pulses' of therapy each consisting of two doses of high dose araC (separated by 12 h) followed by a single dose of mitoxantrone. The pulses were separated by 96 h. Amifostine was then administered tiw. The median age of the population was 68 years with 88% of patients having had either a prior MDS, MPD or toxic exposure. The acute leukemia of 58% of patients either entered a CR or reverted to preleukemic state. For patients under 70 years of age, treatment produced 62% CRs with a leukemia free decision marrow in 77%. For patients over 70 years the CR rate was 27% with 36% of patients having a leukemia free decision marrow.

Adult↗
PubMed2000

Effects of cytokines on CD20 antigen expression on tumor cells from patients with chronic lymphocytic leukemia.

Anti-CD20 antibody is an established treatment for low-grade non-Hodgkin's lymphoma (NHL). Augmenting the expression of CD20 antigen on the tumor cells may increase the cell kill and therefore increase the effectiveness of the antibody. To study this, we incubated peripheral blood lymphocytes from CLL patients with the following cytokines: EPO, SCF, TNFalpha, TGFbeta, GMCSF, TPO, IL-1, IL-2, IL-3, IL-4, GCSF. CD20 expression was studied by flow cytometry at baseline, 24 and 72 h after exposure to these cytokines. Upregulation of CD20 antigen expression was observed with IL-4, TNFalpha and GMCSF.

Antigens, CD20↗
PubMed2000

Clinicopathological features of aggressive large granular lymphocyte leukaemia resemble Fas ligand transgenic mice.

Fas ligand triggers cell death after interaction with its receptor Fas. Altered expression of Fas has been associated with lymphoproliferation and autoimmune disorders in both mice and man. Apoptosis of lung and liver tissue is seen in Fas ligand transgenic mice. It is not known whether constitutive expression of Fas ligand can cause a similar human disease. Four patients with aggressive large granular lymphocyte (LGL) leukaemia involving lung and liver were studied. All four patients were severely ill with pulmonary involvement. Two patients presented with hypoxia and were oxygen dependent; the other two patients had severe pulmonary hypertension. Lung biopsies showed interstitial infiltration by leukaemic LGL. The infiltrating lymphocytes expressed both Fas and Fas ligand, whereas normal pneumocytes expressed only Fas. Similar findings were observed in liver biopsies from these patients. Features mimicking the pathological changes of graft-versus-host disease were observed, including pneumocyte apoptosis. All four patients had high levels of circulating Fas ligand. Successful treatment with oral methotrexate or 2-chlorodeoxyadenosine was associated with disappearance or marked reduction of circulating Fas ligand. These results suggest that dysregulated expression of Fas ligand can lead to human disease with pathological features resembling graft-versus-host disease.

Adult↗
PubMed2000

Signal antonymy unique to myelodysplastic marrows correlates with altered expression of E2F1.

Myelodysplastic syndromes (MDS) have previously been reported to show competitively high rates of apoptosis and proliferation in the bone marrow (BM). Using a double-labelling technique in the present study, we demonstrated that a significantly high number of S-phase cells were simultaneously apoptotic (signal antonymy; SA) in MDS (mean +/- s.e.m. 53.5 +/- 6.7%, n = 24, P < 0.001). In contrast, SA was negligible in all other specimens studied, including normal control BM (n = 13) from non-Hodgkin's lymphoma (NHL) patients, BM from patients with de novo acute myelogenous leukaemia (1'AML; n = 5), or secondary AML that had transformed from MDS (2'AML; n = 10), or the solid tumours from patients with NHL (n = 9) or head and neck squamous cell carcinoma (HNSCC; n = 10). Subsequently, the expression of a transcription factor, E2F1, was studied in density-separated BM aspirate mononuclear cells from MDS patients (n = 9) and a normal control. Two separate sets of primers were used that recognized the regulatory retinoblastoma (Rb) protein-binding region and the functional DNA-binding region of E2F1. Interestingly, although the latter manifested the expected band (280 bp) in all samples, the Rb-specific primers showed the expected band (380 bp) in the normal and in 4/9 MDS specimens. Two other MDS specimens also showed a smaller band ( approximately 325 bp), whereas 3/9 MDS patients showed exclusively the smaller band. The levels of SA were significantly higher in those MDS cases that showed the smaller Rb-specific band either alone or in addition to the expected band (median 19.5%, n = 4, P = 0.037) than in those showing exclusively the expected band (median 0.4%, n = 3). Our present studies show SA as a characteristic feature of MDS and, importantly, demonstrate its link with an altered expression of E2F1 in some MDS patients.

Apoptosis↗
PubMed2000

Effect of interferon-alpha on CD20 antigen expression of B-cell chronic lymphocytic leukemia.

Chimeric CD20 monoclonal antibody as alternative therapy in relapsed low-grade non-Hodgkin's lymphoma (NHL) has produced responses in nearly 50% of patients. Augmenting CD20 expression on tumor cells and/or inducing its expression may increase the cell kill and effectiveness of antibody therapy. Peripheral blood lymphocytes from 19 patients with B-cell chronic lymphocytic leukemia (B-CLL) were incubated in vitro in the presence of interferon-alpha (IFN-alpha) (500 U/ml and 1,000 U/ml) for 24 and 72 hours. The effect on CD20 expression was studied by flow cytometry. The differences in the percentage positivity, the mean fluorescence intensity (MFI), and the product of percentage positivity and MFI were used to assess upregulation. There was a significant upregulation of CD20 expression on B cells seen at both concentrations after 24-hour priming (p < 0.01). B-CLL cells cultured for 72 hours in the presence of IFN-alpha also showed upregulation of CD20 expression; however, the degree of upregulation was much lower than that seen at 24 hours. There was no statistically significant increase in CD20 antigen expression on normal lymphocytes following cytokine exposure. These results suggest that IFN-alpha priming may augment the effectiveness of antibody therapy by directly upregulating CD20 antigen expression in addition to its indirect action through effector cells of the host.

Antigens, CD↗
PubMed2000

Suppression of telomerase activity and cytokine messenger RNA levels in acute myelogenous leukemia cells in vivo in patients by amifostine and interleukin 4.

High levels of telomerase activity and high rates of cell proliferation are associated with a poor prognosis in acute myelogenous leukemia. Furthermore, cytokine production by leukemia cells is believed to play an important role in determining the proliferative characteristics of leukemia. The in vivo effects of two noncytotoxic agents on these parameters were determined in 33 acute myelogenous leukemia patients. Three daily doses of interleukin (IL) 4 or a single dose of amifostine reduced telomerase activity in the leukemia marrow cells in 7 of 9 and 11 of 13 patients, respectively. The administration of a single dose of amifostine resulted in a reduction in tumor necrosis factor alpha and IL-6 transcript levels in the marrow cells of 10 of 13 and 12 of 13 patients in which these transcripts were present. The administration of only three doses of IL-4 or a single dose of amifostine has a significant effect on leukemia cell parameters, which are believed to have a significant impact on the in vivo biology of the disease and on its response to remission induction therapy.

Adult↗
PubMed1999

Correlation of tumor necrosis factor alpha (TNF alpha) with high Caspase 3-like activity in myelodysplastic syndromes.

Increased intramedullary apoptotic death of hematopoietic cells is thought to contribute to the ineffective hematopoiesis in myelodysplastic syndromes (MDS). Furthermore, high amounts of tumor necrosis factor alpha (TNF alpha) have previously been correlated with apoptosis in MDS marrows. The present studies were undertaken to examine the status of two key downstream effectors of TNF alpha signaling, i.e. Caspase 1 and Caspase 3 enzymes, using a fluorometric assay in the bone marrow aspirate mononuclear cells (BMMNC) in relation to apoptotic DNA fragmentation detected by in situ end-labeling (ISEL) of DNA and with localization of TNF alpha in the corresponding biopsies from 14 MDS patients. Both Caspase 1 and 3 were detectable in freshly harvested BMMNC, albeit median Caspase 3 levels (47.5 units/mg protein) being almost 10 times higher than Caspase 1 (4.0 units/mg protein). Upon short-term culture for 4 h in a serum-supplemented medium in vitro a significant increase was seen in Caspase 3 activity (58.8 +/- 13.9 at 0 h vs. 177.8 +/- 55.2 units/mg protein at 4 h, n = 14, P = 0.017) and in percent cells labeled by ISEL (apoptotic index or AI%: 0.76% +/- 0.25% vs. 3.99% +/- 1.1%, n = 14, P = 0.004, respectively). Caspase 1 activity increased after 15 min in culture. Interestingly, TNF alpha levels measured by immunohistochemistry correlated with the net increase in Caspase 3 activity after 4 h (p = 0.517, n = 13, P = 0.07) and the starting levels of Caspase 1 at 0 h correlated with the Caspase 3 levels attained at 4 h (p = 0.593, n = 13, P = 0.033). Additionally when TNF alpha-positive bone marrows (8/14) were compared with the negative marrows (6/14) the Caspase 3 levels were significantly higher in the TNF alpha-positive marrows (189.6 +/- 66.2 vs. 25.0 +/- 14.6 units/mg protein, respectively, P = 0.043). The increase in AI%, though not statistically significant, was also higher in the TNF alpha-positive marrows. Finally in HL60 cells the effects of different Caspase inhibitors and pentoxifylline (PTX) (interferes with lipid signaling of cytokines) on TNF alpha-induced apoptosis were evaluated. TNF alpha treatment significantly increased AI% (P < 0.003) as compared to the untreated controls. A co-treatment with three Caspase inhibitors, zVAD.FMK (inhibitor of Caspases 1 and 3, 10 microM/l), Ac.YVAD.FMK (Caspase 1 inhibitor, 1 microM/l), Ac.DEVD.FMK (Caspase 3 inhibitor, 10 microM/l) as well as PTX (250 microM/l) significantly curtailed the AI% induced by TNF alpha. The present studies thus identify the downstream effectors of TNF alpha-inducible apoptosis in MDS and so also the suppressors of TNF alpha apoptotic signaling. These results may have significant clinical implications in the therapy of MDS in the future.

Apoptosis↗
PubMed1999

Imbalanced expression of the glucocorticoid receptor isoforms in cultured lymphocytes from a patient with systemic glucocorticoid resistance and chronic lymphocytic leukemia.

The human glucocorticoid receptor (GR) is expressed as two alternatively spliced isoforms, GRalpha and GRbeta. Whereas GRalpha is a hormone-activated transcription factor, GRbeta does not bind glucocorticoids (GCs), is transcriptionally inactive, and is a potential inhibitor of activated GRalpha. Differential expression of GR isoforms may play a role in generalized or tissue-specific GC resistance. GCs induce apoptosis in neoplastic lymphoid cells; and, defective apoptosis is implicated in the genesis of chronic lymphocytic leukemia (CLL). We studied a patient with generalized GC resistance and CLL. GR number in the patient's transformed lymphocytes was approximately one half that of control cells with a approximately 10-fold reduction in binding affinity for dexamethasone. In vitro apoptosis induction in CLL cells was delayed in response to GCs, but not to other apoptosis inducers. Sequencing of the GR cDNA and gene including the 2.3-kb coding region, the intron/exon junctions, the known 5'-regulatory region, and approximately 300 bp of the 3'-region revealed no alterations. Western blot with an N-terminal antibody showed normal levels of immunoreactive GR, but quantitative analysis with isoform-specific C-terminal antibodies revealed a markedly reduced GRalpha expression, and high GRbeta expression. These findings indicate that imbalanced expression of the GR isoforms may be a mechanism of GC resistance, and may have implications for tumorigenesis by enhancing cell survival.

Adult↗
PubMed1999

Evidence for involvement of tumor necrosis factor-alpha in apoptotic death of bone marrow cells in myelodysplastic syndromes.

We previously reported excessive apoptosis and high levels of tumor necrosis factor-alpha (TNF-alpha) in the bone marrows of patients with myelodysplastic syndromes (MDS), using histochemical techniques. The present studies provide further circumstantial evidence for the involvement of TNF-alpha in apoptotic death of the marrow cells in MDS. Using our newly developed in situ double-labeling technique that sequentially employs DNA polymerase (DNA Pol) followed by terminal deoxynucleotidyl transferase (TdT) to label cells undergoing apoptosis, we have characterized DNA fragmentation patterns during spontaneous apoptosis in MDS bone marrow and in HL60 cells treated with TNF-alpha or etoposide (VP16). Clear DNA laddering detected by gel electrophoresis in MDS samples confirmed the unique length of apoptotic DNA fragments (180-200 bp). Surprisingly, however, phenotypically heterogeneous population of MDS cells as well as the homogenous population of HL60 cells showed three distinct labeling patterns after double labeling--only DNA-Pol reaction, only TdT reaction, and a combined DNA Pol + TdT reaction, albeit in different cohorts of cells. Each labeling pattern was found at all morphological stages of apoptosis. MDS mononuclear cells, during spontaneous apoptosis in 4 hr cultures, showed highest increase in double-labeled cells (DNA Pol + TdT reaction). Interestingly, this was paralleled by TNF-alpha-induced apoptosis in HL60 cells. In contrast, VP16 treatment of HL60 cells led to increased apoptosis in cells showing only TdT reaction. The double-labeling technique was applied to normal bone marrow and peripheral blood mononuclear cells after treatment with known endonucleases that specifically cause 3' recessed (BamHI), 5' recessed (PstI), or blunt ended (DraI) double-stranded DNA breaks. It was found that the DNA-Pol reaction in MDS and HL60 cells corresponds to 3' recessed DNA fragments, the TdT reaction to 5' recessed and/or blunt ended fragments, and a combined "DNA Pol + TdT reaction" corresponds to a copresence of 3' recessed with 5' recessed and/or blunt ended fragments. Clearly, therefore, apoptotic DNA fragments, in spite of a unique length, may have differently staggered ends that could be cell (or tissue) specific and be selectively triggered by different inducers of apoptosis. The presence of TNF-alpha-inducible apoptotic DNA fragmentation pattern in MDS supports its involvement in these disorders and suggests that anti-TNF-alpha (or anticytokine) therapy may be of special benefit to MDS patients, where no definitive treatment is yet available.

Apoptosis↗
PubMed1999

The relative extent and propensity of CD34+ vs. CD34- cells to undergo apoptosis in myelodysplastic marrows.

The paradox of peripheral cytopenias despite cellular bone marrow (BM) observed in myelodysplastic syndromes (MDS) has been associated with excessive intramedullary apoptosis of hematopoietic cells. Since MDS is regarded as a stem cell disorder, the present studies were undertaken to examine the relative susceptibility and propensity of early progenitor CD34+ cells to undergo apoptosis as compared to more maturing/matured CD34- cells. Five serial studies were performed on 4 independent groups of 36 newly diagnosed MDS patients. First, in 2 separate groups of 16 and 8 patients each, measurement of the extent of apoptosis in CD34+ and CD34- fractions of the BM aspirate mononuclear cells was carried out using independent biparametric flow cytometry methods, CD34 labeling/terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) (n = 16), and CD34 labeling/reduced uptake of nucleic acid staining dye LDS751 (n = 8). The difference in the median degrees of apoptosis in CD34+ vs. CD34- cells was not statistically significant by either technique (P = 0.583 and P = 0.674 for TUNEL and LDS751, respectively). In the next group of 4 MDS patients, a double-labeling was performed on plastic embedded marrow biopsy sections, to detect CD34 antigen with specific monoclonal antibody and apoptosis by in situ end labeling (ISEL) of fragmented DNA. Despite high overall apoptosis (56.2% +/- 18.4%), only an occasional CD34+ cell was found to be simultaneously labeled with ISEL. Finally, in the last group of 8 MDS patients, CD34+ cells were separated from CD34- cells on affinity column and cultured in serum containing medium for 4 hours. At 0- and 4-hour time points, ISEL was carried out to label apoptotic cells. In addition, a fluorometric assay was employed to estimate the activity of a proapoptotic enzyme, Caspase 3. Both the net increase in % ISEL labeled cells (apoptotic index or AI) and Caspase-3 activity were significantly lower in CD34+ cells as compared to CD34- cells (AI, 0.87% +/- 0.5% vs. 3.97% +/- 1.4%, n = 6, P = 0.028 and Caspase-3 Units/mg protein, 46.9 +/- 25.0 vs. 71.7 +/- 23.03, n = 5, P = 0.042, respectively). We conclude that when estimated in a total population of mononuclear cells, CD34+ cells and CD34- cells show comparable degrees of apoptosis. However, once separated the CD34+ fraction demonstrates lower propensity to undergo apoptosis, thereby suggesting the CD34- fraction as being a possible source for proapoptotic signaling.

Aged↗
PubMed1999

Spontaneous down-regulation of Fas-associated phosphatase-1 may contribute to excessive apoptosis in myelodysplastic marrows.

In this study, we examined the role of Fas-signaling in the apoptotic pathway in myelodysplastic syndromes (MDS). Ficoll-separated mononuclear cells from 18 bone marrow aspirate specimens obtained from 17 MDS patients, 4 normal healthy donors, and 3 acute myeloid leukemia patients transformed from MDS (t-AML) were studied for mRNA expression of Fas-L, Fas, and the effectors of their signaling, Caspase 1 and Caspase 3, using reverse transcriptase polymerase chain reaction. Fas-L, Fas, and Caspase 1 were detectable in all of the samples in the three groups. Caspase 3 was detectable both in MDS and t-AML specimens but was negligible in normal cells. The apoptotic index (AI%) determined by in situ end labeling of fragmented DNA in 4-hour cultures of mononuclear cells was significantly higher in MDS cells compared to normal or t-AML cells (mean +/- SEM: 2.3% +/- 0.4% in MDS, n = 10 vs. 0.6% +/- 0.2%, n = 4, P = 0.014 in normal cells, and 0.2% +/- 0.2%, n = 3, P = 0.007 in t-AML cells). Treatment of MDS cells with anti-Fas-L antibody suppressed apoptosis (AI%: 2.1% +/- 0.6% in untreated vs. 1.37% +/- 0.5% in treated, n = 6, P = 0.02), indicating functional participation of Fas-signaling in MDS. Further, it was found that Fas-L, Fas, and Caspase 1 mRNA expression remained unchanged in 4 hours. Caspase 3 expression appeared in normal cells after 4 hours and was present at both 0 and 4 hours in MDS and t-AML cells. In contrast to persistent expression in normal and t-AML cells, cells from the 5 MDS patients studied consistently showed significantly lowered or undetectable expression of a negative regulator of Fas, called Fas-associated phosphatase-1 (Fap-1) after 4 hours. Thus, the high AI% in MDS corresponds to a rapid decline in Fap-1. Furthermore, in tumor necrosis factor alpha (TNF-alpha) treated HL60 promyelocytic cells, a definite periodicity in the expression of different mRNAs was observed with upregulation of TNF-alpha itself at 30 minutes, increased expression of Fas and the appearance of Fas-L after 2 hours, and a decrease in Fap-1 expression after 8 hours. These results suggest that TNF-alpha not only induces the effectors of Fas-signaling but also may downregulate the inhibitor. We conclude that a spontaneous and rapid down-regulation of Fap-1, possibly induced by TNF-alpha, a cytokine shown to be present in excess in MDS marrows, may underlie the increased apoptotic death of hematopoietic cells in these patients. Interference with Fap-1 turnover may provide a new therapeutic modality for MDS.

Apoptosis↗