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P L Tazzari

Publications and source records attributed to P L Tazzari.

At least 19 recordsLinked to original sources
PubMed2007

Multidrug resistance-associated protein 1 expression is under the control of the phosphoinositide 3 kinase/Akt signal transduction network in human acute myelogenous leukemia blasts.

A high incidence of relapses following induction chemotherapy is a major hindrance to patient survival in acute myelogenous leukemia (AML). There is strong evidence that activation of the phosphoinositide 3 kinase (PI3K)/Akt signaling network plays a significant role in rendering AML blasts drug resistant. An important mechanism underlying drug resistance is represented by overexpression of membrane drug transporters such as multidrug resistance-associated protein 1 (MRP1) or 170-kDa P-glycoprotein (P-gp). Here, we present evidence that MRP1, but not P-gp, expression is under the control of the PI3K/Akt axis in AML blasts. We observed a highly significant correlation between levels of phosphorylated Akt and MRP1 expression in AML cells. Furthermore, incubation of AML blasts with wortmannin, a PI3K pharmacological inhibitor, resulted in lower levels of phosphorylated Akt, downregulated MRP1 expression, and decreased Rhodamine 123 extrusion in an in vitro functional dye efflux assay. We also demonstrate that wortmannin-dependent PI3K/Akt inhibition upregulated p53 protein levels in most AML cases, and this correlated with diminished MRP1 expression and enhanced phosphorylation of murine double minute 2 (MDM2). Taken together, these data suggest that PI3K/Akt activation may lead to the development of chemoresistance in AML blasts through a mechanism involving a p53-dependent suppression of MRP1 expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2006

The "in situ" expression of human leukocyte antigen class I antigens is not altered by cryopreservation in human arterial allografts.

This study was aimed to establish whether the cryopreservation procedure we currently use in clinics can modify arterial homograft antigenicity. To this purpose, we performed an immunohistochemical study on fresh and cryopreserved human arterial homografts to visualize the expression of HLA class I heavy and light chains "in situ" by using the HC-10 and Namb-1 monoclonal antibodies. Human femoral arteries and thoracic aortas were harvested from 18 heart-beating donors and sampled before and after cryopreservation. Arterial segments were frozen in liquid nitrogen vapors in a controlled rate freezing system. After thawing, samples were processed for routine immunohistochemistry. To standardize immunostaining, flow-cytometry indirect immunofluorescence analysis was performed on HUVEC; immunohistochemistry of human ovarian cortical vessels was performed as an additional positive control. Negative controls were performed by omitting tissue incubation with primary antibodies. HLA-class I antigens were markedly expressed by endothelial cells lining surface intima and adventitial vasa vasorum; a moderate expression was found in medial smooth muscle cells. Except for the surface unreactivity caused by loss of endothelium, results from cryopreserved arterial allografts were strictly comparable to those observed in fresh, unfrozen tissues. These results support the view that cryopreserved arterial allografts are immunogenic as their fresh counterparts; apart from smooth muscle cells which retained a moderate expression of HLA class I antigens following cryopreservation, our study suggests that the highly HC-10 positive endothelial cells we found to line the rich adventitial network of vasa vasorum are expected to be one of the major targets of the serological response in the recipient.

Adult↗
PubMed2006

Smooth muscle cell injury after cryopreservation of human thoracic aortas.

The cryopreservation protocol we use for arterial reconstructive surgery has been studied to evaluate smooth muscle cell (SMC) structural integrity and viability before implantation. Samples of human thoracic aortas (HTA) were harvested from five multi-organ donors. Sampling included unfrozen and cryopreserved specimens. Cryopreservation was performed using RPMI with human albumin and 10% Me(2)SO in a controlled-rate freezing apparatus. Thawing was accomplished by submerging bags in a water bath (39 degrees C) followed by washings in cooled saline. In situ cell preservation as investigated by light and transmission electron microscopy showed that SMCs from cryopreserved HTA had nuclear and cytoplasmic changes. A TUNEL assay, performed to detect DNA fragmentation in situ, showed increased SMC nuclear positivity in cryopreserved HTA when compared to unfrozen samples. 7-AAD flow cytometry assay of cells derived from cryopreserved HTA showed that an average of 49+/-16% cells were unlabeled after cryopreservation. Organ cultures aimed to study cell ability to recover cryopreservation damage showed a decreasing number of SMCs from day 4 to day 15 in cryopreserved HTA. In conclusion, the cryopreservation protocol applied in this study induces irreversible damage of a significant fraction of arterial SMCs.

Aorta, Thoracic↗
PubMed2006

Frequent elevation of Akt kinase phosphorylation in blood marrow and peripheral blood mononuclear cells from high-risk myelodysplastic syndrome patients.

The serine/threonine kinase Akt, a downstream effector of phosphatidylinositol 3-kinase (PI3K), is known to play an important role in antiapoptotic signaling and has been implicated in the aggressiveness of a number of different human cancers including acute myeloid leukemia (AML). The progression of myelodysplastic syndromes (MDSs) to AML is thought to be associated with abrogation of apoptotic control mechanisms. However, little is known about signal transduction pathways which may be involved in enhanced survival of MDS cells. In this report, we have performed immunocytochemical and flow cytometric analysis to evaluate the levels of activated Akt in bone marrow or peripheral blood mononuclear cells from patients diagnosed with MDS. We observed high levels of Ser473 phosphorylated Akt (p-Akt) staining in 90% of the cases (n=22) diagnosed as high-risk MDS, whereas mononuclear cells from normal bone marrow or low-risk MDS patients showed low or absent Ser473 p-Akt staining. Furthermore, all high-risk MDS patients also demonstrated high expression of the Class I PI3K p110delta catalytic subunit and a decreased expression of PTEN. Taken together, our results suggest that Akt activation might be one of the factors contributing to the decreased apoptosis rate observed in patients with high-risk MDS.

Adult↗
PubMed2006

Phosphoinositide 3-kinase/Akt signaling pathway and its therapeutical implications for human acute myeloid leukemia.

The phosphoinositide 3-kinase (PI3K)/Akt signaling pathway is crucial to many aspects of cell growth, survival and apoptosis, and its constitutive activation has been implicated in the both the pathogenesis and the progression of a wide variety of neoplasias. Hence, this pathway is an attractive target for the development of novel anticancer strategies. Recent studies showed that PI3K/Akt signaling is frequently activated in acute myeloid leukemia (AML) patient blasts and strongly contributes to proliferation, survival and drug resistance of these cells. Upregulation of the PI3K/Akt network in AML may be due to several reasons, including FLT3, Ras or c-Kit mutations. Small molecules designed to selectively target key components of this signal transduction cascade induce apoptosis and/or markedly increase conventional drug sensitivity of AML blasts in vitro. Thus, inhibitory molecules are currently being developed for clinical use either as single agents or in combination with conventional therapies. However, the PI3K/Akt pathway is important for many physiological cellular functions and, in particular, for insulin signaling, so that its blockade in vivo might cause severe systemic side effects. In this review, we summarize the existing knowledge about PI3K/Akt signaling in AML cells and we examine the rationale for targeting this fundamental signal transduction network by means of selective pharmacological inhibitors.

Acute Disease↗
PubMed2005

Antiapoptotic role of p38 mitogen activated protein kinase in Jurkat T cells and normal human T lymphocytes treated with 8-methoxypsoralen and ultraviolet-A radiation.

A combination of 8-methoxypsoralen and ultraviolet-A radiation (320-400 nm) (PUVA) is used for the treatment of T cell-mediated disorders, including chronic graft-versus-host disease, autoimmune disorders, and cutaneous T-cell lymphomas. The mechanisms of action of this therapy, referred to as extracorporeal phototherapy, have not been fully elucidated. PUVA is known to induce apoptosis in T lymphocytes collected by apheresis, however no information is available concerning the underlying signaling pathways which are activated by PUVA. In this study, we found that PUVA treatment of Jurkat cells and human T lymphocytes up-regulates the p38 MAPK pathway but not the p42/44 MAPK or the SAPK/JNK signaling networks. The use of a pharmacological inhibitor selective for the p38 MAPK pathway, SB203580, allowed us to demonstrate that this network exerts an antiapoptotic effect in PUVA-treated Jurkat cells and T lymphocytes from healthy donors. Moreover, the effect of SB203580 was not due to a down-regulation of the Akt survival pathway which was not activated in response to PUVA. These results may suggest that p38 MAPK-dependent signaling is very important for the regulation of survival genes after exposure to PUVA. Since the therapeutic effect of PUVA seems to depend, at least in part, on apoptosis, further studies on the apoptosis signaling networks activated by this treatment might lead to the use of signal transduction modulators in combination with PUVA, to increase the efficacy of this form of therapy.

Apoptosis↗
PubMed2005

Short- and long-term haematological surveillance of healthy donors of allogeneic peripheral haematopoietic progenitors mobilized with G-CSF: a single institution prospective study.

Healthy allogeneic donors, who were treated with G-CSF and underwent peripheral blood haematopoietic precursor collection at our Institution, were enrolled in a short- and long-term haematological surveillance protocol for a 5--7--year period. To date, 94 donors have been assessed with a mean follow-up of 30 months (4--84); for 30 subjects, the follow-up is >or=48 months. During G-CSF administration, 23/94 donors showed a significant platelet count decrease from the baseline. Pre-apheresis platelet decrement correlated with the total G-CSF dose administered, baseline platelet level and donor age. Normal platelet counts returned within 4--8 months. PMN and/or lymphocyte lower values were observed in 55/94 donors 2 weeks after G-CSF administration, with mean drops from the baseline of 40 and 36% for PMN and lymphocytes, respectively. The PMN decrease correlated inversely with donor age, as younger donors were more affected than older ones, whereas the lymphocyte decrease correlated directly with the total blood volumes processed in the apheresis courses, in particular for donors subjected to large volume leukaphereses. Long-term observation showed moderate neutrophil reduction (25% count drop from the baseline) in four of the 30 donors observed for four years or more. 14 donors showed persistent, slight lymphocytopenia (mean drop of 13%) until the third year, with recovery in the fourth year of follow-up.

Adult↗
PubMed2005

Febrile nonhaemolytic transfusion reaction caused by antibodies against human platelet antigen 5a.

Anti-human platelet antigens (HPA) alloantibodies are seldom involved in febrile nonhaemolytic reactions (FNHTRs). We describe a case in which anti-HPA-5a alloantibodies are related to an FNHTR. We studied the specificity of the alloantibodies by flow cytometry, ELISA and MACE. Typing of donors and the patient was performed by sequence-specific polymerase chain reaction. The alloantibodies were found reactive with HPA-5a antigens. The patient was HPA-5b/b, whereas the donor of the platelet apheresis involved in the FNHTR was HPA-5a/a. Despite the low frequency of anti-HPA-5a antibodies, they might be responsible for FNHTR.

Adult↗
PubMed2005

Involvement of the phosphoinositide 3-kinase/Akt signaling pathway in the resistance to therapeutic treatments of human leukemias.

A major factor undermining successful cancer treatment is the occurrence of resistance to conventional treatments such as chemotherapy and ionizing radiation. Evidence accumulated over the recent years has indicated the phosphoinositide 3-kinase/Akt signal transduction pathway as one of the major factors implicated in cancer resistance to conventional therapies. Indeed, the phosphoinositide 3-kinase/Akt axis regulates the expression and/or function of many anti-apoptotic proteins which strongly contributes to cancer cell survival. As a result, small molecules designed to specifically target key components of this signaling network are now being developed for clinical use as single therapeutic agents and/or in combination with other forms of therapy to overcome resistance. Initially, the phosphoinositide 3-kinase/Akt signal transduction pathway has been mainly investigated in solid tumors. Recently, however, this network has also been recognized as an important therapeutic target in human leukemias. Specific inhibition of this signalling pathway may be a valid approach to treat these diseases and increase the efficacy of standard types of therapy.

Drug Resistance, Neoplasm↗
PubMed2004

The conjugate Rituximab/saporin-S6 completely inhibits clonogenic growth of CD20-expressing cells and produces a synergistic toxic effect with Fludarabine.

Immunotoxins are chimeric proteins consisting of a toxin coupled to an antibody. To date, several clinical trials have been conducted, and some are still ongoing, to evaluate their anti-tumor efficacy. In this view, we chemically constructed an anti-CD20 immunotoxin with the mAb Rituximab and the type 1 ribosome-inactivating protein (RIP) saporin-S6, designed for B cells non-Hodgkin's lymphoma (NHL) therapy. This immunotoxin showed a specific cytotoxicity for the CD20+ cell lines Raji and D430B, evidenced by inhibition of protein synthesis, evaluation of apoptosis and clonogenic assay. Upon conjugation, saporin-S6 increased its toxicity on target cells by at least 2 logs, with IC(50) values of 0.1-0.3 nM. The percentage of AnnexinV+ cells was over 95% in both cell lines treated with 10 nM immunotoxin. A complete elimination of Raji clones was reached with the 10 nM immunotoxin, whereas a mixture of free RIP and mAb gave about 90% of clonogenic growth. Rituximab/saporin-S6, at 10 nM concentration, also induced apoptosis in 80% of lymphoma cells from NHL patients. Moreover, sensitivity of Raji to Rituximab/saporin-S6 was augmented when cells were coincubated with Fludarabine. The synergistic toxic effect of the two drugs led to a total elimination of the neoplastic population.

Antibodies, Monoclonal↗
PubMed2004

Expression of CTLA-4 in nonhuman primate lymphocytes and its use as a potential target for specific immunotoxin-mediated apoptosis: results of in vitro studies.

T-cell-mediated immunoregulation is one of the main mechanisms implicated in induction and maintenance of transplantation tolerance. In this regard, deletion or modulation of xeno/alloantigen-specific T cells, as well as blocking of their interactions with other cell populations, are currently being pursued for tolerance induction in humans as well as nonhuman primates. In order to investigate whether cytotoxic T-lymphocyte antigen-4 (CTLA-4) may represent a suitable target for a T cell depletion approach in nonhuman primate models, we analysed CTLA-4 expression in peripheral blood mononuclear cells (PBMCs) from nonhuman primates and the potential role of two anti-CTLA-4 saporin-conjugated immunotoxins. The analysis was performed in PBMCs from 8 cynomolgus monkeys from Philippines and from Mauritius both at protein level by flow cytometry and at transcriptional level by RT-PCR. In addition, the apoptotic role of the immunotoxins was investigated. The results showed that CTLA-4 was expressed at variable levels depending on the origin of the cynomolgus monkeys and the resting or activated cell condition. CTLA-4 was not expressed on resting Mauritius PBMCs and showed a lower up-regulation upon PMA/PHA activation compared to the Philippines PBMCs that expressed CTLA-4 also before activation. Two CTLA-4 RNA transcripts (672 and 550 bp) were detected with levels variations after cell stimulation. Two anti-CTLA-4 immunotoxins induced in vitro apoptosis of activated PBMCs from both sources of cynomolgus monkeys. This is the first report that documents CTLA-4 expression both at protein and transcriptional level by nonhuman primate PBMCs and provides novel perspectives of xeno/allograft rejection immunotherapy based on CTLA-4 targeting.

Animals↗
PubMed2003

Reduced incidence of GVHD without increase in relapse with low-dose rabbit ATG in the preparative regimen for unrelated bone marrow transplants in CML.

SUMMARY: Antithymocyte globulin (ATG) treatment prevents graft failure and results in a low incidence of GVHD, but an increased risk of relapse could be expected as a consequence of reduced GVHD. From September 1995 to June 2001, 28 consecutive chronic myeloid leukemia (CML) patients underwent unrelated bone marrow transplants: 21 were in chronic phase (CP) and seven in advanced phase (AP). Median age was 35.5 years (range 20-50). HLA typing was based on high-resolution molecular techniques; in eight cases there were one or more allele mismatches. The preparative regimen consisted of TBI, EDX 120 mg/kg and rabbit ATG 15 mg/kg. All patients engrafted and no rejection occurred. Acute GVHD grade III-IV occurred in six patients (21%). Chronic GVHD occurred in 10 (40%) and it was extensive in one. Four out of seven patients transplanted in AP had a hematological relapse. Of 21 in CP, there was one cytogenetic and one molecular relapse: these two patients are now in complete remission with imatinib mesylate. With a median follow-up of 45.7 months, the 5-year survival is 76.2% for those transplanted in CP. These data demonstrate that transplants performed in CP, with low-dose ATG, are associated with a good outcome, low incidence of GVHD and no increase of relapse.

Adult↗
PubMed2003

Constitutively active Akt1 protects HL60 leukemia cells from TRAIL-induced apoptosis through a mechanism involving NF-kappaB activation and cFLIP(L) up-regulation.

TRAIL is a member of the tumor necrosis factor superfamily which induces apoptosis in cancer but not in normal cells. Akt1 promotes cell survival and blocks apoptosis. The scope of this paper was to investigate whether a HL60 human leukemia cell clone (named AR) with constitutively active Akt1 was resistant to TRAIL. We found that parental (PT) HL60 cells were very sensitive to a 6 h incubation in the presence of TRAIL and died by apoptosis. In contrast, AR cells were resistant to TRAIL concentrations as high as 2 microg/ml for 24 h. Two pharmacological inhibitors of PI3K, Ly294002 and wortmannin, restored TRAIL sensitivity of AR cells. AR cells stably overexpressing PTEN had lower Akt1 activity and were sensitive to TRAIL. Conversely, PT cells stably overexpressing a constitutive active form of Akt1 became TRAIL resistant. TRAIL activated caspase-8 but not caspase-9 or -10 in HL60 cells. We did not observe a protective effect of Bcl-X(L) or Bcl-2 against the cytotoxic activity of TRAIL, even though TRAIL induced cleavage of BID. There was a close correlation between TRAIL sensitivity and intranuclear presence of the p50 subunit of NF-kappaB. Higher levels of the FLICE inhibitory protein, cFLIP(L), were observed in TRAIL-resistant cells. Both the cell permeable NF-kappaB inhibitor SN50 and cycloheximide lowered cFLIP(L)expression and restored sentivity of AR cells to TRAIL. Our results suggest that Akt1 may be an important regulator of TRAIL sensitivity in HL60 cells through the activation of NF-kappaB and up-regulation of cFLIP(L) synthesis.

Apoptosis↗
PubMed2003

A new selective AKT pharmacological inhibitor reduces resistance to chemotherapeutic drugs, TRAIL, all-trans-retinoic acid, and ionizing radiation of human leukemia cells.

It is now well established that the reduced capacity of tumor cells of undergoing cell death through apoptosis plays a key role both in the pathogenesis of cancer and in therapeutic treatment failure. Indeed, tumor cells frequently display multiple alterations in signal transduction pathways leading to either cell survival or apoptosis. In mammals, the pathway based on phosphoinositide 3-kinase (PI3K)/Akt conveys survival signals of extreme importance and its downregulation, by means of pharmacological inhibitors of PI3K, considerably lowers resistance to various types of therapy in solid tumors. We recently described an HL60 leukemia cell clone (HL60AR cells) with a constitutively active PI3K/Akt pathway. These cells were resistant to multiple chemotherapeutic drugs, all-trans-retinoic acid (ATRA), and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Treatment with two pharmacological inhibitors of PI3K, wortmannin and Ly294002, restored sensitivity of HL60AR cells to the aforementioned treatments. However, these inhibitors have some drawbacks that may severely limit or impede their clinical use. Here, we have tested whether or not a new selective Akt inhibitor, 1L-6-hydroxymethyl-chiro-inositol 2(R)-2-O-methyl-3-O-octadecylcarbonate (Akt inhibitor), was as effective as Ly294002 in lowering the sensitivity threshold of HL60 cells to chemotherapeutic drugs, TRAIL, ATRA, and ionizing radiation. Our findings demonstrate that, at a concentration which does not affect PI3K activity, the Akt inhibitor markedly reduced resistance of HL60AR cells to etoposide, cytarabine, TRAIL, ATRA, and ionizing radiation. This effect was likely achieved through downregulation of expression of antiapoptotic proteins such as c-IAP1, c-IAP2, cFLIP(L), and of Bad phosphorylation on Ser 136. The Akt inhibitor did not influence PTEN activity. At variance with Ly294002, the Akt inhibitor did not negatively affect phosphorylation of protein kinase C-zeta and it was less effective in downregulating p70S6 kinase (p70S6K) activity. The Akt inhibitor increased sensitivity to apoptotic inducers of K562 and U937, but not of MOLT-4, leukemia cells. Overall, our results indicate that selective Akt pharmacological inhibitors might be used in the future for enhancing the sensitivity of leukemia cells to therapeutic treatments that induce apoptosis or for overcoming resistance to these treatments.

Antineoplastic Agents↗
PubMed2003

The phosphoinositide 3-kinase/Akt pathway regulates cell cycle progression of HL60 human leukemia cells through cytoplasmic relocalization of the cyclin-dependent kinase inhibitor p27(Kip1) and control of cyclin D1 expression.

The serine/threonine protein kinase Akt, a downstream effector of phosphoinositide 3-kinase (PI3K), plays a pivotal role in tumorigenesis because it affects the growth and survival of cancer cells. Several laboratories have demonstrated that Akt inhibits transcriptional activation of a number of related forkhead transcription factors now referred to as FoxO1, FoxO3, and FoxO4. Akt-regulated forkhead transcription factors are involved in the control of the expression of both the cyclin-dependent kinase (cdk) inhibitor p27(Kip1) and proapoptotic Bim protein. Very little information is available concerning the importance of the PI3K/Akt pathway in HL60 human leukemia cells. Here, we present our findings showing that the PI3K/Akt axis regulates cell cycle progression of HL60 cells through multiple mechanisms also involving the control of FoxO1 and FoxO3. To this end, we took advantage of a HL60 cell clone (HL60AR cells) with a constitutively activated PI3K/Akt axis. When compared with parental (PT) HL60 cells, HL60AR cells displayed higher levels of phosphorylated FoxO1 and FoxO3. In AR cells forkhead factors localized predominantly in the cytoplasm, whereas in PT cells they were mostly nuclear. AR cells proliferated faster than PT cells and showed a lower amount of the cdk inhibitor p27(Kip1), which was mainly found in the cytoplasm and was hyperphosphorylated on threonine residues. AR cells also displayed higher levels of cyclin D1 and phosphorylated p110 Retinoblastoma protein. The protein levels of cdk2, cdk4, and cdk6 were not altered in HL60AR cells, whereas the activities of both ckd2 and cdk6 were higher in AR than in PT cells. These results show that in HL60 cells the PI3K/Akt signaling pathway may be involved in the control of the cell cycle progression most likely through mechanisms involving the activation of forkhead transcription factors.

Androstadienes↗
PubMed2003

Flow cytometry characterization of white cell-reduced blood: apoptosis markers and morphology of postfiltration elements.

BACKGROUND AND OBJECTIVES: Apoptosis affects white blood cells (WBCs) contained in packed red blood cell (RBC) units. This phenomenon was recently described also in residual WBCs after filtration. The aim of this study was to better characterize the residual WBCs postfiltration by using apoptosis markers and morphology. MATERIALS AND METHODS: Immunofluorescence, flow cytometry and cell-sorting techniques were utilized. RESULTS: Residual leucocytes of leucodepleted packed RBC units showed increasing values of apoptotic elements in a time-course experiment. We also demonstrated that these elements are positive for APO 2.7 monoclonal antibody (mAb), poly ADP-ribose polymerase (PARP) cleavage and fluorescein isothiocyanate (FITC)-conjugated N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), all of which indicate that programmed death is a feature of this population of cells. Phenotypic analysis with CD45 side-scatter gating demonstrated also that CD15 and CD16 granulocyte-associated antigens are present on a subset of postfiltration leucocytes. Moreover, the expression of human leucocyte antigen (HLA) class I antigens is maintained. Sorting of CD45-positive cells and morphological analysis of these samples confirmed that leucocytes in postfiltration units have morphological characteristics of dying cells. CONCLUSIONS: Our study extends previous observations regarding the morphology and function of apoptotic cells in leucodepleted blood units, which suggested the presence of apoptotic cells in postfiltration leucocytes. Cleaved PARP, APO 2.7 mAb and positivity for the FITC-conjugated Z-VAD-analogous reagent strongly suggest the activation of programmed death pathways. In addition, the maintained granulocyte-associated and HLA class I antigens might recall an immune response in multitransfused patients.

Apoptosis↗
PubMed2003

Enhanced telomere shortening in transformed lymphoblasts from patients with X linked dyskeratosis.

AIM: Dyskeratosis congenita (DC) is characterised by the failure of those tissues that are rapidly dividing in the adult, particularly the skin, mucosae, and haemopoietic system. The X linked form of the disease is caused by mutations of the DKC1 gene, which encodes dyskerin, a protein that is necessary for the function of telomerase. Cultured DC lymphoblastoid cells are characterised by a reduced expansion of the cell population because of the progressive increase in apoptosis compared with the number of cell divisions. This report aimed to verify whether this is caused by a defect in telomerase function. METHODS: Variations in telomere length over time were evaluated in two cultured lymphoblastoid cell lines derived from patients with X linked DC and control cells derived from a non-affected individual. In addition, the effect of inhibiting poly (ADP-ribose) polymerase (PARP), which is involved in the cellular response to excessive telomere shortening, was assessed. One DC cell line and the control cells were treated with the specific PARP inhibitor 1,5-dihydroxyquinoline (IQ). RESULTS: In DC cells the increase in cell death was associated with progressive telomere shortening, and this was not seen in the control cells. Treatment with IQ delayed the increase of apoptosis in DC cells. CONCLUSIONS: These observations indicate that the reduced expansion that characterises cultured cells obtained from patients with X linked DC is caused by premature telomere shortening.

Apoptosis↗