Dabrafenib in metastatic melanoma: a monocentric 'real life' experience.

Dabrafenib is a potent BRAF-kinase inhibitor. Its activity was evaluated on 40 consecutive metastatic melanoma patients (pts) harboring the V600BRAF mutations. Dabrafenib was administered orally at the dosage of 150 mg b.i.d. daily. ORR was 82%, with 7% CR, 62% PR, 13% SD and 18% PD. The median PFS and OS were seven and 17 months, respectively (median follow-up: 8.5 months). Increased risk of progression was found in pts with elevated LDH, ECOG PS >1 and more than two metastatic sites. Grade 3-4 adverse events were recorded in 4 pts. In this retrospective analysis, Dabrafenib confirmed its role as the standard clinical option in metastatic melanoma pts.

Risk of second primary malignancies among 1537 melanoma patients and risk of second primary melanoma among 52 354 cancer patients in Northern Italy.

BACKGROUND: The number of melanoma survivors has been increasing for decades due to early diagnosis and improved survival. These patients have an increased risk of developing a second primary cancer (SPC); also, melanoma is frequently diagnosed among patients firstly diagnosed with an extracutaneous malignancy. OBJECTIVE: We evaluated the risk of developing a SPC among 1537 melanoma patients, and the risk of second primary melanoma (SPM) in 52 354 extracutaneous cancer patients, who were treated at the European Institute of Oncology in Milan, Italy, during 2000-2010. MATERIAL AND METHODS: We calculated standardized incidence ratios (SIR) by applying gender-, age-, year- and region-specific reference rates to the follow-up time accrued between the diagnosis of the first and the second primary malignancies. RESULTS: Seventy-six SPC were diagnosed during a median follow-up of 4 years, of which 49 (64%) during the first 2 years upon melanoma diagnosis. The SIR was increased for cancer of breast (4.10, 95% CI 2.79-6.03), thyroid (4.67, 95% CI 1.94-11.22), brain (6.13, 95% CI 2.30-16.33) and for non-Hodgkin lymphoma (3.12, 95% CI 1.30-7.50). During a median follow-up of 4 years, 127 SPM were diagnosed: thick lesions were less frequent than for melanoma diagnosed as first cancer. The SIR was increased for cancer of breast (5.13, 95%CI 3.91-6.73), thyroid (16.2, 95%CI: 5.22-50.2), head and neck (5.62, 95%CI 1.41-22.50), soft tissue (8.68, 95%CI 2.17-34.70), cervix (12.5, 95% CI 3.14-50.20), kidney (3.19, 95%CI 1.52-6.68), prostate (4.36, 95%CI 2.63-7.24) and acute myeloid leukaemia (6.44, 95%CI 2.42-17.20). CONCLUSIONS: The most likely causes of these associations are the clustering of lifestyle risk factors in the same subgroups of population, mainly on a sociocultural basis and surveillance bias. This raises important questions about how to best follow cancer survivors by avoiding an inefficient use of resources and an excessive medicalization of these patients' lives.

Baseline neutrophils and derived neutrophil-to-lymphocyte ratio: prognostic relevance in metastatic melanoma patients receiving ipilimumab.

BACKGROUND: Clinical responses to ipilimumab are variable in terms of onset, magnitude and duration. Upfront identification of patients who are more likely or unlikely to benefit from treatment is a major need. PATIENTS AND METHODS: Prospectively collected data from 720 advanced melanoma patients treated with ipilimumab 3 mg/kg within the Italian expanded access program were analyzed. The derived neutrophil-to-lymphocyte ratio (dNLR) was calculated from baseline peripheral blood cell counts, and receiver operating characteristic curve was used to evaluate the best cutoff for this marker. Patients were stratified according to dichotomized baseline absolute neutrophil counts (ANC), dNLR and their combination. The prognostic values of ANC and dNLR for survival were assessed using multivariate Cox proportional hazard models. A subgroup analysis including LDH in the models was also carried out. RESULTS: The median follow-up was 16.5 months. The optimal cutoff for dNLR was 3. Baseline ANC and dNLR were significantly associated with the outcome of ipilimumab-treated melanoma patients, in terms of disease progression and death (P < 0.0001 for all). Furthermore, for each elevated variable, prognosis worsened. Patients with both ANC ≥ 7500 and dNLR ≥ 3 had a significantly and independently increased risk of death [hazard ratio(HR) = 5.76; 95% confidence interval (CI) 4.29-7.75] and of progression (HR = 4.10; 95% CI 3.08-5.46) compared with patients with both lower ANC and dNLR. Patients with one of the two factors elevated displayed an intermediate risk of progression and death. The 1- and 2-year survival rates were 2% and 0%, respectively, for patients with ANC ≥ 7500 and dNLR ≥ 3, and 43% and 24%, respectively, for patients with both lower ANC and dNLR. CONCLUSIONS: Although these findings need to be confirmed and validated, we suggest that a neutrophil-based index may help risk-group stratification and assist disease-management strategies. Furthermore, the potential predictive value of this index for response to ipilimumab should be investigated in randomized clinical trials.

Personalised medicine: Development and external validation of a prognostic model for metastatic melanoma patients treated with ipilimumab.

PURPOSE: The purpose of this study was to set up a prognostic model for the identification of survival predictors specific for melanoma patients treated with ipilimumab. EXPERIMENTAL DESIGN: The following prospectively collected data were utilised: patient and primary tumour characteristics, relapse-free-interval, site and number of metastases, previous therapies and level of serum biomarkers (lactic dehydrogenase (LDH), C-reactive protein, ß2-microglobulin, vascular endothelial growth factor (VEGF), IL2, IL6, S-100, alkaline phosphatase (ALP), transaminases, leucocyte count, lymphocytes subpopulations). A multivariate prognostic model was developed using the Cox regression model fitted to the data of 113 consecutive metastatic patients treated with ipilimumab (3 mg/kg, q3w) at Veneto Institute of Oncology (IOV). External validation was obtained using the data of 69 and 34 patients treated at European Oncology Institute (IEO) and University of Torino (UT), respectively. RESULTS: Median survival was 8.3, 4.9 and 7.1 months from first ipilimumab administration at IOV, IEO and UT, respectively. Both higher baseline levels of LDH (Hazard Ratio [HR] v=1.36, 95% Confidence Interval [CI] 1.16-1.58, P<.001) and neutrophils (HR=1.76, 95% CI 1.41-2.10, P<.001) were associated with worse prognosis. Model performance was satisfactory both upon internal validation (Dxy=0.42) and external validation (Dxy=0.40). Serum LDH and neutrophil count discriminated patients who lived more (low neutrophils and low LDH) or less (high LDH or neutrophils) than 24 months. CONCLUSION: Serum LDH and neutrophil count were significant independent prognostic factors. This externally validated prognostic nomogram, could help clinicians to identify the patients who would benefit most from ipilimumab and consequently to improve resource allocation. These easily available biomarkers deserve further validation.

Baseline neutrophil-to-lymphocyte ratio is associated with outcome of ipilimumab-treated metastatic melanoma patients.

BACKGROUND: Ipilimumab improves the survival of metastatic melanoma patients. Despite documented, durable objective responses, a significant number of patients fails to benefit from treatment. The aim of this study was to identify an upfront marker for treatment benefit. METHODS: A total of 187 metastatic melanoma patients treated in three Italian Institutions with 3 mg kg(-1) ipilimumab, and 27 patients treated with 10 mg kg(-1) ipilimumab, were evaluated. Neutrophil-to-lymphocyte ratio (NLR) was calculated from pre-therapy full blood counts. Progression-free survival (PFS) and overall survival (OS) were assessed using the Kaplan-Meier method, and multivariate Cox models were applied, adjusting for confounders and other prognostic factors. RESULTS: In the training cohort of 69 patients treated at European Institute of Oncology, pre-therapy NLR was identified as the strongest and independent marker for treatment benefit in multivariate analyses. Patients with baseline NLR<5 had a significantly improved PFS (HR=0.38; 95% CI: 0.22-0.66; P=0.0006) and OS (HR=0.24; 95% CI: 0.13-0.46; P<0.0001) compared with those with a NLR⩾5. Associations of low NLR with improved survival were confirmed in three validation cohorts of patients. CONCLUSION: Our findings show that baseline NLR is strongly and independently associated with outcome of patients treated with ipilimumab, and may serve to identify patients most likely to benefit from this therapy.

Ipilimumab retreatment in patients with pretreated advanced melanoma: the expanded access programme in Italy.

BACKGROUND: Retreatment with ipilimumab has been shown to re-establish disease control in some patients with disease progression. Here, we report the efficacy and safety of retreatment with ipilimumab 3 mg kg(-1) among patients participating in an expanded access programme in Italy. METHODS: Patients who achieved disease control during induction therapy were retreated with ipilimumab upon progression (3 mg kg(-1) every 3 weeks for up to four doses), providing they had not experienced toxicity that precluded further dosing. Tumour assessments were conducted after retreatment, and patients were monitored throughout for adverse events. RESULTS: Of 855 patients treated with ipilimumab, 51 were retreated upon disease progression. Of these, 28 (55%) regained disease control upon retreatment and 42% were alive 2 years after the first induction dose of ipilimumab; median overall survival was 21 months. Eleven patients (22%) had a treatment-related adverse event of any grade during retreatment. These were generally mild-to-moderate and resolved within a median of 4 days. No new types of toxicity were reported. CONCLUSIONS: For patients who meet predefined criteria, retreatment with ipilimumab is generally well tolerated and can translate into clinical benefit. This strategy should be compared with other therapeutic options in randomised controlled trials.

Newly identified tumor antigens as promising cancer vaccine targets for malignant melanoma treatment.

Immunogenicity of tumour cells, immunomodulation and direct targeting of signalling pathways are promising avenues and matter of dated and innovative research in melanoma. Unfortunately, tumour cells are considered to be antigenic, but not immunogenic, either due to presentation of weakly recognized antigens or to the inability of the immune system to recognize them. However, spontaneous complete remission can be rarely observed in patients affected by melanoma, which are mainly attributed to the immune response against the tumour. Also, an elevated frequency of spontaneous humoral immune responses against tumour antigens was occasionally found in patients. These data confirm the existence of an interaction of the immune system with the tumour which can be used as a promising pathway for intervention and incorporates all portions of the immune system. The cancer immunotherapy approach is based on artificial activation of the immune system against the tumour and groups several types of treatments including immunization/vaccination but also modulation of immunity by cytokines or antibodies. Immunization approaches could either be based on undefined tumour antigens (e.g. whole tumour cells, tumour cell lysates, or tumour-antigen enriched fractions) or aimed at eliciting T-cell responses against specific tumour antigens. Novel and contemporary antigen-targeted therapy strategies, mainly directed to Cancer Testis and Heat Shock Proteins, leading to a possible active immunization against melanoma through T-cell specific activation, are discussed in this review.

Efficacy of 90Y ibritumomab-tiuxetan treatment in a case of resistant gastric MALT non-Hodgkin's lymphoma.

Treatment modalities for resistant/relapsing gastric mucosa associated lymphoid tissue (MALT) non-Hodgkin's lymphoma (NHL) are not yet well standardized. In the past, most patients were treated surgically with a gastrectomy, while, more recently, radiotherapy and systemic approaches (chemotherapy and immunotherapy) have been used with improving results.Here, we report the case of a patient affected by MALT NHL resistant to antibiotics, chemotherapy and immunotherapy, who achieved a durable complete remission after radio-immunotherapy treatment with Zevalin ((90)Y ibritumomab-tiuxetan), administered in a single-standard dose. This observation must be confirmed on a larger series but suggests that radio-immunotherapy may be a valid approach in treating relapsing MALT NHL patients, or those resistant to conventional therapies, so avoiding more aggressive and toxic approaches.

A new comprehensive gene expression panel to study tumor micrometastasis in patients with high-risk breast cancer.

The incidence and prognostic relevance of bone marrow (BM) and leukapheresis (PBPC) tumor cell contamination (TCC) in breast cancer patients is still to be circumstantiated. We developed a new comprehensive gene expression panel to study cytokeratins (CK), maspin (MAS) and mammaglobin (MAM) as possible predictors of prognosis. Forty-eight patients undergoing high dose chemotherapy (HDCT) and PBPC support were enrolled and analyzed for TCC on 116 PBPC apheresis and 96 BM obtained at basal conditions. All of the patients were evaluated by reverse transcriptase nested PCR (RT-PCR) for MAM and MAS gene expression and by immunocytochemistry (ICC) and nested RT-PCR to evaluate CK expression. PBPC and BM frequency of CK-positive (+) cells was 12-13% by ICC and 71-73% by RT-PCR respectively. Sixty-seven percent of CK ICC+ samples were MAM RT-PCR+ and 89% of them were MAS RT-PCR+. PBPC and BM frequency of MAM+ cells was 21% and 31% respectively, while for MAS+ cells it was 48% and 52% respectively by RT-PCR. After 71 mo median FU, 16 patients (33%) relapsed and 14 (88%) had BM/PBPC TCC. No marker had an impact on overall survival (OS) but MAS expression on BM and MAM expression on PBPC correlated with a statistically significant improved (p=0.05) and worsened RFS (p=0.06) respectively. These data confirm the activity of MAM as a negative prognostic factor and show for the first time that MAS could work as a tumor suppressor gene even in a clinical setting, since it protects from recurrence.

ACOD, a modified CHOP regimen for elderly patients with aggressive non-Hodgkin's lymphoma.

The aim of this study is to verify the feasibility and the clinical activity of a new CHOP-like schedule (ACOD) with a fractionated days 1 and 8 administration in elderly patients. This regimen was chosen in the attempt to allow a sufficient dose intensity (DI) of each drug with better compliance. Fifty-two patients, (74 years, median age), with diffuse large B cell non-Hodgkin's lymphoma were retrospectively evaluated. Patients received ADM 25 mg/sqm, CTX 500 mg/sqm, VCR 1.2 mg/sqm (max 2 mg intravenously) days 1 and 8 and PDN 50 mg orally, days 1-8. Results showed that 54% of patients reached a complete remission, 21% a partial remission with an overall response rate of 75%. Two-thirds of the patients received at least 70% of the planned dose of cyclophosphamide and doxorubicin and 50% of vincristine and prednisone. The median duration of follow up was 12.6 months (range 0.7-61.4). The estimated median OS was 15.2 months (95%CI = [11.6, not estimable]); the estimated median PFS was 5.7 months (95%CI = [5.12, not estimable]). After 2 years, the proportion of patients alive was 47% (95%CI = 34-64%) and the proportion of patients free from progression was 39% (95%CI = 27-57%). Grade 3-4 leukopenia was observed in 61% of patients with 11% of febrile neutropenia. In conclusion, the ACOD chemotherapy regimen seems safe and feasible in elderly patients. This schedule allowed a sufficient DI of chemotherapic agents with clinical results very similar to those recorded with the standard CHOP regimen in young adults.

Thalidomide in multiple myeloma, myelodysplastic syndromes and histiocytosis. Analysis of clinical results and of surrogate angiogenesis markers.

BACKGROUND: Thalidomide, as a single agent, has been recently found to induce a clinical response in one third of refractory or relapsed myeloma patients. Although it has been reported that thalidomide significantly inhibits angiogenesis. it is still unclear whether its clinical effect is mediated, at least in part, by its anti-angiogenic properties. PATIENTS AND METHODS: We evaluated thalidomide as a single agent in myeloma, myelodysplastic syndromes (MDS) and histiocytosis, i.e. hematological diseases characterized by increased angiogenesis, and measured prospectively a number of surrogate angiogenesis markers. RESULTS: Clinical responses were observed in 7 of 17 myeloma and 2 of 5 MDS patients. The histiocytosis patient had a partial response. At the time of the best clinical response, plasma levels of angiogenic growth factors, vascular endothelial growth factor (VEGF) and basic-fibroblast growth factor (b-FGF), were significantly decreased, and flow cytometry indicated a decrease of activated endothelial cells in the bone marrow of responding MDS patients. CONCLUSIONS: These observations confirm thalidomide efficacy in myeloma, suggest a possible use in MDS and histiocytosis and may contribute to the prediction of clinical response and to understanding the mechanism of thalidomide's action.

Endostatin, an antiangiogenic drug, induces tumor stabilization after chemotherapy or anti-CD20 therapy in a NOD/SCID mouse model of human high-grade non-Hodgkin lymphoma.

Both chemotherapy and chimeric anti-CD20 monoclonal antibodies are effective agents against B-cell non-Hodgkin lymphoma (NHL). However, patients achieving remission are at risk of relapse. To evaluate the effect of the antiangiogenic drug endostatin used alone and after the administration of cyclophosphamide (CTX) or the anti-CD20 antibody rituximab, we generated a new model of human NHL by transplanting Namalwa cells intraperitoneally into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. First, we determined the most effective treatment schedule for the drugs assessed. When administered alone, CTX (3 courses of 75 mg/kg of body weight given intraperitoneally), rituximab (3 courses of 25 mg/kg given intraperitoneally), and endostatin (5 courses of 50 microg given subcutaneously) delayed tumor growth, and CTX was the most effective in controlling bulky disease. When given after chemotherapy or immunotherapy, endostatin effectively induced tumor stabilization. When mice given CTX or rituximab on days 3, 5, and 7 after transplantation were randomly assigned to receive endostatin or phosphate-buffered saline on days 15 to 19, tumor growth was prevented in endostatin-treated mice as long as the drug was administered. Furthermore, administration of endostatin on days 25 to 29 after tumor regrowth still induced significant tumor regression, whereas CTX and rituximab were not effective. The specific antiangiogenic action of endostatin was confirmed by in vitro and in vivo studies indicating that the drug inhibited proliferation and induced apoptosis of endothelial (but not of NHL) cells. In conclusion, sequential administration of chemotherapy and endostatin seems promising for treating bulky NHL, and the less toxic sequential administration of rituximab and endostatin is promising for treating limited disease. (

Evaluation of acute toxicities associated with autologous peripheral blood progenitor cell reinfusion in patients undergoing high-dose chemotherapy.

Peripheral blood progenitor cell reinfusion (PBPC) in patients undergoing high-dose chemotherapy (HDC) for poor prognosis malignancies, has been described as causing possible acute gastrointestinal (nausea, vomiting), allergic (oedema, bronchospasm, anaphyl- axis), renal (proteinuria, haematuria) and/or cardiovascular (hypotension, arrhythmia, conduction disturbances, transient ischaemic phenomena) toxicities. To establish the clinical relevance of these observations and the possible relationship with different HDC regimens used, we performed a clinical and instrumental evaluation on 33 patients with advanced breast cancer, non-Hodgkin's lymphoma, Hodgkin's disease, relapsed ovarian cancer, Ewing's sarcoma, extragonadal germinal tumour and small cell lung cancer. They underwent at least one reinfusion each for a total of 51 studied procedures. No patient had a previous history of cardiovascular disease or significant intercurrent illness such as diabetes or liver, renal or neurologic impairment. All patients had totally implanted central venous catheters, through which the transplants had been collected and reinfused without technical consequences. To evaluate cardiovascular function, we continuously monitored 12-lead ECGs, with arterial pressure (AP) measurements every 5 min from the beginning of the procedure to 15 min after the reinfusion ended. We did not observe any significant differences between basal and subsequent steps in AP, heart rate, PQ and QTc time, P wave and QRS complex duration or P wave and QRS electrical axes. No patient showed any ST-T tract pathological abnormality, but one patient developed a transient ectopic atrial rhythm, without any haemodynamic disfunction and with spontaneous reversion to sinus rhythm. No patient complained of symptoms of haemodynamic failure. Gastrointestinal side-effects appeared to be strictly related to speed of reinfusion and to the number of packs reinfused, probably reflecting on the amount of dimethylsulphoxide infused. In one patient a tonic-clonic seizure occurred during a vomiting episode, but no patient developed allergic or renal toxicities. We conclude that PBPC reinfusion, if managed according to the procedure we propose in patients without organic impairment, is a safe procedure not associated either with increased risk of acute arrhythmias or ischaemic or significant systemic acute toxicities. Bone Marrow Transplantation (2000) 25, 173-177.

Idarubicinol myelotoxicity: a comparison of in vitro data with clinical outcome in patients treated with high-dose idarubicin.

We evaluated in vitro the toxicity of idarubicin and its active metabolite idarubicinol on haematopoietic progenitors, using human umbilical cord blood and peripheral blood progenitors to obtain dose-response curves. We treated 16 patients with poor prognosis lymphoma in a phase I-II trial of high-dose idarubicin and melphalan and investigated if idarubicinol persisting in patients' plasma at the time of transplantation (day 0), on day +1 and +2 could result in an inhibition of infused progenitors. Colony inhibition was correlated with pharmacokinetic data and with the time of patients' engraftment. Plasma samples obtained before idarubicin treatment demonstrated a colony-stimulating effect, increasing the cloning efficiency by 72%. The inhibitory activity on colony forming unit granulocyte-macrophage (CFU-GM) of patients' plasma collected on the day of transplantation was lower than expected from dose-response curves (21% measured vs 70% expected). The time to patients' WBC and PLT recovery correlated with the amount of CD34+ cells reinfused and, to a lesser extent, with the colony-inhibiting effect of patients' plasma. The correlation between idarubicinol concentration and CFU-GM inhibition was not significant. These data suggest that plasma drug concentration on the day of stem cell reinfusion may overestimate the toxicity of residual anthracyclines to the transplanted cells.

Angiogenesis in myelodysplastic syndromes.

It is now well established that solid tumour growth depends on angiogenesis. However, less is known about the generation of new vessels in haematological malignancies and, in particular, in preleukaemic-myelodysplastic syndromes (MDS). In this study, bone marrow microvessel density (MVD) was assessed by immunohistochemistry and compared in trephine biopsies from 14 controls, five infectious disease (ID), 82 MDS, 15 acute myeloid leukaemia (AML) and 14 myeloproliferative disorder (MPD) patients. Statistical analysis (P < 0.001) demonstrated that MDS MVD was higher than in controls and ID (21 +/- 9 vs 6 +/- 2 and 10 +/- 8 respectively) but lower than AML (30 +/- 12) and MPD (40 +/- 12). Among MDS-FAB subtypes, MVD was significantly higher in RAEB-t, CMML and fibrosis subsets compared to RA, RARS and RAEB subsets (P= 0.008). To further investigate angiogenesis machinery, the expression of vascular endothelial growth factor (VEGF) was evaluated by means of immunohistochemistry in control, MDS, AML and MPD biopsies. Even though VEGF mRNA expression was reported in the past in AML cell cultures and cell lines, in our samples VEGF expression was found to be particularly strong in most of the megakaryocytes but significantly less prominent in other cell populations including blasts. Since our findings suggest a correlation between angiogenesis and progression to leukaemia, additional work is now warranted to determine what regulates the generation of new vessels in MDS and leukaemia.

Angiogenic growth factors and endostatin in non-Hodgkin's lymphoma.

A number of clinical studies have demonstrated the prognostic significance of angiogenesis and angiogenic growth factors in solid tumours; however, very little is known about the relevance of these parameters in haematological malignancies. We evaluated circulating levels of angiogenic growth factors and endostatin in 36 non-Hodgkin's lymphoma (NHL) patients. Baseline vascular endothelial growth factor (VEGF) levels of patients in complete remission (CR) after a median follow-up of 21 months were significantly lower than those of patients with progressive disease (P = 0.016). Event-free survival (EFS) rate was significantly higher in patients who had baseline VEGF and basic-fibroblast growth factor (b.FGF) levels below the median values of 147 and 19.5 pg/ml (P = 0.018 and 0.039 by log-rank test, respectively). Conversely, the levels of endostatin, angiogenin and leptin were not different in CR patients compared to relapsed patients and did not correlate with EFS. Our data suggest that b-FGF and, particularly, VEGF might be considered prognostic factors in NHL staging and management.

Totally implantable central venous access ports for high-dose chemotherapy administration and autologous stem cell transplantation: analysis of overall and septic complications in 68 cases using a single type of device.

Sixty-eight patients suffering from breast cancer, ovarian cancer, lymphoma or multiple myeloma were treated with high-dose chemotherapy and autologous stem cell transplantation. They underwent placement of a central venous port via the subclavian vein for delivery of chemotherapy and reinfusion of stem cells. All patients were followed prospectively for device-related and overall complications, comprising a total of 18,213 days in situ (median: 267 days, range: 90-480). One patient experienced a pneumothorax (1.4%) spontaneously resolved, as an acute toxicity. Two patients (2.8%, 0.1 episodes/1000 days of use) were forced to have the port removed due to infection, caused by Streptococcus mitis in one case, while the causative agent was not identified by laboratory tests in the second. The other 66 patients completed the therapeutic programme, including peripheral stem cell reinfusions and supportive care, such as i.v. antibiotics, antiemetics or fluid administration and blood sample collection, without additional complications. In conclusion, the use of totally implantable central venous access ports has resulted in good long-term access to central veins, in spite of the severe neutropenia and increased septic risk of this category of oncology patients.

Caspases mediate retinoic acid-induced degradation of the acute promyelocytic leukemia PML/RARalpha fusion protein.

All-trans-retinoic acid (RA) treatment induces morphological remission in acute promyelocytic leukemia (APL) patients carrying the t(15;17) and expressing the PML/RARalpha product by inducing terminal differentiation of the leukemic clone. RA treatment induces downregulation of PML/RARalpha and reorganization of the PML-nuclear bodies. These events have been proposed to be essential for the induction of APL cell differentiation by RA. Here, we show that in the APL-derived NB4 cell line as well as in myeloid precursor U937 cells expressing the PML/RARalpha (U937/PR9) and in blasts from APL patients, the PML/RARalpha fusion protein is cleaved by a caspase 3-like activity induced by RA treatment. In fact, a caspase 3-like activity is detectable in PML/RARalpha expressing cells after RA treatment, and selective caspase inhibitor peptides are able to prevent the RA-induced degradation of the fusion protein in vivo and in vitro. Using recombinant caspases and PML/RARalpha deletion mutants we mapped a caspase 3 cleavage site (Asp 522) within the alpha-helix region of the PML component of the fusion protein. The extent of PML/RARalpha cleavage directly correlates with the ability of RA to restore the normal PML nuclear bodies (NBs) pattern. However, RA-induced differentiation is not prevented by the persistence of the fusion product and occurs in the absence of normally structured PML NBs. These results indicate that PML/RARalpha is directly involved in conferring RA sensitivity of APL cells and that the RA-induced reassembly of PML NBs is the consequence of the disappearance of PML/RARalpha.