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The APL0406 study showed that arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) are not inferior to standard ATRA and chemotherapy (CHT) in newly diagnosed, low-intermediaterisk acute promyelocytic leukaemia (APL). We analysed the kinetics of promyelocytic leukaemia-retinoic acid receptor-α (PML-RARα) transcripts by real-time quantitative PCR (RQ-PCR) in bone marrow samples from 184 patients and assessed the prognostic impact of fms-related tyrosine kinase 3-internal tandem duplication (FLT3-ITD) in 159 patients enrolled in this trial in Italy. After induction therapy, the reduction of PML-RARα transcripts was significantly greater in patients receiving ATRA-CHT as compared with those treated with ATRA-ATO (3.4 vs 2.9 logs; P=0.0182). Conversely, at the end of consolidation, a greater log reduction of PML-RARα transcripts was detected in the ATRA-ATO as compared with the ATRA-CHT group (6.3 vs 5.3 logs; P=0.0024). FLT3-ITD mutations had no significant impact on either event-free survival (EFS) or cumulative incidence of relapse in patients receiving ATRA-ATO, whereas a trend for inferior EFS was observed in FLT3-ITD-positive patients receiving ATRA-CHT. Our study shows at the molecular level that ATRA-ATO exerts at least equal and probably superior antileukaemic efficacy compared with ATRA-CHT in low-intermediaterisk APL. The data also suggest that ATRA-ATO may abrogate the negative prognostic impact of FLT3-ITD.

Purpose: A randomized clinical trial compared efficacy and toxicity of standard all-trans-retinoic acid (ATRA) plus chemotherapy versus ATRA plus arsenic trioxide in patients with newly diagnosed, low- or intermediate-risk acute promyelocytic leukemia (APL). Here, we report health-related quality-of-life (HRQOL) results., Patients and Methods: HRQOL was a secondary end point of this trial. The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 was used to assess HRQOL at end of induction and after consolidation therapy. All analyses were based on 156 patients who received at least one dose of treatment, with groups defined according to randomly assigned treatment. Primary analysis was performed, estimating mean HRQOL score over time and differences between treatment arms using a linear mixed model., Results: Overall, 162 patients age 18 to 70 years were enrolled. Of these, 150 and 142 patients were evaluable for HRQOL after induction therapy and third consolidation course, respectively. Overall compliance with HRQOL forms was 80.1%. The largest difference, favoring patients treated with ATRA plus arsenic trioxide, was found for fatigue severity (mean score difference, -9.3; 95% CI, -17.8 to -0.7; P = .034) at end of induction therapy. This difference was also clinically relevant. HRQOL differences between treatment arms at end of consolidation showed that for several scales, differences between treatment arms were marginal., Conclusion: Overall, current HRQOL findings further support the use of ATRA plus arsenic trioxide as preferred first-line treatment in patients with low- or intermediate-risk APL., (© 2014 by American Society of Clinical Oncology.)

Background: All-trans retinoic acid (ATRA) with chemotherapy is the standard of care for acute promyelocytic leukemia (APL), resulting in cure rates exceeding 80%. Pilot studies of treatment with arsenic trioxide with or without ATRA have shown high efficacy and reduced hematologic toxicity., Methods: We conducted a phase 3, multicenter trial comparing ATRA plus chemotherapy with ATRA plus arsenic trioxide in patients with APL classified as low-to-intermediate risk (white-cell count, ≤10×10(9) per liter). Patients were randomly assigned to receive either ATRA plus arsenic trioxide for induction and consolidation therapy or standard ATRA-idarubicin induction therapy followed by three cycles of consolidation therapy with ATRA plus chemotherapy and maintenance therapy with low-dose chemotherapy and ATRA. The study was designed as a noninferiority trial to show that the difference between the rates of event-free survival at 2 years in the two groups was not greater than 5%., Results: Complete remission was achieved in all 77 patients in the ATRA-arsenic trioxide group who could be evaluated (100%) and in 75 of 79 patients in the ATRA-chemotherapy group (95%) (P=0.12). The median follow-up was 34.4 months. Two-year event-free survival rates were 97% in the ATRA-arsenic trioxide group and 86% in the ATRA-chemotherapy group (95% confidence interval for the difference, 2 to 22 percentage points; P<0.001 for noninferiority and P=0.02 for superiority of ATRA-arsenic trioxide). Overall survival was also better with ATRA-arsenic trioxide (P=0.02). As compared with ATRA-chemotherapy, ATRA-arsenic trioxide was associated with less hematologic toxicity and fewer infections but with more hepatic toxicity., Conclusions: ATRA plus arsenic trioxide is at least not inferior and may be superior to ATRA plus chemotherapy in the treatment of patients with low-to-intermediate-risk APL. (Funded by Associazione Italiana contro le Leucemie and others; ClinicalTrials.gov number, NCT00482833.).

We investigated whether body mass index (BMI) correlates with distinct outcomes in newly diagnosed acute promyelocytic leukemia (APL). The study population included 144 patients with newly diagnosed and genetically confirmed APL consecutively treated at a single institution. All patients received All-trans retinoic acid and idarubicin according to the GIMEMA protocols AIDA-0493 and AIDA-2000. Outcome estimates according to the BMI were carried out together with multivariable analysis for the risk of relapse and differentiation syndrome. Fifty-four (37.5%) were under/normal weight (BMI < 25), whereas 90 (62.5%) patients were overweight/obese (BMI ≥ 25). An increased BMI was associated with older age (P < .0001) and male sex (P = .02). BMI was the most powerful predictor of differentiation syndrome in multivariable analysis (odds ratio = 7.24; 95% CI, 1.50-34; P = .014). After a median follow-up of 6 years, the estimated cumulative incidence of relapse at 5 years was 31.6% (95% CI, 22.7%-43.8%) in overweight/obese and 11.2% (95% CI, 5.3%-23.8%) in underweight/normal weight patients (P = .029). Multivariable analysis showed that BMI was an independent predictor of relapse (hazard ratio = 2.45, 95% CI, 1.00-5.99, in overweight/obese vs under/normal weight patients, P = .049). An increased BMI at diagnosis is associated with a higher risk of developing differentiation syndrome and disease relapse in APL patients treated with AIDA protocols.

After the identification of discrete relapse-risk categories in patients with acute promyelocytic leukemia (APL) receiving all-trans retinoic and idarubicin (AIDA)-like therapies, the Gruppo Italiano Malattie Ematologiche dell'Adulto (GIMEMA) designed a protocol for newly diagnosed APL (AIDA-2000) in which postremission treatment was risk-adapted. Patients with low/intermediate risk received remission at 3 anthracycline-based consolidation courses, whereas high-risk patients received the same schedule as in the previous, non-risk-adapted AIDA-0493 trial including cytarabine. In addition, all patients in the AIDA-2000 received all-trans retinoic acid (ATRA) for 15 days during each consolidation. After induction, 600 of 636 (94.3%) and 420 of 445 (94.4%) patients achieved complete remission in the AIDA-0493 and AIDA-2000, respectively. The 6-year overall survival and cumulative incidence of relapse (CIR) rates were 78.1% versus 87.4% (P = .001) and 27.7% versus 10.7% (P < .0001). Significantly lower CIR rates for patients in the AIDA-2000 were most evident in the high-risk group (49.7% vs 9.3%, respectively, P < .0001). Our data confirm that anthracycline-based consolidation is at least equally effective as cytarabine-containing regimens for low-/intermediate-risk patients and suggest that a risk-adapted strategy including ATRA for consolidation improves outcome in newly diagnosed APL. Furthermore, our results highlight the role of cytarabine coupled to anthracyclines and ATRA during consolidation in the high-risk group.

Although the occurrence of thrombosis in acute promyelocytic leukemia (APL) has been reported during retinoic acid treatment, no studies carried out in large clinical cohorts have specifically addressed this issue. We analyzed 124 APL patients treated with the all-trans retinoic acid and idarubicin protocol and compared clinico-biologic characteristics of 11 patients who developed thrombosis with those of 113 patients who had no thrombosis. In seven patients, the events were recorded during induction, whereas in four patients deep vein thrombosis occurred in the post-induction phase. Comparison of clinico-biological characteristics of patients with and without thrombosis revealed in the former group higher median white blood cell (WBC) count (17 x 10(9)/l, range 1.2-56, P=0.002), prevalence of the bcr3 transcript type (72 vs 48%, P=0.01), of FLT3-ITD (64 vs 28%, P=0.02), CD2 (P=0.0001) and CD15 (P=0.01) expression. No correlation was found with sex, age, French-American-British subtype, all-trans-retinoic acid syndrome or with thrombophilic state that was investigated in 5/11 patients. Our findings suggest that, in APL patients consistent biologic features of leukemia cells may predict increased risk of developing thrombosis.

The vitamin A derivative, all-trans retinoic acid (ATRA), induces differentiation of leukaemic promyelocytes in patients with acute promyelocytic leukaemia (APL). As a result, the majority of patients achieve complete remission either with ATRA alone or with combined ATRA and chemotherapy. The most important complication is the retinoic acid syndrome, which is usually successfully treated with the early administration of dexamethasone. Prospective randomized trials have shown that ATRA is better than conventional chemotherapy in newly diagnosed patients, that ATRA combined with chemotherapy confers an advantage with respect to relapse rate, compared to ATRA alone for induction followed by chemotherapy for consolidation, and that maintenance therapy with ATRA or ATRA plus low-dose chemotherapy is beneficial. The presence of adverse prognostic factors, including older age, presenting white blood cell count and platelet count, expression of CD56 and presence of mutations in the FLT3 gene, identify patients at risk for relapse for whom new strategies are needed.

In all, 134 elderly patients (median age 66 years, range 60-75 years) with newly diagnosed acute promyelocytic leukemia (APL) were enrolled in two successive protocols of the Italian multicenter group GIMEMA. All patients received an identical induction with all-trans retinoic acid and idarubicin; 116 (86%) entered complete remission (CR), two (2%) were resistant and 16 (12%) died during induction. After CR, 106 patients received further therapy whereas 10 did not, because of refusal (n=5) or toxicity (n=5). Consolidation consisted of three chemotherapy courses in the AIDA protocol (AIDA, 67 patients) or, since 1997, of an amended protocol including only the first cycle (amended AIDA, aAIDA, 39 patients). In the AIDA group, 43 patients (64%) completed consolidation, while seven (11%) and 17 (25%) patients were withdrawn after first and second courses, respectively; nine patients (13%) died in CR and 12 (18%) relapsed. In the aAIDA group, all patients received the assigned treatment; two patients (5%) died in CR and six (15%) relapsed. In the AIDA and aAIDA series, the 3-year overall and discase-free survival rates were 81 and 83% (P=NS), 73 and 72% (P=NS), respectively. We highlight here the frequency and severity of complications linked to intensive chemotherapy in this clinical setting and suggest that, in APL of the elderly, less intensive postremission therapy allows significant reduction of severe treatment-related toxicity and may be equally effective.

Alterations in the FLT3 gene, including internal tandem duplications (ITDs) and D835 mutations occur frequently in acute myelogenous leukemia. We investigated the prevalence and clinico-biological correlations of FLT3 ITDs and D835 mutations in 90 patients with acute promyelocytic leukemia (APL) receiving the AIDA protocol. Twenty patients in which both presentation and relapse material was available were analyzed sequentially. Thirty-three patients (37%) harbored the ITD, and seven (7.7%) the D835 mutation in blasts obtained at diagnosis. Presence of ITDs was strongly associated with high WBC count (P = 0.0001), M3 variant (P = 0.0004), and the short (BCR3) PML/RARalpha isoform (P = 0.003). There was no difference in response to induction in the two ITD+ve and ITD-ve groups, while a trend towards inferior outcome was observed for ITD+ve cases when analyzing disease-free survival (DFS) and relapse risk (RR). These differences, however, did not reach statistical significance. Sequential studies showed variable patterns in diagnostic and relapse material, ie ITD (-ve/-ve, +ve/+ve, +ve/-ve, -ve/+ve) and D835 (-ve/-ve, +ve/-ve, -ve/+ve). Our results indicate that FLT3 alterations are associated in APL with more aggressive clinical features and suggest that these lesions may not play a major role in leukemia progression.

Purpose: Recent reports of extramedullary disease (EMD) at recurrence in acute promyelocytic leukemia (APL) have raised increasing concern about a possible role of retinoic acid (RA) therapy., Patients and Methods: We analyzed the risk of developing EMD localization at relapse in APL patients enrolled onto two consecutive studies of the Gruppo Italiano Malattie Ematologiche dell'Adulto. The studies investigated chemotherapy alone (LAP0389) versus RA plus chemotherapy (AIDA)., Results: When all relapse types were taken into account, 94 (51%) of 184 patients and 131 (18%) of 740 patients who attained hematologic remission underwent relapse in the LAP0389 and AIDA studies, respectively (P < .0001). EMD localization was documented in five (5%) of 94 and 16 (12%) of 131 patients (P = .08). Hematologic and/or molecular relapse was diagnosed concomitantly in all but two patients with EMD in the AIDA study. For patients in the LAP0389 and AIDA series, the probability of EMD localization of any type at relapse was 3% and 4.5%, respectively (P = .79), while the probability of CNS involvement was 0.6% and 2% (P = .28). No significant differences were found with regard to mean WBC count and promyelocytic leukemia/retinoic acid receptor-alpha junction type in comparisons of patients with EMD and hematologic relapse., Conclusion: APL patients receiving all-trans retinoic acid in addition to chemotherapy have no increased risk of developing EMD at relapse as compared with those treated with chemotherapy alone.

A total of 622 consecutive patients with acute promyelocytic leukaemia (APL) treated within the Gruppo Italiano per le Malattie Ematologiche dell'Adulto (GIMEMA) group during 1989-97 have been reviewed to assess the clinical effectiveness of all-trans retinoic acid (ATRA) on the incidence of early haemorrhagic deaths and on APL-associated coagulopathy. Of them, 499 were treated with idarubicin plus ATRA (study A) and 123 with Idarubicin alone (study B). In both studies, similar guidelines for supportive treatment were used. Haemorrhagic symptoms were evaluated according to a reproducible score system. Deaths occurring within 10 d of starting treatment were 19 (3.8%) in study A and nine (7.3%) in study B (P = 0.09), with 15 (3%) and five (4.1%) (P not significant) due to haemorrhage. Overall, induction mortality was 7.6% and 16.2% respectively (P < 0.003). In study A, days with platelet counts 30 x 109/l (P < 0.001) in both studies, and by a haemorrhagic score of 3 in study A (P < 0.001). Although the reduction of early fatal haemorrhages was not significant, a substantial clinical improvement was evident in terms of reduction of the severity of bleeding symptoms, blood product consumption and overall induction mortality when ATRA was combined with idarubicin.

Since in vitro observations indicated that all-trans retinoic acid (ATRA), especially in combination with IFNalpha, can exert significant suppressive effects on Ph+ cells, we investigated the effects and the pharmacokinetic profile of ATRA in a selected cohort of patients with Ph+ chronic myeloid leukemia (CML) in chronic phase. Eighteen patients were treated with ATRA at a dose of 80 mg/m2/day (p.o.), divided into two equal doses after meals, for 7 consecutive days every other week for a maximum of 12 courses (1 course = 1 week on and 1 week off). Pharmacokinetic profiles of ATRA were evaluated during intermittent therapy on days 1 and 7 of course 1; on day 1 of course 2; on day 1 of course 6. Out of the 18 patients treated with ATRA, 11 (61%) went off study before the sixth course of treatment because of progressive hyperleukocytosis (seven cases), or thrombocytosis (one case), or refusal (three cases). Seven (39%) patients completed the first six courses (12 weeks) of treatment with ATRA and two of them (11%) maintained a white blood cell (WBC) <10 x 10[9]/l which was induced by the pretreatment with hydroxyurea. One patient completed the 12th course of ATRA maintaining WBC <10 x 10(9)/l, platelets <500 x 10(9)/l and spleen not palpable. The treatment with ATRA was well tolerated and only one patient discontinued the therapy because of non-hematological side-effects. The area under the concentration-time curve (AUC) decreased significantly (P< 0.001) during the first week of therapy. By adopting an intermittent dosing regimen, 1 week on/ 1 week off (1 course), at the start of courses 2 and 6, we obtained the ATRA AUCs equivalent to the ones achieved on day 1 of course 1. In conclusion, our results showed that ATRA alone appeared to be unable to control the WBC expansion in the CML patients in chronic phase. Moreover, it did not induce any remarkable cytoreductive effects on the platelet count and on the hemoglobin level. The major interest of ATRA would be in combination with other therapies. If ATRA was given in combination with IFNalpha or other agents, dose reduction of these would not be planned. On the basis of the pharmacokinetic profile, ATRA should be administered intermittently rather than continuously.

Background: Retinoids, which are derivatives of vitamin A, induce differentiation of acute promyelocytic leukemia (APL) cells in vitro and in patients. However, APL cells develop resistance to retinoic acid treatment. Arsenic trioxide (As2O3) can induce clinical remission in patients with APL, including those who have relapsed after retinoic acid treatment, by inducing apoptosis (programmed cell death) of the leukemia cells. In this study, we investigated the molecular mechanisms by which As2O3 induces apoptosis in retinoic acid-sensitive NB4 APL cells, in retinoic acid-resistant derivatives of these cells, and in fresh leukemia cells from patients., Methods: Apoptosis was assessed by means of DNA fragmentation analyses, TUNEL assays (i.e., deoxyuridine triphosphate labeling of DNA nicks with terminal deoxynucleotidyl transferase), and flow cytometry. Expression of the PML/RAR alpha fusion protein in leukemia cells was assessed by means of western blotting, ligand binding, and immunohistochemistry. Northern blotting and ribonuclease protection assays were used to evaluate changes in gene expression in response to retinoic acid and As2O3 treatment., Results and Conclusions: As2O3 induces apoptosis without differentiation in retinoic acid-sensitive and retinoic acid-resistant APL cells at concentrations that are achievable in patients. As2O3 induces loss of the PML/RAR alpha fusion protein in NB4 cells, in retinoic-acid resistant cells derived from them, in fresh APL cells from patients, and in non-APL cells transfected to express this protein. As2O3 and retinoic acid induce different patterns of gene regulation, and they inhibit the phenotypes induced by each other. Understanding the molecular basis of these differences in the effects of As2O3 and retinoic acid may guide the clinical use of arsenic compounds and provide insights into the management of leukemias that do not respond to retinoic acid.

Background: To evaluate the role and toxicity of ATRA therapy in newly-diagnosed APL patients aged > 60 yrs, the outcome of 16 consecutive elderly APL patients observed between January 1990 and June 1996 were analyzed., Patients and Methods: Their median age was 65.5 yrs (range 60-81 years), the male/female ratio was 7:9, and molecular biology analysis showed a PML/RARa rearrangement in all patients. Seven patients had a concomitant cardiovascular disease. ATRA 45 mg/sqm/day was given to all patients, and in 11 was associated with idarubicin (AIDA protocol); in two patients ATRA was associated with mitoxantrone + ara-C, while the remaining three patients received ATRA alone., Results: Fourteen patients (87.5%) achieved CR, and two patients (12.5%) died during induction. Despite the high CR rate, eight episodes of severe cardiovascular complication were observed in seven patients, three of whom had previously had cardiovascular disease; in addition, three patients had sepsis (two bacterial and one fungal). As of 31 March 1997, 9 of 14 patients were still in first CR after a 19-month (range 7-64 months) median follow-up since attainment of the CR. One patient died in CR of a fungal complication and four patients relapsed after 8, 9, 23 and 35 months following CR: two of them achieved a second CR lasting seven and +15 months with ATRA alone. Of the nine patients still in first CR, only three have received the planned consolidation therapy and five have been in CR for more than 24 months (+25, +33, +34, +38, +63)., Conclusions: Despite the fact that most of these patients received shorter consolidation treatments than do younger patients, the good results achieved in them might be considered an indication for modifying treatment schedules in order to reduce severe toxicity and improve protocol compliance.

The bcr1- and bcr3- promyelocytic leukemia/retinoic acid receptor alpha (PML/RAR alpha) are the two major fusion proteins expressed in acute promyelocytic leukemia (APL) patients. These proteins, which are present in different lengths of PML (amino acids 1-552 and 1-394, respectively), contain most of the functional domains of PML and RAR alpha, bind all-trans-retinoic acid (t-RA), and act as t-RA-dependent transcription factors. T-RA is an effective inducer of clinical remission only in patients carrying the t(15;17) and expressing the PML/RAR alpha products. However, in APL patients achieving complete remission with t-RA therapy the bcr3-PML/RAR alpha product has been found associated with a poorer prognosis than bcr1-PML/RAR alpha. In the present study we have investigated the structural and functional properties of the bcr3-PML/RAR alpha in comparison to the previously characterized bcr1-PML/RAR alpha. In particular, we have measured the binding properties of the two endogenous ligands t-RA and 9-cis-RA to both of these isoforms. T-RA binding analysis of nuclear and cytosolic extracts prepared from bcr3-PML/RAR alpha APL patients and from bcr3-PML/RAR alpha COS-1 transfected cells indicates that this protein is present only as high-molecular-weight nuclear complexes. Using saturation binding assays and Scatchard analyses we found that t-RA binds with slightly less affinity to the bcr3-PML/RAR alpha receptor than to bcr1-PML/RAR alpha or RAR alpha (Kd = 0.4 nmol/L, 0.13 nmol/L or 0.09 nmol/L, respectively). Moreover, two different high-affinity 9-cis-RA binding sites (Kd = 0.45 and 0.075 nmol/L) were detectable in the bcr3-PML/RAR alpha product but not in the bcr1-PML/RAR alpha product (Kd = 0.77 nmol/L). By competition binding experiments we showed that 9-cis-RA binds with higher specificity to the bcr3-PML/RAR alpha isoform than to the bcr1-PML/RAR alpha or RAR alpha. Consistent with these data, the binding of 9-cis-RA to the bcr3-PML/RAR alpha product resulted in increased transcriptional activation of the RA-responsive element (RARE) TRE, but not of the betaRARE, in transiently transfected COS-1 cells. These results provide evidence indicating that preferential retinoid binding to the different PML/RAR alpha products can be measured.

Background and Objective: During the past ten years, the study of retinoids has undergone a total transformation. The Italian Society of Experimental Hematology decided to discuss these advances at a meeting in Florence on April 18, 1996., Information Sources: The material examined in the present review includes articles and abstracts published in journals covered by the Science Citation Index and Medline. In addition, all the authors of the present article have been actively working in the field of retinoids and have contributed several papers. Summaries of their oral presentations at the Florence meeting are reported in the Appendix to this review article., State of Art and Perspectives: One of the most important advances has been the elucidation of new molecular mechanisms of control of gene expression by retinoids. A number of new retinoids have been synthesized by chemists, some of which are being screened for potential clinical use, and a few have already had a tremendous impact on clinical practice. The most important achievements have been obtained in acute promyelocytic leukemia. In 1988 a Chinese group working in Shanghai showed that using all-trans retinoic acid (ATRA) alone 94% of acute promyelocytic leukemic patients obtained complete remission through differentiation of the leukemic clone. This result transformed a dream into reality and allowed researchers to move from laboratory experience to clinical applications of this differentiating therapy. Expanding the spectrum of hematological malignancies that may respond to ATRA remains a challenge; however, several results show some activity of retinoids alone or in combination with other drugs in juvenile chronic myeloid leukemia (CML), myelodysplastic syndrome, cutaneous T-cell lymphoma and CML. Particularly interesting are the studies that explored the potential clinical synergism of ATRA-based combination therapies with growth factors, other differentiating agents such as vitamin D3, immunomodulators like interferons, or chemotherapeutic agents, in particular Ara-C, all of which show promising in vitro effects when used in combination with retinoids.

From March 1993 to October 1993, 20 consecutive, newly diagnosed acute promyelocytic leukemia (APL) patients from 13 Italian institutions entered in a pilot study named AIDA, combining all-trans retinoic acid (ATRA) with idarubicin (IDA). ATRA was administered orally beginning on the first day of induction at the dosage of 45 mg/m2/d until complete remission (CR), whereas IDA was administered intravenously at the dosage of 12 mg/m2/d on days 2, 4, 6, and 8 of the induction. Patients who achieved CR were consolidated with 3 courses of chemotherapy without ATRA; thereafter, they were followed up for molecular and hematologic CR. The median age was 35.3 years (range, 6.5 to 67.6 years); 8 patients were males and 12 females; 4 had the hypogranular variant of APL (M3v), and 4 (2 with M3v) presented with leukocyte counts > or = 10,000/microL. Molecular analysis for the promyelocytic leukemia-retinoic acid receptor alpha (PML-RAR alpha) hybrid gene at diagnosis was performed in 16 patients by means of reverse transcription-polymerase chain reaction (RT-PCR) analysis, and all were RT-PCR+ for the hybrid gene. In the remaining 4 patients, the cytogenetic study showed the presence of the t(15;17). After a median time of 36 days (range, 28 to 52 days) 18 (90%) patients achieved CR; the remaining 2 patients died 12 and 34 days after diagnosis from myocardial infarction caused by fungal myocarditis and from massive hemoptysis, respectively. ATRA syndrome was observed in only 2 patients, and, after the prompt discontinuation of ATRA and initiation of dexamethasone, both recovered from the syndrome. However, after recovering, 1 patient achieved CR, whereas the other died at day 34 because of massive hemoptysis; other side effects were very limited. At recovery from the third consolidation course, only 3 of 14 (21.4%) tested patients were RT-PCR+ for the PML-RAR alpha hybrid gene. Of these, 2 relapsed shortly afterwards; however, in the last patient, the PML-RAR alpha disappeared at successive testing performed 2 months later. As of September 30, 1995, after a median follow-up period from diagnosis of 27 months (range, 24 to 31 months), the overall survival and event-free survival durations are 85% and 69%, respectively; moreover, 14 of 18 (78%) patients who achieved CR are still alive and in first molecular and hematologic CR. Of the 4 relapsed patients, 3 achieved a second CR with ATRA and, after further treatment, are now in molecular and hematologic CR after 4+, 16+, and 17+ months from the second CR. These results indicate that (1) the AIDA protocol is highly effective in treating APL; (2) after 3 consolidation courses, the majority of patients who achieved CR are RT-PCR- for the hybrid gene PML-RAR alpha; (3) the persistence of an RT-PCR positivity for the PML-RAR alpha hybrid gene after 3 consolidation courses is indicative of early relapse, thus these patients still require additional treatment. These results have prompted the Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto (GIMEMA) to initiate, in cooperation with the Associazione Italiana di Ematologia ed Oncologia Pediatrica and some European Organization for Research and Treatment of Cancer (EORTC) centers, a new multicentric clinical trial named AIDA LAP 0493 for the treatment of adult and pediatric APL patients. All patients are considered eligible if APL diagnosis is confirmed with molecular or cytogenetic studies for PML-RAR alpha hybrid gene or t(15;17) and are enrolled to receive the same induction and consolidation therapy of this pilot study. After consolidation, patients who are RT-PCR- for PML-RAR alpha hybrid gene are randomized to four arms, whereas patients who are RT-PCR+ after consolidation undergo, if eligible, an allogenic transplantation procedure.

All-trans retinoic acid (t-RA) administration leads to complete remission in acute promyelocytic leukemia (APL) patients by inducing growth arrest and differentiation of the leukemic clone. In the present study, we show that t-RA treatment dramatically induced type II transglutaminase (type II TGase) expression in cells carrying the t(15;17) translocation and expressing the PML-RARalpha product such as the APL-derived NB4 cell line and fresh leukemic cells from APL patients. This induction correlated with t-RA-induced growth arrest, granulocytic differentiation, and upregulation of the leukocyte adherence receptor beta subunit (CD18) gene expression. The increase in type II TGase was not abolished by cycloheximide treatment, suggesting that synthesis of a protein intermediate was not required for the induction. t-RA did not significantly alter the rate of growth arrest and did not stimulate differentiation and type II TGase activity in NB4.306 cells, a t-RA-resistant subclone of the NB4 cell line, or in leukemic cells derived from two patients morphologically defined as APL but lacking the t(15;17). However, in NB4.306 cells, t-RA treatment was able to increase CD18 mRNA expression in a manner similar to NB4 cells. The molecular mechanisms involved in the induction of these genes were investigated. In NB4 cells, using novel receptor-selective ligands such as 9-cis-RA, TTNPB, AM580, and SR11217, we found that RAR- and RARalpha-selective retinoids were able to induce growth arrest, granulocytic differentiation, and type II TGase, whereas the RXR-selective retinoid SR11217 was inactive. Moreover, an RAR alpha-antagonist completely inhibited the expression of type II TGase and CD18 induced by these selective retinoids in NB4 cells. In NB4.306 cells, an RARalpha-dependent signaling pathway was found involved in the modulation of CD18 expression. In addition, expression of the PML-RARalpha gene in myeloid U937 precursor cells resulted in the ability of these cells to induce type II TGase in response to t-RA. On the basis of these results we hypothesize a specific involvement of a signaling pathway involving PML-RAR alpha for the induction of growth arrest, granulocytic differentiation, and type II TGase by retinoids in APL cells.

The advent of retinoic acid (RA) in the treatment of acute promyelocytic leukemia (APL) has led to a high frequency of short-lasting complete remissions (CR). We studied the response to RA by molecularly analyzing the RA receptor alpha (RAR alpha) locus, which has recently been shown to be rearranged in all APLs. Southern blot analysis demonstrated that the RAR alpha rearrangements persisted in the APL samples containing maturing myeloid cells 2 to 3 weeks after the start of RA treatment, but disappeared after 5 to 8 weeks, when the patients achieved CR. Our investigations provide clear evidence that CR occurs at molecular level and that there is reconstitution of an apparently normal, nonclonal hematopoiesis. Further, it shows that RA acts by triggering differentiation rather than by exerting a cytotoxic effect on the leukemic clone.

The Second International Symposium on Acute Promyelocytic Leukemia (APL) was held in Rome in 12-14 November 1997. Clinical and basic investigators had the opportunity to discuss in this meeting the important advances in the biology and treatment of this disease achieved in the last 4 years, since the First Roman Symposium was held in 1993. The first part of the meeting was dedicated to relevant aspects of laboratory research, and included the following topics: molecular mechanisms of leukemogenesis and of response/resistance to retinoids, biologic and therapeutic effects of new agents such as arsenicals and novel synthetic retinoids; characterization of APL heterogeneity at the morphological, cytogenetic and immunophenotypic level. The updated results of large cooperative clinical trials using variable combinations of all-trans retinoic acid (ATRA) and chemotherapy were presented by the respective group chairmen, and formed the 'core' part of the meeting. These studies, which in most cases integrated the molecular assessment of response to treatment, provided a stimulating framework for an intense debate on the most appropriate front-line treatment options to be adopted in the future. The last day was dedicated to special entities such as APL in the elderly and in the child, as well as the role of bone marrow transplantation. The prognostic value of molecular monitoring studies was also discussed in the final session of the meeting. In this article, we review the major advances and controversial issues in APL biology and treatment discussed in this symposium and emerging from very recent publications. We would like to credit the successful outcome of this meeting to the active and generous input of all invited speakers and to participants from all over the world who provided constructive and fruitful discussions. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the pharmacokinetics of tretinoin during alternating cycles of 1 week of tretinoin treatment and 1 week drug-free in patients with Ph1+ chronic myelogenous leukaemia (CML) in the chronic phase. Patients: Eighteen patients with CML were treated with tretinoin 80 mg/m/day (in two divided doses) for 7 consecutive days every other week (one cycle = 1 week on/1 week off). Results: Body systemic exposure to tretinoin as determined by the area under the plasma concentration-time curve (AUC) decreased significantly during the first week of drug administration, from (mean ± SD) 678.3 ± 498.1 to 258.7 ± 272.4 µg/L·h. In about 40% of the patients the decline in plasma concentrations was ≥80%, while 17% of the population did not experience any decline. On day 7 of cycle 1, the mean apparent oral clearance (CL/F) was 2.6 times the corresponding value on day 1. After 1 week without tretinoin, the mean AUC on day 1 of cycle 2 was lower (down 15%) but not statistically different from the corresponding value observed on day 1 of cycle 1; 62% of patients showed an increase in the AUC, which was 40% higher than the corresponding value on day 7 of cycle 1. On day 1 of cycle 6, the AUC and CL/F of tretinoin during a dosage interval were not statistically different from those observed on day 1 of cycle 1 and cycle 2. On all occasions the peak plasma concentration (C) was strongly correlated to the corresponding AUC. No significant change in the time to observed C (t) and in the elimination half-life (t) was observed during the whole study. These results confirmed that the metabolism of tretinoin is rapidly up-regulated in CML patients, with significant declines in plasma drug exposure during the first week of drug administration. After tretinoin was discontinued, a return to the noninduced state followed a mean time-cycle similar to the induction. The strong decrease in the apparent oral drug clearance and the absence of significant variations in the drug half-life demonstrated that the presystemic extraction of tretinoin is the main cause of the marked decline in plasma drug exposure. Conclusion: The favourable pharmacokinetic profile of tretinoin obtained by an intermittent regimen, 1 week on/1 week off therapy (vs continuous administration), suggests that such a therapeutic schedule is the most appropriate for the assessment of clinical efficacy in those pathologies in which its use is suitable. [ABSTRACT FROM AUTHOR]