Implication of the Autologous Immune System in BCR-ABL Transcript Variations in Chronic Myelogenous Leukemia Patients Treated with Imatinib.

International audienceImatinib and other tyrosine kinase inhibitors (TKI) have improved treatment of chronic myelogenous leukemia (CML); however, most patients are not cured. Deeper mechanistic understanding may improve TKI combination therapies to better control the residual leukemic cell population. In analyzing our patients' data, we found that many patients who otherwise responded well to imatinib therapy still showed variations in their BCR-ABL transcripts. To investigate this phenomenon, we applied a mathematical model that integrates CML and an autologous immune response to the patients' data. We define an immune window or a range of leukemic loads for which the autologous immune system induces an improved response. Our modeling results suggest that, at diagnosis, a patient's leukemic load is able to partially or fully suppress the autologous immune response developed in a majority of patients, toward the CML clone(s). Imatinib therapy drives the leukemic population into the "immune window," allowing the patient's autologous immune cells to expand and eventually mount an efficient recognition of the residual leukemic burden. This response drives the leukemic load below this immune window, allowing the leukemic population to partially recover until another weaker immune response is initiated. Thus, the autologous immune response may explain the oscillations in BCR-ABL transcripts regularly observed in patients on imatinib

Chronic myeloid leukemia stem cells are not dependent on Bcr-Abl kinase activity for their survival

Recent evidence suggests CML stem cells are insensitive to kinase inhibitors and responsible for minimal residual disease in treated patients. We investigated whether CML stem cells, in a transgenic mouse model of CML-like disease or derived from patients, are dependent on Bcr-Abl. In the transgenic model, following re-transplantation, donor-derived CML stem cells in which Bcr-Abl expression had been induced and subsequently shut off, were able to persist in vivo and re-initiate leukemia in secondary recipients upon Bcr-Abl re-expression. Bcr-Abl knockdown in human CD34+ CML cells cultured for 12 days in physiological growth factors achieved partial inhibition of Bcr-Abl and downstream targets p-CrkL and p-STAT5, inhibition of proliferation and colony forming cells, but no reduction of input cells. The addition of dasatinib further inhibited p-CrkL and p-STAT5, yet only reduced input cells by 50%. Complete growth factor withdrawal plus dasatinib further reduced input cells to 10%, however the surviving fraction was enriched for primitive leukemic cells capable of growth in long-term culture initiating cell assay and expansion upon removal of dasatinib and addition of growth factors. Together these data suggest that CML stem cell survival is Bcr-Abl kinase independent and suggest curative approaches in CML must focus on kinase-independent mechanisms of resistance

A randomised Phase II trial of Hydroxychloroquine and Imatinib versus Imatinib alone for patients with Chronic Myeloid Leukaemia in Major Cytogenetic Response with residual disease

In chronic-phase chronic myeloid leukaemia (CP-CML), residual BCR-ABL1+ leukaemia stem cells are responsible for disease persistence despite TKI. Based on in vitro data, CHOICES (CHlorOquine and Imatinib Combination to Eliminate Stem cells) was an international, randomised phase II trial designed to study the safety and efficacy of imatinib (IM) and hydroxychloroquine (HCQ) compared with IM alone in CP-CML patients in major cytogenetic remission with residual disease detectable by qPCR. Sixty-two patients were randomly assigned to either arm. Treatment ‘successes’ was the primary end point, defined as ≥0.5 log reduction in 12-month qPCR level from trial entry. Selected secondary study end points were 24-month treatment ‘successes’, molecular response and progression at 12 and 24 months, comparison of IM levels, and achievement of blood HCQ levels >2000 ng/ml. At 12 months, there was no difference in ‘success’ rate (p = 0.58); MMR was achieved in 80% (IM) vs 92% (IM/HCQ) (p = 0.21). At 24 months, the ‘success’ rate was 20.8% higher with IM/HCQ (p = 0.059). No patients progressed. Seventeen serious adverse events, including four serious adverse reactions, were reported; diarrhoea occurred more frequently with combination. IM/HCQ is tolerable in CP-CML, with modest improvement in qPCR levels at 12 and 24 months, suggesting autophagy inhibition maybe of clinical value in CP-CML

Risk of progression in chronic phase-chronic myeloid leukemia patients eligible for tyrosine kinase inhibitor discontinuation: Final analysis of the TFR-PRO study

Disease progression to accelerated/blast phase (AP/BP) in patients with chronic phase chronic myeloid leukemia (CP-CML) after treatment discontinuation (TD) has never been systematically reported in clinical trials. However, recent reports of several such cases has raised concern. To estimate the risk of AP/BP among TD-eligible patients, we conducted TFR-PRO, a cohort retro-prospective study: 870 CP-CML patients eligible for TD formed a discontinuation cohort (505 patients) and a reference one (365 patients). The primary objective was the time adjusted rate (TAR) of progression in relation to TD. Secondary endpoints included the TAR of molecular relapse, that is, loss of major molecular response (MMR). With a median follow up of 5.5 years and 5188.2 person-years available, no events occurred in the TD cohort. One event of progression was registered 55 months after the end of TD, when the patient was contributing to the reference cohort. The TAR of progression was 0.019/100 person-years (95% CI [0.003-0.138]) in the overall group; 0.0 (95% CI [0-0.163]) in the discontinuation cohort; and 0.030 (95% CI [0.004-0.215]) in the reference cohort. These differences are not statistically significant. Molecular relapses occurred in 172/505 (34.1%) patients after TD, and in 64/365 (17.5%) patients in the reference cohort, p < .0001. Similar rates were observed in TD patients in first, second or third line of treatment. CML progression in patients eligible for TD is rare and not related to TD. Fears about the risk of disease progression among patients attempting TD should be dissipated

Immunothérapie des leucémies aiguës myéloïdes (apport de l'IL-13)

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Vers la thérapie génique de la drépanocytose (description et évaluation d'un modèle de cellules hématopoïétiques primitives humaines permettant d'étudier le transfert de gène rétroviral de la b-globine dans leur descendance érythtoïde)

La drépanocytose est une maladie héréditaire monogénique de la b-globine, pour laquelle il n'existe aucun traitement éradicateur en dehors de l'allogreffe de cellules souches hématopoïétiques, lorsqu'elle est possible. Une thérapeutique par thérapie génique de cette maladie est proposée. Dans ce contexte, nous avons développé un modèle permettant d'étudier l'érythropoïèse humaine, in vitro et in vivo (souris NOD/SCID ou b2 microglobuline"nulles" NOD/SCID), ainsi que ses modifications après transfert rétroviral de la b-globine dans les cellules souches hématopoïétiques humaines parentales. Nous avons pu démontrer que le foie foetal humain contenait un grand nombre de cellules hématopoïétiques primitives (LTC-IC, CFU-GEMM et CRU) et différenciées (CFU-GM, CFU-MK, BFU-E, érythroblastes), par comparaison à d'autres sources cellulaires plus tardives. En outre, les capacités du foie foetal humain à produire in vivo des cellules érythroïdes matures et immatures (LTC-IC, CD34+38- et CRU), sont supérieurs à celles observées avec le sang de cordon et la moelle osseuse adulte. Ces propriétés uniques ont été exploitées dans un second volet où l'on a transféré in vitro, par rétrovirus, le gène de la b-globine humaine (+HS-2), couplé à la GFP dans les cellules hématopoïétiques primitives (LTC-IC et CRU) de foie foetal humain et de sang de cordon ombilical, et obtenu l'expression du transgène (au niveau de l'ARN messager), dans les cellules érythroïdes matures générées in vivo et régénérées in vivo. Nous avons enfin détaillé les caractéristiques fonctionnelles des LTC-IC du sang périphérique de patients drépanocytaires, pouvant éventuellement représenter une population cellulaire cible de choix pour transfert du gène de la b-globine, dans un système autologue. Le succès récent de notre groupe dans le traitement de deux modèles de souris transgéniques drépanocytaires, au moyen de vecteurs lentiviraux (R.Pawliuk et coll., Science, 2001; 294; 2368-2371), ouvre de nouvelles perspectives intéressantes quant au traitement de le maladie humaine par transfert de gènes.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Revealing stiffening and brittling of chronic myelogenous leukemia hematopoietic primary cells through their temporal response to shear stress

Cancer cell transformation is often accompanied by a modification of their viscoelastic properties. When capturing the stress-to-strain response of primary chronic myelogenous leukemia (CML) cells, from two data sets of CD34+ hematopoietic cells isolated from healthy and leukemic bone marrows, we show that the mean shear relaxation modulus increases upon cancer transformation. This stiffening of the cells comes along with local rupture events, detected as reinforced sharp local maxima of this modulus, suggesting that these cancer cells respond to a local mechanical stress by a cascade of local brittle failure events.Physique de la morphogenèse des plantes: propriétés dynamiques et mécaniques de la paroi des cellules du méristèm