Practical management of toxicities associated with bosutinib in patients with Philadelphia chromosome-positive chronic myeloid leukemia.

Bosutinib (SKI-606) is an oral, dual Src/Abl tyrosine kinase inhibitor (TKI) approved for treatment of patients with Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) that is resistant or intolerant to prior TKI therapy or for whom other TKIs are not appropriate choices. The objective of this review is to provide a longitudinal summary of toxicities that may arise during treatment with second-line or later bosutinib in patients with Ph+ chronic phase CML and to provide strategies for managing these toxicities. As bosutinib is not currently indicated for newly diagnosed CML, toxicities associated with first-line treatment are not reviewed. Recognition and optimal management of these toxicities can facilitate patient compliance and affect treatment outcomes.

A phase 2 trial of ponatinib in Philadelphia chromosome-positive leukemias.

BACKGROUND: Ponatinib is a potent oral tyrosine kinase inhibitor of unmutated and mutated BCR-ABL, including BCR-ABL with the tyrosine kinase inhibitor-refractory threonine-to-isoleucine mutation at position 315 (T315I). We conducted a phase 2 trial of ponatinib in patients with chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL). METHODS: We enrolled 449 heavily pretreated patients who had CML or Ph-positive ALL with resistance to or unacceptable side effects from dasatinib or nilotinib or who had the BCR-ABL T315I mutation. Ponatinib was administered at an initial dose of 45 mg once daily. The median follow-up was 15 months. RESULTS: Among 267 patients with chronic-phase CML, 56% had a major cytogenetic response (51% of patients with resistance to or unacceptable side effects from dasatinib or nilotinib and 70% of patients with the T315I mutation), 46% had a complete cytogenetic response (40% and 66% in the two subgroups, respectively), and 34% had a major molecular response (27% and 56% in the two subgroups, respectively). Responses were observed regardless of the baseline BCR-ABL kinase domain mutation status and were durable; the estimated rate of a sustained major cytogenetic response of at least 12 months was 91%. No single BCR-ABL mutation conferring resistance to ponatinib was detected. Among 83 patients with accelerated-phase CML, 55% had a major hematologic response and 39% had a major cytogenetic response. Among 62 patients with blast-phase CML, 31% had a major hematologic response and 23% had a major cytogenetic response. Among 32 patients with Ph-positive ALL, 41% had a major hematologic response and 47% had a major cytogenetic response. Common adverse events were thrombocytopenia (in 37% of patients), rash (in 34%), dry skin (in 32%), and abdominal pain (in 22%). Serious arterial thrombotic events were observed in 9% of patients; these events were considered to be treatment-related in 3%. A total of 12% of patients discontinued treatment because of an adverse event. CONCLUSIONS: Ponatinib had significant antileukemic activity across categories of disease stage and mutation status. (Funded by Ariad Pharmaceuticals and others; PACE ClinicalTrials.gov number, NCT01207440 .).

Somatic SF3B1 mutation in myelodysplasia with ring sideroblasts.

BACKGROUND: Myelodysplastic syndromes are a diverse and common group of chronic hematologic cancers. The identification of new genetic lesions could facilitate new diagnostic and therapeutic strategies. METHODS: We used massively parallel sequencing technology to identify somatically acquired point mutations across all protein-coding exons in the genome in 9 patients with low-grade myelodysplasia. Targeted resequencing of the gene encoding RNA splicing factor 3B, subunit 1 (SF3B1), was also performed in a cohort of 2087 patients with myeloid or other cancers. RESULTS: We identified 64 point mutations in the 9 patients. Recurrent somatically acquired mutations were identified in SF3B1. Follow-up revealed SF3B1 mutations in 72 of 354 patients (20%) with myelodysplastic syndromes, with particularly high frequency among patients whose disease was characterized by ring sideroblasts (53 of 82 [65%]). The gene was also mutated in 1 to 5% of patients with a variety of other tumor types. The observed mutations were less deleterious than was expected on the basis of chance, suggesting that the mutated protein retains structural integrity with altered function. SF3B1 mutations were associated with down-regulation of key gene networks, including core mitochondrial pathways. Clinically, patients with SF3B1 mutations had fewer cytopenias and longer event-free survival than patients without SF3B1 mutations. CONCLUSIONS: Mutations in SF3B1 implicate abnormalities of messenger RNA splicing in the pathogenesis of myelodysplastic syndromes. (Funded by the Wellcome Trust and others.).

Idiopathic erythrocytosis: a germline disease?

Polycythemia Vera (PV) is typically caused by V617F or exon 12 JAK2 mutations. Little is known about Polycythemia cases where no JAK2 variants can be detected, and no other causes identified. This condition is defined as idiopathic erythrocytosis (IE). We evaluated clinical-laboratory parameters of a cohort of 56 IE patients and we determined their molecular profile at diagnosis with paired blood/buccal-DNA exome-sequencing coupled with a high-depth targeted OncoPanel to identify a possible underling germline or somatic cause. We demonstrated that most of our cohort (40/56: 71.4%) showed no evidence of clonal hematopoiesis, suggesting that IE is, in large part, a germline disorder. We identified 20 low mutation burden somatic variants (Variant allelic fraction, VAF, < 10%) in only 14 (25%) patients, principally involving DNMT3A and TET2. Only 2 patients presented high mutation burden somatic variants, involving DNMT3A, TET2, ASXL1 and WT1. We identified recurrent germline variants in 42 (75%) patients occurring mainly in JAK/STAT, Hypoxia and Iron metabolism pathways, among them: JAK3-V722I and HIF1A-P582S; a high fraction of patients (48.2%) resulted also mutated in homeostatic iron regulatory gene HFE-H63D or C282Y. By generating cellular models, we showed that JAK3-V722I causes activation of the JAK-STAT5 axis and upregulation of EPAS1/HIF2A, while HIF1A-P582S causes suppression of hepcidin mRNA synthesis, suggesting a major role for these variants in the onset of IE.

In vivo eradication of human BCR/ABL-positive leukemia cells with an ABL kinase inhibitor.

BACKGROUND: The leukemia cells of approximately 95% of patients with chronic myeloid leukemia and 30%-50% of adult patients with acute lymphoblastic leukemia express the Bcr/Abl oncoprotein, which is the product of a fusion gene created by a chromosomal translocation [(9:22) (q34;q11)]. This oncoprotein expresses a constitutive tyrosine kinase activity that is crucial for its cellular transforming activity. In this study, we evaluated the antineoplastic activity of CGP57148B, which is a competitive inhibitor of the Bcr/Abl tyrosine kinase. METHODS: Nude mice were given an injection of the Bcr/Abl-positive human leukemia cell lines KU812 or MC3. Tumor-bearing mice were treated intraperitoneally or orally with CGP57148B according to three different schedules. In vitro drug wash-out experiments and in vivo molecular pharmacokinetic experiments were performed to optimize the in vivo treatment schedule. RESULTS: Treatment schedules administering CGP57148B once or twice per day produced some inhibition of tumor growth, but no tumor-bearing mouse was cured. A single administration of CGP57148B caused substantial (>50%) but short-lived (2-5 hours) inhibition of Bcr/Abl kinase activity. On the basis of the results from in vitro wash-out experiments, 20-21 hours was defined as the duration of continuous exposure needed to block cell proliferation and to induce apoptosis in these two leukemia cell lines. A treatment regimen assuring the continuous block of the Bcr/Abl phosphorylating activity that was administered over an 11-day period cured 87%-100% of treated mice. CONCLUSION: These data indicate that the continuous block of the oncogenic tyrosine kinase of Bcr/Abl protein is needed to produce important biologic effects in vivo.

Role of alpha1 acid glycoprotein in the in vivo resistance of human BCR-ABL(+) leukemic cells to the abl inhibitor STI571.

BACKGROUND: Chronic myeloid leukemia is caused by a chromosomal translocation that results in an oncogenic fusion protein, Bcr-Abl. Bcr-Abl is a tyrosine kinase whose activity is inhibited by the antineoplastic drug STI571. This drug can cure mice given an injection of human leukemic cells, but treatment ultimately fails in animals that have large tumors when treatment is initiated. We created a mouse model to explore the mechanism of resistance in vivo. METHODS Nude mice were injected with KU812 Bcr-Abl(+) human leukemic cells. After 1 day (no evident tumors), 8 days, or 15 days (tumors >1 g), mice were treated with STI571 (160 mg/kg every 8 hours). Cells recovered from relapsing animals were used for in vitro experiments. Statistical tests were two-sided. RESULTS: Tumors regressed initially in all STI571-treated mice, but all mice treated 15 days after injection of tumor cells eventually relapsed. Relapsed animals did not respond to further STI571 treatment, and their Bcr-Abl kinase activity in vivo was not inhibited by STI571, despite high plasma concentrations of the drug. However, tumor cells from resistant animals were sensitive to STI571 in vitro, suggesting that a molecule in the plasma of relapsed animals may inactivate the drug. The plasma protein alpha1 acid glycoprotein (AGP) bound STI571 at physiologic concentrations in vitro and blocked the ability of STI571 to inhibit Bcr-Abl kinase activity in a dose-dependent manner. Plasma AGP concentrations were strongly associated with tumor load. Erythromycin competed with STI571 for AGP binding. When animals bearing large tumors were treated with STI571 alone or with a combination of STI571 and erythromycin, greater tumor reductions and better long-term tumor-free survival (10 of 12 versus one of 13 at day 180; P:<.001) were observed after the combination treatment. CONCLUSION: AGP in the plasma of relapsed animals binds to STI571, preventing this compound from inhibiting the Bcr/Abl tyrosine kinase. Molecules such as erythromycin that compete with STI571 for binding to AGP may enhance the therapeutic potential of this drug.

Arsenic trioxide as an inducer of apoptosis and loss of PML/RAR alpha protein in acute promyelocytic leukemia cells.

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.

Lysis by activated lymphocytes of melanoma and small cell lung cancer cells surviving in vitro treatment with mafosfamide.

Six short term-cultured melanoma cell lines and one small cell lung cancer cell line were treated in vitro with the alkylating agent mafosfamide. The sensitivity of the surviving cells to in vitro lysis by recombinant interleukin 2-activated autologous and allogeneic lymphocytes was then investigated. In no case did chemo-surviving tumor cells appear less sensitive to lymphocyte-mediated lysis than untreated counterparts. In three of seven cases (two of which were derived from the same patient), chemo-selected cells were even more sensitive to cytotoxic lymphocytes, a difference not explained by a different distribution of neoplastic cells in the various cell cycle phases. We also studied the inhibitory activity of activated lymphocytes on the clonogenic potential of chemo-surviving tumor cells by the human tumor clonogenic assay. Inhibitions of tumor cell growth in the two patients tested were 100 and 94%, respectively; the activity of lymphocytes was dependent on the coculture time and the effector/target cell ratio. These data indicate that in vitro treatment with mafosfamide does not select cells resistant to the action of activated lymphocytes and that, given the right experimental conditions, these immune effectors can completely lyse tumor cells.

Inhibition of promyelocytic leukemia (PML)/retinoic acid receptor-alpha and PML expression in acute promyelocytic leukemia cells by anti-PML peptide nucleic acid.

The fusion protein promyelocytic leukemia (PML)/retinoic acid receptor (RAR)alpha is tightly linked to the pathogenesis of acute promyelocytic leukemia (APL); hence, it represents a tumor-associated, transformation-related molecule. In this study, three anti-PML adamantyl-conjugated peptide nucleic acid (PNA) oligomers previously described as in vitro inhibitors of PML/RARalpha translation were combined and used to block PML/RARalpha synthesis in NB4 cells. Cationic liposomes were used to achieve sufficient delivery of PNAs into the cells. Upon treatment of cells with the liposome/PNA mixture, enhanced cellular uptake of PNA (approximately 5-fold compared with control) was obtained. Concomitantly, a substantial reduction (>90%) of the expression of PML/RARalpha was observed when all of the three PNAs were used together. This resulted in a dramatic effect on the number and viability of NB4 cells in culture after 48 h of treatment. This phenomenon was preceded by induction of apoptosis that could be observed 24 h after treatment. No sign of granulocytic differentiation was observed after treatment. These effects were also noted on other leukemic cell lines that express PML but not the fusion transcript. These results show that it is possible to deliver PNA into hematopoietic cells and obtain specific gene inhibition, and they suggest that a growth inhibitory effect on acute promyelocytic leukemia cells can be obtained through the block of PML/RARalpha and PML expression.

Susceptibility of chemoresistant murine and human tumor cells to lysis by interleukin 2-activated lymphocytes.

The sensitivity of three different human and murine doxorubicin (Dx)-sensitive or -resistant pairs of tumor cells to recombinant interleukin 2 (rIL2)-activated lymphocytes was studied. In two pairs of these sublines (LoVo human colon carcinoma and B16 mouse melanoma sublines), resistance to Dx was induced in vitro, while in the third pair (9229 human metastatic melanoma clones), Dx resistance was spontaneously present in clone 9229.24. Dx-resistant cells were efficiently lysed by rIL2-activated lymphocytes in a short-term 51Cr release assay; in some experiments a trend toward higher lysis of Dx-resistant cells was present. We then tested the tumor cell growth-inhibitory activity of rIL2-activated lymphocytes in the human tumor clonogenic assay after lymphocyte-tumor coculture. Complete inhibition of tumor cell growth was obtained with five of six sublines or clones (both Dx sensitive and resistant) after 3 to 6 days of coculture at effector lymphocyte/target tumor cell ratios of 5 to 50/1; a maximum 99% inhibition was observed with the melanoma clone 9229.4 even after coculture for 6 days at an effector lymphocyte/target tumor cell ratio of 50/1. By using lower effector lymphocyte/target tumor cell coculture ratios (1, 5, 25/1), it was shown that all the three Dx-resistant cell types were significantly more affected by activated lymphocytes than their Dx-sensitive counterparts. The LoVo/DX subline was also more lysed than its Dx-sensitive counterpart LoVo/H subline by an antitumor monoclonal antibody in a complement-mediated cytotoxicity assay, despite the fact that both sublines expressed a similar amount of antigen on the cell surface. These data indicate that Dx-resistant cancer cells are more susceptible to the lysis by rIL2-activated lymphocytes than their Dx-sensitive counterparts and that a complete inhibition of their clonogenic potential can be obtained in vitro.

Cancer procoagulant in human tumor cells: evidence from melanoma patients.

It has repeatedly been proposed that fibrin plays a role in tumor growth and metastasis. Among tumor cell products or activities which may promote clot formation, cancer procoagulant (CP), a direct activator of coagulation factor X, has been suggested to be selectively associated with the malignant phenotype. We report here the enzymatic and immunological identification of this cysteine proteinase procoagulant in extracts and cells from human melanoma. CP activity was independent of both the intrinsic and extrinsic pathways of blood coagulation, using factor IX and factor VII deficient plasmas, and was inhibited by the cysteine proteinase inhibitors iodoacetamide and HgCl2. CP activity was detectable in extracts and cell suspensions from all 32 patients studied and was higher in extracts from metastases (14.8 +/- 3.9 units/mg protein) than from the primary tumors (3.7 +/- 1.0 units/mg protein). CP activity was not affected by an anti-apoprotein III antibody or by concanavalin A, a known inhibitor of thromboplastin. In contrast, no CP activity or antigen was detected in extracts from six benign melanocytic lesions. The procoagulant activity was dependent on factor VII and was inhibited by anti-apoprotein III antibody and by concanavalin A, properties that suggest that the procoagulant was tissue thromboplastin. These data indicate that CP can be expressed by human tumor cells and that, among melanotic lesions, its presence is associated with the malignant phenotype and its activity is particularly high in metastatic cells.

In vivo interleukin 2-induced activation of lymphokine-activated killer cells and tumor cytotoxic T-cells in cervical lymph nodes of patients with head and neck tumors.

To study whether regional injection of recombinant interleukin 2 (rIL-2) can induce an in vivo lymphocyte activation in cervical lymph nodes (LNs) of patients with head and neck carcinoma, 12 patients, candidates for prophylactic dissection, were treated for 7-10 days prior to surgery with rIL-2, 10(5) units/day, injected in the perimastoid region. A marked induction of cytotoxic activity against allogeneic (K562 and Daudi lines) and autologous target cells (fresh spindle cell carcinomas of the tongue) was observed in lymphocytes obtained from jugular, spinal, and, to a lesser extent, submandibular LNs of all treated patients. An increase of cytotoxicity was also present in LNs contralateral to the rIL-2 injection side. On the other hand, only a borderline increase in spontaneous proliferation was detected. Moreover, in the two cases tested, a marked and apparently autologous tumor (Auto-Tu)-specific lysis was found in CD5+ lymphocytes obtained from LNs, whereas lymphokine-activated killer activity was mainly exerted by CD16+ natural killer cells. T-lymphocytes, when cultured with irradiated Auto-Tu cells and low doses of rIL-2, showed an increased Auto-Tu lysis, while cytotoxicity against allogeneic tumor cells (including K562) was not observed. These data indicate that regional injection of rIL-2 can activate lymphokine-activated killer cells from LN lymphocytes but also induce and/or expand a T-cell population expressing a restricted Auto-Tu cytotoxicity.

Differences between in vivo and in vitro activation of cancer patient lymphocytes by recombinant interleukin 2: possible role for lymphokine-activated killer cell infusion in the in vivo-induced activation.

In this study 15 consecutive melanoma patients were treated with two courses of bolus recombinant interleukin 2 (rIL2) and rIL2 plus in vitro-generated lymphokine-activated killers (LAK), respectively. The immunological monitoring performed after 4 days of rIL2 or rIL2 plus LAK, indicate that the in vivo peripheral blood lymphocyte (PBL), activation (spontaneous proliferation, tumor cytotoxicity, number of DR+ PBL, obtained after the second cycle of rIL2 plus LAK is significantly higher than after the first cycle of rIL2 alone. During the 5-day interval between the two courses, PBL activation returns to baseline levels and no evidence for increased sensitivity of PBL to rIL2 is present. To further confirm this, two additional patients were studied, in whom rIL2 was administered by continuous i.v. infusion. In these two patients the in vitro versus in vivo PBL activation could be directly and simultaneously compared by using in vitro the same concentration of rIL2 reached and maintained in the patients' sera. The PBL activation induced in vivo by a cycle of rIL2 alone was significantly less (about 10 times) than that obtained in vitro with a comparable rIL2 concentration. Thus, the infusion of in vitro highly activated PBL could explain the increased in vivo lymphocyte activation of the second cycle of rIL2 plus LAK over the first cycle of rIL2 alone.

Effect of imatinib on haematopoietic recovery following idarubicin exposure.

SCF is a potent pro-proliferative cytokine crucial for haematopoiesis, which binds to c-kit and activates its tyrosine kinase activity. Inactivating mutations of either SCF or c-kit have been described in mice and lead to increased sensitivity to treatment with ionising radiation. Imatinib is a tyrosine kinase inhibitor with high affinity for c-Abl, PDGFR and c-kit. In this study we investigated the effect of concomitant administration of imatinib and idarubicin, an anthracycline with haematosuppressive activity, in nu/nu mice and murine bone marrow cells. Double-treated animals showed significantly increased mortality compared to mice that received imatinib or idarubicin alone only when idarubicin and imatinib were given simultaneously. The combined treatment induced a more severe neutropenia with a slower recovery when compared to mice treated with idarubicin alone. The myeloid metaplasia usually observed in the spleen after idarubicin treatment was absent in mice co-treated with imatinib. Bone marrow from double-treated animals also showed decreased numbers of megakaryocytes and myeloid precursor cells. In vitro culture of murine bone marrow cells in the presence of imatinib inhibited SCF-induced proliferation and recovery from treatment with idarubicin. Our results indicate that the simultaneous administration of imatinib enhances idarubicin-induced haematopoietic toxicity in vivo and in vitro.

Mapping of HLA class I binding motifs in forty-four fusion proteins involved in human cancers.

Chromosomal translocations coding for abnormal proteins are present in several human cancers. The junctional region of fusion proteins represents a potential target for a T cell-mediated antitumor response. T lymphocytes recognize antigens in the form of short peptides that must bind to HLA molecules. Different HLA specificities can bind different peptides, thus depicting different "peptide binding motifs." It would be useful to know whether a certain fusion protein presents, within its fusion region, the binding motif(s) for a certain HLA molecule. This information would allow a more focused immunological analysis. Here we present data obtained from the screening of the fusion regions of 44 different fusion proteins for the presence of binding motifs to 34 class I HLA molecules, including all of the most frequently encountered specificities. A total of 201 independent peptides was identified (range, 0-11 peptides/fusion protein). A marked heterogeneity among the 44 different fusion proteins analyzed is evident. For example, the pml/RARalpha fusion protein present in acute promyelocytic leukemia presents no binding motif (BCR 3) at all or to a single HLA molecule (Cw*0301, BCR 1). Alternatively, the fusion proteins BCR/ABL, ALL1/AF-6, EWS/ATF-1, or NPM/ALK exhibit motifs for several common HLA specificities. Heterogeneity is also present inside a single translocation (in ALL1/ENL, for example, different subtypes match motifs with cumulative frequencies in the population from 108 to 0%). In two cases where the relative frequency of different fusion protein subtypes was available, a tendency toward an inverse relationship between frequency and the percentage of population covered by the identified binding motifs was observed. Peptides with motifs for HLA A*0201, A3, and Cw*0702 were also tested for actual binding using a stabilization assay; 13-40% showed significant HLA binding, using this assay. However, fewer fusion protein-derived peptides bound to HLA A*0201 and A3 than non-fusion protein-derived peptides. These data provide the first list of peptides derived from fusion proteins that may be assessed as potential tumor-specific antigens.

Differential recognition of a BCR/ABL peptide by lymphocytes from normal donors and chronic myeloid leukemia patients.

The BCR/ABL oncogenic fusion protein transforms normal bone marrow stem cells into neoplastic cells. It has been shown that peptides derived from the junctional region of this oncogenic fusion protein can be recognized by human T-lymphocytes obtained from normal donors. In this study, we investigated the immunogenicity in patients with chronic myeloid leukemia (CML) of a 17 mer b3/a2 Bcr/abl peptide (B/A1), which was shown to induce proliferative responses in lymphocytes from normal donors. A total of 56 CML patients in chronic phase were studied. Twenty-two patients were studied at diagnosis without any treatment (group I). Fourteen patients were receiving IFN (group II), 14 patients were being treated with hydroxyurea (group III), and 6 patients were on different regimens (group IV). Patients were initially assessed for general immunological competence using both in vivo and in vitro assays. Patients were also selected for the expression of HLA-DR0401, the HLA specificity known to present peptide B/A1 to CD4 lymphocytes. With the exception of the six patients in group IV, the results of all these assays (in vitro phytohemagglutinin/tetanus toxoid responses, in vivo skin reaction to ubiquitous antigens) in CML patients did not significantly differ from those obtained in normal donors, thus excluding the presence of generalized immunosuppression. Eight patients with HLA-DR0401 and a b3/a2 type of fusion were identified and further studied. In these eight patients dendritic cells were obtained from adherent peripheral blood mononuclear cells and used to stimulate CD4 lymphocytes. No patient developed a specific response to the bcr/abl peptide, although patients' lymphocytes proliferated in response to a promiscuous tetanus toxoid peptide in all but one case. In contrast, response to the bcr/abl peptide was observed in seven of eight HLA-DR0401 healthy donors tested. These data suggest that immunocompetent, HLA-DR0401+ CML patients are unable to respond to peptide B/A1, at difference from healthy donors. The implication of these results for the immunotherapy of CML is discussed.

Lack of T-cell-mediated recognition of the fusion region of the pml/RAR-alpha hybrid protein by lymphocytes of acute promyelocytic leukemia patients.

In previous studies, it was shown that the fusion region of the pml/RAR-alpha protein, expressed by acute promyelocytic leukemia (APL) cells, can be specifically recognized in vitro by donor (D. E. ) CD4 T cells in a HLA class II DR11-restricted fashion. We present here the results on the recognition of several pml/RAR-alpha peptides by APL patients expressing HLA DR11. The in vitro immunization of peripheral blood lymphocytes from four patients in remission (S. R., F. R., M. M., P. G.) with BCR1/25, a 25-mer pml/RAR-alpha, did not elicit either a polyclonal or a clonal immune response specific to the peptide. We then generated new donor anti-pml/RAR-alpha CD4(+) T-cell clones. These clones were tested for their recognition of BCR1/25. One clone (C3/5, CD3(+), CD4(+), CD8(-)) was selected for further analysis. Clone C3/5 showed specific proliferation, cytotoxicity, and cytokine (tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor) production when challenged with autologous lymphoblastic cell lines pulsed with peptide BCR1/25. C3/5 cells developed specific proliferation and cytotoxicity when challenged with peptide-pulsed lymphoblastic cell lines and peripheral blood lymphocytes from the four DR11(+) APL patients. APL blasts, available only from patients F. R. and P. G., were not lysed by C3/5 and were unable to present peptide BCR1/25. Incubation of APL cells with IFN-gamma failed to induce HLA class II molecules and recognition by the C3/5 clone. Since APL cells do not express HLA class II molecules, we tested in two donors (D. E. and C. H. R.) and in patients S. R. and P. G. whether the use of 9-mer peptides (BCR1/9) would generate a CD8/HLA class I-restricted response. No peptide-specific T-cell line or clone could be generated from both donors and patients. These findings are discussed in relation to possible therapeutic approaches to the immunotherapy of APL.

Treatment Efficacy and Resistance Mechanisms Using the Second-Generation ALK Inhibitor AP26113 in Human NPM-ALK-Positive Anaplastic Large Cell Lymphoma.

UNLABELLED: ALK is a tyrosine kinase receptor involved in a broad range of solid and hematologic tumors. Among 70% to 80% of ALK(+) anaplastic large cell lymphomas (ALCL) are caused by the aberrant oncogenic fusion protein NPM-ALK. Crizotinib was the first clinically relevant ALK inhibitor, now approved for the treatment of late-stage and metastatic cases of lung cancer. However, patients frequently develop drug resistance to Crizotinib, mainly due to the appearance of point mutations located in the ALK kinase domain. Fortunately, other inhibitors are available and in clinical trial, suggesting the potential for second-line therapies to overcome Crizotinib resistance. This study focuses on the ongoing phase I/II trial small-molecule tyrosine kinase inhibitor (TKI) AP26113, by Ariad Pharmaceuticals, which targets both ALK and EGFR. Two NPM-ALK(+) human cell lines, KARPAS-299 and SUP-M2, were grown in the presence of increasing concentrations of AP26113, and eight lines were selected that demonstrated resistance. All lines show IC50 values higher (130 to 1,000-fold) than the parental line. Mechanistically, KARPAS-299 populations resistant to AP26113 show NPM-ALK overexpression, whereas SUP-M2-resistant cells harbor several point mutations spanning the entire ALK kinase domain. In particular, amino acid substitutions: L1196M, S1206C, the double F1174V+L1198F and L1122V+L1196M mutations were identified. The knowledge of the possible appearance of new clinically relevant mechanisms of drug resistance is a useful tool for the management of new TKI-resistant cases. IMPLICATIONS: This work defines reliable ALCL model systems of AP26113 resistance and provides a valuable tool in the management of all cases of relapse upon NPM-ALK-targeted therapy.

Acute promyelocytic leukaemia cells resistant to retinoic acid show further perturbation of the RAR alpha signal transduction system.

Acute promyelocytic leukaemia (APL) cell lines resistant to all-trans retinoic acid (ATRA) have been previously derived from the NB4 cell line, and characterized as having lost the expression of the intact pml/RAR alpha fusion protein. To confirm the association between ATRA-resistance and alteration in the fusion protein at the clonal level, 16 clones were generated from ATRA-resistant APL cell lines. All clones show immunological (HLA class I and II, CD11b and c, CD13 and 33), molecular and growth features similar to the parental cell lines. To investigate whether the irradiation protocol used to generate the previously reported retinoic acid-resistant NB4.306 cell line induced additional alterations that could render these cells able to escape the anti-proliferative effect of retinoic acid (ATRA), an additional ATRA-resistant APL cell line, [NB4.007/6], was generated, under the selective pressure of ATRA, from the NB4 cell line without previous radiation. This cell line shows resistance to the anti-proliferative and differentiating action of ATRA. The NB4.007/6 cell line contains the t(15;17) chromosome translocation, shows the usual pml/RAR alpha hybrid DNA but expresses no detectable amount of the usual pml/RAR alpha protein in Western blot analysis, similarly to the NB4.306 cell line. Finally, the relative resistance to ATRA of NB4.306 and NB4.007/6 was evaluated by comparing the phenotypic (CD11b) changes induced by ATRA in these two lines with those induced in the parental, ATRA-sensitive, NB4 cell line. It is estimated that NB4.306 and NB4.007/6 are about 300 and 70 times less sensitive to ATRA than the original NB4 cell line.