Assessment of bone marrow lymphocytic status during tyrosine kinase inhibitor therapy and its relation to therapy response in chronic myeloid leukaemia

PURPOSE

Tyrosine kinase inhibitors (TKIs) used in the treatment of chronic myeloid leukaemia have been reported to induce immunomodulatory effects. We aimed to assess peripheral blood (PB) and bone marrow (BM) lymphocyte status at the diagnosis and during different TKI therapies and correlate it with treatment responses.

METHODS

BM and PB samples were acquired from 105 first-line TKI-treated patients. Relative number of BM lymphocytes was evaluated from MGG-stained BM aspirates, and immunophenotypic analyses were performed with multicolour flow cytometry.

RESULTS

Early 3-month expansion of BM lymphocytes was found during all different TKIs (imatinib n = 71, 20 %; dasatinib n = 25, 21 %; nilotinib n = 9, 22 %; healthy controls n = 14, 12 %, p < 0.0001). Increased PB lymphocyte count was only observed during dasatinib therapy. The BM lymphocyte expansion was associated with early molecular response; patients with 3-month BCR-ABL1 <10 % showed higher lymphocyte counts than patients with BCR-ABL1 >10 % (23 vs. 17 %, p < 0.05). Detailed phenotypic analysis showed that BM lymphocyte expansion consisted of various lymphocyte subclasses, but especially the proportion of CD19+ B cells and CD3negCD16/56+ NK cells increased from diagnostic values. During dasatinib treatment, the lymphocyte balance in both BM and PB was shifted more to cytotoxic direction (increased CD8+CD57+ and CD8+HLA-DR+ cells, and low T regulatory cells), whereas no major immunophenotypic differences were observed between imatinib and nilotinib patients.

CONCLUSIONS

Early BM lymphocytosis occurs with all current first-line TKIs and is associated with better treatment responses. PB and BM immunoprofile during dasatinib treatment markedly differs from both imatinib- and nilotinib-treated patients.

LGL leukemia and autoimmunity - the borderline between autoimmune disease and cancer is becoming blurred

Large granular lymphocyte (LGL) leukemia is a chronic hematological disease, in which the diseased cells consist of clonal large, mature T or NK cells. Major symptoms and findings of the disease include anemia, neutropenia and rheumatoid arthritis. Immunosuppressive treatments, such as methotrexate, usually relieve the symptoms in patients. In LGL leukemia, next-generation sequencing has recently revealed mutations in the STAT3 and STAT5B genes that lead to the activation of these proteins. Similar mutations have been detected in hereditary autoimmune diseases, disorders of bone marrow and malignancies of lymphocyte origin.

T cells and cancer - why do the killers become exhausted?

Nascent tumors are mostly eliminated by the immune system. During carcinogenesis mutated cells find a way to escape from the immune system´s surveillance. As the tumor microenvironment evolves it becomes increasingly difficult for T cells to recognize and kill cancer cells. Recently, novel immunological targets have been recognized and potent immunomodulatory drugs discovered in clinical trials. This has resulted in the emergence of immunotherapy as a novel potent therapy for cancer in addition to chemotherapy, targeted therapy, operative therapy and radiotherapy.

Abstract 606: Novel somatic mutations in the DNA-binding and coiled-coil domain of the STAT3 gene in LGL-leukemia

Introduction

T-cell large granular lymphocyte (T-LGL) leukemia is a rare, clonal disease characterized by the expansion of CD8+ cytotoxic T-cells. We recently discovered that 40% of T-LGL leukemia patients have somatic mutations in the SH2-domain of the STAT3 gene (Koskela et al. NEJM 2012). As aberrant STAT3 activation can be observed in all patients with LGL-leukemia, we now aimed to discover whether patients without mutations in the STAT3 hotspot area harbor mutations in the other parts of the STAT3 gene.

Methods

Targeted STAT3 sequencing covering all 23 coding exons was done with in-house developed deep amplicon sequencing panel using the Illumina Miseq platform. The data was analyzed with a bioinformatics pipeline, which is based on calling of variants with specific counts/frequencies and filtering out false positives using the estimated error rate and quality data of amplicon reads. All samples with a frequency ratio ≥0.9 were considered to be true mutations after filtering of SNPs and low coverage variants. 111 LGL-leukemia patients with no known STAT3-mutations in the SH2 domain were analyzed.

To explore the functional effects of mutations, expression constructs were generated with the identified variants and wild-type STAT3. The variants were expressed in HEK-293 cells carrying a STAT3-responsive SIE-reporter driven luciferase expression sequence to establish increased basal and IL6-stimulated STAT3 activity.

Results

With targeted amplicon sequencing, 3 patients were discovered to have STAT3 missense mutations in the DNA-binding domain. Two patients presented with the same H410R mutation with a variant allele frequency (VAF) of 49% and 8.8% respectively while another patient had a S381Y mutation (VAF 7%). The mutation H410R occurs in the DNA-binding domain in a highly conserved position, and results in conversion of histidine to arginine, which would predict for a slight increase in hydrophilicity.

In addition to STAT3 DNA-binding domain mutations, one T-LGL patient had a novel F174S mutation in the coiled-coil domain of STAT3 (VAF 43%). The coiled-coil domain of STAT3 has previously been shown to be essential in SH2-domain mediated receptor binding and subsequent activation.

Luciferase measurements of SIE-reporter HEK-293 cells transfected with constructs expressing either wild-type, variant F174S, H410R or Y640F STAT3 (the most common activating mutation in LGL leukemia) revealed the F174S and H410R variants to be as activating as the Y640F mutation in both unstimulated and IL-6 stimulated conditions.

Conclusions

T-LGL leukemia patients without STAT3 SH2-domain mutations harbor novel activating mutations in the DNA-binding and coiled-coil domain of STAT3. The frequency of mutations was 3.6% (4 of 111 patients). These findings further highlight the importance of screening the whole STAT3 gene in the diagnostic workup of LGL-leukemia and the central role of STAT3 in the pathogenesis of the disease.

Citation Format: Emma I. Andersson, Hanna Rajala, Heikki Kuusanmäki, Arjan van Adrichem, Samuli Eldfors, Sonja Lagström, Thomas Olson, Michael Clemente, Pekka Ellonen, Caroline Heckman, Thomas P. Loughran, Jaroslaw P. Maciejewski, Satu Mustjoki. Novel somatic mutations in the DNA-binding and coiled-coil domain of the STAT3 gene in LGL-leukemia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 606. doi:10.1158/1538-7445.AM2015-606

Novel drug candidates for blast phase chronic myeloid leukemia from high-throughput drug sensitivity and resistance testing

Chronic myeloid leukemia in blast crisis (CML BC) remains a challenging disease to treat despite the introduction and advances in tyrosine kinase inhibitor (TKI) therapy. In this study we set out to identify novel candidate drugs for CML BC by using an unbiased high-throughput drug testing platform. We used three CML cell lines representing different types of CML blast phases (K562, EM-2 and MOLM-1) and primary leukemic cells from three CML BC patients. Profiling of drug responses was performed with a drug sensitivity and resistance testing platform comprising 295 anticancer agents. Overall, drug sensitivity scores and the drug response profiles of cell line and primary cell samples correlated well and were distinct from other types of leukemia samples. The cell lines were highly sensitive to TKIs and the clinically TKI-resistant patient samples were also resistant ex vivo. Comparison of cell line and patient sample data identified new candidate drugs for CML BC, such as vascular endothelial growth factor receptor and nicotinamide phosphoribosyltransferase inhibitors. Our results indicate that these drugs in particular warrant further evaluation by analyzing a larger set of primary patient samples. The results also pave way for designing rational combination therapies.

The tyrosine kinase inhibitors imatinib and dasatinib reduce myeloid suppressor cells and release effector lymphocyte responses

Immune escape mechanisms promote tumor progression and are hurdles of cancer immunotherapy. Removing immunosuppressive cells before treatment can enhance efficacy. Tyrosine kinase inhibitors (TKI) may be of interest to combine with immunotherapy, as it has been shown that the inhibitor sunitinib reduces myeloid suppressor cells in patients with renal cell carcinoma and dasatinib promotes expansion of natural killer-like lymphocytes in chronic myeloid leukemia (CML). In this study, the capacity of dasatinib and imatinib to reduce myeloid suppressor cells and to induce immunomodulation in vivo was investigated ex vivo. Samples from CML patients treated with imatinib (n = 18) or dasatinib (n = 14) within a Nordic clinical trial (clinicalTrials.gov identifier: NCT00852566) were investigated for the presence of CD11b(+)CD14(-)CD33(+) myeloid cells and inhibitory molecules (arginase I, myeloperoxidase, IL10) as well as the presence of natural killer cells, T cells (naïve/memory), and stimulatory cytokines (IL12, IFNγ, MIG, IP10). Both imatinib and dasatinib decreased the presence of CD11b(+)CD14(-)CD33(+) myeloid cells as well as the inhibitory molecules and the remaining myeloid suppressor cells had an increased CD40 expression. Monocytes also increased CD40 after therapy. Moreover, increased levels of CD40, IL12, natural killer cells, and experienced T cells were noted after TKI initiation. The presence of experienced T cells was correlated to a higher IFNγ and MIG plasma concentration. Taken together, the results demonstrate that both imatinib and dasatinib tilted the immunosuppressive CML tumor milieu towards promoting immune stimulation. Hence, imatinib and dasatinib may be of interest to combine with cancer immunotherapy.

Novel TBL1XR1, EPHA7 and SLFN12 mutations in a Sezary syndrome patient discovered by whole exome sequencing

Sezary syndrome (SS) is an aggressive leukaemic variant of cutaneous T-cell lymphoma. Recurrent chromosomal aberrations have been found in SS, but the whole genetic mutation spectrum is unknown. To better understand the molecular pathogenesis of SS, we performed exome sequencing, copy number variation (CNV) and gene expression analysis of primary SS cells. In our index patient with typical SS, we found novel somatic missense mutations in TBL1XR1, EPHA7 and SLFN12 genes in addition to larger chromosomal changes. The mutations are located in biologically relevant genes affecting apoptosis and T-cell maturation. They may play a role in the pathobiology of the disease, but no recurrent mutations were discovered in nine additional patients with SS studied. Thus, screening of larger patient cohorts is needed to confirm their prevalence and biological significance in SS.

The analysis of clonal diversity and therapy responses using STAT3 mutations as a molecular marker in large granular lymphocytic leukemia

T-cell large granular lymphocytic leukemia and chronic lymphoproliferative disorder of natural killer cells are intriguing entities between benign and malignant lymphoproliferation. The molecular pathogenesis has partly been uncovered by the recent discovery of somatic activating STAT3 and STAT5b mutations. Here we show that 43% (75/174) of patients with T-cell large granular lymphocytic leukemia and 18% (7/39) with chronic lymphoproliferative disorder of natural killer cells harbor STAT3 mutations when analyzed by quantitative deep amplicon sequencing. Surprisingly, 17% of the STAT3-mutated patients carried multiple STAT3 mutations, which were located in different lymphocyte clones. The size of the mutated clone correlated well with the degree of clonal expansion of the T-cell repertoire analyzed by T-cell receptor beta chain deep sequencing. The analysis of sequential samples suggested that current immunosuppressive therapy is not able to reduce the level of the mutated clone in most cases, thus warranting the search for novel targeted therapies. Our findings imply that the clonal landscape of large granular lymphocytic leukemia is more complex than considered before, and a substantial number of patients have multiple lymphocyte subclones harboring different STAT3 mutations, thus mimicking the situation in acute leukemia.

Abstract 2587: Dasatinib-induced reduction of tumor growth is accompanied by the changes in the immune profile in melanoma B16.OVA mouse model

Dasatinib, a tyrosine kinase inhibitor used in the treatment of chronic myeloid leukemia and acute lymphoblastic leukemia, has been shown to exert immunomodulatory effects in addition to direct oncokinase inhibition. Recently, we observed that dasatinib induces a rapid (within one hour after oral administration) and marked mobilization of lymphocytes (up to 8-fold increase in lymphocyte count), which closely follows the drug plasma concentration. In addition, in a subgroup of patients a clonal expansion of large granular lymphocytes occurs, which is correlated with good therapy response.

As dasatinib-induced immunomodulatory effects are not leukemia specific, we aimed to exploit this activity to slow down or inhibit the growth of a syngeneic murine melanoma model and to characterize in detail the anti-tumor immune responses.

Ovalbumin expressing murine melanoma cell line B16.OVA was grown under the skin of immunocompetent mice. The mice (n=6/group) were treated daily i.g. either with 30 mg/kg dasatinib or vehicle only. Blood was collected before tumor transplantation, before treatment, and on treatment days 4, 7 and 10. Tumor volumes were measured manually and specific growth rate was calculated based on the first and the last day of the treatment. In addition to white blood cell differential counts, immunophenotyping of blood and tumor homogenate was done by flow cytometry using antibodies against CD45.1, CD3, CD4, CD8b and NK1.1, and SIINFEKL-pentamer to detect B16.OVA-specific cells. To assess the functional properties of lymphocytes, we used antibodies against immune checkpoint inhibitors CTLA-4 and PD-1, and a degranulation marker CD107.

On the 10th day of treatment, the tumor volumes were smaller in dasatinib group compared to control group, and there was a significant decrease in the tumor growth rate (0.06 vs. 0.18, p=0.01). Furthermore, dasatinib treated mice had increased proportion of CD8+ cells in the circulation (21% vs. 14%, p=0.04) and the CD4/CD8 ratio was significantly decreased (1.39 vs. 1.52, p= 0.04). During the tumor growth the mean CTLA-4 expression on CD8+ cells increased from 1.2% to 9% in the control group, whereas, in dasatinib group the increase was more modest (1.2% to 5.7%). Interestingly, 80% of tumor infiltrating CD8+ cells expressed PD1 antigen compared to &lt;5% of PD1 positive CD8+ cells in the peripheral blood suggesting lymphocyte anergy or exhaustion induced by tumor cells.

To conclude, dasatinib treatment slowed down the tumor growth in B16.OVA mouse model, which could be associated with the immunomodulatory effects of dasatinib. However, combinatorial treatment regimens may be needed as dasatinib is not able to fully break the immune cell anergy induced by tumor cells.

Citation Format: Can Hekim, Mette Ilander, Markus Vähä-Koskela, Paula Savola, Siri Tähtinen, Akseli Hemminki, Kimmo Porkka, Satu Mustjoki. Dasatinib-induced reduction of tumor growth is accompanied by the changes in the immune profile in melanoma B16.OVA mouse model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2587. doi:10.1158/1538-7445.AM2014-2587

Dasatinib induces fast and deep responses in newly diagnosed chronic myeloid leukaemia patients in chronic phase: clinical results from a randomised phase-2 study (NordCML006)

We randomised 46 newly diagnosed patients with chronic myeloid leukaemia (median age 56) to receive dasatinib 100 mg QD or imatinib 400 mg QD and report outcome as an intention-to-treat analysis with 36 months follow-up. Early cytogenetic and molecular responses were superior in the dasatinib group, with a tendency that imatinib patients caught up with time. For instance, MR^3.0 was reached at 3 months in 36% vs. 8% (P = 0.02), at 12 months in 81% vs. 46% (P = 0.02) and at 18 months in 73% vs. 65% (n.s.) of the patients in the two groups. In contrast, MR^4.5 was consistently superior in the dasatinib group at all time points from 6 months onwards, reaching 61% vs. 21% (P < 0.05) at 36 months. Sixty-four vs. 71% of the patients in the dasatinib and imatinib arms, respectively, remained on assigned drug. Dasatinib dose was frequently reduced, but with maintained excellent effect. One imatinib patient progressed to blastic phase, but no CML-related deaths occurred. In conclusion, our data compare favourably with those of the dasatinib registration study, DASISION. The fast and deep molecular responses induced by dasatinib compared with imatinib may be exploited to increase the proportion of patients who can achieve a treatment-free remission after treatment discontinuation.

Activating germline mutations in STAT3 cause early-onset multi-organ autoimmune disease

Monogenic causes of autoimmunity provide key insights into the complex regulation of the immune system. We report a new monogenic cause of autoimmunity resulting from de novo germline activating STAT3 mutations in five individuals with a spectrum of early-onset autoimmune disease, including type 1 diabetes. These findings emphasize the critical role of STAT3 in autoimmune disease and contrast with the germline inactivating STAT3 mutations that result in hyper IgE syndrome.

Dasatinib promotes Th1-type responses in granzyme B expressing T-cells

Tyrosine kinase inhibitors (TKIs) have dramatically improved the outcome of chronic myeloid leukemia (CML). Besides inhibiting target kinases in leukemic cells, 2nd generation TKI dasatinib also inhibits off-targets in immune effector cells resulting in atypical immune responses in some patients. Dasatinib has been described to increase the proportion of late effector memory T-cells, however, to date no follow-up studies have been performed in first-line patients. In this study, we explored the functional properties of T-cells using primary samples from CML patients (n = 28) on TKI therapy. Granzyme B (GrB) was used as a marker for late phase antigen experienced CD4+ and CD8+ T-cells. Dasatinib treatment increased the numbers of both GrB expressing memory CD4+ and CD8+ T-cells when compared with healthy controls. Functionally, the GrB+CD4+ T-cells were highly active and differentiated into Th1-type T-cells capable of producing IFN-γ, which is important for tumor control. Similar kind of increase was not observed during imatinib or nilotinib therapy. These data support the dual mode of action of dasatinib: potent BCR-ABL1 inhibition in leukemic cells is accompanied by the enhancement of cellular immunity, which may have implications in the long-term control of leukemia.

Uncovering the pathogenesis of large granular lymphocytic leukemia-novel STAT3 and STAT5b mutations

Large granular lymphocytic (LGL) leukemia is an incurable chronic disease, characterized by clonal expansion of cytotoxic T- or NK-cells in blood and bone marrow. Cytopenias (anemia, neutropenia) and autoimmune disorders such as rheumatoid arthritis are the most common clinical manifestations of LGL leukemia. Recently, somatic activating STAT3 gene mutations were shown to be specific for LGL leukemia with a prevalence of up to 70%. Analogous mutations in the STAT5b gene were seen in a smaller proportion of patients. These gain-of-function mutations are located in the SH2 domain of STAT3 and affect the phosphotyrosine-SH2 interaction required for dimerization of STAT3. The mutations increase the phosphorylation of STAT3 and STAT5b and enhance the transcriptional activity of the mutated proteins. STAT3 and STAT5b mutations can be used as molecular markers for LGL leukemia diagnostics, and they present novel therapeutic targets for STAT3 and STAT5b inhibitors, which currently are in development for treatment of cancer and autoimmune disorders.

IFNα induces prolonged remissions modeling curative immunologic responses in chronic myeloid leukemia

Tyrosine kinase inhibitor therapy has dramatically changed the outcome of chronic myeloid leukemia (CML) patients. However, the treatment is not considered to be curative and may present deleterious side effects, such that additional therapy options are warranted. Here, we discuss the beneficial immunomodulatory effects of interferon α (IFNα) therapy and the immunological changes related to optimal treatment responses.

Enlarged memory T-cell pool and enhanced Th1-type responses in chronic myeloid leukemia patients who have successfully discontinued IFN-α monotherapy

A small proportion of chronic myeloid leukemia patients treated with interferon-α (IFN-α) monotherapy are able to discontinue the treatment without disease relapse although residual leukemia cells are present. Recently, we showed that these patients have increased amount of NK-cells and a distinct blood cytokine profile. We now aimed to study the function of NK- and T-cells in order to understand the role of the immune system in maintaining the treatment response after IFN-α discontinuation. The study included 13 patients: 5 patients were still treated with IFN-α monotherapy (IFN-ON, median treatment time 163 months) and 8 had stopped the treatment successfully (IFN-OFF, median time without therapy 42 months). Detailed immunophenotype and cytokine production of NK- and T-cells was analyzed with flow cytometry. In addition, the cytotoxicity of NK-cells was studied using K562 as target cells and both the degranulation and direct killing was measured. Compared to healthy controls, IFN-OFF patients had increased proportion of CD4⁺ effector memory (CCR7⁻CD45RA⁻; median 23% vs. healthy 16%, p = 0.009) and CD8⁺ central memory T-cells (CCR7⁺CD45RA⁻; median 26% vs. healthy 14%, p = 0.004). Further, upon stimulation the IFN-γ/TNF-α cytokine secretion by CD4⁺ T-cells was significantly enhanced in IFN-OFF patients (median 13.7% vs. healthy 7.8%, p = 0.01), and CD4+ effector and central memory cells were the main cytokine producers. No similar increase was observed in IFN-ON group (6.5%). In addition, the proportion of NK-cells was significantly increased in IFN-OFF patients (median IFN-OFF 24%, healthy 13%, p = 0.04), but their direct killing of K562 cells was impaired. The cytotoxicity of NK-cells was also diminished in IFN-ON patients. To conclude, in addition to elevated NK-cell count, IFN-OFF patients have increased amount of memory T-cells, which are able to induce strong cytokine response upon stimulation. This activity may contribute to the maintenance of prolonged remission after successful IFN-α discontinuation.

Individualized systems medicine strategy to tailor treatments for patients with chemorefractory acute myeloid leukemia

We present an individualized systems medicine (ISM) approach to optimize cancer drug therapies one patient at a time. ISM is based on (i) molecular profiling and ex vivo drug sensitivity and resistance testing (DSRT) of patients' cancer cells to 187 oncology drugs, (ii) clinical implementation of therapies predicted to be effective, and (iii) studying consecutive samples from the treated patients to understand the basis of resistance. Here, application of ISM to 28 samples from patients with acute myeloid leukemia (AML) uncovered five major taxonomic drug-response subtypes based on DSRT profiles, some with distinct genomic features (e.g., MLL gene fusions in subgroup IV and FLT3-ITD mutations in subgroup V). Therapy based on DSRT resulted in several clinical responses. After progression under DSRT-guided therapies, AML cells displayed significant clonal evolution and novel genomic changes potentially explaining resistance, whereas ex vivo DSRT data showed resistance to the clinically applied drugs and new vulnerabilities to previously ineffective drugs.

SIGNIFICANCE

Here, we demonstrate an ISM strategy to optimize safe and effective personalized cancer therapies for individual patients as well as to understand and predict disease evolution and the next line of therapy. This approach could facilitate systematic drug repositioning of approved targeted drugs as well as help to prioritize and de-risk emerging drugs for clinical testing.

Down-regulation of miR-181c in imatinib-resistant chronic myeloid leukemia

The association of microRNA alterations with progression and treatment outcome has been revealed in different types of cancers. To find miRNAs involved in imatinib response we performed miRNA microarray followed by RT-qPCR verification of 9 available diagnostic bone marrow core biopsies from 9 CML patients including 4 imatinib-resistant and 5 imatinib-responder patients. Only one differentially expressed miRNA, miR-181c, was found when the imatinib-resistant group was compared with imatinib-responders. Significant down-regulation of miR-181c in imatinib-resistant versus imatinib-responders was confirmed by qRT-PCR. Some miR-181c target genes such as PBX3, HSP90B1, NMT2 and RAD21 have been associated with drug response.

Rapid mobilization of cytotoxic lymphocytes induced by dasatinib therapy

Tyrosine kinase inhibitors (TKIs) have potent effects on malignant cells, and they also target kinases in normal cells, which may have therapeutic implications. Using a collection of 55 leukemia patients treated with TKI therapy (chronic myeloid leukemia, n=47; acute lymphoblastic leukemia, n=8), we found that dasatinib, a second-generation broad-spectrum TKI, induced a rapid, dose-dependent and substantial mobilization of non-leukemic lymphocytes and monocytes in blood peaking 1-2 h after an oral intake and the blood counts closely mirrored drug plasma concentration. A preferential mobilization was observed for natural killer (NK), NK T, B and γδ+ T cells. Mobilization was coupled with a more effective transmigration of leukocytes through an endothelial cell layer and improved cytotoxicity of NK cells. Platelet numbers decreased markedly after the drug intake in a proportion of patients. Similar effects on blood cell dynamics and function were not observed with any other TKI (imatinib, nilotinib and bosutinib). Thus, dasatinib induces a unique, rapid mobilization and activation of cytotoxic, extravasation-competent lymphocytes, which may not only enhance antileukemia immune responses but can also be causally related to the side-effect profile of the drug (pleural effusions, thrombocytopenia).