unplugging jak/stat in chronic myelomonocytic …...2016/03/12 · unplugging jak/stat in chronic...

Unplugging JAK/STAT in Chronic Myelomonocytic Leukemia Eric Solary1,2

1Inserm U1170, Gustave Roussy, 114 rue Edouard Vaillant, Villejuif, France; 2Faculty of Medicine, University Paris-Saclay, Le Kremlin-Bicêtre, France.

Corresponding Author: Eric Solary, INSERM U1170, Gustave Roussy Cancer Campus, 114 rue Edouard Vaillant, F-94805 Villejuif, France. Phone: 33 1 42 11 51 58; Fax: 33 1 42 11 52 40; E-mail: [email protected]

Running Title: Ruxolitinib in Chronic Myelomonocytic Leukemia

Grant Support: E. Solary is supported by the Ligue Nationale Contre le Cancer (Equipe Labellisée) and

by grants from the French National Cancer Institute (INCa).

Disclosure of Potential Conflicts of Interest: No potential conflicts of interest were disclosed.

Research. on July 11, 2020. © 2016 American Association for Cancerclincancerres.aacrjournals.org Downloaded from

Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Author Manuscript Published OnlineFirst on March 15, 2016; DOI: 10.1158/1078-0432.CCR-16-0372

http://clincancerres.aacrjournals.org/

Summary

The proliferative component of chronic myelomonocytic leukemia, related to an increased sensitivity

of myeloid progenitors to granulocyte macrophage-colony stimulating factor, suggests dedicated

therapeutic approaches. In this issue, ruxolitinib, a janus activated kinase (JAK)-1 and -2 inhibitory

drug, is shown to induce objective responses in chronic myelomonocytic leukemia patients.




In this issue of Clinical Cancer Research, Eric Padron and colleagues report a phase I trial showing that

ruxolitinib, a janus activated kinase (JAK)-1 and -2 inhibitory drug currently approved for patients

with severe myelofibrosis, can induce objective responses in patients with a chronic myelomonocytic

leukemia (CMML) (1). CMML is a clonal malignancy of the hematopoietic stem cell that affects mostly

elderly people. This disease has long been associated with myelodyplastic syndromes (MDS) in

clinical trials. The increasing recognition of CMML biological specificities however suggests specific

therapeutic approaches. Accordingly, ruxolitinib was selected following the demonstration that a

committed myeloid progenitor population with enhanced sensitivity to granulocyte macrophage-

colony stimulating factor (GM-CSF) can be detected in the bone marrow of CMML patients (2).

Fifteen years ago, the World Health Organization (WHO) created a category of overlapping myeloid

malignancies that associate dysplastic and proliferative features, of which CMML is the most

frequent entity. The MDS / myeloproliferative neoplasm (MPN) category was confirmed in 2008. The

main biological feature of CMML is monocytosis, which can be associated with bone marrow cell

dysplasia. The disease diagnosis could be improved by using a multiparametric flow cytometry assay

showing an expansion of classical CD14+,CD16- monocytes over 94% of total monocytes, which

rapidly distinguishes CMML from reactive monocytosis, the main confounding diagnosis (3). CMML

identification is supported also by the detection of clonal genetic abnormalities. The disease

molecular fingerprint associates somatic mutations in TET2 (~60% of cases), SRSF2 (~50%), ASXL1

(~40%) and a signaling gene (~50%). Whole exome and whole genome sequencing of peripheral

blood monocyte DNA detect a mean number of 14 variants in the coding regions, and a mutational

signature of ageing, respectively (4). Mutations accumulate almost linearly in the stem cell

compartment, and the most mutated cells demonstrate a growth advantage with differentiation (5).

Overall survival of CMML patients is currently ~30 months. Allogeneic stem cell transplantation,

which is the only potentially curative therapeutic option, is rarely feasible because of age. In other

patients, hydroxyurea can be used in proliferative CMML to reduce leukocytosis and spleen size (6).

The Federal Drug Administration also approved the use of azacytidine and decitabine in severe

CMML. These drugs restore a balanced hematopoiesis in 35-40% of them (7). However, they do not

significantly reduce the mutated allele burden in leukemic cells, nor they prevent clonal genetic

evolution, ultimately leading to fatal cytopenia or transformation into acute leukemia (5). There is

therefore a need for new therapeutic options that would modify the course of the disease.

By pooling CMML with MDS in clinical trials, the proliferative component of CMML has long been

neglected. Juvenile myelomonocytic leukemia is a rare pediatric MDS/MPN sharing various features

with CMML. In this disease, monocytosis is related to a constitutive activation of the Ras pathway

that induces a specific hypersensitivity of myeloid progenitors to GM-CSF, leading to signal




transducer and activator of transcription (STAT)-5 activation (8). In CMML, such a cytokine-specific

hypersensitivity of myeloid progenitors was initially thought to be restricted to a subgroup of

patients with mutations in signaling genes (5,9). By using hematopoietic colony forming assays and

phosphospecific STAT5 flow cytometry, Eric Padron and colleagues demonstrated that hypersensivity

of myeloid progenitors to GM-CSF was measurable in 90% of CMML patients. In response to GM-CSF,

the specific alpha-chain and the shared beta chain that form the GM-CSF receptor combine into an

active heterodimer that interacts with JAK2. The subsequent phosphorylation of JAK2 leads to a

specific evoked STAT5 signature that can be used as a read-out of the response to GM-CSF (8) (Figure

1). Preclinical studies using either an antibody that prevents GM-CSF binding to its cognate receptor

or chemical inhibitors of JAK2 supported a role for the GM-CSF/JAK2/STAT5 pathway in the

proliferation of CMML myeloid progenitors, providing the rationale for testing JAK2 inhibitors in this

disease (2).

The trial reported by Eric Padron and colleagues is a multicentric “rolling six” phase I trial testing

ruxolitinib at doses ranging from 5 to 20 mg BID. All the 20 enrolled patients had a CMML-1

according to the WHO criteria, indicating that the percentage of blast cells in their bone marrow

never exceeded 10%. A majority of them had a so-called proliferative CMML, based on their

leukocyte count higher than 13 G/L, and eight had been treated previously with a hypomethylating

drug. Importantly, ruxolitinib was safe in CMML patients in whom the hematological toxicity

described in primary myelofibrosis patients was not observed. The lack of dose-limiting toxicity

during the two cycle evaluation period led to recommend a dose of 20 mg BID for the phase 2 trial.

Importantly, the peripheral plasma of patients under therapy down-regulates GM-CSF-dependent

pSTAT5 in a model cell line, validating the anticipated effect of the treatment. A decrease in the size

of the spleen was measured in 5 out of 9 patients with a splenomegaly, hematologic improvement

was noticed in 4 cases, and a partial response according to IWG criteria for MDS was observed in one

patient.

The pattern of mutations observed in the treated cohort did not strictly reflect the pattern described

in larger cohorts of CMML patients. This may be due to the inclusion criteria that excluded those with

severe thrombocytopenia, which is often associated with RUNX1 gene mutation, and the preferential

enrolment of patients with a proliferative disease. Nevertheless, the observed responses were not

restricted to patients with somatic mutations in signaling genes, suggesting that targeting signaling

pathways makes senses even in the absence of genetic alteration of these pathways. As in patients

with a myelofibrosis, ruxolitinib did not demonstrate a significant impact on mutation allele burden.

Because the MDS criteria are not well appropriate for adult MDS/MPN, an international consortium

recently proposed specific response criteria for these diseases (10). The difficulty in capturing the




drug effect on constitutional symptoms by the use of scales that have not been specifically

developed for CMML, illustrates the need for more specific response criteria. Importantly, the

authors measured an effect of ruxolitinib on bone marrow plasma inflammatory cytokines, which

could account for the suspected improvement in B-symptoms, as described in ruxolitinib-treated

MPN patients.

The modulation of cytokine secretion as a consequence of JAK1 and JAK2 inhibition in leukemic and

surrounding cells could have an impact on the disease course. In a mouse model of chronic myeloid

leukemia, inflammatory cytokines control leukemic multipotent progenitor cell fate, thereby

promoting leukemia development (11). Conversely, interleukin-10 was proposed to antagonize

CMML myeloid progenitor hypersensitivity to GM-CSF (12). Altogether, cytokine synthesis and

secretion by cells of the leukemic clone and their environment probably modulate CMML progression

and could be therapeutic targets.

Ruxolitinib alone will not cure CMML. Nevertheless, the reported trial demonstrates that targeting

the proliferative component of this overlap syndrome could favorably influence the course of the

disease. This first biology-driven trial paves the way for testing drug combinations based on the

careful investigation of the cell autonomous and non-cell autonomous pathogenic components that

generates the CMML phenotype.

References

1. Padron E, Dezern A, Andrade-Campos M, Vaddi K, Scherle P, Zhang Q, et al. A multi-

institution phase I trial of ruxolitinib in patients with chronic myelomonocytic leukemia

(CMML). Clin Cancer Res 2016 Feb 8. [Epub ahead of print].

2. Padron E, Painter JS, Kunigal S, Mailloux AW, McGraw K, McDaniel JM, et al. GM-CSF-

dependent pSTAT5 sensitivity is a feature with therapeutic potential in chronic

myelomonocytic leukemia. Blood 2013;121:5068-77.

3. Selimoglu-Buet D, Wagner-Ballon O, Saada V, Bardet V, Itzykson R, Bencheikh L, et al.

Characteristic repartition of monocyte subsets as a diagnostic signature of chronic

myelomonocytic leukemia. Blood 2015;125:3618-26.

4. Merlevede J, Droin N, Qin T, Meldi K, Yoshida K, Morabito M, et al. Mutation allele burden

remains unchanged in chronic myelomonocytic leukemia responding to hypomethylating

agents. Nature Commun 2016;7:10767.




5. Itzykson R, Kosmider O, Renneville A, Morabito M, Preudhomme C, Berthon C, et al. Clonal

architecture of chronic myelomonocytic leukemias. Blood 2013;121:2186-98.

6. Wattel E, Guerci A, Hecquet B, Economopoulos T, Copplestone A, Mahé B, et al. A

randomized trial of hydroxyurea versus VP16 in adult chronic myelomonocytic leukemia.

Groupe Français des Myélodysplasies and European CMML Group. Blood 1996;88:2480-7.

7. Meldi K, Qin T, Buchi F, Droin N, Sotzen J, Micol JB, et al. Specific molecular signatures predict

decitabine response in chronic myelomonocytic leukemia. J Clin Invest 2015;125:1857-72.

8. Kotecha N, Flores NJ, Irish JM, Simonds EF, Sakai DS, Archambeault S, et al. Single-cell

profiling identifies aberrant STAT5 activation in myeloid malignancies with specific clinical

and biologic correlates. Cancer Cell 2008;14:335-43.

9. Ricci C, Fermo E, Corti S, Molteni M, Faricciotti A, Cortelezzi A, et al. RAS mutations

contribute to evolution of chronic myelomonocytic leukemia to the proliferative variant. Clin

Cancer Res 2010;16:2246-56.

10. Savona MR, Malcovati L, Komrokji R, Tiu RV, Mughal TI, Orazi A, et al. An international

consortium proposal of uniform response criteria for myelodysplastic/myeloproliferative

neoplasms (MDS/MPN) in adults. Blood 2015;125:1857-65.

11. Reynaud D, Pietras E, Barry-Holson K, Mir A, Binnewies M, Jeanne M, et al. IL-6 controls

leukemic multipotent progenitor cell fate and contributes to chronic myelogenous leukemia

development. Cancer Cell. 2011;20:661-73.

12. Geissler K, Ohler L, Födinger M, Virgolini I, Leimer M, Kabrna E, et al. Interleukin 10 inhibits

growth and granulocyte/macrophage colony-stimulating factor production in chronic

myelomonocytic leukemia cells. J Exp Med. 1996;184:1377-84.




Figure 1: The GM-CSF/JAK2/STAT5 pathway. GM-CSF receptor (also known as CD116) is made of a

specific alpha-chain subunit (α) encoded by CSFR2A gene, and a common beta chain (βc) shared with

IL-3 and IL-5 receptors. The GM-CSF hematopoietic growth factor induces the formation of the

heterodimeric receptor. In turn, JAK2 is recruited and phosphorylated, which activates several STAT

pathways, including STAT5 whose phosphorylation is used in the present study as a read-out of the

response to GM-CSF. Upon JAK2 activation, the βc chain becomes phosphorylated and recruits

adaptor molecules, leading to the activation of other signaling pathways (gray ovals).




Published OnlineFirst March 15, 2016.Clin Cancer Res Eric Solary Unplugging JAK/STAT in Chronic Myelomonocytic Leukemia

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