Immunosurveillance markers may predict patients who can discontinue imatinib therapy without relapse

Leukemic stem cell persistence in chronic myeloid leukemia patients in deep molecular response induced by tyrosine kinase inhibitors and the impact of therapy discontinuation

During the last decade, the use of tyrosine kinase inhibitor (TKI) therapy has modified the natural history of chronic myeloid leukemia (CML) allowing an increase of the overall and disease-free survival, especially in patients in whom molecular residual disease becomes undetectable. However, it has been demonstrated that BCR-ABL1- expressing leukemic stem cells (LSCs) persist in patients in deep molecular response. It has also been shown that the discontinuation of Imatinib leads to a molecular relapse in the majority of cases. To determine a possible relationship between these two phenomena, we have evaluated by clonogenic and long-term culture initiating cell (LTC-IC) assays, the presence of BCR-ABL1-expressing LSCs in marrow samples from 21 patients in deep molecular response for three years after TKI therapy (mean duration seven years). LSCs were detected in 4/21 patients. Discontinuation of TKI therapy in 13/21 patients led to a rapid molecular relapse in five patients (4 without detectable LSCs and one with detectable LSCs). No relapse occurred in the eight patients still on TKI therapy, whether LSCs were detectable or not. Thus, this study demonstrates for the first time the in vivo efficiency of TKIs, both in the progenitor and the LSC compartments. It also confirms the persistence of leukemic stem cells in patients in deep molecular response, certainly at the origin of relapses. Finally, it emphasizes the difficulty of detecting residual LSCs due to their rarity and their low BCR-ABL1 mRNA expression.

Monocytic myeloid-derived suppressor cells as prognostic factor in chronic myeloid leukaemia patients treated with dasatinib

Myeloid suppressor cells are a heterogeneous group of myeloid cells that are increased in patients with chronic myeloid leukaemia (CML) inducing T cell tolerance. In this study, we found that therapy with tyrosine kinase inhibitors (TKI) decreased the percentage of granulocytic MDSC, but only patients treated with dasatinib showed a significant reduction in the monocytic subset (M‐MDSC). Moreover, a positive correlation was observed between number of persistent M‐MDSC and the value of major molecular response in dasatinib‐treated patients. Serum and exosomes from patients with CML induced conversion of monocytes from healthy volunteers into immunosuppressive M‐MDSC, suggesting a bidirectional crosstalk between CML cells and MDSC. Overall, we identified M‐MDSC as prognostic factors in patients treated with dasatinib. It might be of interest to understand whether MDSC may be a candidate predictive markers of relapse risk following TKI discontinuation, suggesting their potential significance as practice of precision medicine.

Considerations for Successful Treatment-free Remission in Chronic Myeloid Leukemia

BCR-ABL1 tyrosine kinase inhibitors have dramatically improved outcomes for patients with chronic myeloid leukemia, and current studies are investigating whether some patients may be able to suspend therapy yet maintain response in a state known as "treatment-free remission" (TFR). Results from ongoing studies suggest that ≈ 40% to 60% of patients in sustained (generally ≥ 2 years) deep molecular response (defined as a 4-log or deeper reduction in BCR-ABL1 transcripts, depending on the study) who attempt TFR may successfully remain off treatment. Results from TFR clinical trials, patient considerations for attempting TFR, and potential predictive factors associated with successful TFR are reviewed herein.

Can any patients with chronic myeloid leukemia outside of a clinical trial have their tyrosine kinase inhibitor discontinued?

PURPOSE OF REVIEW

This article critically appraises the state of treatment-free remission as a strategy for patients with chronic myeloid leukemia (CML) in deep remission after therapy with tyrosine kinase inhibitors (TKIs).

RECENT FINDINGS

Approximately half of patients with CML defined fairly narrowly by trial criteria - TKI sensitive, in deep molecular remission for a defined period - can successfully maintain protective levels of response after TKI cessation. Those who cannot appear at very low risk of disease control loss and can promptly regain remission with TKI resumption. Increasing numbers of patients followed longer term in trials have proven as well as a lack of additional late relapse in either group and that 'functional cure' of CML is feasible. Both the definition of remission sufficient to attempt treatment-free remission and the trigger to resume treatment have been relaxed somewhat while outcomes have remained the same. Based on repeated confirmatory data, economic pressures, and pragmatism, the question of feasibility and safety of TKI cessation outside of clinical trials is at hand.

SUMMARY

TKI cessation outside of clinical trials, if performed under strict guidelines, utilizing optimal monitoring techniques, with counsel available from experts in the field, and after full disclosure of the risks and benefits with the patient, may be safe (see video, supplemental digital content 1, which summarizes the abstract and offers the author's perspective,http://links.lww.com/COH/A15).

Prognostic impact of the expression of NCR1 and NCR3 NK cell receptors and PD-L1 on advanced non-small cell lung cancer

The putative contribution of natural killer (NK) cells to immunosurveillance in non-small cell lung cancer (NSCLC) has been an ongoing conundrum. Here, we used a readily standardizable quantitative real time polymerase chain reaction (qRT-PCR) to measure the expression of NK cell receptors in total peripheral blood mononuclear cells (PBMC) from healthy volunteers (HV), patients with gastrointestinal stromal tumors (GIST), neuroblastoma (NB), melanoma or NSCLC. We quantified NCR1 (which codes for NKp46) and NCR3 (which codes for NKp30), as well as that of three NCR3 splice variants (which give rise to immunostimulatory NKp30A and NKp30B, as well as to immunosuppressive NKp30C). NSCLC patients expressed lower levels of NCR1 than did HV. Remarkably, NCR3 was lower in NSCLC patients than in HV as well as in all other malignancies. Moreover, a discrete proportion of NSCLC patients exhibited a particular low ratio between NKp30B and NKp30C (ΔBC). In the overall cohort, low expression of NCR3 correlated with poor overall and progression-free survival (PFS). When patients were stratified according to the level of PD-L1 expression by NSCLC cells, within the PD-L1^high category (>5% positive tumors), the sole parameter that affected prognosis was the expression of NCR1. However, in patients bearing tumors with negative PD-L1 expression on tumor or tumor-infiltrating stromal cells, the ΔBC^low patients exhibited a dismal prognosis. Altogether, these results strongly suggest that NK cells mediate immunosurveillance against NSCLC and that measuring NK cell receptor expression by blood cells can yield useful biomarkers for patient stratification.

Downregulation of Plasma miR-215 in Chronic Myeloid Leukemia Patients with Successful Discontinuation of Imatinib

Approximately 40% of chronic myeloid leukemia (CML) patients who discontinue imatinib (IM) therapy maintain undetectable minimal residual disease (UMRD) for more than one year (stopping IM (STOP-IM)). To determine a possible biomarker for STOP-IM CML, we examined plasma miRNA expression in CML patients who were able to discontinue IM. We first screened candidate miRNAs in unselected STOP-IM patients, who had sustained UMRD after discontinuing IM for more than six months, in comparison with healthy volunteers, by using a TaqMan low-density array for plasma or exosomes. Exosomal miR-215 and plasma miR-215 were downregulated in the STOP-IM group compared to the control, indicating that the biological relevance of the plasma miR-215 level is equivalent to that of the exosomal level. Next, we performed real-time quantitative RT-PCR in 20 STOP-IM patients, 32 patients with UMRD on continued IM therapy (IM group) and 28 healthy volunteers. The plasma miRNA-215 level was significantly downregulated in the STOP-IM group (p < 0.0001); we determined the cut-off level and divided the IM group patients into two groups according to whether the plasma miR-215 was downregulated or not. The IM group patients with a low plasma miR-215 level had a significantly higher total IM intake, compared to the patients with elevated miR-215 levels (p = 0.0229). Functional annotation of miR-215 target genes estimated by the Database for Annotation, Visualization and Integrated Discovery (DAVID) bioinformatic tools involved cell cycle, mitosis, DNA repair and cell cycle checkpoint. Our study suggests a possible role of miR-215 in successful IM discontinuation.

Myeloid derived suppressor cells in chronic myeloid leukemia

The suppression of the immune system creates a permissive environment for development and progression of cancer. One population of immunosuppressive cells that have become the focus of intense study is myeloid derived suppressor cells (MDSCs), immature myeloid cells able to induce immune-escape, angiogenesis, and tumor progression. Two different subpopulations have been identified and studied: granulocytic and monocytic MDSCs, with a different immunophenotype and immunosuppressive properties. Recently, an accumulation of both Gr-MDSCs and Mo-MDSCs cells has been found in the peripheral blood of chronic myeloid leukemia (CML) patients. They are part of the tumor clone showing BCR/ABL expression. Imatinib therapy decreases both MDSCs and arginase 1 levels to normal ones. This review will focus on actual knowledge for human MDSCs and their immunosuppressive activity in CML patients, with a critical attention to comparison of Gr-MDSCs and polymorphonuclear cells (PMNs). We will then suggest the monitoring of MDSCs in patients who have discontinued tyrosine kinase inhibitors (TKIs) therapy to evaluate if their increase could correlate with disease relapse.

Loss of STAT3 in murine NK cells enhances NK cell–dependent tumor surveillance

Loss of STAT3 in NK cells enhances the expression of granzyme B, perforin, and DNAM-1, resulting in enhanced tumor surveillance. STAT3 binds the IFN-γ promoter and interferes with cytokine-induced IFN-γ production in NK cells.