Erika Falisi

Tumor-Induced Tolerance and Immune Suppression Depend on the C/EBPβ Transcription Factor

Tumor growth is associated with a profound alteration in myelopoiesis, leading to recruitment of immunosuppressive cells known as myeloid-derived suppressor cells (MDSCs). We showed that among factors produced by various experimental tumors, the cytokines GM-CSF, G-CSF, and IL-6 allowed a rapid generation of MDSCs from precursors present in mouse and human bone marrow (BM). BM-MDSCs induced by GM-CSF+IL-6 possessed the highest tolerogenic activity, as revealed by the ability to impair the priming of CD8(+) T cells and allow long term acceptance of pancreatic islet allografts. Cytokines inducing MDSCs acted on a common molecular pathway and the immunoregulatory activity of both tumor-induced and BM-derived MDSCs was entirely dependent on the C/EBPbeta transcription factor. Adoptive transfer of tumor antigen-specific CD8(+) T lymphocytes resulted in therapy of established tumors only in mice lacking C/EBPbeta in the myeloid compartment, suggesting that C/EBPbeta is a critical regulator of the immunosuppressive environment created by growing cancers.

IL4Rα+ Myeloid-Derived Suppressor Cell Expansion in Cancer Patients

Myeloid-derived suppressor cells (MDSC) contribute to immune dysfunctions induced by tumors both in experimental models and patients. In mice, MDSC are phenotypically heterogeneous cells that vary in their surface markers, likely depending on soluble factors produced by different tumors. We recently described a subset of inflammatory monocytes with immunosuppressive properties that can be found within the tumor mass, blood, and lymphoid organs of tumor-bearing mice. These cells expressed the α-chain of the receptor for IL-4 (IL4Rα) that was critical for their negative activity on CD8+ T cells. In cancer patients, the nature of MDSC is still poorly defined because evidence exists for both monocytic and granulocytic features. We show in this study that myeloid cells with immunosuppressive properties accumulate both in mononuclear and polymorphonuclear fractions of circulating blood leukocytes of patients with colon cancer and melanoma, thus unveiling a generalized alteration in the homeostasis of the myeloid compartment. Similarly to mouse MDSC, IL4Rα is up-regulated in both myeloid populations but its presence correlates with an immunosuppressive phenotype only when mononuclear cells, but not granulocytes, of tumor-bearing patients are considered.

A human promyelocytic-like population is responsible for the immune suppression mediated by myeloid-derived suppressor cells

We recently demonstrated that human BM cells can be treated in vitro with defined growth factors to induce the rapid generation of myeloid-derived suppressor cells (MDSCs), hereafter defined as BM-MDSCs. Indeed, combination of G-CSF + GM-CSF led to the development of a heterogeneous mixture of immature myeloid cells ranging from myeloblasts to band cells that were able to suppress alloantigen- and mitogen-stimulated T lymphocytes. Here, we further investigate the mechanism of suppression and define the cell subset that is fully responsible for BM-MDSC-mediated immune suppression. This population, which displays the structure and markers of promyelocytes, is however distinct from physiologic promyelocytes that, instead, are devoid of immuosuppressive function. In addition, we demonstrate that promyelocyte-like cells proliferate in the presence of activated lymphocytes and that, when these cells exert suppressive activity, they do not differentiate but rather maintain their immature phenotype. Finally, we show that promyelocyte-like BM-MDSCs are equivalent to MDSCs present in the blood of patients with breast cancer and patients with colorectal cancer and that increased circulating levels of these immunosuppressive myeloid cells correlate with worse prognosis and radiographic progression.

Myeloid cell diversification and complexity: an old concept with new turns in oncology

Tumour development is accompanied by an enhanced haematopoiesis. This is not a widespread activation since only cells belonging to the myelo-monocytic compartment are expanded and mobilized from primary sites of haematopoiesis to other organs, reaching also the tumour stroma. This process occurs early during tumour formation but becomes more evident in advanced disease. Far from being a simple, unwanted consequence of cancer development, accumulation of myelo-monocytitc cells plays a role in tumour vascularization, local spreading, establishment of metastasis at distant sites, and contribute to create an environment unfavourable for the adoptive immunity against tumour-associated antigens. Myeloid populations involved in these process are likely different but many cells, expanded in primary and secondary lymphoid organs of tumour-bearing mice, share various levels of the CD11b and Gr-1 (Ly6C/G) markers. CD11b+Gr-1+ cells are currently named myeloid-derived suppressor cells for their ability to inhibit T lymphocyte responses in tumour-bearing hosts. In this manuscript, we review the recent literature on tumour-conditioned myeloid subsets that assist tumour growth, both in mice and humans.

B-cell receptor configuration and adverse cytogenetics are associated with autoimmune hemolytic anemia in chronic lymphocytic leukemia

The development of autoimmune hemolytic anemia (AIHA) in patients with chronic lymphocytic leukemia (CLL) is associated with specific biological features. The occurrence of AIHA was hereby investigated in a retrospective series of 585 CLL patients with available immunoglobulin heavy chain variable (IGHV) gene status. AIHA occurred in 73 patients and was significantly associated with an IGHV unmutated (UM) status (P < 0.0001) and unfavorable [del(17)(p13) and del(11)(q23)] cytogenetic lesions (P < 0.0001). Stereotyped HCDR3 sequences were identified in 29.6% of cases and were similarly represented among patients developing or not AIHA; notably, subset #3 was associated with a significantly higher risk of AIHA than the other patients (P = 0.004). Multivariate analysis showed that UM IGHV, del(17)(p13) and del(11)(q23), but not stereotyped subset #3, were the strongest independent variables associated with AIHA. Based on these findings, we generated a biological risk score for AIHA development according to the presence of none (low risk), one (intermediated risk), or two (high risk) of the independent risk factors. Overall, our data indicate that UM IGHV status and/or unfavorable cytogenetic lesions are associated with the risk of developing secondary AIHA in CLL patients and suggest a possible role of specific stereotyped B‐cell receptor subsets in a proportion of cases. Am. J. Hematol. 2013.

B-cell receptor configuration and mutational analysis of patients with chronic lymphocytic leukaemia and trisomy 12 reveal recurrent molecular abnormalities

Trisomy 12 (+12) is the third most frequent cytogenetic aberration in chronic lymphocytic leukaemia (CLL) retrievable both as the sole chromosomal abnormality or in association with additional alterations. NOTCH1 mutations are known to be more prevalent among +12 patients, whereas mutations of FBXW7, a gene involved in NOTCH1 degradation, that lead to the constitutional activation of NOTCH1 have not been investigated in this setting. We analyzed a unicentric cohort of 44 +12 patients with CLL for mutations of TP53, NOTCH1 and FBXW7 genes, and we correlated them with B‐cell receptor (BCR) configurations. FBXW7, TP53 and NOTCH1 mutations were identified in 4.5%, 6.8% and 18.2% of patients, respectively. FBXW7 and NOTCH1 mutations appeared in a mutually exclusive fashion, suggesting that both aberrations might affect the same biological pathway. We found that 44.1% of +12 CLL patients had stereotyped B‐cell receptors, which is significantly higher than that observed in patients with CLL and no +12 (27%, p = 0.01).

Clinical significance of LAIR1 (CD305) as assessed by flow cytometry in a prospective series of patients with chronic lymphocytic leukemia

Most patients affected by chronic lymphocytic leukemia are diagnosed by flow cytometry. Several immunophenotypic markers have been identified as significant and independent prognostic variables, especially from retrospective cohorts. However, while attractive because their detection is inexpensive and feasible in most laboratories, only few have been validated by independent series. The expression of leukocyte-associated immunoglobulin-like receptor-1 (also known as LAIR1, LAIR-1 or CD305), an inhibitor of B-cell receptor-mediated signaling, has been reported to be lacking in high-risk chronic lymphocytic leukemia. However, its correlation with biological variables and its prognostic significance remain unknown. We investigated 311 consecutive patients, prospectively enrolled since 2007. Methods for studying patients were standardized and included clinical assessment, immunophenotype, fluorescence in situ hybridization, and status of immunoglobulin heavy chain variable region genes. Overall, 22.1% of patients had Binet stage B or C disease, 38.5% had unmutated immunoglobulin genes, 15.1% had high-risk cytogenetic abnormalities, 23.4% were CD38+, 37.8% CD49d+, and 59.8% LAIR1+. Expression of LAIR1 was inversely related to that of CD38 (P=0.0005), but was not associated with CD49d expression (P=0.96). A significantly lower expression of LAIR1 was observed in patients with Binet stage B or C disease (P=0.023), and in the presence of high-risk cytogenetic abnormalities (P=0.048) or unmutated immunoglobulin heavy chain variable region genes (P<0.0001). At univariate analysis LAIR1+ was significantly associated with longer time to first treatment (P=0.0002). This favorable effect of LAIR1+ was confirmed by multivariate analysis (hazard ratio=2.1, P=0.03 for LAIR1). Our results indicate that LAIR1 expression is a reliable and inexpensive marker capable of independently predicting time to first treatment in newly diagnosed unselected patients with chronic lymphocytic leukemia.

Autoimmune cytopenias in chronic lymphocytic leukemia at disease presentation in the modern treatment era: is stage C always stage C?

Abstract Anemia and thrombocytopenia at chronic lymphocytic leukemia (CLL) presentation have long been considered to be predictive of a poor prognosis, irrespective of the cause of cytopenia, yielding an advanced stage of the disease. We identified 86 patients with CLL who were diagnosed after year 2000 with Binet C disease at first presentation. Cytopenia was considered related to autoimmune conditions in 27 (31.3%; stage C “immune”) or secondary to bone marrow failure in 59 (68.6%; stage C “infiltrative”). No difference in clinical characteristics, mutational status, cytogenetics, TP53 and NOTCH1 mutations was observed between stage C “immune” and “infiltrative.” Patients with stage C “immune” had a trend toward a better overall survival than patients with stage C “infiltrative” (median 74 vs. 63 months), but the difference was not statistically significant (p = 0.30). This difference was not modified by adjustment for CLL tumor burden at presentation, and survival of stage C “immune” patients was significantly inferior compared to an unselected cohort of patients with stage A, but similar to stage B. Our findings suggest that autoimmune cytopenias at CLL diagnosis have a negative impact on patient outcome.

Double productive immunoglobulin sequence rearrangements in patients with chronic lymphocytic leukemia

The immunoglobulin heavy chain variable (IGHV) gene mutational status represents a major prognostic marker in chronic lymphocytic leukemia (CLL). Usually, the prognostic implications of IGHV gene analysis can be reliably ascertained but, occasionally, double productive rearrangements have been detected. Clinical presentation and biological features of such cases are unknown. Sixty patients with morphologically and phenotypically monoclonal CLL but double productive IGHV rearrangements were retrospectively identified by mRNA analysis from three Hematology Institutions. Clinical and biological features and survival of these 60 patients were compared with a control group of patients with CLL and single IGHV rearrangement. A prospective registry was used to assess the epidemiology of double productive IGHV among incidental patients with CLL. Using standard criteria to define IGHV‐mutated (M) or unmutated (U) cases, 39 of the 60 patients (65%) with double productive IGHV rearrangement had concordant status (23 MM, 16 UU), while 21 (35%) had discordant IGHV status. As compared with M patients, the MM ones had lower CD38 expression, more favorable cytogenetics and more indolent clinical behavior. Cases with UU had similar characteristics of U patients. Discordant cases presented with adverse prognostic features and had an aggressive clinical behavior requiring early treatment, similar to U patients. The prevalence of double IGHV was 3.1%. Patients with CLL with double concordant mutational status (MM or UU) have a clinical course similar to that of the corresponding single IGHV status, while those exhibiting discordant status represent a high risk population. This may help correct stratification within clinical trials. Am. J. Hematol. 88:277–282, 2013.

Integration of B-cell receptor-induced ERK1/2 phosphorylation and mutations of SF3B1 gene refines prognosis in treatment naive chronic lymphocytic leukemia.

Signaling events downstream of the B-cell receptor (BCR) are key determinants of the clinical behavior of chronic lymphocytic leukemia (CLL).[1][1],[2][2] Extracellular signal-regulated kinase 1/2 (ERK1/2) is a major pathway downstream of BCR stimulation.[3][3],[4][4] In a recent study, applying a