Quantitative, phenotypic, and functional evaluation of basophils in myelodysplastic syndromes

Association of peripheral basophils with tumor M2 macrophage infiltration and outcomes of the anti-PD-1 inhibitor plus chemotherapy combination in advanced gastric cancer

BACKGROUND

Although the anti-programmed death-1 (PD-1) inhibitor plus chemotherapy combination has been approved as the standard first-line treatment for advanced gastric cancer, a proportion of patients do not significantly benefit from this therapy. Who would respond poorly to this treatment and the underlying mechanisms of treatment failure are far from clear.

METHODS

We retrospectively analyzed the associations between the peripheral basophils at baseline and clinical outcomes in 63 advanced gastric cancer patients treated with anti-PD-1 plus chemotherapy and 54 patients treated with chemotherapy alone. Immunohistochemistry and immunofluorescence staining in gastric cancer samples were utilized to investigate the basophil-related immunophenotype.

RESULTS

The optimal cutoff of basophil count to distinguish responders to anti-PD-1 plus chemotherapy from non-responders was 20.0/μL. Compared with the low basophil group (≤ 20.0/μL, n = 40), the high basophil group (> 20.0/μL, n = 23) had a significantly lower objective response rate (ORR 17.4% vs. 67.5%, p = 0.0001), worse progression-free survival (median PFS 4.0 vs. 15.0 months, p = 0.0003), and worse overall survival (median OS not reached, p = 0.027). Multivariate analyses identified a basophil count of > 20.0/μL as an independent risk factor for a worse ORR (OR 0.040, 95% CI 0.007-0.241, p = 0.0004), worse PFS (HR 3.720, 95% CI 1.823-7.594, p = 0.0003) and worse OS (HR 3.427, 95% CI 1.698-6.917, p = 0.001). In contrast, there was no significant association between peripheral basophil counts and tumor response or survival in the chemotherapy-alone group (p > 0.05). In primary gastric cancer samples, we observed a correlation between higher peripheral basophil counts and the accumulation of tumor-infiltrating basophils (r = 0.6833, p = 0.005). Tumor-infiltrating basophils were found to be spatially proximate to M2 macrophages within TME and positively correlated with tumor M2 macrophage infiltration (r = 0.7234, p = 0.0023). The peripheral basophil counts also had a significant positive correlation with tumor-infiltrating M2 macrophage counts (r = 0.6584, p = 0.003). Further validation in tumor samples treated with the neoadjuvant anti-PD-1 inhibitor plus chemotherapy combination suggests that the peripheral basophils, tumor infiltration of basophils, and M2 macrophages were significantly more abundant in non-responders than in responders (p = 0.0333, p = 0.0007, and p = 0.0066, respectively).

CONCLUSIONS

The peripheral basophil count was observed to be a potential biomarker of anti-PD-1 efficacy for advanced gastric cancer. Moreover, basophils may induce an immune-evasive tumor microenvironment by increasing M2 macrophage infiltration, which could be a potential immunotherapeutic target for advanced gastric cancer.

Secondary basophilic leukemia in Ph-negative myeloid neoplasms: A distinct subset with poor prognosis

During progression of myeloid neoplasms, the basophil compartment may expand substantially and in some of these patients, a basophilic leukemia is diagnosed. In patients with Ph-chromosome+ chronic myeloid leukemia, acceleration of disease is typically accompanied by marked basophilia. In other myeloid neoplasms, secondary leukemic expansion of basophils is rarely seen. We report on 5 patients who suffered from a myelodysplastic syndrome, myeloproliferative neoplasm, or acute leukemia and developed a massive expansion of basophils during disease progression. In 4 of 5 patients, peripheral blood basophil counts reached 40%, and the diagnosis “secondary basophilic leukemia” was established. As assessed by flow cytometry, neoplastic basophils expressed CD9, CD18, CD25, CD33, CD63, PD-L1, CD123, and CLL-1. In addition, basophils were found to display BB1 (basogranulin), 2D7, tryptase and KIT. In 4 of 5 patients the disease progressed quickly and treatment with azacitidine was started. However, azacitidine did not induce major clinical responses, and all patients died from progressive disease within 3 Y. In in vitro experiments, the patients´ cells and the basophilic leukemia cell line KU812 showed variable responses to targeted drugs, including azacitidine, venetoclax, hydroxyurea, and cytarabine. A combination of venetoclax and azacitidine induced cooperative antineoplastic effects in these cells. Together, secondary basophilic leukemia has a poor prognosis and monotherapy with azacitidine is not sufficient to keep the disease under control for longer time-periods. Whether drug combination, such as venetoclax+azacitidine, can induce better outcomes in these patients remains to be determined in future clinical studies.

Human mast cells and basophils-How are they similar how are they different?

Mast cells and basophils are key contributors to allergies and other inflammatory diseases since they are the most prominent source of histamine as well as numerous additional inflammatory mediators which drive inflammatory responses. However, a closer understanding of their precise roles in allergies and other pathological conditions has been marred by the considerable heterogeneity that these cells display, not only between mast cells and basophils themselves but also across different tissue locations and species. While both cell types share the ability to rapidly degranulate and release histamine following high-affinity IgE receptor cross-linking, they differ markedly in their ability to either react to other stimuli, generate inflammatory eicosanoids or release immunomodulating cytokines and chemokines. Furthermore, these cells display considerable pharmacological heterogeneity which has stifled attempts to develop more effective anti-allergic therapies. Mast cell- and basophil-specific transcriptional profiling, at rest and after activation by innate and adaptive stimuli, may help to unravel the degree to which these cells differ and facilitate a clearer understanding of their biological functions and how these could be targeted by new therapies.

Basophils Promote Tumor Rejection via Chemotaxis and Infiltration of CD8+ T Cells

Elevated numbers of regulatory T cells (Treg) in patient tumors are known to inhibit efficient antitumor T-cell responses. To study the mechanisms controlling tumor rejection, we assessed different mouse models for Treg depletion. In Foxp3DTR knock-in mice, about 99% Treg depletion was achieved, resulting in complete rejection of transplanted HCmel12 melanomas in a CD8⁺ T-cell-dependent way. In contrast, about 90% Treg depletion obtained in BAC transgenic Foxp3.LuciDTR4 mice failed to induce complete rejection of HCmel12 melanomas, demonstrating that residual Tregs were able to control CD8⁺ T-cell responses against the tumor. Ninety-nine percent of Treg depletion provoked drastic changes in the tumor microenvironment, such as strong infiltration of CD8⁺ T cells and basophils. Intratumoral basophils enhanced CD8⁺ T-cell infiltration via production of chemokines CCL3 and CCL4; antibody-based blocking of these chemokines inhibited CD8⁺ T-cell infiltration. Therapeutic induction of basophilia by IL3/anti-IL3 antibody complexes, combined with transfer of CD8⁺ T cells, resulted in enhanced T-cell infiltration and tumor rejection. Our study identifies a critical role basophils play in tumor rejection and that this role can be exploited for therapeutic intervention. Cancer Res; 77(2); 291-302. ©2016 AACR.

Identification of campath-1 (CD52) as novel drug target in neoplastic stem cells in 5q-patients with MDS and AML

PURPOSE

The CD52-targeted antibody alemtuzumab induces major clinical responses in a group of patients with myelodysplastic syndromes (MDS). The mechanism underlying this drug effect remains unknown.

EXPERIMENTAL DESIGN

We asked whether neoplastic stem cells (NSC) in patients with MDS (n = 29) or acute myelogenous leukemia (AML; n = 62) express CD52.

RESULTS

As assessed by flow cytometry, CD52 was found to be expressed on NSC-enriched CD34(+)/CD38(-) cells in 8/11 patients with MDS and isolated del(5q). In most other patients with MDS, CD52 was weakly expressed or not detectable on NSC. In AML, CD34(+)/CD38(-) cells displayed CD52 in 23/62 patients, including four with complex karyotype and del(5q) and one with del(5q) and t(1;17;X). In quantitative PCR (qPCR) analyses, purified NSC obtained from del(5q) patients expressed CD52 mRNA. We were also able to show that CD52 mRNA levels correlate with EVI1 expression and that NRAS induces the expression of CD52 in AML cells. The CD52-targeting drug alemtuzumab, was found to induce complement-dependent lysis of CD34(+)/CD38(-)/CD52(+) NSC, but did not induce lysis in CD52(-) NSC. Alemtuzumab also suppressed engraftment of CD52(+) NSC in NSG mice. Finally, CD52 expression on NSC was found to correlate with a poor survival in patients with MDS and AML.

CONCLUSIONS

The cell surface target Campath-1 (CD52) is expressed on NSC in a group of patients with MDS and AML. CD52 is a novel prognostic NSC marker and a potential NSC target in a subset of patients with MDS and AML, which may have clinical implications and may explain clinical effects produced by alemtuzumab in these patients.

Mixed-lineage eosinophil/basophil crisis in MDS: a rare form of progression

BACKGROUND

Basophilic crisis and eosinophilia are well recognized features of advanced chronic myeloid leukaemia. In other myeloid neoplasms, however, transformation with marked basophilia and eosinophilia is considered unusual.

DESIGN

We examined the long-term follow-up of 322 patients with de novo myelodysplastic syndromes (MDS) to define the frequency of basophilic, eosinophilic and mixed lineage (basophilic and eosinophilic) transformation.

RESULTS

Of all patients, only one developed mixed lineage crisis (>or= 20% basophils and >or= 20% eosinophils). In this patient, who initially suffered from chronic myelomonocytic leukaemia, basophils increased to 48% and eosinophils up to 31% at the time of progression. Mixed lineage crisis was not accompanied by an increase in blast cells or organomegaly. The presence of BCR/ABL and other relevant fusion gene products (FIP1L1/PDGFRA, AML1/ETO, PML/RAR alpha, CBF beta/MYH11) were excluded by PCR. Myelomastocytic transformation/myelomastocytic leukaemia and primary mast cell disease were excluded by histology, KIT mutation analysis, electron microscopy and immunophenotyping. Basophils were thus found to be CD123+, CD203c+, BB1+, KIT- cells, and to express a functional IgE-receptor. Among the other patients with MDS examined, 4(1.2%) were found to have marked basophilia (>or= 20%) and 7(2.1%) were found to have massive eosinophilia ( >or= 20%), whereas mixed-lineage crisis was detected in none of them.

CONCLUSIONS

Mixed basophil/eosinophil crisis may develop in patients with MDS but is an extremely rare event.

The basophil-specific ectoenzyme E-NPP3 (CD203c) as a marker for cell activation and allergy diagnosis

Basophils are effector cells of allergic reactions. These cells produce and store a number of vasoactive and immunomodulatory mediators. During an allergic reaction, basophils can release their mediator substances into the extracellular space and thus contribute to the clinical picture and symptoms in allergy. The phenotypic hallmark of basophils is expression of high-affinity IgE receptors (Fc epsilon RI) on their cell surface together with expression of the activation-linked molecule CD203c. This ectoenzyme is located both on the plasma membrane and in the cytoplasmic compartment of basophils. Cross-linking of the Fc epsilon RI by an allergen or anti-IgE antibody results in a rapid upregulation of intracellular CD203c molecules to the cell surface and is accompanied by mediator release. CD203c is therefore a promising target molecule for a flow cytometry-based test to analyze sensitized individuals and patients with type I allergy. In the present article, we review the current knowledge of CD203c with special regard to its tissue distribution and regulation in basophil activation. In addition, we discuss the application of CD203c in allergy diagnosis.

Histamine chloramine reactivity with thiol compounds, ascorbate, and methionine and with intracellular glutathione

Histamine is stored in granules of mast cells and basophils and released by inflammatory mediators. It has the potential to intercept some of the HOCl generated by the neutrophil enzyme, myeloperoxidase, to produce histamine chloramine. We have measured rate constants for reactions of histamine chloramine with methionine, ascorbate, and GSH at pH 7.4, of 91 M(-1)s(-1), 195 M(-1)s(-1), and 721 M(-1)s(-1), respectively. With low molecular weight thiols, the reaction was with the thiolate and rates increased exponentially with decreasing thiol group pK(a). Comparing rate constants for different chloramines reacting with ascorbate or a particular thiol anion, these were higher when there was less negative charge in the vicinity of the chloramine group. Histamine chloramine was the most reactive among biologically relevant chloramines. Consumption of histamine chloramine and oxidation of intracellular GSH were examined for human fibroblasts. At nontoxic doses, GSH loss over 10 min was slightly greater than that with HOCl, but the cellular uptake of histamine chloramine was 5-10-fold less. With histamine chloramine, GSSG was a minor product and most of the GSH was converted to mixed disulfides with proteins. HOCl gave a different profile of GSH oxidation products, with significantly less GSSG and mixed disulfide formation. There was irreversible oxidation and losses to the medium, as observed with HOCl and other cell types. Thus, histamine chloramine shows high preference for thiols both in isolation and in cells, and in this respect is more selective than HOCl.