CD44 activation enhances acute monoblastic leukemia cell survival via Mcl-1 upregulation

CD44: a cancer stem cell marker and therapeutic target in leukemia treatment

CD44 is a ubiquitous leukocyte adhesion molecule involved in cell-cell interaction, cell adhesion, migration, homing and differentiation. CD44 can mediate the interaction between leukemic stem cells and the surrounding extracellular matrix, thereby inducing a cascade of signaling pathways to regulate their various behaviors. In this review, we focus on the impact of CD44s/CD44v as biomarkers in leukemia development and discuss the current research and prospects for CD44-related interventions in clinical application.

Phase I clinical study of RG7356, an anti-CD44 humanized antibody, in patients with acute myeloid leukemia

RG7356, a recombinant anti-CD44 immunoglobulin G1 humanized monoclonal antibody, inhibits cell adhesion and has been associated with macrophage activation in preclinical models. We report results of a phase I dose-escalation study of RG7356 in relapsed/refractory acute myeloid leukemia (AML).Eligible patients with refractory AML, relapsed AML after induction chemotherapy, or previously untreated AML not eligible for intensive chemotherapy were enrolled and received intravenous RG7356 at dosages ≤ 2400 mg every other week or ≤ 1200 mg weekly or twice weekly; dose escalation started at 300 mg.Forty-four patients (median age, 69 years) were enrolled. One dose-limiting toxicity occurred (grade 3 hemolysis exacerbation) after one 1200 mg dose (twice-weekly cohort). The majority of adverse events were mild/moderate. Infusion-related reactions occurred in 64% of patients mainly during cycle 1. Two patients experienced grade 3 drug-induced aseptic meningitis. Pharmacokinetics increased supraproportionally, suggesting a target-mediated drug disposition (TMDD) at ≥ 1200 mg. Two patients achieved complete response with incomplete platelet recovery or partial response, respectively. One patient had stable disease with hematologic improvement.RG7356 was generally safe and well tolerated. Maximum tolerated dose was not reached, but saturation of TMDD was achieved. The recommended dose for future AML evaluations is 2400 mg every other week.

Identification of miRNA-mRNA Network Associated with Acute Myeloid Leukemia Survival

Background

Acute myeloid leukemia (AML) is a common hematologic malignancy of adults. The pathophysiological mechanism of AML is not well understood. The purpose of this study was to examine the crucial miRNAs and mRNAs associated with AML survival.

Material/Methods

The full clinical dataset of miRNA and mRNA expression profiling of AML patients was downloaded from The Cancer Genome Atlas database. Univariate Cox regression analysis was performed to obtain those miRNAs and mRNAs associated with AML survival. A miRNA-mRNA interaction network was constructed. The underlying functions of mRNAs were predicted through Kyoto Encyclopedia of Genes and Genomes (KEEG) pathway enrichment. The expression levels of miRNAs and mRNAs were detected by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

Fourteen miRNAs and 830 mRNAs associated with AML survival were identified. Of the 14 miRNAs, hsa-mir-425, hsa-mir-1201, and hsa-mir-1978 were identified as risk factors and the other 11 miRNAs were identified as protective factors of AML survival. For target-genes of miRNAs, GTSF1, RTN4R, and CD44 were the top risk factor target-genes associated with AML survival. An interaction network was constructed that including 607 miRNA-target gene pairs associated with AML survival. Target-genes associated with AML survival were significantly enriched in several pathways including pancreatic secretion, calcium signaling pathway, natural killer cell mediated cytotoxicity, and Alzheimer’s disease. The qRT-PCR results were consistent with our bioinformatics analyses.

Conclusions

The miRNA hsa-mir-425 was identified as the top risk factor miRNA of AML survival and CD44 was identified as one of the top three risk factor target-genes associated with AML survival. Both hsa-mir-425 and CD44 may play key roles in progression and development of AML through calcium signaling pathway and natural killer cell mediated cytotoxicity.

CD44S-hyaluronan interactions protect cells resulting from EMT against anoikis

The detachment of normal epithelial cells from matrix triggers an apoptotic response known as anoikis, during homeostatic turnover. Metastatic tumor cells evade anoikis, by mechanisms that are only partly characterized. In particular, the epithelial–mesenchymal transition (EMT) in a subset of invasive tumor cells confers anoikis-resistance. In some cases, EMT up-regulates the cancer stem cell marker CD44S and the enzyme hyaluronic acid synthase-2 (HAS2). CD44S is the major receptor for hyaluronan in the extracellular matrix. Herein, we demonstrate that CD44S, unlike the CD44E isoform expressed in normal epithelial cells, contributes to the protection against anoikis. This protection requires the interaction of CD44S with hyaluronan (HA). CD44S–HA interaction is proposed to play an important role in tumor metastasis through enhanced cell survival under detached conditions.

CD44 in canine leukemia: analysis of mRNA and protein expression in peripheral blood

Hyaluronan receptor CD44 mediates interaction between cells and extracellular matrix. The expression of standard form and its variants is dysregulated in human leukemias and is associated with metastasis and prognosis. The aim of this work is the evaluation of CD44 mRNA and protein expression in canine leukemia. Peripheral blood from 20 acute leukemias (AL) (10 acute lymphoblastic, 6 acute myeloid and 4 acute undifferentiated leukemias), 21 chronic lymphocytic leukemias (CLL) and thirteen healthy dogs were collected. The mRNA expression of all CD44 variants presenting exons 1-5 and/or 16-20 (CD44_ex1-5 and CD44_ex16-20) and CD44 protein were determined by real-time RT-PCR and flow cytometry, using the mean fluorescent index (MFI), respectively. CD44 MFI was significantly higher in leukemic samples compared to controls and a higher expression was found in AL in respect with CLL. No significant differences were found when considering different phenotypic subtypes of AL and CLL. CD44_ex1-5 mRNA expression was significantly higher in AL compared to controls, whereas there was no difference in CLL compared to controls and AL. CD44_es16-20 showed the same trend, but without differences among groups. The high CD44 expression found in canine leukemias could be considered a step toward the definition of their molecular features.

Leukemia cells induce changes in human bone marrow stromal cells

Background

Bone marrow stromal cells (BMSCs) are multipotent cells that support angiogenesis, wound healing, and immunomodulation. In the hematopoietic niche, they nurture hematopoietic cells, leukemia, tumors and metastasis. BMSCs secrete of a wide range of cytokines, growth factors and matrix proteins which contribute to the pro-tumorigenic marrow microenvironment. The inflammatory cytokines IFN-γ and TNF-α change the BMSC secretome and we hypothesized that factors produced by tumors or leukemia would also affect the BMSC secretome and investigated the interaction of leukemia cells with BMSCs.

Methods

BMSCs from healthy subjects were co-cultured with three myeloid leukemia cell lines (TF-1, TF-1α and K562) using a trans-well system. Following co-culture, the BMSCs and leukemia cells were analyzed by global gene expression analysis and culture supernatants were analyzed for protein expression. As a control, CD34+ cells were also cocultured with BMSCs.

Results

Co-culture induced leukemia cell gene expression changes in stem cell pluripotency, TGF-β signaling and carcinoma signaling pathways. BMSCs co-cultured with leukemia cells up-regulated a number of proinflammatory genes including IL-17 signaling-related genes and IL-8 and CCL2 levels were increased in co-culture supernatants. In contrast, purine metabolism, mTOR signaling and EIF2 signaling pathways genes were up-regulated in BMSCs co-cultured with CD34+ cells.

Conclusions

BMSCs react to the presence of leukemia cells undergoing changes in the cytokine and chemokine secretion profiles. Thus, BMSCs and leukemia cells both contribute to the creation of a competitive niche more favorable for leukemia stem cells.