Homing of chronic lymphocytic leukemia (CLL) cells to sites favoring growth, a critical step in disease progression, is principally coordinated by the CXCL12/CXCR4 axis. A cohort of 62 CLL patients was divided into migrating and nonmigrating subsets according to chemotaxis toward CXCL12. Migrating patients phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) proteins more than nonmigrating patients (Po0.0002). CD38 expression was the parameter most strongly associated with heightened CXCL12 signaling (Po0.0001), confirmed by independent statistical approaches. Consistent with this observation, CD38À CLL cells in samples with bimodal CD38 expression responded less to CXCL12 than the intact clone (P ¼ 0.003). Furthermore, lentivirus-induced de novo expression of CD38 was paralleled by increased responses to CXCL12, as compared with cells infected with a control virus. CD38 ligation with agonistic monoclonal antibodies (mAbs) enhanced CXCL12 signaling, whereas blocking anti-CD38 mAbs inhibited chemokine effects in vitro. This is attributed to physical proximity on the membrane between CD38 and CXCR4 (the CXCL12 receptor), as shown by (i) coimmunoprecipitation and (ii) confocal microscopy experiments. Blocking anti-CD38 mAbs significantly compromised homing of CLL cells from blood to lymphoid organs in a mouse model. These results indicate that CD38 synergizes with the CXCR4 pathway and support the working hypothesis that migration is a central step in disease progression.

Cancer treatment is often complicated by resistance to conventional anti-cancer treatment and to more recently developed immunotherapy and gene therapy. These therapeutic modalities aim at activating death pathways within cancer cells. Attempts to activate the apoptotic death pathway, by overexpressing proapoptotic signals, are compromised by cancer defense mechanisms, which disrupt the apoptotic-signaling cascade downstream of the overexpressed component. Here, we describe a therapeutic option of triggering apoptosis without activating the apoptotic-signaling cascade or using the native apoptosis executioner nuclease. We have engineered Deoxyribonuclease-1 (DNase1), a waste-management enzyme, by deleting its signal peptide, adding a nuclear localization signal, and mutating its actin-binding site. Apoptosis studies and colony-forming assay for assessing cell viability were conducted in apoptosis-resistant Mel-Juso human melanoma cells. The modified DNase1 reduced cell viability by 77% relative to controls. It also induced typical microscopic features of cellular apoptosis, such as Terminal Transferase dUTP Nick-End Labelingpositive cells and DNA fragmentation. Quantification of apoptosis by Laser scanning cytometry demonstrated high-killing efficiency of 70-100%. The results suggest that this modified DNase1 can efficiently eliminate apoptosis-resistant cancer cells through apoptosis. Coupled to different tissue-specific gene expression elements, this recombinant DNase1 may serve as a platform for eliminating a variety of cancer types.

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CommentaryThe tumor microenvironment is rich extracellular mono-and dinucleotides (ATP, NAD+), which are metabolized by cell surface ecto enzymes to produce increased local concentrations of adenosine (Ado), a nucleoside involved the control of inflammation and immune responses [1]. A recent study by our group demonstrated that adenosinergic pathways contribute to customize the immune homeostasis of multiple myeloma (MM) [2]. A plasma cell malignancy, MM prevalently develops and expands with bone marrow (BM) niches [3]. Malignant plasma cells at all stages of the disease overexpress CD38 [4], a molecule with widespread tissue distribution and complex functions not yet fully elucidated. CD38 is a 45-kDa type II (or III) trans membrane glycoprote expressed by several immune and nonimmune cell types, and it plays a dual role as a receptor and as an ectoenzyme [5]. As a nucleotide-metabolizing ectoenzyme, CD38 catalyzes at neutral pH the extracellular conversion of a dinucleotide of adenine (NAD + ) to cADPR and ADPR. At acidic pH, CD38 can also catalyze the exchange of the nicotinamide group of NADP + with nicotinic acid and produce NAADP + and ADPRP.All of the final products are basic regulators of calcium signaling [6]. The initial disassembly of NAD + is followed by adenosinergic activity, provided that CD38 is operating the presence of other ectoenzymes (ectonucleotide pyrophosphatase/phosphodiesterase CD203a and 5'-nucleotidase CD73). These findings point to the existence of an alternative axis for extracellular production of the immunosuppressive Ado. Such a pathway would be able to flank and, some instances, to bypass the canonical pathway based on the conversion of ATP by the ecto-nucleoside triphosphate diphosphohydrolase CD39 [7,8]. These coordinated networks may be hijacked by the tumour for its own purposes.These observations are relevant to myeloma homeostasis the BM. For energy production and the synthesis of nucleotides and other macromolecules, malignant plasma cells favour glycolysis over oxidative phosphorylation (the Warburg effect), thus sacrificing efficiency for speed. This metabolic shift is hallmarked by hypoxic conditions, and leads to a decrease ATP concentrations and a concurrent increase NAD+ levels to susta high-rate glycolysis. this context, extracellular Ado may originates and be released from tumor cells depleted of ATP, or it may derive from extracellular ATP and NAD+ leaked from damaged tumor tissues.As a consequence, Ado may assume the role of a local hormone, adjusting cellular metabolism either via low or high affinity specific receptors expressed by normal and tumor cells [5]. Evidence for this is our finding that CD56 bright CD16 + NK cells produce Ado through a CD38-mediated pathway [9]. The functional relevance is that these NK cells operate as activated immune effector/regulatory cells inhibiting autologous CD4+ T cell proliferation. This strategy of immune escape has already been observed: melanoma cells produce Ado through a CD38/CD203a/CD73 pathway and suppress CD4+ T ce...

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