Key Points• FcgRIIb-dependent internalization of therapeutic mAbs is dependent on antibody specificity.• FcgRIIb can be activated in both cis and trans configurations.A major feature that distinguishes type I from type II anti-CD20 monoclonal antibodies (mAbs) and reduces their therapeutic efficacy is the tendency to internalize from the cell surface. We have shown previously that the extent of internalization correlates with the capacity of type I mAb to simultaneously engage both CD20 and the inhibitory Fcg receptor, FcgRIIb, in a bipolar configuration. Here, we investigated whether mAbs directed at other B-cell surface receptors also engaged FcgRIIb and whether this interaction promoted internalization. Most mAbs engaged and activated FcgRIIb, with the strength of activation related to the level of mAb bound to the cell surface. However, engagement did not affect internalization of most mAb-ligated receptors, either in cell lines or primary chronic lymphocytic leukemia cells with the exception of CD19 and CD38. Furthermore, at high cell concentrations/density both cis and trans interactions between cell-surface bound mAb and FcgRIIb were evident, but trans interactions did not inhibit type I anti-CD20 mAb-mediated internalization. These data identify that FcgRIIb is engaged by many mAbs in both cis and trans configurations, triggering its activation, but that internalization via FcgRIIb occurs for only a select subset. These findings have implications when designing new antibody-based therapeutics. (Blood. 2014;123(5):669-677)

Intravascular large-B-cell lymphoma (IVLBCL) is a unique type of extranodal lymphoma characterized by selective growth of tumor cells in small vessels without lymphadenopathy. Greater understanding of the molecular pathogenesis of IVLBCL is hampered by the paucity of lymphoma cells in biopsy specimens, creating a limitation in obtaining sufficient tumor materials. To uncover the genetic landscape of IVLBCL, we performed whole-exome sequencing (WES) of 21 patients with IVLBCL using plasma-derived cell-free DNA (cfDNA) (n = 18), patient-derived xenograft tumors (n = 4), and tumor DNA from bone marrow (BM) mononuclear cells (n = 3). The concentration of cfDNA in IVLBCL was significantly higher than that in diffuse large-B-cell lymphoma (DLBCL) (P < 0.0001) and healthy donors (P = 0.0053), allowing us to perform WES, and most mutations detected in BM tumor DNA were successfully captured in cfDNA and xenograft. IVLBCL showed a high frequency of genetic lesions characteristic of activated-B-cell-type DLBCL; with the former showing conspicuously higher frequencies (compared to nodal DLBCL) of mutations in MYD88 (57%), CD79B (67%), SETD1B (57%), and HLA-B (57%). We also found that 8 (38%) IVLBCL harbored rearrangements of PD-L1/PD-L2 involving the 3′-UTR; such rearrangements are implicated in immune evasion via PD-L1/PD-L2 overexpression. Our data demonstrate the utility of cfDNA and imply important roles for immune evasion in IVLBCL pathogenesis and PD-1/PD-L1/PD-L2 blockade in therapeutics for IVLBCL.

Fcγ receptors (FcγRs) are key immune receptors responsible for the effective control of both humoral and innate immunity and are central to maintaining the balance between generating appropriate responses to infection and preventing autoimmunity. When this balance is lost, pathology results in increased susceptibility to cancer, autoimmunity, and infection. In contrast, optimal FcγR engagement facilitates effective disease resolution and response to monoclonal antibody immunotherapy. The underlying genetics of the FcγR gene family are a central component of this careful balance. Complex in humans and generated through ancestral duplication events, here we review the evolution of the gene family in mammals, the potential importance of copy number, and functionally relevant single nucleotide polymorphisms, as well as discussing current approaches and limitations when exploring genetic variation in this region.

Cancer‐associated fibroblasts (CAF) are a key component in the tumor microenvironment and play functional roles in tumor metastasis and resistance to chemotherapies. We have previously reported that CAF isolated from lymphoma samples increase anaerobic glycolysis and decrease intracellular production of reactive oxygen species, promoting the survival of tumor cells. Herein, we analyzed the mechanisms underlying this support of tumor‐cell survival by CAF. As direct contact between lymphoma cells and CAF was not indispensable to survival support, we identified that the humoral factor pyruvate was significantly secreted by CAF. Moreover, survival of lymphoma cells was promoted by the presence of pyruvate, and this promotion was canceled by inhibition of monocarboxylate transporters. Metabolome analysis of lymphoma cells in coculture with CAF demonstrated that intermediates in the citric acid cycle were significantly increased, indicating that tumor cells produced energy by aerobic metabolism. These findings indicate that energy production in lymphoma cells is regulated in coordination not only with anaerobic glycolysis, but also with aerobic metabolism termed the reverse‐Warburg effect, involving the secretion of pyruvate from CAF resulting in increased use of the citric acid cycle in lymphoma cells.

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By using a conventional two-hybrid technique with an Src homology 3 (SH3) domain of Nesh as the bait protein, a novel full-length cDNA was isolated and sequenced from a human placenta cDNA library. This cDNA consists of 3023 bp and has a predicted open reading frame that encodes 486 amino acids. It possesses an SH3 binding motif, a nuclear targeting sequence, and no catalytic domain. Overall, it has no similarity to known molecules involved in a signaling cascade. Polymerase Chair reaction-based mapping with both a monochromosomal hybrid panel and radiation hybrid cell panels localized the gene on human chromosome 3q12 near the marker D3S1271.

Using a conventional two-hybrid technique with MAWD as bait protein, a novel full-length cDNA was isolated and sequenced from a human liver cDNA library. This cDNA consists of 2575 base pairs and has a predicted open reading frame encoding 255 amino acids. Overall, it is similar to the catalytic enzyme PHZF, catalyzing the hydroxylation of phenazine-1-carboxylic acid to 2-hydroxyphenazine-1-carboxylic acid. Polymerase chain reactionbased mapping with both a monochromosomal hybrid panel and radiation hybrid cell panels placed the gene to human chromosome 10q21.1 near the marker D10S210.