Biased Expression of the FOXP3Δ3 Isoform in Aggressive Bladder Cancer Mediates Differentiation and Cisplatin Chemotherapy Resistance.

PURPOSE: The transcriptional regulation mediating cancer cell differentiation into distinct molecular subtypes and modulating sensitivity to existing treatments is an enticing therapeutic target. Our objective was to characterize the ability of the forkhead/winged transcription factor FOXP3 to modulate the differentiation of bladder cancer. EXPERIMENTAL DESIGN: Expression of FOXP3 was analyzed by immunohistochemistry in a tumor microarray of 587 samples and overall survival in a subset of 187 patients following radical cystectomy. Functional assays were performed in SW780 and HT1376 cell lines in vitro and in vivo and gene expression profiling performed by RNA-Seq. Validation was undertaken using gene expression profiles of 131 patients from The Cancer Genome Atlas (TCGA) consortium in bladder cancer. RESULTS: FOXP3 expression correlates with bladder cancer stage and inversely with overall survival, with biased expression of the FOXP3Δ3 isoform. Functional assays of FOXP3Δ3 demonstrated resistance to chemotherapy in vitro, whereas subcutaneous xenografts overexpressing FOXP3Δ3 developed larger and more poorly differentiated bladder cancers. RNA expression profiling revealed a unique FOXP3Δ3 gene signature supporting a role in chemotherapy resistance. Accordingly, knockdown of Foxp3 by siRNA in HT1376 cells conferred sensitivity to cisplatin- and gemcitabine-induced cytotoxicity. Validation in TCGA dataset demonstrated increased expression of FOXP3 in subtypes II to IV and skewing of molecular subtypes based on FOXP3Δ3-specific gene expression. CONCLUSIONS: (i) Biased expression of the FOXP3Δ3 isoform in bladder cancer inversely correlates with overall survival, (ii) FOXP3Δ3 induces a unique gene program that mediates cancer differentiation, and (iii) FOXP3Δ3 may augment chemotherapy resistance. Clin Cancer Res; 22(21); 5349-61. ©2016 AACR.

Loss of MyD88 leads to more aggressive TRAMP prostate cancer and influences tumor infiltrating lymphocytes.

BACKGROUND: The influence of pattern recognition receptor (PRR) signaling in the prostate tumor microenvironment remains unclear. Although there may be a role for PRR agonists as adjuvants to therapy, prior evidence suggests tumor promoting as well as tumor inhibiting mechanisms. The purpose of this study is to examine the role of the key Toll-like receptor (TLR) signaling adaptor protein myeloid differentiation primary response gene 88 (MyD88) in prostate cancer development. METHODS: MyD88(-/-) mice in a C57Bl6 background were crossed with transgenic adenocarcinomas of the mouse prostate (TRAMP) mice to create MyD88(-/-) TRAMP(Tg+/-) animals, which were compared to MyD88(+/+) TRAMP(Tg+/-) animals and their non-transgenic counterparts at 30 weeks. Prostates were examined histologically, by immunohistochemistry and immunofluorescence staining, and by qPCR, to characterize tumor-infiltrating immune populations as well as activation of the downstream NF-κB pathway and androgen receptor (AR) expression. Splenocytes were examined for development of distinct immune cell populations. RESULTS: Absence of MyD88 led to increased prostatic intraepithelial neoplasm (PIN) and areas of well-differentiated adenocarcinoma in TRAMP transgenic mice. Analysis of infiltrating immune populations revealed an increase in CD11b(+) Gr1(+) myeloid-derived suppressor cells (MDSCs), as evidenced by increased expression of prostatic arginase-1 and iNOS as well as the cytokine IL-10, and a deficiency in NK cells in prostates from MyD88(-/-) TRAMP(Tg+/-) compared to MyD88(+/+) TRAMP(Tg+/-) mice, whereas a decrease in splenocytic NK cell differentiation was observed in MyD88(-/-) mice. Prostate tumors revealed no significant differences in NF-κB or AR expression in MyD88(+/+) TRAMP(Tg+/-) compared to MyD88(-/-) TRAMP(Tg+/-) mice. CONCLUSIONS: During prostate cancer development in the TRAMP model, MyD88 may play a role in limiting prostate tumorigenesis by altering tumor-infiltrating immune populations. This suggests that in the context of specific cancers, distinct PRRs and signaling pathways of innate immune signaling may influence the tumor microenvironment and represent a novel therapeutic strategy.

Stromal modulation of bladder cancer-initiating cells in a subcutaneous tumor model.

The development of new cancer therapeutics would benefit from incorporating efficient tumor models that mimic human disease. We have developed a subcutaneous bladder tumor regeneration system that recapitulates primary human bladder tumor architecture by recombining benign human fetal bladder stromal cells with SW780 bladder carcinoma cells. As a first step, SW780 cells were seeded in ultra low attachment cultures in order to select for sphere-forming cells, the putative cancer stem cell (CSC) phenotype. Spheroids were combined with primary human fetal stromal cells or vehicle control and injected subcutaneously with Matrigel into NSG mice. SW780 bladder tumors that formed in the presence of stroma showed accelerated growth, muscle invasion, epithelial to mesenchymal transition (EMT), decreased differentiation, and greater activation of growth pathways compared to tumors formed in the absence of fetal stroma. Tumors grown with stroma also demonstrated a greater similarity to typical malignant bladder architecture, including the formation of papillary structures. In an effort to determine if cancer cells from primary tumors could form similar structures in vivo using this recombinatorial approach, putative CSCs, sorted based on the CD44(+)CD49f(+) antigenic profile, were collected and recombined with fetal bladder stromal cells and Matrigel prior to subcutaneous implantation. Retrieved grafts contained tumors that exhibited the same structure as the original primary human tumor. Primary bladder tumor regeneration using human fetal bladder stroma may help elucidate the influences of stroma on tumor growth and development, as well as provide an efficient and accessible system for therapeutic testing.

Loss of CD20 and bound CD20 antibody from opsonized B cells occurs more rapidly because of trogocytosis mediated by Fc receptor-expressing effector cells than direct internalization by the B cells.

We previously reported that 1 h after infusion of CD20 mAb rituximab in patients with chronic lymphocytic leukemia (CLL), >80% of CD20 was removed from circulating B cells, and we replicated this finding, based on in vitro models. This reaction occurs via an endocytic process called shaving/trogocytosis, mediated by FcγR on acceptor cells including monocytes/macrophages, which remove and internalize rituximab-CD20 immune complexes from B cells. Beers et al. reported that CD20 mAb-induced antigenic modulation occurs as a result of internalization of B cell-bound mAb-CD20 complexes by the B cells themselves, with internalization of ∼40% observed after 2 h at 37°C. These findings raise fundamental questions regarding the relative importance of shaving versus internalization in promoting CD20 loss and have substantial implications for the design of mAb-based cancer therapies. Therefore, we performed direct comparisons, based on flow cytometry, to determine the relative rates and extent of shaving versus internalization. B cells, from cell lines, from patients with CLL, and from normal donors, were opsonized with CD20 mAbs rituximab or ofatumumab and incubated for varying times and then reacted with acceptor THP-1 monocytes to promote shaving. We find that shaving induces considerably greater loss of CD20 and bound mAb from opsonized B cells in much shorter time periods (75-90% in <45 min) than is observed for internalization. Both shaving/trogocytosis and internalization could contribute to CD20 loss when CLL patients receive rituximab therapy, but shaving should occur more rapidly and is most likely to be the key mechanism of CD20 loss.

Penetration of antibody-opsonized cells by the membrane attack complex of complement promotes Ca(2+) influx and induces streamers.

We have reported that during complement-mediated cytolysis of B cells promoted by the CD20 mAbs rituximab or ofatumumab (OFA), long, thin structures that we call streamers (≥ 3 cell diameters) are rapidly generated and grow out from the cell surface. Streamers appear before cells are killed and contain opsonizing mAbs and membrane lipids. By exploiting the differential Ca(2+) requirements of discrete steps in the complement cascade, we determined that mAb-opsonized cells first tagged with C3b using C5-depleted serum are killed on addition of serum and EDTA, but the cells do not produce streamers. Also, cells first opsonized with OFA are lysed in serum containing Mg-EGTA by the alternative complement pathway but streamers are not produced. These findings indicate that Ca(2+) influx is necessary for streamer formation. Other mAbs that promote complement-mediated cytolysis also induce streamers on target cells. Streamer-like structures called nanotubes have been reported in several cellular systems, and are thought to promote intercellular communication/signaling. We tested whether this signaling could influence the susceptibility of neighboring cells contacted by streamers to complement attack and found that complement-mediated cytolysis of OFA-opsonized cells increases the resistance of unopsonized indicator cell populations to subsequent lysis when these cells are exposed to OFA and complement.

A novel approach to preventing the hemolysis of paroxysmal nocturnal hemoglobinuria: both complement-mediated cytolysis and C3 deposition are blocked by a monoclonal antibody specific for the alternative pathway of complement.

The clinical hallmark of paroxysmal nocturnal hemoglobinuria (PNH) is chronic intravascular hemolysis that is a consequence of unregulated activation of the alternative pathway of complement (APC). Intravascular hemolysis can be inhibited in patients by treatment with eculizumab, a monoclonal antibody that binds complement C5 thereby preventing formation of the cytolytic membrane attack complex of complement. However, in essentially all patients treated with eculizumab, persistent anemia, reticulocytosis, and biochemical evidence of hemolysis are observed; and in a significant proportion, their PNH erythrocytes become opsonized with complement C3. These observations suggest that PNH patients treated with eculizumab are left with clinically significant immune-mediated hemolytic anemia because the antibody does not block APC activation. With a goal of improving PNH therapy, we characterized the activity of anti-C3b/iC3b monoclonal antibody 3E7 in an in vitro model of APC-mediated hemolysis. We show that 3E7 and its chimeric-deimmunized derivative H17 block both hemolysis and C3 deposition on PNH erythrocytes. The antibody is specific for the APC C3/C5 convertase because classical pathway-mediated hemolysis is unaffected by 3E7/H17. These findings suggest an approach to PNH treatment in which both intravascular and extravascular hemolysis can be inhibited while preserving important immune functions of the classical pathway of complement.