Anti-PD-1 antibody combined with chemotherapy suppresses the growth of mesothelioma by reducing myeloid-derived suppressor cells.

BACKGROUND: The combination of anti-PD-1/PD-L1 antibody with chemotherapy has been approved for the first-line therapy of lung cancer. However, the effects against malignant mesothelioma (MPM) and the immunological mechanisms by which chemotherapy enhances the effect of targeting PD-1/PD-L1 in MPM are poorly understood. MATERIALS AND METHODS: We utilized syngeneic mouse models of MPM and lung cancer and assessed the therapeutic effects of anti-PD-1 antibody and its combination with cisplatin (CDDP) and pemetrexed (PEM). An immunological analysis of tumor-infiltrating cells was performed with immunohistochemistry. RESULTS: We observed significant therapeutic effects of anti-PD-1 antibody against MPM. Although the effect was associated with CD8+ and CD4+ T cells in tumors, the number of Foxp3+ cells was not reduced but rather increased. Consequently, combination with CDDP/PEM significantly enhanced the antitumor effects of anti-PD-1 antibody by decreasing numbers of intratumoral myeloid-derived suppressor cells (MDSCs) and vessels probably through suppression of VEGF expression by CDDP + PEM. CONCLUSIONS: The combination of anti-PD-1 antibody with CDDP + PEM may be a promising therapy for MPM via inhibiting the accumulation of MDSCs and vessels in tumors.

Fibroblast-specific ERK5 deficiency changes tumor vasculature and exacerbates tumor progression in a mouse model.

The roles of cancer-associated fibroblasts (CAFs) have been studied in the tumor progression, and CAFs are expected to become the new targets for cancer pharmacotherapies. CAFs contribute to tumor cell survival and proliferation, tumor angiogenesis, immune suppression, tumor inflammation, tumor cell invasion and metastasis, and extracellular matrix remodeling. However, detailed mechanisms of how CAFs function in the living system remain unclear. CAFs include α-smooth muscle actin, expressing activated fibroblasts similar to myofibroblasts, and are highly capable of producing collagen. Several reports have demonstrated the contributions of extracellular-signal-regulated kinase 5 (ERK5) in fibroblasts to the fibrotic processes; however, the roles of CAF-derived ERK5 remain unclear. To investigate the roles of CAF-derived ERK5 in the tumor progression, we created mice lacking the ERK5 gene specifically in fibroblasts. Colon-26 mouse colon cancer cells were implanted into the mice subcutaneously, and the histological analyses of the tumor tissue were performed after 2 weeks. Immunofluorescence analyses showed that recipient-derived fibroblasts existed within the tumor tissue. The present study demonstrated that fibroblast-specific ERK5 deficiency exacerbated tumor progression and it was accompanied with thicker tumor vessel formation and the increase in the number of activated fibroblasts. We combined the results of The Cancer Genome Atlas (TCGA) database analysis with our animal studies, and indicated that regulating ERK5 activity in CAFs or CAF invasion into the tumor tissue can be important strategies for the development of new targets in cancer pharmacotherapies.

A novel targeting therapy of malignant mesothelioma using anti-podoplanin antibody.

Podoplanin (Aggrus), which is a type I transmembrane sialomucin-like glycoprotein, is highly expressed in malignant pleural mesothelioma (MPM). We previously reported the generation of a rat anti-human podoplanin Ab, NZ-1, which inhibited podoplanin-induced platelet aggregation and hematogenous metastasis. In this study, we examined the antitumor effector functions of NZ-1 and NZ-8, a novel rat-human chimeric Ab generated from NZ-1 including Ab-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity against MPM in vitro and in vivo. Immunostaining with NZ-1 showed the expression of podoplanin in 73% (11 out of 15) of MPM cell lines and 92% (33 out of 36) of malignant mesothelioma tissues. NZ-1 could induce potent ADCC against podoplanin-positive MPM cells mediated by rat NK (CD161a(+)) cells, but not murine splenocytes or human mononuclear cells. Treatment with NZ-1 significantly reduced the growth of s.c. established tumors of MPM cells (ACC-MESO-4 or podoplanin-transfected MSTO-211H) in SCID mice, only when NZ-1 was administered with rat NK cells. In in vivo imaging, NZ-1 efficiently accumulated to xenograft of MPM, and its accumulation continued for 3 wk after systemic administration. Furthermore, NZ-8 preferentially recognized podoplanin expressing in MPM, but not in normal tissues. NZ-8 could induce higher ADCC mediated by human NK cells and complement-dependent cytotoxicity as compared with NZ-1. Treatment with NZ-8 and human NK cells significantly inhibited the growth of MPM cells in vivo. These results strongly suggest that targeting therapy to podoplanin with therapeutic Abs (i.e., NZ-8) derived from NZ-1 might be useful as a novel immunotherapy against MPM.

View of physicians on and barriers to patient enrollment in a multicenter clinical trial: experience in a Japanese rural area.

BACKGROUND: Clinical trials in the general practice setting are important for providing evidence on the effectiveness and safety of different agents under various conditions. In conducting these trials, the participation of physicians and patient recruitment are important issues. Various investigations in the literature have reported views and attitudes of physicians on various types of clinical trials. Nevertheless, there is still little information concerning physicians participating in a clinical trial and among them, those who could not recruit any patients (unsuccessful physician recruiters). METHODS: In 2003, we collaborated in a large-scale multicenter study of Japanese hypertensive patients (COPE Trial). In Tokushima University Hospital and 18 other medical institutions, we investigated the views and attitudes of unsuccessful physician recruiters in comparison with successful physician recruiters, using a questionnaire. RESULTS: The questionnaire was provided by mail to 47 physicians and 27 (57%) responded. The response rate was 79% for successful physician recruiters compared to 43% (P = 0.014) for unsuccessful physician recruiters. More successful physician recruiters (73%) than unsuccessful physician recruiters (42%) stated they had participated and enrolled patients in previous multicenter clinical trials. A significantly higher number of successful physician recruiters than unsuccessful physician recruiters (42%; P = 0.040) considered the presence of a support system with clinical research coordinators (CRC) as the reason for participation (80%). A large number of unsuccessful physician recruiters experienced difficulty in obtaining informed consent (67%), whereas a significantly smaller number of successful physician recruiters experienced such difficulty (20%; P = 0.014). The difficulties experienced by unsuccessful physician recruiters in the trial were as follows: inability to find possible participants (100%), difficulty in obtaining informed consent (58%), cumbersome procedures (58%), difficulty in long-term follow up (33%), and insufficient tools for explanation and obtaining informed consent (8%). CONCLUSION: This survey showed that successful physician recruiters consider a support system with CRC of value, and that they are skillful in obtaining informed consent. These views and attitudes may have originated from past experience involving clinical trials. In this regard, we need to develop an infrastructure to enlighten physicians on this support system for the promotion of clinical trials.

Expression of soluble vascular endothelial growth factor receptor-1 in human monocyte-derived mature dendritic cells contributes to their antiangiogenic property.

The soluble form of vascular endothelial growth factor receptor-1 (sVEGFR-1) is produced from endothelial cells by alternative splicing of VEGFR-1 mRNA, and can inhibit angiogenesis by blocking the biological effects of VEGF. In this study, we show the expression of a large amount of sVEGFR-1 in human monocyte-derived mature dendritic cells (mDCs). As compared with monocytes and immature DCs, mDCs generated by TNF-alpha or soluble CD40L with IFN-gamma, but not LPS or other stimuli, preferentially produce sVEGFR-1. We also detected the mRNA of sVEGFR-1 generated by alternative splicing of VEGFR-1 mRNA in mDCs induced by TNF-alpha. The production of sVEGFR-1 showed a distinct contrast to those of VEGF in each DC matured with various stimuli. The supernatant of DCs matured with TNF-alpha or soluble CD40L with IFN-gamma showed inhibition of the tube formation of HUVECs, which was neutralized by anti-VEGFR-1 Ab, indicating that sVEGFR-1 secreted from mDCs was biologically active. Interestingly, the supernatant of mDCs generated with LPS increased HUVEC capillary-like formation in vitro. The ratio of sVEGFR-1 to VEGF clearly reflected the net angiogenic property of mDCs. Administration of mDCs induced by TNF-alpha into the s.c. tumor of PC-14 cells implanted in SCID mice demonstrated the inhibition of tumor growth via reduction of the number of CD31-positive vessels, indicating their in vivo antiangiogenic potential. These results suggest that sVEGFR-1 produced by mDCs contribute to their antiangiogenic property, and the ratio of sVEGFR-1 to VEGF might be a useful tool for evaluating their ability to regulate angiogenesis mediated by VEGF.

HM1.24 (CD317) is a novel target against lung cancer for immunotherapy using anti-HM1.24 antibody.

HM1.24 antigen (CD317) was originally identified as a cell surface protein that is preferentially overexpressed on multiple myeloma cells. Immunotherapy using anti-HM1.24 antibody has been performed in patients with multiple myeloma as a phase I study. We examined the expression of HM1.24 antigen in lung cancer cells and the possibility of immunotherapy with anti-HM1.24 antibody which can induce antibody-dependent cellular cytotoxicity (ADCC). The expression of HM1.24 antigen in lung cancer cells was examined by flow cytometry as well as immunohistochemistry using anti-HM1.24 antibody. ADCC was evaluated using a 6-h (51)Cr release assay. Effects of various cytokines on the expression of HM1.24 and the ADCC were examined. The antitumor activity of anti-HM1.24 antibody in vivo was examined in SCID mice. HM1.24 antigen was detected in 11 of 26 non-small cell lung cancer cell lines (42%) and four of seven (57%) of small cell lung cancer cells, and also expressed in the tissues of lung cancer. Anti-HM1.24 antibody effectively induced ADCC in HM1.24-positive lung cancer cells. Interferon-beta and -gamma increased the levels of HM1.24 antigen and the susceptibility of lung cancer cells to ADCC. Treatment with anti-HM1.24 antibody inhibited the growth of lung cancer cells expressing HM1.24 antigen in SCID mice. The combined therapy with IFN-beta and anti-HM1.24 antibody showed the enhanced antitumor effects even in the delayed treatment schedule. HM1.24 antigen is a novel immunological target for the treatment of lung cancer with anti-HM1.24 antibody.