HM-1 Cells Research Articles

Immune vulnerability of ovarian cancer stem-like cells due to low CD47 expression is protected by surrounding bulk tumor cells

ABSTRACT Recurrence of advanced epithelial ovarian cancer is common despite optimal surgical debulking and initial favorable responses to chemotherapy. Evidences suggest that cancer stem cells (CSCs) have inherent resistance to conventional therapies such as chemotherapy and play a decisive role in cancer recurrence. Cancer stem cells are also believed to be able to evade immunological attack. However, this study showed a different scenario in which cancer stem-like cells are more vulnerable to immunosurveillance. Our study demonstrated that isolated murine cancer stem-like cells, stem cell antigen (SCA)-1+ ID8 and CD133+ HM-1 cells, were susceptible to phagocytosis by macrophages and consequent CD8+ T cell immunity. The increased phagocytosis of these stem cell-like cells is attributed to low CD47 protein expression. SCA-1+ ID8 cells were able to grow in syngeneic mice but were soon rejected. Restoring CD47 expression delayed this immune-mediated rejection. SCA-1+ ID8 cells showed rapid growth by mixing with bulk ID8 cells. These results suggest that stem-like cells could be protected by surrounding non-stem cancer cells from immune attack. Similarly, both isolated human CD24−/low SKOV3 stem-like cells and spheroid OVCAR3 cells expressed lower CD47 levels. Our study provided novel insights into the immune characteristics of CSCs within a tumor microenvironment. The results might lead to the design of more effective treatment strategies for ovarian cancer.

Glypican-3 gene silencing for ovarian cancer using siRNA-PLGA hybrid micelles in a murine peritoneal dissemination model

Small interfering RNA (siRNA) has received much attention and for possible therapeutic applications to treat incurable chronic and genetic diseases, including cancer. However, the development of safe and efficient carriers for siRNA delivery still remains formidable hurdles for in vivo. The purpose of this study is to prepare siRNA–PLGA hybrid micelles to deliver the siRNA into the ovarian cancer cells and to evaluate of gene silencing effects in mice model. Here we focused on glypican-3 (Gpc3) gene silencing, which involved in tumor progression and inflammatory reaction, as a siRNA target in a murine ovarian cancer cells, HM-1. As a result, linear polyethyleneimine (LPEI)-coated siRNA–PLGA hybrid micelles were shown to effectively inhibit GPC3 expression in vitro in HM-1 cells, compared with siRNA in solution, because of their superior intracellular uptake and enhanced gene silencing effects. In addition, intraperitoneal administration of the cationic LPEI-coated siRNA–PLGA hybrid micelles decreased the number of tumor nodes in the mesentery, compared with the siRNA sole solution, in a HM-1 peritoneal dissemination model. These results suggested that siRNA–PLGA hybrid micelles could be an effective siRNA delivery tool in a murine ovarian cancer model, especially in case it targets molecules, such as Gpc3.

Intratumoral Delivery of an Adenoviral Vector Carrying the SOCS-1 Gene Enhances T-Cell-Mediated Antitumor Immunity By Suppressing PD-L1.

Ovarian cancer is the leading cause of gynecologic cancer-related deaths and novel therapeutic strategies are required. Programmed cell death 1 and programmed cell death ligand 1 (PD-L1), which are key mediators of host immune tolerance, are associated with ovarian cancer progression. Recent evidence indicates the importance of IFNγ-induced PD-L1 for immune tolerance in ovarian cancer. This study aimed to reveal the therapeutic potential of suppressor of cytokine signaling 1 (SOCS-1), an endogenous inhibitor of the Janus kinase (JAK)-STAT signaling pathway, for the treatment of ovarian cancer. IHC assessment revealed that patients with ovarian cancer with high intratumoral STAT1 activation exhibited poor prognosis compared with patients with low STAT1 activation (P < 0.05). Stimulation of OVISE, OVTOKO, OV2944-HM-1 (HM-1), and CT26 cell lines with IFNγ induced STAT1 phosphorylation and PD-L1 expression. Adenovirus-mediated SOCS-1 gene delivery (AdSOCS-1) in HM-1 and CT26 cells in vitro potently inhibited IFNγ-induced STAT1 phosphorylation and PD-L1 upregulation, similar to the addition of JAK inhibitor I, but failed to inhibit their proliferation. Notably, intratumoral injection of AdSOCS-1, but not AdLacZ, significantly inhibited the tumor growth of HM-1 and CT26 cells subcutaneously transplanted in immunocompetent syngeneic mice. AdSOCS-1 reduced PD-L1 expression on tumors and restored the activation of tumor-infiltrating CD8+ T cells. Moreover, the antitumor effect of AdSOCS-1 was significantly attenuated by PD-L1 Fc-fusion protein administration in vivo, suggesting that the effect of AdSOCS-1 is mainly attributable to enhancement of tumor immunity. This study highlights the potential clinical utility of SOCS-1 as an immune checkpoint inhibitor. Mol Cancer Ther; 17(9); 1941-50. ©2018 AACR.

PI3K inhibitor enhances the cytotoxic response to etoposide and cisplatin in a newly established neuroendocrine cervical carcinoma cell line.

BackgroundNeuroendocrine cervical carcinoma (NECC) is a rare and aggressive subtype of cervical cancer. To date, no NECC cell-based model is available, which hinders the development of new therapeutic strategies for NECC. In this study, we derived a new NECC cell line from an ex vivo biopsy and used it to explore novel drug combination approach for NECC.ResultsThe stable HM-1 cell line displayed high expression levels of the neuroendocrine marker, synaptophysin. HM-1 cell transplantation could induce tumor growth in nude mice. As expected, the combination of etoposide and cisplatin synergistically inhibited HM-1 cell proliferation. Strikingly, when etoposide and cisplatin were combined with PI3K inhibitor BEZ235, the growth of HM-1 cells was significantly reduced. Taken together, the data implied the combination of etoposide and cisplatin with BEZ235 not only inhibited HM-1 cell proliferation but also increased cell apoptosis.Materials and MethodsA NECC tissue sample from a 75-year-old female patient was processed to derive a primary cell line annotated as HM-1. The features of HM-1 were analyzed to establish its characteristic profile. Next, HM-1 was treated with PI3K inhibitors, BKM120 and/or BEZ235, in combination with two well-known genotoxic drugs, etoposide and/or cisplatin, to evaluate which combination could serve as a more effective treatment approach. Their inhibiting effects on HM-1 were evaluated by cell viability, apoptosis, and target kinase expression.ConclusionsThe newly established NECC cell line HM-1 could serve as a cell-based model for NECC research. The synergistic drug combination of PI3K inhibitor with genotoxic drugs might become a potential new treatment strategy against NECC.

AG490, a Jak2 inhibitor, suppressed the progression of murine ovarian cancer

Ovarian cancer is the major cause of cancer death among female genital malignancies, and requires developing novel therapeutic measures. Immune escape and acquisition of tolerance by tumor cells are essential for cancer growth and progression. An immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO) overexpression in tumors is essential for host immune tolerance. Janus-activated kinase-signal transducer and activator of transcription (JAK–STAT) pathway is involved in various kinds of tumor biology. Thus, we examined the effects of STAT1 inhibition by AG490 (a JAK2 inhibitor) on ovarian cancer progression in mice. In vitro study, IFN-γ treatment up-regulated Ido mRNA expression with STAT1 activation in OV2944-HM-1 cells, whereas AG490 treatment significantly inhibited this effect with the suppression of STAT1 phosphorylation. In vivo model, OV2944-HM-1 cells were intraperitoneally/subcutaneously transplanted into syngeneic immunocompetent female mice. AG490 treatment significantly suppressed subcutaneous tumor growth, compared with control. Consistently, in mice intraperitoneally inoculated HM-1 cells, the same treatment significantly improved survival rate with the reduced number of intraperitoneal tumors. Actually, intratumoral IDO expression was significantly suppressed with the reduction of STAT1 activation in AG490-treated mice. Moreover, in tumor microenvironment of mice treated with AG490, the accumulation of anti-tumor leukocytes such as CD8+ T-cells, M1 macrophages, and NK cells was apparently exaggerated with the reciprocal reduction of regulatory T cells. Furthermore, intratumoral expression of anti-tumor cytokines such as IL-1α, IL-1β and IL-12 expression was significantly enhanced in mice treated with AG490. Collectively, JAK/STAT signal pathways may be good molecular target for immunotherapy of ovarian cancer.

Biomarker discovery for neuroendocrine cervical cancer.

Neuroendocrine cervical cancer is an aggressive but rare form of cervical cancer. The majority of neuroendocrine cervical cancer patients present with advanced-stage diseases. However, the limited numbers of neuroendocrine tumor markers are insufficient for clinical purposes. Thus, we used a proteomic approach combining lysine labeling 2D-DIGE and MALDI-TOF MS to investigate the biomarkers for neuroendocrine cervical cancer. By analyzing the global proteome alteration between the neuroendocrine cervical cancer line (HM-1) and non-neuroendocrine cervical cancer lines (CaSki cells, ME-180 cells, and Hela cells), we identified 82 proteins exhibiting marked changes between HM-1 and CaSki cells, and between ME-180 and Hela cells. Several proteins involved in protein folding, cytoskeleton, transcription control, signal transduction, glycolysis, and redox regulation exhibited significant changes in abundance. Proteomic and immunoblot analyses indicated respective 49.88-fold and 25-fold increased levels of transgelin in HM-1 cells compared with that in other non-neuroendocrine cervical cancer cell lines, implying that transgelin is a biomarker for neuroendocrine cervical cancer. In summary, we used a comprehensive neuroendocrine/non-neuroendocrine cervical cancer model based proteomic approach for identifying neuroendocrine cervical cancer markers, which might contribute to the prognosis and diagnosis of neuroendocrine cervical cancer.

Paradoxical Augmentation of Tumor Angiogenesis Combined with Down-Regulation of IP-10 after Adenovirus-Mediated Transfer of Vasohibin-1 Gene in Cancer Cells

Vasohibin-1 (VASH1) is an endogenous angiogenesis inhibitor produced by the endothelium. Here we examined the efficacy of local adenovirus-mediated VASH1 gene transfer for anti-angiogenic cancer treatment. When non-proliferative adenovirus vector encoding the human VASH1 gene (AdhVASH1) was injected locally into the peritoneal cavity and HM-1 ovarian cancer cells were inoculated into the peritoneal cavity thereafter, we observed a significant inhibition of tumor angiogenesis. However, to our surprise, when HM-1 cells were infected with AdhVASH1 (HM-1/hVASH1) and then inoculated in mice, we observed a paradoxical augmentation of tumor angiogenesis and tumor growth. To explore the mechanism of this augmented tumor angiogenesis, we investigated the expression of various angiogenesis regulators. The level of angiogenesis stimulators such as VEGF and FGF-2 was unchanged; however we noticed a marked down-regulation of one angiogenesis inhibitor, namely interferon- γ-inducible protein-10 (IP-10). Moreover, this down-regulation of IP-10 and augmented tumor angiogenesis were not seen when HM-1/hVASH1 cells were inoculated into severe combined immunodeficiency mice. Our present analysis reveals that there is a mutual interaction between 2 angiogenesis inhibitors; VASH1 and IP-10, and the immune reaction might be responsible for this interaction through hitherto unknown mechanism. It also discloses the importance of endogenous IP-10 in tumors, as down-regulation of IP-10 results in the paradoxical augmentation of tumor angiogenesis. Care must be taken when VASH1 gene is transiently transferred to cancer cells for the antiangiogenesis treatment.

Oncolytic viral therapy with a combination of HF10, a herpes simplex virus type 1 variant and granulocyte–macrophage colony‐stimulating factor for murine ovarian cancer

Ovarian cancer is the most frequent cause of gynecological cancer-related mortality as a majority of patients are diagnosed at an advanced stage with intraperitoneal dissemination because of the absence of initial symptoms. Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in the maturation of specialized antigen-presenting cells. In this study, we utilized a herpes simplex virus (HSV) amplicon expressing murine GM-CSF combined with HF10 (mGM-CSF amplicon), a highly attenuated HSV type 1 strain functioning as a helper virus to strengthen anti-tumor immune response, for the treatment of ovarian cancer with intraperitoneal dissemination. A mouse ovarian cancer cell line, OV2944-HM-1 (HM-1), was intraperitoneally injected, following which HF10 only or the mGM-CSF amplicon was injected intraperitoneally three times. HF10 injection prolonged survival and decreased intraperitoneal dissemination, but to a lesser extent than the mGM-CSF amplicon. Although HF10 replication was not observed in HM-1 cells, expression of VP5, a late gene coding the major capsid protein of HSV, was detected. Moreover, mGM-CSF production was detected in transfected HM-1 cells. Immunohistochemical staining revealed the infiltration of CD4- and CD8-positive cells into the peritoneal tumor(s). A significantly increased CD4+ T cell concentration was observed in the spleen. Murine splenic cells after each treatment were stimulated with HM-1 cells, and the strongest immune response was observed in the mice that received mGM-CSF amplicon injections. These results suggested that the mGM-CSF amplicon is a promising agent for the treatment of advanced ovarian cancer with intraperitoneal dissemination.

Abstract A83: Induction of PD-L1 expression by cytotoxic agents through activation of NF-kB signal

Abstract Recently, growing evidence has shown that the therapeutic efficacy of chemotherapy largely depends on the host immune system. We analyzed gene expression microarray dataset GSE13525 to examine how cytotoxic agents influence the immune system. Expression of programmed cell death 1 ligand 1 (PD-L1) was increased following carboplatin (CBDCA) treatment in the human ovarian cancer cell line 36M2 from GSE13525 (p&amp;lt;0.05). Previously, we reported PD-L1 expression is associated with poor prognosis in ovarian cancer (Hamanishi J, PNAS, 2007), and that PD-L1 promotes progression of ovarian cancer by inducing host immune tolerance through its receptor programmed cell death 1 (PD-1) on peripheral cytotoxic T lymphocytes (Abiko K, Clin Can Res, 2013). The aim of this study was to investigate the molecular mechanism of chemotherapy-induced PD-L1 expression in ovarian cancer cells and to examine if inhibition of the PD-L1/PD-1 signal increases the efficacy of chemotherapy in ovarian cancer. Pathway analysis of gene expression microarray data from clinical ovarian cancer samples collected before and after chemotherapy (GSE15622) showed that both paclitaxel (PTX) (n=20) and CBDCA (n=14) treatment activated the NF-kB signaling pathway (single-sample Gene Set Enrichment Analysis; p&amp;lt;0.01, respectively). We treated human ovarian cancer cell lines (OVCAR8, ovary1847, RMG-II and SKOV3) and mouse ovarian cancer cell lines (ID8 and HM-1) with CBDCA (100uM), PTX (10uM), gemcitabine (GEM: 120uM), liposomal doxorubicine (2ug/ml) or endoxan (7uM) for 24 hours. All of these cytotoxic agents increased NF-kB-p65 and PD-L1 protein expression detected by Western blotting in all of the cell lines tested. Increased expression of PD-L1 was also confirmed using flow cytometry in HM1 and ID8 cells treated with PTX or GEM (p&amp;lt;0.05, respectively). Following siRNA-mediated knockdown of NF-kB in HM1, ID8, ovary1847 and OVCAR8, induction of PD-L1 expression was drastically impaired by the cytotoxic agents PTX or GEM. This change was independent of IFN-gamma signaling, which is a well-known activator of PD-L1 expression, because IFN-gamma was not secreted from the treated cells, and because shRNA-mediated knock down of IFN-gamma receptor 1 also did not change PD-L1 expression. In order to determine if PD-L1 expression on ovarian cancer cells induced by cytotoxic agents could serve as a molecular target in ovarian cancer, we performed in vivo experiments. We performed lentiviral transduction into ID8 cells using PD-L1 cDNA (ID8-PDL1), vector control (ID8-control) and microRNA targeting PD-L1 mRNA (ID8-mirPDL1). Following intraperitoneal injection of these ID8 cells into syngeneic C57/BL6 mice, we injected PTX or vehicle intraperitoneally (6 groups, n=12 in each group). The ID8-PD-L1 mice without PTX showed the worst prognosis, while ID8-mirPDL1 mice with PTX showed the best prognosis (p&amp;lt;0.01). In an independent experiment using GEM instead of PTX, the ID8-mirPDL1 with GEM treatment again showed the best prognosis (p&amp;lt;0.01). In summary, we found chemotherapeutic agents upregulate PD-L1 expression through activation of NF-kB signaling. Immunotherapeutic targeting of the PD-L1/PD-1 signal combined with chemotherapy may be a promising treatment modality against ovarian cancer. Citation Format: Junzo Hamanishi, Noriomi Matsumura, Peng Jin, Kaoru Abiko, Naoki Horikawa, Ken Yamaguchi, Tsukasa Baba, Susan K. Murphy, Ikuo Konishi, Masaki Mandai. Induction of PD-L1 expression by cytotoxic agents through activation of NF-kB signal. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A83.

Autofluorescence properties of murine embryonic stem cells during spontaneous differentiation phases

The autofluorescence (AF) analysis allows in vivo, real-time assessment of cell functional activities, depending on the presence of biomolecules strictly involved in metabolic reactions and acting as endogenous fluorophores. Pluripotent stem cells during differentiation are known to undergo changes in their morphofunctional properties, with particular reference to bioenergetic metabolic signatures involving endogenous fluorophores such as NAD(P)H, flavins, lipofuscin-like lipopigments. Since the development of regenerative therapies based on pluripotent cells requires a careful monitoring of the successful maturation into the desired phenotype, aim of our work is to evaluate the AF potential to assess the differentiation phases in a murine stem cell model. Mouse embryonic stem cells (ESCs) maintained with and without leukemia inhibitory factor (LIF), embryoid bodies (EBs), and EB-derived cells undergoing spontaneous differentiation toward the hematopoietic lineage have been used as a sample models. Cell AF properties have been characterized upon 366-nm excitation, under living conditions and in the absence of exogenous markers. Imaging, microspectrofluorometric techniques, and spectral fitting analysis based on the spectral parameters of each endogenous fluorophore have been applied to estimate their contribution to the whole cell AF emission spectra. Specific cytochemical labeling has been performed to validate AF data. Depending on the differentiation phases, cells undergo changes in morphology, AF distribution patterns, and AF emission spectral profiles. These latter reflect variations in the single endogenous fluorophore contribution to the overall emission. The coenzyme NAD(P)H accounts for up to 80% of the whole spectral area. The free form prevails on the bound one, and their changes have been investigated in terms of NAD(P)Hbound/free and redox ratios. These values vary in agreement with a slow metabolic activity and prevailing glycolytic metabolism in the undifferentiated HM1 cells, an increased metabolic activity still relying on glycolysis during the early differentiation phases, and an increased oxidative phosphorylation in EB and hematopoietic precursor cells. Lipofuscin-like lipopigments decrease following differentiation, and porphyrins contributing for less than 5%, prevail in the more actively differentiating cells. These results reflect the shift between anaerobic and aerobic respiration following differentiation, consistently with a decreased autophagy of cell organelles (i.e., mitochondria, as a strategy reported in the literature to keep the undifferentiated homeostasis state), higher mitochondrial activity with more numerous NADH binding sites and synthesis of heme as prosthetic group of proteins, that is, cytochromes. These data open promising perspectives for the monitoring of stem cells differentiation under living conditions without labeling with exogenous agents (inducing perturbations when used in vivo), or immunomarkers not always available for veterinary and zootechnics, by exploiting endogenous fluorophores as intrinsic biomarkers of cell morphofunctional changes.

Evaluation of Monocytes as Carriers for Armed Oncolytic Adenoviruses in Murine and Syrian Hamster Models of Cancer

Replication-competent (oncolytic) adenoviruses (OAV) can be adapted as vectors for the delivery of therapeutic genes, with the aim of extending the antitumor effect beyond direct cytolysis. Transgene expression using these vectors is usually intense but short-lived, and repeated administrations are hampered by the rapid appearance of neutralizing antibodies (NAbs). We have studied the performance of monocytes as cell carriers to improve transgene expression in cancer models established in athymic mice and immunocompetent Syrian hamsters. Human and hamster monocytic cell lines (MonoMac6 and HM-1, respectively) were loaded with replication-competent adenovirus-expressing luciferase. Intravenous administration of these cells caused a modest increase in transgene expression in tumor xenografts, but this effect was virtually lost in hamsters. In contrast, intratumoral administration of HM-1 cells allowed repeated cycles of expression and achieved partial protection from NAbs in preimmunized hamsters bearing pancreatic tumors. To explore the therapeutic potential of this approach, HM-1 cells were loaded with a hypoxia-inducible OAV expressing the immunostimulatory cytokine interleukin-12 (IL-12). Three cycles of treatment achieved a significant antitumor effect in the hamster model, and transgene expression was detected following each administration, in contrast with the rapid neutralization of the free virus. We propose monocytes as carriers for multiple intratumoral administrations of armed OAVs.

The activated transforming growth factor‐beta signaling pathway in peritoneal metastases is a potential therapeutic target in ovarian cancer

Peritoneal dissemination including omental metastasis is the most frequent route of metastasis and an important prognostic factor in advanced ovarian cancer. We analyzed the publicly available microarray dataset (GSE2109) using binary regression and found that the transforming growth factor (TGF)-beta signaling pathway was activated in omental metastases as compared to primary sites of disease. Immunohistochemical analysis of TGF-beta receptor type 2 and phosphorylated SMAD2 indicated that both were upregulated in omental metastases as compared to primary disease sites. Treatment of the mouse ovarian cancer cell line HM-1 with recombinant TGF-β1 promoted invasiveness, cell motility and cell attachment while these were suppressed by treatment with A-83-01, an inhibitor of the TGF-β signaling pathway. Microarray analysis of HM-1 cells treated with TGF-β1 and/or A-83-01 revealed that A-83-01 efficiently inhibited transcriptional changes that are induced by TGF-β1. Using gene set enrichment analysis, we found that genes upregulated by TGF-β1 in HM-1 cells were also significantly upregulated in omental metastases compared to primary sites in the human ovarian cancer dataset, GSE2109 (false discovery rate (FDR) q = 0.086). Therapeutic effects of A-83-01 in a mouse model of peritoneal dissemination were examined. Intraperitoneal injection of A-83-01 (150 μg given three times weekly) significantly improved survival (p = 0.015). In summary, these results show that the activated TGF-β signaling pathway in peritoneal metastases is a potential therapeutic target in ovarian cancer.

Activated Local Immunity by CC Chemokine Ligand 19-Transduced Embryonic Endothelial Progenitor Cells Suppresses Metastasis of Murine Ovarian Cancer

Although tumor microenvironments play a key role in successful tumor immunotherapy, effective manipulation of local immunity is difficult because of the lack of an appropriate target system. It is well known that bone marrow-derived endothelial progenitor cells (EPCs) are actively recruited during tumor angiogenesis. Using this feature, we attempted to establish a novel therapeutic modality that targets tumor vessels of multiple metastases using embryonic endothelial progenitor cells (eEPCs) transduced with an immune-activating gene. The eEPCs were retrovirally transduced with the mouse CC chemokine ligand 19 (CCL19) gene, a lymphocyte-migrating chemokine. The mouse ovarian cancer cell line OV2944-HM-1 (HM-1) was inoculated subcutaneously into B6C3F1 mice, along with CCL19-tranduced eEPCs (eEPC-CCL19), resulting in immunologic activity and tumor-inhibitory effects. In this model, eEPC-CCL19 showed tumor repression accompanied by increased tumor-infiltrating CD8+ lymphocytes compared with the control group. In contrast, no tumor repression was observed when the same experiment was done in immunodeficient (SCID) mice, suggesting a crucial role of T-cell function in this system. Next, we established a lung metastasis model by injecting HM-1 cells or B16 melanoma cells via the tail vein. Subsequent intravenous injection of eEPC-CCL19 leads to a decrease in the number of lung metastasis and prolonged survival. Antitumor effects were also observed in a peritoneal dissemination model using HM-1. These results suggest that systemic delivery of an immune-activating signal using EPCs can alter the tumor immune microenvironment and lead to a therapeutic effect, which may provide a novel strategy for targeting multiple metastases of various malignancies.

Generation of a syngeneic mouse model to study the intraperitoneal dissemination of ovarian cancer with in vivo luciferase imaging

In order to facilitate the discovery and investigation of anti-cancer therapeutics under physiological conditions, we have engineered the ovarian cancer cell line, HM-1/luc, in mice. This cell stably expresses firefly luciferase and produces light that can be detected using an in vivo imaging system (IVIS). Parental HM-1 cells cause severe carcinomatous peritonitis to B6C3F1 mice, but not to C57BL6 mice. Established HM-1/luc cells showed pathologically similar findings to HM-1 cells. HM-1/luc cells were injected into the peritoneal cavity of B6C3F1 mice and IVIS 2000 was conducted weekly after inoculation to monitor intra-peritoneal tumor growth. The mice were divided into three groups: non-CDDP-treated (control) and CDDP-treated (0.2 and 0.4 mg). A disease-suppressive effect of the CDDP was reflected by the significantly prolonged survival of the CDDP-treated mice (control 23 +/- 1.9 days, CDDP 0.2 mg 29.6 +/- 2.9 days; p < 0.05); the total photon and area of flux were decreased. The optical imaging of intraperitoneal tumors via in vivo bioluminescence is effective for noninvasive monitoring and semi-quantitative analysis. Our syngeneic mouse model has the relevant clinical features of ovarian cancer, which makes it a useful model for developing new ovarian cancer therapies.

Inhibition of Calcium Release-activated Calcium Current by Rac/Cdc42-inactivating Clostridial Cytotoxins in RBL Cells

Using large clostridial cytotoxins as tools, the role of Rho GTPases in activation of RBL 2H3 hm1 cells was studied. Clostridium difficile toxin B, which glucosylates Rho, Rac, and Cdc42 and Clostridium sordellii lethal toxin, which glucosylates Rac and Cdc42 but not Rho, inhibited the release of hexosaminidase from RBL cells mediated by the high affinity antigen receptor (FcepsilonRI). Additionally, toxin B and lethal toxin inhibited the intracellular Ca(2+) mobilization induced by FcepsilonRI-stimulation and thapsigargin, mainly by reducing the influx of extracellular Ca(2+). In patch clamp recordings, toxin B and lethal toxin inhibited the calcium release-activated calcium current by about 45%. Calcium release-activated calcium current, the receptor-stimulated Ca(2+) influx, and secretion were inhibited neither by the Rho-ADP-ribosylating C3-fusion toxin C2IN-C3 nor by the actin-ADP-ribosylating Clostridium botulinum C2 toxin. The data indicate that Rac and Cdc42 but not Rho are not only involved in late exocytosis events but are also involved in Ca(2+) mobilization most likely by regulating the Ca(2+) influx through calcium release-activated calcium channels activated via FcepsilonRI receptor in RBL cells.

Initial steps in lymph node metastasis formation in an experimental system: possible involvement of recognition by macrophage C-type lectins.

We used histological observations and experiments with fluorescent cell tracers to investigate the roles of tissue macrophages in recognition through a galactose/N-acetylgalactosamine-specific C-type lectin (mMGL) in lymph node metastasis formation by mouse ovarian tumor OV2944-HM-1 (HM-1) cells. Lymph node metastasis from subcutaneous sites was shown to be initiated by the entry of tumor cells into the subcapsular sinus of lymph nodes where mMGL-positive cells were mainly located. To investigate whether mMGL-positive cells contributed to host resistance against lymph node metastasis, we repeatedly treated mice bearing transplanted tumors with an mMGL-blocking monoclonal antibody that was known to inhibit mMGL binding to its ligands. The number of HM-1 cells recovered from lymph nodes 2 weeks after subcutaneous injections was significantly greater when the mice were treated with the blocking anti-mMGL antibody. These results suggested that mMGL-positive macrophages contributed to the host's defense against lymph node metastasis.

Active nuclear import and export is independent of lumenal Ca2+ stores in intact mammalian cells.

The nuclear pore complex (NPC) mediates communication between the cytoplasm and nucleus in eukaryotic cells. Active transport of large polypeptides as well as passive diffusion of smaller (approximately 10 kD) macromolecules through the NPC can be inhibited by depletion of intracellular Ca2+ stores. However, the physiological relevance of this process for the regulation of nucleocytoplasmic trafficking is not yet clear. We expressed green fluorescent protein (GFP)-tagged glucocorticoid receptor (GR) and mitogen-activated protein (MAP) kinase-activated protein kinase 2 (MK2) to study the effect of Ca2+ store depletion on active transport in HM1 cells, a human embryonic kidney cell line stably transfected with the muscarinic M1 receptor. Dexamethasone-induced nuclear import of GR-GFP and anisomycin-induced nuclear export of GFP-MK2 was monitored by confocal microscopy. We found that store depletion by carbachol, thapsigargin or ionomycin had no effect on GR-GFP import, whereas pretreatment with 1,2-bis-(o-aminophenoxy) ethane-N,N,N', N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM) attenuated import significantly. Export of GFP-MK2 was not influenced by any pretreatment. Moreover, carbachol stimulated GFP-MK2 translocation to the cytoplasm in the absence of anisomycin. These results demonstrate that Ca2+ store depletion in intact HM1 cells is not directly linked to the inhibition of active protein transport through the NPC. The inhibition of GR-GFP import but not GFP-MK2 export by BAPTA-AM presumably involves a depletion-independent mechanism that interferes with components of the nuclear import pathway.

In vitro and in vivo study of pluripotency in intraspecific hybrid cells obtained by fusion of murine embryonic stem cells with splenocytes.

Hypoxanthine phosphoribosyltransferase-deficient (HPRT-) mouse embryonic stem (ES) cells, HM-1 cells (genotype XY), were fused with adult female DD/c mouse spleen cells. As a result, a set of HAT-resistant clones was isolated. Four hybrid clones most similar in morphology and growth characteristics to the HM-1 cells were studied in detail with respect to their pluripotency. Of these, three clones contained 41-43 chromosomes, and one clone was nearly tetraploid. All the clones had the XXY set of sex chromosomes and expressed the HPRT of the somatic partner only. The hybrid clones shared features with the HM-1 cells, indicating that they retained their pluripotent properties: (1) embryonic ECMA-7 antigen, not TROMA-1 antigen, was present in most cells; (2) the hybrid cells showed high activity of endogenous alkaline phosphatase (AP); (3) all the hybrid clones were able to form complex embryoid bodies containing derivatives of all the embryonic germinal layers; (4) the hybrid cells contained synchronously replicating X chromosomes, indicating that they were in an active state; and (5) a set of chimeric animals was generated by injecting hybrid cells into BALB/c and C57BL/6J mouse blastocysts. Evidence for chimerism was provided by the spotted coat derived from 129/Ola mice and identification of 129/Ola glucose phosphate isomerase (GPI) in many organs. Thus the results obtained demonstrated that the hybrid cells retain their high pluripotency level despite the close contact of the "pluripotent" HM-1 genome with the "somatic" spleen cell genome during hybrid cell formation and the presence of the "somatic" X chromosome during many cell generations. The presence of HPRT of the somatic partner in many organs and tissues, including the testes in chimeric animals, shows that the "somatic" X chromosome segregates weakly, if at all, during development of the chimeras. There were no individuals with the 129/Ola genotype among the more than 50 offspring from chimeric mice. The lack of the 129/Ola genotype is explained by the imbalance of the sex chromosomes in the hybrid cells rendering the passage of hybrid cell descendants through meiosis in chimeras impossible. As a result, chimeras become unable to produce gametes of the hybrid cell genotype.

Influence of Clostridium botulinum C2 toxin on Fc epsilonRI-mediated secretion and tyrosine phosphorylation in RBL cells.

We studied the effects of the binary Clostridium botulinum C2 toxin on stimulated [3H]serotonin release and protein tyrosine phosphorylation in RBL 2H3 hm1 cells. Actin was specifically ADP-ribosylated by C2 toxin in intact cells resulting in a 2-3 fold increase in antigen- or calcium ionophore (A23187)-induced degranulation. The effects of C2 toxin were time- and concentration-dependent. Toxin treatment, which dramatically changes the morphology of RBL cells, was not sufficient to induce mediator release in the absence of activators of secretion. Antigen- and A23187-stimulated tyrosine phosphorylation of 60-80 kDa and 110-120 kDa proteins was reduced or blocked after C2 toxin incubation. Treatment of RBL cells with the tyrosine phosphatase inhibitor pervanadate reversed the inhibitory effect of C2 toxin on stimulated protein tyrosine phosphorylation indicating activation of phosphatases by C2 toxin. The data indicate that disassembly of the actin cytoskeleton by C2 toxin facilitates Fc epsilonRI-mediated signal-secretion coupling and suggest a role of the actin cytoskeleton in phosphatase regulation in RBL cells.

Doxorubicin-induced DNA breaks, topoisomerase II activity and gene expression in human melanoma cells

We have analyzed five human melanoma cell lines, displaying variable doxorubicin resistance (1- to 6-fold), for drug-induced DNA breaks, topoisomerase II activity and mRNA expression. Enhanced drug efflux was not the reason for doxorubicin resistance of these tumor cells although they overexpressed the transmembrane 170 kDa P-glycoprotein. Doxorubicin-induced DNA lesions (2-fold) and topoisomerase II activity (7-fold) were higher in HM-1 and G361 cells than in the less doxorubicin-sensitive NH and FCCM-9 cells. Topoisomerase II mRNA expression was also 2-fold higher in HM-1 and G361 cells. Doxorubicin-induced DNA breaks and topoisomerase II activity inversely correlated with the degree of doxorubicin sensitivity. Southern blot analysis showed variation in the hybridization pattern of topoisomerase II gene in doxorubicin-resistant cells when compared to sensitive cells. This study portrays the low doxorubicin sensitivity of NH and FCCM-9 cells as “atypical” and emphasizes the importance of DNA damage and topoisomerase II activity in cellular low doxorubicin resistance.