DSP-0509, a systemically available TLR7 agonist, exhibits combination effect with immune checkpoint blockade by activating anti-tumor immune effects

TLR7 is an innate immune receptor that recognizes single-stranded RNAs, and its activation leads to anti-tumor immune effects. Although it is the only approved TLR7 agonist in cancer therapy, imiquimod is allowed to be administered with topical formulation. Thus, systemic administrative TLR7 agonist is expected in terms of expanding applicable cancer types. Here, we demonstrated the identification and characterization of DSP-0509 as a novel small-molecule TLR7 agonist. DSP-0509 is designed to have unique physicochemical features that could be administered systemically with a short half-life. DSP-0509 activated bone marrow-derived dendritic cells (BMDCs) and induced inflammatory cytokines including type I interferons. In the LM8 tumor-bearing mouse model, DSP-0509 reduced tumor growth not only in subcutaneous primary lesions but also in lung metastatic lesions. DSP-0509 inhibited tumor growth in several syngeneic tumor-bearing mouse models. We found that the CD8⁺ T cell infiltration of tumor before treatment tended to be positively correlated with anti-tumor efficacy in several mouse tumor models. The combination of DSP-0509 with anti-PD-1 antibody significantly enhanced the tumor growth inhibition compared to each monotherapy in CT26 model mice. In addition, the effector memory T cells were expanded in both the peripheral blood and tumor, and rejection of tumor re-challenge occurred in the combination group. Moreover, synergistic anti-tumor efficacy and effector memory T cell upregulation were also observed for the combination with anti-CTLA-4 antibody. The analysis of the tumor-immune microenvironment by using the nCounter assay revealed that the combination of DSP-0509 with anti-PD-1 antibody enhanced infiltration by multiple immune cells including cytotoxic T cells. In addition, the T cell function pathway and antigen presentation pathway were activated in the combination group. We confirmed that DSP-0509 enhanced the anti-tumor immune effects of anti-PD-1 antibody by inducing type I interferons via activation of dendritic cells and even CTLs. In conclusion, we expect that DSP-0509, a new TLR7 agonist that synergistically induces anti-tumor effector memory T cells with immune checkpoint blockers (ICBs) and can be administered systemically, will be used in the treatment of multiple cancers.

Abstract 2309: CDK9 as a potential therapeutic target in sarcomas

Sarcomas are a heterogeneous group of over 80 different tumors which arise from mesenchymal or connective tissue, accounting for 1% of adult malignancies. The annual incidence of soft tissue sarcoma (STS) is approximately 11,000 cases in the United States and STS is among the top five causes of cancer deaths for those under 20 years old. Cyclin-dependent kinase 9 (CDK9) is a serine/threonine protein kinase involved in transcription elongation through phosphorylation and activation of RNA polymerase II (RPB1), which increases the levels of key oncogenic genes like myeloid cell leukemia-1 (MCL-1) and c-Myc. CDK9 inhibition reduces their expression, leading to cell cycle arrest and apoptosis. TP-1287 is an orally delivered phosphate pro-drug of alvocidib, a potent CDK9 inhibitor. We hypothesized that alvocidib, the pharmaceutically active form of TP-1287, can inhibit the CDK9 signaling pathway and suppress tumor growth of sarcoma cells. Alvocidib demonstrated the suppression of the phosphorylation of RPB1 (p-RPB1) and MCL-1 expression in an A-673 Ewing sarcoma cell line and U-2 OS and MG-63 osteosarcoma cell lines after 6-hr treatment. In U-2 OS cells, 24-hr treatment with alvocidib induced the cleavage of PARP-1, an indicator of apoptosis, whereas less than 6-hr treatment with alvocidib failed to induce PARP-1 cleavage, suggesting that long-term CDK9 suppression would be necessary for the apoptosis induction in sarcoma cells. In cell viability assays using CellTiter-Glo, alvocidib demonstrated an IC50 of around 100 nM: 32 - 90 nM in sarcoma cell lines after 4-day treatment and 24 - 174 nM in sarcoma cells, which were obtained from patient derived xenograft (PDX) models, after 6-day treatment. In the sarcoma cells from PDX models, MCL-1 mRNA expression was moderately correlated with alvocidib sensitivity. Further bioinformatic analysis to predict alvocidib sensitivity is currently underway. In immunofluorescence analysis, alvocidib induced the activation of caspase-3/7, another indicator of apoptosis, after 2-day treatment in the sarcoma cells from PDX models. In an in vivo pharmacodynamic (PD) study using BALB/c mice, p-RPB1 and MCL-1 suppression in peripheral blood mononuclear cells (PBMCs) was observed after single administration of TP-1287. In an in vivo efficacy study using the A-673 model, TP-1287 showed a trend of tumor growth inhibition (TGI) at 2.5 mg/kg (QD), but not at 7.5 mg/kg (Q3D). These in vivo studies suggest that CDK9 signaling pathway was inhibited after TP-1287 administration in vivo and that continuous CDK9 inhibition would be needed for TGI in sarcoma models. In vivo efficacy and PD studies using sarcoma PDX models are currently ongoing. Taken together, alvocidib has shown activity in inhibiting the growth of sarcoma cells and TP-1287 could be a viable therapeutic option targeting the CDK9 pathway in sarcomas. TP-1287 is being investigated for solid tumors including sarcomas (clinicaltrials.gov, NCT03604783).

Citation Format: Yuta Matsumura, Hiroki Umehara, Jun Oishi, Adam Siddiqui, Jason M. Foulks, Setsuko Yamamoto, Steven L. Warner. CDK9 as a potential therapeutic target in sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2309.

Establishment of patient-derived organoids and a characterization-based drug discovery platform for treatment of pancreatic cancer

BACKGROUND

Pancreatic cancer is one of the most lethal tumors. The aim of this study is to provide an effective therapeutic discovery platform for pancreatic cancer by establishing and characterizing patient-derived organoids (PDOs).

METHODS

PDOs were established from pancreatic tumor surgical specimens, and the mutations were examined using a panel sequence. Expression of markers was assessed by PCR, immunoblotting, and immunohistochemistry; tumorigenicity was examined using immunodeficient mice, and drug responses were examined in vitro and in vivo.

RESULTS

PDOs were established from eight primary and metastatic tumors, and the characteristic mutations and expression of cancer stem cell markers and CA19-9 were confirmed. Tumorigenicity of the PDOs was confirmed in subcutaneous transplantation and in the peritoneal cavity in the case of PDOs derived from disseminated nodules. Gemcitabine-sensitive/resistant PDOs showed consistent responses in vivo. High throughput screening in PDOs identified a compound effective for inhibiting tumor growth of a gemcitabine-resistant PDO xenograft model.

CONCLUSIONS

This PDO-based platform captures important aspects of treatment-resistant pancreatic cancer and its metastatic features, suggesting that this study may serve as a tool for the discovery of personalized therapies.

Abstract 3595: DSP-0692, a selective SCD inhibitor, enhances the anti-tumor activity of anti-PD1 antibody

SCD (Stearoyl-CoA Desaturase), a key enzyme for lipid metabolism, is overexpressed in various types of cancer and plays an important role in cancer cell proliferation. We have previously shown that the identification and the functional characterization of DSP-0692, a novel and selective SCD inhibitor. SCD expression was induced in tumor cells cultured in sphere conditions, which were resistant to conventional agents within therapeutic concentration. DSP-0692 showed strong growth inhibition when tumor cells were cultured in sphere conditions, but had little impact on cells cultured under adherent conditions. In addition, DSP-0692 decreased the expression of stemness-related genes in tumor cells as well as in tumor tissues. Treatment with DSP-0692 suppressed tumor growth in multiple models both in single agent or in combination with conventional chemotherapies. DSP-0692 also inhibited WNT/beta-catenin signaling pathway through two different mechanisms (inhibition of Wnt3A secretion and nuclear translocation of beta-catenin). DSP-0692 exhibited lower IC50 value to sphere cells carrying mutations related to WNT/beta-catenin signaling pathway than those without these mutations. Blockade of the coinhibitory checkpoint molecule PD-1 has emerged as an effective treatment for many cancers. However, despite successes in the clinical setting, only a limited subpopulation respond to PD-1 blockade. We hypothesized that the deregulated lipid metabolism of tumor cells and microenvironment function as a barrier to antitumor immunity, and therefore that normalization of lipid metabolism with DSP-0692 might restore response to immunotherapy. Combination of DSP-0692 with anti-PD-1 antibody in the syngeneic CT-26 colon model, a resistant model to anti-PD-1 antibody, augmented tumor regressions relative to each single agent alone. DSP-0692 induced PD-L1 and PD-L2 expression in CT-26 cells, indicating that it is one of a mechanism of restoration of the effect of anti-PD-1 antibody. Our data suggest that remodeling the lipogenic tumor microenvironment has potential to convert patients resistant to immunotherapy into those who may receive clinical benefit of immunotherapy.

Citation Format: Eiji Sugaru, Yudai Furuta, Yoshikazu Nagagaki, Satoshi Ikeda, Yuichi Fukunaga, Hiroki Umehara, Tsuguteru Otsubo, Manabu Watanabe, Shingo Tojo, Miki Hashizume, Yasushi Matsuki, Hitoshi Ban. DSP-0692, a selective SCD inhibitor, enhances the anti-tumor activity of anti-PD1 antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3595.

Abstract 5480: Colorectal cancer cell lines harboring mutation in Wnt/β-catenin pathway shows enhanced sensitivity to the stearoyl-CoA desaturase (SCD) inhibitor, DSP-0692

Colorectal cancer (CRC) is one of the most frequent malignant diseases worldwide. Recent studies suggest that a small subpopulation of cells known as cancer stem cells (CSCs) may promote the high metastasis and relapse associated with CRC. It has been reported that Wnt/β-catenin signaling is aberrantly activated in a variety of cancer including colorectal cancer, and plays a critical role in CSC maintenance.

Here it is shown that a novel SCD inhibitor, DSP-0692, may inhibited Wnt/β-catenin signaling pathway through two different mechanisms in CRC. The effect of SCD inhibition on Wnt3A secretion, in which process post-translational fatty acylation (with palmitoleic acid) is required, was investigated. DSP-0692 led to reduced Wnt3A protein levels secreted in the media in Wnt3A-overexpressing cell line. This result was further confirmed by the TCF/LEF reporter assay in HCT116 incubated with conditional media from L-Wnt3A cells, with or without DSP-0692. DSP-0692 also inhibited exogenous Wnt3A-induced reporter activity. This indicates DSP-0692 may inhibit the β-catenin/Tcf transactivation by additional mechanism in addition to inhibiting Wnt secretion. To clarify this additional mechanism, the effect of DSP-0692 on nuclear translocation of β-catenin was investigated. SCD inhibition led to a decrease of β-catenin amounts within the nucleus. Currently, how SCD inhibition affects nuclear translocation of β-catenin is being investigated. It was confirmed that DSP-0692 exhibited lower IC50 value to sphere cells carrying mutations related to Wnt/β-catenin signaling pathway than those without these mutations. Next, the effect of SCD inhibition on Wnt/β-catenin signaling pathway in vivo was investigated. Treatment with DSP-0692 in a SW620 colorectal cancer xenograft model suppressed mRNA expression of the Wnt/β-catenin target genes, as well as CSC marker gene.

Taken together, these results suggest fatty acid desaturation in tumor cells may have an impact on Wnt/β-catenin signaling pathway and involve in CSC maintenance. The approaches targeting SCD could be a new therapeutic strategy for anti-CSC therapy in CRC.

Citation Format: Yudai Furuta, Yuichi Fukunaga, Satoshi Ikeda, Erina Koga, Hiroki Umehara, Tsuguteru Otsubo, Manabu Watanabe, Futoshi Hasegawa, Hitoshi Ban, Eiji Sugaru. Colorectal cancer cell lines harboring mutation in Wnt/β-catenin pathway shows enhanced sensitivity to the stearoyl-CoA desaturase (SCD) inhibitor, DSP-0692 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5480.

Abstract 3069: DSP-0692, a novel and selective stearoyl-CoA desaturase (SCD) inhibitor targeting cancer stem cells

In recent years evidence has accumulated in support of the cancer stem cells (CSCs) model in cancer chemotherapy resistance, highlighting the urgency and necessity of identifying CSC-specific targets for new cancer therapeutics.

SCD, a key enzyme for lipid metabolism, is overexpressed in various types of cancer and plays an important role in cancer cell proliferation. In particular, recent studies have implicated SCD involved also in the maintenance of CSCs.

Here, the identification and the functional characterization of DSP-0692, a novel and selective SCD inhibitor, is reported, using various pharmacological approaches to address the mechanism of SCD inhibition in cancer cells and its efficacy in preclinical tumor models. In these preclinical models, DSP-0692 inhibited human SCD activity with low nanomolar IC50 values. SCD expression was induced in tumor cells cultured in sphere conditions, which were resistant to conventional agents within therapeutic concentration. DSP-0692 showed strong growth inhibition when tumor cells were cultured in sphere conditions, but had little impact on cells cultured under normal two-dimensional conditions. In addition, DSP-0692 inhibited the CSC-related signaling pathway and decreased CSC markers expression in tumor cells as well as in tumor tissues. Treatment of DSP-0692 as single agent suppressed tumor growth in multiple models. Furthermore, this efficacy was enhanced in combination with conventional chemotherapies in those tumor models. Of note, SCD protein expression in tumor tissues was useful as a predictive marker for the susceptibility to DSP-0692 treatment.

Taken together, these data suggest that inhibition of fatty acid desaturation by DSP-0692 could be a new therapeutic strategy in SCD-positive cancer, with potential to overcome resistance to standard chemotherapies.

Citation Format: Eiji Sugaru, Yudai Furuta, Yuichi Fukunaga, Hiroki Umehara, Tsuguteru Otsubo, Manabu Watanabe, Futoshi Hasegawa, Shingo Tojo, Miki Hashizume, Hitoshi Ban. DSP-0692, a novel and selective stearoyl-CoA desaturase (SCD) inhibitor targeting cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3069.

Intravenous administration of the selective toll-like receptor 7 agonist DSR-29133 leads to anti-tumor efficacy in murine solid tumor models which can be potentiated by combination with fractionated radiotherapy

Strategies to augment anti-cancer immune responses have recently demonstrated therapeutic utility. To date clinical success has been achieved through targeting co-inhibitory checkpoints such as CTLA-4, PD-1, and PD-L1. However, approaches that target co-activatory pathways are also being actively being developed. Here we report that the novel TLR7-selective agonist DSR-29133 is well tolerated in mice and leads to acute immune activation. Administration of DSR-29133 leads to the induction of IFNα/γ, IP-10, TNFα, IL-1Ra and IL-12p70, and to a reduction in tumor burden in syngeneic models of renal cancer (Renca), metastatic osteosarcoma (LM8) and colorectal cancer (CT26). Moreover, we show that the efficacy of DSR-29133 was significantly improved when administered in combination with low-dose fractionated radiotherapy (RT). Effective combination therapy required weekly administration of DSR-29133 commencing on day 1 of a fractionated RT treatment cycle, whereas no enhancement of radiation response was observed when DSR-29133 was administered at the end of the fractionated RT cycle. Combined therapy resulted in curative responses in a high proportion of mice bearing established CT26 tumors which was dependent on the activity of CD8+ T-cells but independent of CD4+ T-cells and NK/NKT cells. Moreover, long-term surviving mice originally treated with DSR-29133 and RT were protected by a tumor-specific memory immune response which could prevent tumor growth upon rechallenge. These results demonstrate that DSR-29133 is a potent selective TLR7 agonist that when administered intravenously can induce anti-tumor immune responses that can be further enhanced through combination with low-dose fractionated RT.

TLR7 tolerance is independent of the type I IFN pathway and leads to loss of anti-tumor efficacy in mice

Systemic administration of small molecule toll-like receptor (TLR)-7 agonists leads to potent activation of innate immunity and to the generation of anti-tumor immune responses. However, activation of TLRs with small molecule agonists may lead to the induction of TLR tolerance, defined as a state of hyporesponsiveness to subsequent agonism, which may limit immune activation, the generation of anti-tumor responses and clinical response. Our data reveal that dose scheduling impacts on the efficacy of systemic therapy with the selective TLR7 agonist, 6-amino-2-(butylamino)-9-((6-(2-(dimethylamino)ethoxy)pyridin-3-yl)methyl)-7,9-dihydro-8H-purin-8-one (DSR-6434). In a preclinical model of renal cell cancer, systemic administration of DSR-6434 dosed once weekly resulted in a significant anti-tumor response. However, twice weekly dosing of DSR-6434 led to the induction of TLR tolerance, and no anti-tumor response was observed. We show that TLR7 tolerance was independent of type I interferon (IFN) negative feedback because induction of TLR7 tolerance was also observed in IFN-α/β receptor knockout mice treated with DSR-6434. Moreover, our data demonstrate that treatment of bone marrow-derived plasmacytoid dendritic cells (BM-pDC) with DSR-6434 led to downregulation of TLR7 expression. From our data, dose scheduling of systemically administered TLR7 agonists can impact on anti-tumor activity through the induction of TLR tolerance. Furthermore, TLR7 expression on pDC may be a useful biomarker of TLR7 tolerance and aid in the optimization of dosing schedules involving systemically administered TLR7 agonists.

Abstract LB-141: Specific and potent silencing of K-Ras by asymmetric silencing RNA (aiRNA) reveals addiction of cancer stem cells to mutant K-Ras amplification

K-Ras, the first oncogene identified in human cancer, is mutated in about 30% of human solid tumors. K-Ras protein, a small membrane-bound GTP-binding protein, acts as a molecular switch to transduce cell proliferation signals. Activating mutations of K-Ras lock the Ras protein into the hyper-active GTP-bound state, resulting in the activation of numerous signaling pathways that control cell survival and proliferation. Ras is also an important oncoprotein in many cancers where it is not mutated since Ras can be functionally activated through aberrant activation of other signal transduction elements. Activated K-Ras proteins are, therefore, found in a large proportion of all human cancers, and occupy a central position of interest.

Hypermalignant cancer cells, termed cancer stem cells (CSCs), that are highly tumorigenic and metastatic have been isolated from cancer patients with a variety of tumor types and found to have high stemness properties. These stemness-high cancer cells are hypothesized to be fundamentally responsible for cancer metastasis and relapse. Furthermore, a number of stemness genes, such as beta-catenin, nanog, Sox2, Oct3/4 have been implicated in cancer cell stemness. The role of oncogenes such as K-Ras in cancer cell stemness, however, is not clear.

To elucidate the role of K-Ras in the maintenance of cancer cell stemness, we employed asymmetric silencing RNA technology (aiRNA) which is able to silence target genes with high potency and precision. Moreover, aiRNA technology can be readily applied to CSCs. Here we report, to our surprise, that CSCs are not simply addicted to activating mutations of K-Ras, or activation of downstream regulators of the Ras pathway. However, CSCs with amplified mutant K-Ras are highly sensitive to K-Ras silencing. Moreover, the DNA copy number of the mutant K-Ras directly predicts the sensitivity of CSCs to K-Ras silencing. Our studies suggest that amplified mutated K-Ras is required for the maintenance of malignancy and cancer cell stemness, which may have significant implications for understanding the connections between oncogenes and cancer cell stemness, and for developing cancer stem cell inhibitors.

Citation Format: Jun Oishi, Hiroki Umehara, Nithya Jesuraj, Jelena Barbulovic, Xiangao Sun, Chiang J. Li. Specific and potent silencing of K-Ras by asymmetric silencing RNA (aiRNA) reveals addiction of cancer stem cells to mutant K-Ras amplification. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-141. doi:10.1158/1538-7445.AM2015-LB-141

Abstract 2567: Enhancement of antitumor activity of DSP-6434, a novel TLR7 agonist through reduction of TLR tolerance

Introduction: Systemic administration of the small molecule Toll-like receptor (TLR)-7 agonist DSR-6434 leads to potent activation of innate immunity and to the generation of anti-tumor immune responses. However, clinical responses with systemically administered TLR7 agonists have been underwhelming, in part because activation of TLRs with small-molecule agonists can induce TLR tolerance; defined as a state of hyporesponsiveness to subsequent agonism. This study is undertaken to identify conditions to overcome TLR tolerance.

Experimental procedures: To confirm the anti-tumor effect of DSR-6434, mice were inoculated with the mouse renal cell carcinoma cell line, Renca, at day 0, and then administrated DSR-6434 weekly from day 1, or twice weekly from day 6. To examine tolerance, wild-type or IFN-α/β receptor knockout (IFN-AR KO) mice were intravenously administrated DSR-6434 at intervals of 3, 7 or 10 days. Plasma samples were taken 2 hours after the second administration of DSR-6434 and IFN-α levels were measured. Splenocytes were isolated 24 hours following either single or sequential i.v. doses. To measure lymphocyte activation, CD69 expression was assessed and splenocyte-mediated cytotoxicity against YAC-1 target cells was determined. Bone-marrow derived pDC (BM-pDC) were also treated with DSR-6434 for 5 or 48 hours. Expression of TLR7 signaling-related genes was determined by real-time quantitative RT-PCR.

Results: Weekly administration of DSR-6434 significantly reduced tumor burden when compared to vehicle-treated mice. By contrast, pre-inoculation and 2qw administration of DSR-6434 completely abolished anti-tumor activity. IFN-α induction was completely impaired following the second administration of DSR-6434 after 3 days, partially impaired after 7 days, and fully functional when the dosing interval was extended to 10 days. Sequential dosing of DSR-6434 reduced the frequency of activated splenocytes (defined as CD69+) and the level of cytotoxicity, compared with a single administration of DSR-6434. TLR7 tolerance was also observed in IFN-AR KO mice, suggesting this effect was independent of IFN signaling. Interestingly, TLR7 down-regulation was only observed after DSR-6434 dosing, while the expression of other TLR7-signaling related genes was unaltered.

Conclusion: The dosing schedule of systemically administered TLR7 agonists significantly affect TLR tolerance and antitumor activity, offering a potential solution to overcome TLR tolerance . Furthermore, TLR7 expression on BM-pDC cells may serve as a useful biomarker of TLR7 tolerance and aid in the optimization of dosing schedules involving systemically administered TLR7 agonists.

Citation Format: Erina Koga-Yamakawa, Masashi Murata, Simon J. Dovedi, Robert W. Wilkinson, Hiroki Umehara, Eiji Sugaru, Yuko Hirose, Hideyuki Harada, David T. Robinson, Philip J. Jewsbury, Setsuko Yamamoto, Chiang J. Li. Enhancement of antitumor activity of DSP-6434, a novel TLR7 agonist through reduction of TLR tolerance. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2567. doi:10.1158/1538-7445.AM2014-2567

Abstract 2571: Sustained induction of TRAIL and granzyme B as well as intratumor infiltration of cytotoxic T lymphocytes (CTL) by a novel TLR7 agonist, DSR-6434, after systemic administration

Although immediate responses after treatment of TLR7 agonist have been extensively characterized the genes that are directly responsible for the antitumor activity of TLR7 agonists have not been well identified. Moreover, the immediate responses to TLR7 agonist stimulation, such as induction of interferon-alpha, IP-10 and IL-1RA, generally diminish rapidly, and therefore, cannot be used as optimal pharmacodynamic (PD) biomarkers to monitor longer term PD effects. This study was undertaken to investigate the antitumor mechanism of TLR7 agonists and to identify novel PD biomarkers. To identify PD biomarkers, mice were inoculated with mouse renal carcinoma cell line, Renca, and were administered intravenously with DSR-6434 at 0.1 mg/kg once a week, 3 times. Total RNA samples were collected 2 hours or 5 days after final dose from tumor or blood. Global gene expression profiles in tumor or blood were analyzed using GeneChip Mouse Genome 430 2.0 array (Affymetrix). Differentially expressed genes by DSR-6434 were selected compared to vehicle, and pathway analysis was performed using the genes. Expression of TRAIL and granzyme B and its time course after the administration was investigated in peripheral blood leukocytes. In tumor of mouse model, 312 and 53 genes were upregulated and downregulated, respectively, more than 2 fold at 2 hours after DSR-6434 administration. The upregulated genes included those related to immune cell activation and apoptosis pathways. The upregulated immune-related genes included T-cell marker genes (Cd3g, Cd3e), marker genes of cytotoxic T-cells (CTL) (Cd8a), lymphocyte activation (Cd69), dendritic cells activation (Cd83 and Cd86) and cytotoxic factors against tumor (TRAIL and granzyme B). These results suggested that DSR-6434 induced infiltration and activation of CTL and production of cytotoxic factors at tumor site. At 5 days after the administration of TLR7 agonist DSR-6434, 4 genes, including TRAIL, remained upregulated in tumor. Surprisingly, upregulation of TRAIL and granzyme B in blood sustained for 3 or 6 days, respectively.

In conclusion, unbiased gene expression profiling has revealed that TLR7 agonist DSR-6434 triggers CD8+ cells infiltration into tumor and sustained increase of TRAIL and granzyme B in blood for at least 3 days, thus offering novel PD biomarkers that could potentially predict antitumor activity of TLR7 agonists.

Citation Format: Ryosaku Inagaki, Mikio Aoki, Toru Kimura, Yuko Hirose, Hiroki Umehara, Erina Koga, Masashi Murata, Robert W. Wilkinson, David T. Robinson, Philip J. Jewsbury, Chiang J. Li. Sustained induction of TRAIL and granzyme B as well as intratumor infiltration of cytotoxic T lymphocytes (CTL) by a novel TLR7 agonist, DSR-6434, after systemic administration. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2571. doi:10.1158/1538-7445.AM2014-2571

Abstract LB-47: Specific and potent silencing of K-Ras by asymmetric RNA technology reveals addiction of gastric cancer stem cells

The protein K-Ras is a molecular switch that under normal conditions regulates cell growth and cell division. Mutations in this protein lead to the formation of tumors through continuous cell growth. About 30% of human cancers have a mutated Ras protein that is constitutively bound to GTP due to decreased GTPase activity and insensitivity to GAP action. Ras is also an important factor in many cancers in which it is not mutated but rather functionally activated through inappropriate activity of other signal transduction elements. Mutated K-Ras proteins are found in a large proportion of all tumour cells. K-Ras protein occupies a central position of interest. The identification of oncogenically mutated K-Ras in many human cancers led to major efforts to target this constitutively activated protein as a rational and selective treatment. Despite decades of active agent research, significant challenges still remain to develop therapeutic inhibitors of K-Ras.

To elucidate the function of K-Ras in the cancer development and maintenance, we developed asymmetric interfering RNAs (aiRNAs) which are able to silence target genes with high potency leading to long-lasting knockdown, and reducing off-target effects, and investigated the dependency of K-ras on cell survival in several types of human cancer cell lines. Much to our surprise, we found K-Ras plays a more significant role for gastric cancer maintenance compared to other types of cancer. Here we report aiRNA-induced silencing of K-Ras inhibited the cell proliferation of gastric cancer cells and the ability of gastric cancer cells to form colonies compared to other cancer types. Accumulating evidence has revealed that cancer stem cells (CSCs) are highly associated with prognosis, metastasis, and recurrence. To investigate the effect of K-Ras on CSCs, we tested the K-Ras gene silencing effects on an in vitro CSC culturing system. As a result, K-Ras inhibition decreased the colonies derived from gastric CSCs and altered the gene expression patterns of several genes involved in “stemness” compared to other cancer types. The results of these studies suggest that gastric cancer and gastric CSCs are affected by the K-Ras oncogene and that Kras aiRNAs are promising therapeutic candidates for the treatment of gastric cancer.

Citation Format: Xiangao Sun, Youzhi Li, Hiroki Umehara, Jun Oishi, Nithya Jesuraj, Jelena Barbulovic, Xiaoshu Dai, Keyur Gada, Chiang Li. Specific and potent silencing of K-Ras by asymmetric RNA technology reveals addiction of gastric cancer stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-47. doi:10.1158/1538-7445.AM2014-LB-47

Improvement and quantitative performance estimation of the back support muscle suit

We have been developing the wearable muscle suit for direct and physical motion supports. The use of the McKibben artificial muscle has opened the way to the introduction of "muscle suits" compact, lightweight, reliable, wearable "assist-bots" enabling manual worker to lift and carry weights. Since back pain is the most serious problem for manual worker, improvement of the back support muscle suit under the feasibility study and quantitative estimation are shown in this paper. The structure of the upper body frame, the method to attach to the body, and the axes addition were explained as for the improvement. In the experiments, we investigated quantitative performance results and efficiency of the back support muscle suit in terms of vertical lifting of heavy weights by employing integral electromyography (IEMG). The results indicated that the values of IEMG were reduced by about 40% by using the muscle suit.

Preparation and Characterization of Nanocomposite Composed of TiO2 as Active Matrix

Pt/TiO2 nanocomposite films were deposited on quartz glass and ITO glass substrates by the co-sputtering method. As-deposited composite films were amorphous and content of Pt in the films could be easily controlled by the amount Pt wire placed on the TiO2 target. Pt/Ti atomic ratio in the nanocomposite increased as the length of Pt wire on the TiO2 target increased. It was determined by XPS that the chemical states of Pt in as-deposited nanocomposites were Pt metal, Pt-O-Ti and PtO2, which were dependent on the Pt/Ti atomic ratio in the nanocomposite. The size of Pt nanoparticles in the composite films increased as the temperature of heat-treatment and Pt/Ti atomic ratio in the composite films increased. Pt nanoparticles in the nanocomposite films inhibited grain growth of TiO2 during heat-treatment.

Effects of Akt signaling on nuclear reprogramming

Reprogramming of the epigenetic state from differentiated to pluripotent cells can be attained by cell fusion of differentiated somatic cells with embryonic stem (ES) cells or transfer of the nucleus of a differentiated cell into an enucleated oocyte. Activation of Akt signaling is sufficient to maintain pluripotency of ES cells and promotes derivation of embryonic germ (EG) cells from primordial germ cells (PGCs). Here we analyzed the effects of Akt signaling on somatic cell nuclear reprogramming after cell fusion and nuclear transfer. We found that forced activation of Akt signaling stimulated reprogramming after cell fusion of ES cells with thymocytes or mouse embryonic fibroblasts. These hybrid cells showed ES cell characteristics, including in vitro and in vivo differentiation capacity. In contrast, Akt signaling significantly reduced the efficiency of reprogramming with nuclear transfer. Our results demonstrate that Akt signaling plays important roles on the nuclear reprogramming of somatic cells.

Analysis of disease-dependent sedative profiles of H(1)-antihistamines by large-scale surveillance using the visual analog scale

Sedation is the most frequent side effect of H(1)-antihistamines, and, sometimes, it may be life-threatening for patients. Evaluation of the sedative properties of H(1)-antihistamines is important to improve the patients' quality of life (QOL). Therefore, we carried out a large-scale surveillance quantified through a questionnaire using visual analog scale (VAS) from 1,742 patients. The results showed that the degree of sleepiness caused by some nonsedative second-generation antihistamines, including fexofenadine, olopatadine and cetirizine, was disease dependent. In atopic dermatitis, an unexpectedly low VAS score of sleepiness was obtained for the first-generation antihistamine d-chlorpheniramine, which is similar to those obtained for bepotastine and epinastine. d-Chlorpheniramine also showed a high VAS score in efficacy. Meanwhile, fexofenadine showed a higher VAS score of sleepiness in atopic dermatitis than those obtained in the other allergic diseases including allergic rhinitis, urticaria and asthma. In asthma, a higher VAS score of sleepiness was found for olopatadine, ebastine and cetirizine, when compared with d-chlorpheniramine. On the other hand, bepotastine showed the lowest VAS score for sleepiness. Our findings suggest the existence of unknown factors influencing the sedative properties of H(1)-antihistamines. Therefore, appropriate H(1)-antihistamines may need to be selected, depending on allergic diseases, to improve patients' QOL.

Proposal for a new clinical entity, IgG4-positive multiorgan lymphoproliferative syndrome: analysis of 64 cases of IgG4-related disorders

BACKGROUND

Mikulicz's disease (MD) has been considered as one manifestation of Sjögren's syndrome (SS). Recently, it has also been considered as an IgG(4)-related disorder.

OBJECTIVE

To determine the differences between IgG(4)-related disorders including MD and SS.

METHODS

A study was undertaken to investigate patients with MD and IgG(4)-related disorders registered in Japan and to set up provisional criteria for the new clinical entity IgG(4)-positive multiorgan lymphoproliferative syndrome (IgG(4)+MOLPS). The preliminary diagnostic criteria include raised serum levels of IgG(4) (>135 mg/dl) and infiltration of IgG(4)(+) plasma cells in the tissue (IgG(4)+/IgG+ plasma cells >50%) with fibrosis or sclerosis. The clinical features, laboratory data and pathologies of 64 patients with IgG(4)+MOLPS and 31 patients with typical SS were compared.

RESULTS

The incidence of xerostomia, xerophthalmia and arthralgia, rheumatoid factor and antinuclear, antiSS-A/Ro and antiSS-B/La antibodies was significantly lower in patients with IgG(4)+MOLPS than in those with typical SS. Allergic rhinitis and autoimmune pancreatitis were significantly more frequent and total IgG, IgG(2), IgG(4) and IgE levels were significantly increased in IgG(4)+MOLPS. Histological specimens from patients with IgG(4)+MOLPS revealed marked IgG(4)+ plasma cell infiltration. Many patients with IgG(4)+MOLPS had lymphocytic follicle formation, but lymphoepithelial lesions were rare. Few IgG(4)+ cells were seen in the tissue of patients with typical SS. Thirty-eight patients with IgG(4)+MOLPS treated with glucocorticoids showed marked clinical improvement.

CONCLUSION

Despite similarities in the involved organs, there are considerable clinical and pathological differences between IgG(4)+MOLPS and SS. Based on the clinical features and good response to glucocorticoids, we propose a new clinical entity: IgG(4)+MOLPS.

Successful treatment of amegakaryocytic thrombocytopenia with anti-CD20 antibody (rituximab) in a patient with systemic lupus erythematosus

Amegakaryocytic thrombocytopenia is an extremely rare disorder in systemic lupus erythematosus, and its mechanism and treatment are still largely unknown. We describe a 42-year-old woman with systemic lupus erythematosus who presented various clinical manifestations of life-threatening amegakaryocytic thrombocytopenia (10,000 platelets/mm3 with a marked decrease of megakaryocytes in the bone marrow), proteinuria, psychosis, refractory chylothorax, ascites, and type II diabetes caused by the anti-insulin receptor autoantibody. She was initially treated with prednisolone (25-50 mg/day) and cyclosporine A (200 mg/day) without any improvement in severe thrombocytopenia. However, her clinical symptoms, including platelet counts, dramatically improved, with a concurrent decrease in the anti-c-Mpl antibody, an autoantibody against the thrombopoietin receptor, after a subsequent treatment with rituximab (375 mg/m2 intravenously, weekly, for two consecutive weeks). Our case suggested that amegakaryocytic thrombocytopenia in patients with systemic lupus erythematosus might be mediated by the anti-c-Mpl antibody and could be treated with rituximab through elimination of pathogenic B cells producing autoimmune antibodies.

AKT signaling promotes derivation of embryonic germ cells from primordial germ cells

Primordial germ cells (PGCs) are embryonic germ cell precursors. Although the developmental potency of PGCs is restricted to the germ lineage, PGCs can acquire pluripotency, as verified by the in vitro establishment of embryonic germ (EG) cells and the in vivo production of testicular teratomas. PGC-specific inactivation of PTEN, which is a lipid phosphatase antagonizing phosphoinositide-3 kinase (PI3K), enhances both EG cell production and testicular teratoma formation. Here, we analyzed the effect of the serine/threonine kinase AKT, one of the major downstream effectors of PI3K, on the developmental potency of PGCs. We used transgenic mice that expressed an AKT-MER fusion protein, the kinase activity of which could be regulated by the ligand of modified estrogen receptor (MER), 4-hydroxytamoxifen. We found that hyperactivation of AKT signaling in PGCs at the proliferative phase dramatically augmented the efficiency of EG cell establishment. Furthermore, AKT signaling activation substituted to some extent for the effects of bFGF, an essential growth factor for EG cell establishment. By contrast, AKT activation had no effect on germ cells that were in mitotic arrest or that began meiosis at a later embryonic stage. In the transgenic PGCs, AKT activation induced phosphorylation of GSK3, which inhibits its kinase activity; enhanced the stability and nuclear localization of MDM2; and suppressed p53 phosphorylation, which is required for its activation. The p53 deficiency, but not GSK3 inhibition, recapitulated the effects of AKT hyperactivation on EG cell derivation, suggesting that p53 is one of the crucial downstream targets of the PI3K/AKT signal and that GSK3 is not.

Clonality analysis of lymphoproliferative disorders in patients with Sjögren's syndrome

The aim of this study was to clarify the nature of the clonal lymphocyte infiltration in Sjögren's syndrome (SS) patients associated with lymphoproliferative disorders. We examined B cell clonality in lymphoproliferative tissues from six primary SS patients associated with lymphoproliferative disorders or lymphoma by cloning and sequencing of the gene rearrangement of the immunoglobulin heavy chain complementarity determining region 3 (IgVH-CDR3). Three patients with sequential observation showed progressional clonal expansion with the presence of the same subclone in different tissues during the course of disease. Among them, one patient developed mucosa-associated lymphoid tissue (MALT) lymphoma in glandular parotid. The other three SS patients concomitant with malignant B cells lymphomas showed different clonal expansion of B cells between nodal sites and salivary glands. The cloanality analysis indicated that monoclonal B cell population could spread from one glandular site to another site during the course of SS, suggesting that the malignant clone may arise from the general abnormal microenvironment, not restricted to the glandular tissue, in some SS patients.

Efficient derivation of embryonic stem cells by inhibition of glycogen synthase kinase-3

Embryonic stem (ES) cells are derived from the inner cell mass (ICM) of blastocysts. The use of ES cells as a source of differentiated cells holds great promise for cell transplantation therapy. The efficiency of ES cell derivation is affected by genetic variation in mice; that is, some mouse strains, such as C57BL/6, are amenable to ES cell derivation, whereas others, such as BALB/c, are refractory. Developing an efficient method to establish ES cells from strains of various genetic backgrounds should be valuable for derivation of ES cells in various mammalian species, including human. Although it is well-established that various signaling pathways, including phosphoinositide 3-kinase (PI3K)/Akt and Wnt/beta-catenin, regulate the maintenance of ES cell pluripotency, little is known about the signaling pathways involved in the derivation of ES cells from ICMs. In this study, we demonstrated that inhibition of glycogen synthase kinase-3 (GSK-3), one of the crucial molecules in the regulation of the Wnt/beta-catenin, Hedgehog, and Notch signaling pathways, dramatically augmented ES cell derivation from both C57BL/6 and BALB/c mouse strains. In contrast, Akt signaling activation enhanced the growth of ICM but did not increase the efficiency of ES cell derivation. Our study establishes an efficient means for ES cell derivation by pharmacological inhibition of GSK-3.

PGC7/Stella protects against DNA demethylation in early embryogenesis

DNA methylation is an important means of epigenetic gene regulation and must be carefully controlled as a prerequisite for normal early embryogenesis. Although global demethylation occurs soon after fertilization, it is not evenly distributed throughout the genome. Genomic imprinting and epigenetic asymmetry between parental genomes, that is, delayed demethylation of the maternal genome after fertilization, are clear examples of the functional importance of DNA methylation. Here, we show that PGC7/Stella, a maternal factor essential for early development, protects the DNA methylation state of several imprinted loci and epigenetic asymmetry. After determining that PGC7/Stella binds to Ran binding protein 5 (RanBP5; a nuclear transport shuttle protein), mutant versions of the two proteins were used to examine exactly when and where PGC7/Stella functions within the cell. It is likely that PGC7/Stella protects the maternal genome from demethylation only after localizing to the nucleus, where it maintains the methylation of several imprinted genes. These results demonstrate that PGC7/Stella is indispensable for the maintenance of methylation involved in epigenetic reprogramming after fertilization.

The stabilization of β-catenin leads to impaired primordial germ cell development via aberrant cell cycle progression

Primordial germ cells (PGCs) are germ cell precursors that are committed to sperm or oocytes. Dramatic proliferation during PGC development determines the number of founder spermatogonia and oocytes. Although specified to a germ lineage, PGCs produce pluripotent embryonic germ (EG) cells in vitro and testicular teratomas in vivo. Wnt/beta-catenin signaling regulates pluripotency and differentiation in various stem cell systems, and dysregulation of this signaling causes various human cancers. Here, we examined the role of Wnt/beta-catenin signaling in PGC development. In normal PGC development, Wnt/beta-catenin signaling is suppressed by the GSK3beta-mediated active degradation of beta-catenin and the low expression of canonical Wnt molecules. The effects of aberrant activation of Wnt/beta-catenin signaling in PGCs were analyzed using mice carrying a deletion of the exon that encodes the GSK3beta phosphorylation sites in the beta-catenin locus. Despite the potential activity of Wnt/beta-catenin signaling in stem cell maintenance and carcinogenesis in various cell lineages, teratomas were not induced in the mice expressing the nuclear-localized beta-catenin in PGCs. Instead, the mutant mice showed germ cell deficiency caused by the delayed cell cycle progression of the proliferative phase PGCs. Our results show that the suppression of Wnt/beta-catenin signaling is a prerequisite for the normal development of PGCs.

Activation of Akt signaling is sufficient to maintain pluripotency in mouse and primate embryonic stem cells

Embryonic stem (ES) cells can self-renew indefinitely without losing their differentiation ability to any cell types. Phosphoinositide-3 kinase (PI3K)/Akt signaling plays a pivotal role in various stem cell systems, including the formation of embryonic germ (EG) cells from primordial germ cells and self-renewal of neural stem cells. Here, we show that myristoylated, active form of Akt (myr-Akt) maintained the undifferentiated phenotypes in mouse ES cells without the addition of leukemia inhibitory factor (LIF). The effects of myr-Akt were reversible, because LIF dependence and pluripotent differentiation activity were restored by the deletion of myr-Akt. In addition, myr-Akt-Mer fusion protein, whose enzymatic activity is controlled by 4-hydroxy-tamoxifen, also maintained the pluripotency of not only mouse but also cynomolgus monkey ES cells. These results clearly demonstrate that Akt signaling sufficiently maintains pluripotency in mouse and primate ES cells, and support the notion that PI3K/Akt signaling axis regulates 'stemness' in a broad spectrum of stem cell systems.

Redirecting differentiation of hematopoietic progenitors by a transcription factor, GATA-2

GATA-2 is a zinc finger transcription factor essential for differentiation of immature hematopoietic cells. We analyzed the function of GATA-2 by a combined method of tetracycline-dependent conditional gene expression and in vitro hematopoietic differentiation from mouse embryonic stem (ES) cells using OP9 stroma cells (OP9 system). In the presence of macrophage colony-stimulating factor (M-CSF), the OP9 system induced macrophage differentiation. GATA-2 expression in this system inhibited macrophage differentiation and redirected the fate of hematopoietic differentiation to other hematopoietic lineages. GATA-2 expression commencing at day 5 or day 6 induced megakaryocytic or erythroid differentiation, respectively. Expression levels of PU.1, a hematopoietic transcription factor that interferes with GATA-2, appeared to play a critical role in differentiation to megakaryocytic or erythroid lineages. Transcription of PU.1 was affected by histone acetylation induced by binding of GATA-2 to the PU.1 promoter region. This study demonstrates that the function of GATA-2 is modified in a context-dependent manner by expression of PU.1, which in turn is regulated by GATA-2.

Control of ceramide-induced apoptosis by IGF-1: involvement of PI-3 kinase, caspase-3 and catalase

Insulin-like growth factor-1 (IGF-1) inhibited N-acetylsphingosine (C2-ceramide)-induced HL-60 cell apoptosis via relieving oxidative damage. This inhibitory action of IGF-1 was blocked by a phosphatidylinositol-3 (PI-3) kinase inhibitor wortmannin and enhanced by overexpression of the p110 catalytic subunit of PI-3 kinase. Either IGF-1 pretreatment or PI-3 kinase overexpression restored ceramide-depleted catalase function, and this restoration was inhibited by wortmannin. A catalase inhibitor 3-amino-1h-1, 2, 4-triazole (ATZ) blocked the inhibitory action of IGF-1 on ceramide-induced apoptosis, whereas exogenous purified catalase enhanced it. Ceramide-activated caspase-3 was inhibited by IGF-1/PI-3 kinase and enhanced by wortmannin, while the addition of a specific caspase-3 inhibitor DMQD-CHO significantly enhanced the restoration by IGF-1 of ceramide-depleted catalase function. Moreover, IGF-1 inhibited C2-ceramide-induced decrease of mitochondrial membrane potential, and increase of cytochrome c release, caspase-3 cleavage and caspase-3 activity as judged by PhiPhiLux cleaving method. In summary, these results suggest that IGF-1/PI-3 kinase inhibited C2-ceramide-induced apoptosis due to relieving oxidative damage, which resulted from the inhibition of catalase by activated caspase-3.

Fractalkine and vascular injury

The vascular endothelium plays a central role in the recruitment and migration of circulating effector cells into sites of inflammation and immune responses. The unique CX(3)C-chemokine, fractalkine, is expressed on activated endothelial cells, and its receptor, CX(3)CR1, is expressed on natural killer cells, monocytes and some CD8+ T cells, all of which possess cytolytic function. Accumulating evidence that fractalkine is expressed on endothelial cells during glomerulonephritis and cardiac allograft rejection, as well as on cardiac endothelial cells activated by pro-inflammatory cytokines, might provide insight into the pathogenesis of vascular injury. Here, we propose a model in which fractalkine mediates vascular injury through the accumulation and activation of killer cells.

Role of fractalkine in leukocyte adhesion and migration and in vascular injury

Leukocyte adhesion and trafficking at the endothelium requires both cellular adhesion molecules and chemotactic factors. Fractalkine, a recently identified chemokine, has a unique architecture, a Cys-X-X-X-Cys chemokine domain presented on top of an extended mucin-like stalk as a part of transmembrane protein, and is expressed in a membrane-bound form on tumor necrosis factor-alpha and interleukin-1-activated endothelial cells. Fractalkine receptor CX3CR1 is expressed on natural killer (NK) cells, monocytes and some portions of CD8(+) T cells. Interactions between fractalkine and CX3CR1 can mediate not only chemotaxis but also cell adhesion in the absence of substrates for other adhesion molecules. Furthermore, fractalkine activates NK cells, resulting in enhanced cytolysis of fractalkine expressing endothelial cells. Since endothelial cells are primary targets of immunologic attack, fractalkine seems to be involved in pathogenesis of vascular injury.

Fractalkine, a CX3C-chemokine, functions predominantly as an adhesion molecule in monocytic cell line THP-1

A newly identified CX3C-chemokine, fractalkine, expressed on activated endothelial cells plays an important role in leucocyte adhesion and migration. Co-immobilized fractalkine with fibronectin or intercellular adhesion molecule-1 enhanced adhesion of THP-1 cells, which express the fractalkine receptor (CX3CR1), compared with that observed for each alone. That adherence was fractalkine-dependent and was confirmed in blocking studies. However, soluble fractalkine induced little chemotaxis in THP-1 cells in comparison to monocyte chemotactic protein-1 (MCP-1), which induced a strong chemotactic response. Moreover, the membrane form of fractalkine expressed on ECV304 cells reduced MCP-1 mediated chemotaxis of THP-1 cells. These results indicate that fractalkine may function as an adhesion molecule between monocytes and endothelial cells rather than as a chemotactic factor.

Down-regulation of alpha6 integrin, an anti-oncogene product, by functional cooperation of H-Ras and c-Myc

BACKGROUND

The molecular basis of cooperation of H-Ras and c-Myc in regulating cellular behaviour, such as cell adhesiveness, is still poorly understood. To investigate the role of H-Ras and c-Myc in cell adhesiveness, a constitutively active H-RasV12 (H-RasV12) and c-Myc were stably expressed, singly or in combination in a haematopoietic cell line, and the expression and activity of cell adhesion molecules were monitored.

RESULTS

We have shown that the ectopic expression of H-RasV12, but not c-Myc alone, in a haematopoietic cell line, induces the activation of very late antigen-6 (VLA-6, alpha6beta1) integrin. Co-expression of H-RasV12 and c-Myc in the same cells further resulted in the induction of expression of vascular cell adhesion molecule-1 (VCAM-1) and the inhibition of expression of alpha6 integrin, a candidate anti-oncogene product, leading to a loss of adhesiveness to laminin (Lm), a ligand for VLA-6.

CONCLUSIONS

Cooperation of H-Ras and c-Myc reciprocally regulates expression of the adhesion molecules, alpha6 integrin and VCAM-1. Our results represent an unprecedented account of the cooperation of the oncogene products, H-Ras and c-Myc, to inhibit expression of an anti-oncogene product, alpha6 integrin.

Differential interaction of Cbl with Grb2 and CrkL in CD2-mediated NK cell activation

Natural killer (NK) cells participate in both innate and adoptive immunity by their prompt secretion of cytokines and by their ability to lyse virally infected cells or tumor cells. CD2 is surface glycoprotein receptors and crucial for NK cell activation. However, molecular events involved in CD2-mediated NK cell activation have not been fully elucidated. Cbl-Grb2 and Cbl-CrkL interactions have been implicated in T cell and B cell receptor, and cytokine receptor signaling. Here we analyzed tyrosine phosphorylation and interactions of Cbl with adapter proteins, Grb2 and CrkL, in NK3.3 cells. CD2 crosslinking results in the marked tyrosine phosphorylation of Cbl in an antibody concentration- and time-dependent manner. Immunodepletion studies reveal that Grb2-associated tyrosine phosphorylated p120 kDa protein is Cbl. In vitro binding studies using GST-fusion proteins demonstrate that Cbl constitutively associates with the SH3 domains of Grb2, with a preference for the amino-terminal domain. In addition, we demonstrate that CrkL associates with a large portion of tyrosine phosphorylated Cbl after CD2 stimulation of NK3.3 cells. In contrast to constitutive Cbl association with Grb2, tyrosine phosphorylated Cbl interacts with CrkL via its SH2 domain only after CD2 stimulation. Although the precise roles of interactions of Cbl with Grb2 and CrkL in NK cell activation remains to be elucidated, their tyrosine phosphorylation, in addition to the multiple protein interactions described here, strongly suggest that interactions of Cbl with Grb2 and CrkL may play pivotal roles in CD2-mediated NK cell activation.

A novel natural killer cell line (KHYG-1) from a patient with aggressive natural killer cell leukemia carrying a p53 point mutation

We present the establishment of a natural killer (NK) leukemia cell line, designated KHYG-1, from the blood of a patient with aggressive NK leukemia, which both possessed the same p53 point mutation. The immunophenotype of the primary leukemia cells was CD2+, surface CD3-, cytoplasmic CD3epsilon+, CD7+, CD8alphaalpha+, CD16+, CD56+, CD57+ and HLA-DR+. A new cell line (KHYG-1) was established by culturing peripheral leukemia cells with 100 units of recombinant interleukin (IL)-2. The KHYG-1 cells showed LGL morphology with a large nucleus, coarse chromatin, conspicuous nucleoli, and abundant basophilic cytoplasm with many azurophilic granules. The immunophenotype of KHYG-1 cells was CD1-, CD2+, surface CD3-, cytoplasmic CD3epsilon+, CD7+, CD8alphaalpha+, CD16-, CD25-, CD33+, CD34-, CD56+, CD57-, CD122+, CD132+, and TdT-. Southern blot analysis of these cells revealed a normal germline configuration for the beta, delta, and gamma chains of the T cell receptor and the immunoglobulin heavy-chain genes. Moreover, the KHYG-1 cells displayed NK cell activity and IL-2-dependent proliferation in vitro, suggesting that they are of NK cell origin. Epstein-Barr virus (EBV) DNA was not detected in KHYG-1 cells by Southern blot analysis with a terminal repeat probe from an EBV genome. A point mutation in exon 7 of the p53 gene was detected in the KHYG-1 cells by PCR/SSCP analysis, and direct sequencing revealed the conversion of C to T at nucleotide 877 in codon 248. The primary leukemia cells also carried the same point mutation. Although the precise role of the p53 point mutation in leukemogenesis remains to be clarified, the establishment of an NK leukemia cell line with a p53 point mutation could be valuable in the study of leukemogenesis.

CX3C-chemokine, fractalkine-enhanced adhesion of THP-1 cells to endothelial cells through integrin-dependent and -independent mechanisms

Leukocyte adhesion and trafficking at the endothelium requires both cellular adhesion molecules and chemotactic factors. A newly identified CX3C chemokine, fractalkine, expressed on activated endothelial cells, plays an important role in leukocyte adhesion and migration. We examined the functional effects of fractalkine on beta1 and beta2 integrin-mediated adhesion using a macrophage-like cell line, THP-1 cells. In this study, we report that THP-1 cells express mRNA encoding a receptor for fractalkine, CX3CR1, determined by Northern blotting. Scatchard analysis using fractalkine-SEAP (secreted form of placental alkaline phosphatase) chimeric proteins revealed that THP-1 cells express a single class of CX3CR1 with a dissociation constant of 30 pM and a mean expression of 440 sites per cell. THP-1 cells efficiently adhered, in a fractalkine-dependent manner, to full-length of fractalkine immobilized onto plastic and to the membrane-bound form of fractalkine expressed on ECV304 cells or TNF-alpha-activated HUVECs. Moreover, soluble-fractalkine enhanced adhesion of THP-1 cells to fibronectin and ICAM-1 in a dose-dependent manner. Pertussis toxin, an inhibitor of Gi, inhibited the fractalkine-mediated enhancement of THP-1 cell adhesion to fibronectin and ICAM-1. Finally, we found that soluble-fractalkine also enhanced adhesion of freshly separated monocytes to fibronectin and ICAM-1. These results indicate that fractalkine may induce firm adhesion between monocytes and endothelial cells not only through an intrinsic adhesion function itself, but also through activation of integrin avidity for their ligands.

Fractalkine-mediated endothelial cell injury by NK cells

Endothelial cells (ECs) are primary targets of immunological attack, and their injury can lead to vasculopathy and organ dysfunction in vascular leak syndrome and in rejection of allografts or xenografts. A newly identified CX3C-chemokine, fractalkine, expressed on activated ECs plays an important role in leukocyte adhesion and migration. In this study we examined the functional roles of fractalkine on NK cell activity and NK cell-mediated endothelial cell injury. Freshly separated NK cells expressed the fractalkine receptor (CX3CR1) determined by FACS analysis and efficiently adhered to immobilized full-length fractalkine, but not to the truncated forms of the chemokine domain or mucin domain, suggesting that fractalkine functions as an adhesion molecule on the interaction between NK cells and ECs. Soluble fractalkine enhanced NK cell cytolytic activity against K562 target cells in a dose- and time-dependent manner. This enhancement correlated well with increased granular exocytosis from NK cells, which was completely inhibited by the G protein inhibitor, pertussis toxin. Transfection of fractalkine cDNA into ECV304 cells or HUVECs resulted in increased adhesion of NK cells and susceptibility to NK cell-mediated cytolysis compared with control transfection. Moreover, both enhanced adhesion and susceptibility of fractalkine-transfected cells were markedly suppressed by soluble fractalkine or anti-CX3CR1 Ab. Our results suggest that fractalkine plays an important role not only in the binding of NK cells to endothelial cells, but also in NK cell-mediated endothelium damage, which may result in vascular injury.