Treatment rationale and protocol design: an investigator-initiated phase II study of combination treatment of nivolumab and TM5614, a PAI-1 inhibitor for previously treated patients with non-small cell lung cancer.

Background: There is no established standard 3rd line treatment for patients with advanced non-small cell lung cancer (NSCLC). Although cytotoxic chemotherapeutic agents that are not used as 1st or 2nd line treatment are administrated as 3rd line treatment, their anti-tumor efficacy is insufficient. Anti-programmed death ligand-1 (PD-L1)/programmed death-1 (PD1) treatment is more effective and less toxic than chemotherapy in anti-PD-L1/PD-1 treatment-naïve patients with NSCLC. Therefore, anti-PD-L1/PD-1 therapy is considered an appropriate 3rd line treatment. However, the anti-tumor efficacy is limited in patients previously treated with anti-PD-L1/PD-1 antibody. Today, new drugs are needed to increase the efficacy of anti-PD-L1/PD-1 antibodies. Methods: This open-label, single-arm, investigator-initiated phase II study is designed to evaluate combination treatment of nivolumab and TM5614, a plasminogen activator inhibitor (PAI-1) inhibitor as 3rd or more line treatment in NSCLC patients who underwent standard treatment. The primary endpoint is the objective response rate and the secondary endpoints are progression-free survival (PFS), overall survival (OS), duration of response (DOR) and safety. Recruitment began in September 2023 and is expected to continue for approximately three years. Discussion: Currently, there is no standard 3rd line treatment for advanced NSCLC, and we hope that the findings of this study will facilitate more effective treatments in this setting. Ethics and dissemination: the study protocol conformed to the ethical principles outlined in the Declaration of Helsinki. All patients will provide written informed consent prior to enrollment. Results will be published in a peer-reviewed publication. Trial Registration: This study is registered to Japan Registry of Clinical Trials with number: jRCT2061230039 (19/July/2023).

Targeting Podoplanin for the Treatment of Osteosarcoma.

PURPOSE: Osteosarcoma, the most common bone malignancy in children, has a poor prognosis, especially when the tumor metastasizes to the lungs. Therefore, novel therapeutic strategies targeting both proliferation and metastasis of osteosarcoma are required. Podoplanin (PDPN) is expressed by various tumors and is associated with tumor-induced platelet activation via its interaction with C-type lectin-like receptor 2 (CLEC-2) on platelets. We previously found that PDPN contributed to osteosarcoma growth and metastasis through platelet activation; thus, in this study, we developed an anti-PDPN humanized antibody and evaluated its effect on osteosarcoma growth and metastasis. EXPERIMENTAL DESIGN: Nine osteosarcoma cell lines and two osteosarcoma patient-derived cells were collected, and we evaluated the efficacy of the anti-DPN-neutralizing antibody PG4D2 and the humanized anti-PDPN antibody AP201, which had IgG4 framework region. The antitumor and antimetastasis effect of PG4D2 and AP201 were examined in vitro and in vivo. In addition, growth signaling by the interaction between PDPN and CLEC-2 was analyzed using phospho-RTK (receptor tyrosine kinase) array, growth assay, or immunoblot analysis under the supression of RTKs by knockout and inhibitor treatment. RESULTS: We observed that PG4D2 treatment significantly suppressed tumor growth and pulmonary metastasis in osteosarcoma xenograft models highly expressing PDPN. The contribution of PDGFR activation by activated platelet releasates to osteosarcoma cell proliferation was confirmed, and the humanized antibody, AP201, suppressed in vivo osteosarcoma growth and metastasis without significant adverse events. CONCLUSIONS: Targeting PDPN with a neutralizing antibody against PDPN-CLEC-2 without antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity is a novel therapeutic strategy for PDPN-positive osteosarcoma.

Stromal cells' B7-1 is a key stimulatory molecule for interleukin-10 production by HOZOT, a multifunctional regulatory T-cell line.

We have previously shown that xenogeneic stromal cell stimulation of naïve T cells resulted in the generation of a new type of regulatory T (Treg) cell termed HOZOT, which has multifunctional properties and a CD4/CD8 double-positive phenotype. Even after the establishment of HOZOT, stromal cells can function as an antigen-presenting cell (APC) by inducing these cells to produce interleukin (IL)-10. When compared with other stimuli, stromal cells showed an IL-10-producing ability comparable to anti-CD3 antibody (Ab) stimulation, and much greater than dendritic cell (DC) stimulation. Distinct from professional APCs, stromal cells express only major histocompatibility complex (MHC) class I and B7-1 costimulatory molecules, and not MHC class II or other costimulatory molecules, such as ICOSL (CD275), PD-L1 (CD274), PD-L2 (CD273), CD40, OX40L (CD252) and 4-1BBL (CD137L) in the absence of stimulation. Blocking experiments revealed that, in addition to anti-H-2K(d) Ab and anti-human CD8 Ab, anti-mouse B7-1 Ab could effectively block IL-10 production, indicating a key role of the B7-1/CD28 pathway. Using stromal cells expressing different levels of B7-1, IL-10 production correlated with the levels of B7-1 expression. Distinct from ICOSL or PD-L1 expressed on DCs (which are regarded as IL-10-inducing costimulatory molecules), this study showed that B7-1 on stromal cells is a key molecule regulating IL-10 production by multifunctional Treg cells, HOZOT.

The production of IL-10 by human regulatory T cells is enhanced by IL-2 through a STAT5-responsive intronic enhancer in the IL-10 locus.

STAT5 molecules are key components of the IL-2 signaling pathway, the deficiency of which often results in autoimmune pathology due to a reduced number of CD4(+)CD25(+) naturally occurring regulatory T (Treg) cells. One of the consequences of the IL-2-STAT5 signaling axis is up-regulation of FOXP3, a master control gene for naturally occurring Treg cells. However, the roles of STAT5 in other Treg subsets have not yet been elucidated. We recently demonstrated that IL-2 enhanced IL-10 production through STAT5 activation. This occurred in two types of human Treg cells: a novel type of umbilical cord blood-derived Treg cell, termed HOZOT, and Tr1-like Treg cells, IL-10-Treg. In this study, we examined the regulatory mechanisms of IL-10 production in these Treg cells, focusing specifically on the roles of STAT5. By performing bioinformatic analysis on the IL-10 locus, we identified one STAT-responsive element within intron 4, designated I-SRE-4, as an interspecies-conserved sequence. We found that I-SRE-4 acted as an enhancer element, and clustered CpGs around the I-SRE-4 were hypomethylated in IL-10-producing Treg cells, but not in other T cells. A gel-shift analysis using a nuclear extract from IL-2-stimulated HOZOT confirmed that CpG DNA methylation around I-SRE-4 reduced STAT5 binding to the element. Chromatin immunoprecipitation analysis revealed the in situ binding of IL-2-activated STAT5 to I-SRE-4. Thus, we provide molecular evidence for the involvement of an IL-2-STAT5 signaling axis in the expression of IL-10 by human Treg cells, an axis that is regulated by the intronic enhancer, I-SRE-4, and epigenetic modification of this element.

IL-2 activation of STAT5 enhances production of IL-10 from human cytotoxic regulatory T cells, HOZOT.

OBJECTIVE: Interleukin (IL)-10 is an immunosuppressive cytokine produced by many cell types, including T cells. We previously reported that a novel type of regulatory T (Treg) cells, termed HOZOT, which possesses a FOXP3+CD4+CD8+CD25+ phenotype and dual suppressor/cytotoxic activities, produced high levels of IL-10. In this study, we examined the mechanisms of high IL-10 production by HOZOT, focusing on Janus activating kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathway. MATERIALS AND METHODS: We prepared five different types of T cells, including HOZOT from human umbilical cord blood. Cytokine productions of IL-10, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) were compared among these T cells after anti-CD3/CD28 antibody stimulation in the presence or absence of IL-2. Specific inhibitors for JAK/STAT, nuclear factor-kappaB (NF-kappaB), and nuclear factor for activated T cell (NFAT) were used to analyze signal transduction mechanisms. RESULTS: IL-10 production by HOZOTs was greatly enhanced by the addition of IL-2. Little or no enhancement of IFN-gamma and TNF-alpha production was observed under the same conditions. The enhancing effect of IL-2 was specific for both HOZOT and IL-10-secreting Treg cells. T helper type 2 cells, whose IL-10 production mechanisms involve GATA-3, failed to show IL-2-mediated enhancement of IL-10. Similar enhancing effects of IL-15 and IFN-alpha suggested a major role of JAK/STAT activation pathway for high IL-10 production. Further inhibitor experiments demonstrated that STAT5 rather than STAT3 was critically involved in this mechanism. CONCLUSION: Our results demonstrated that IL-2 selectively enhanced production of IL-10 in HOZOT primarily through activation of STAT5, which synergistically acts with NF-kappaB/NFAT activation, implying a novel regulatory mechanism of IL-10 production in Treg cells.

Comprehensive analysis of FOXP3 mRNA expression in leukemia and transformed cell lines.

Studies of FOXP3 expression have thus far focused on T cells, including both normal and malignant T cells. In particular, adult T cell leukemia/lymphoma (ATLL) cells have been studied intensively because their phenotype resembles that of normal CD4(+)CD25(+) regulatory T (Treg) cells. However, a comprehensive study of FOXP3 expression covering all hematopoietic cell lineages has not yet been performed. In this study, FOXP3 mRNA expression was examined by quantitative PCR using a large collection of human hematopoietic cell lines derived from leukemia/lymphoma or virus-transformation, including cells lines with T, B, plasmacytoid, myeloid, monocytic, megakaryocytic, erythroid, and NK lineages. Unexpectedly, we found FOXP3 mRNA expression in a number of cell lines belonging to all of the cell lineages investigated. In sharp contrast, FOXP3 protein expression was found in only three cell lines, all of which were HTLV-I-infected. Several non-T cell lines expressed higher levels of mRNA but were still negative for protein expression. The broad mRNA expression contrasts with the restricted protein expression of FOXP3 in human hematopoietic cell lines, suggesting that post-transcriptional control mechanisms may control FOXP3 protein expression.

IL-2-independent generation of FOXP3(+)CD4(+)CD8(+)CD25(+) cytotoxic regulatory T cell lines from human umbilical cord blood.

OBJECTIVE: Since the existence of mouse naturally occurring CD4(+)CD25(+) T regulatory (Treg) cells was demonstrated, a variety of human Treg subsets have been identified as distinct T cell populations. Here we show the establishment of novel Treg cell lines possessing unique characteristics. METHODS: Novel Treg cell lines, designated HOZOT, were generated by coculturing human umbilical cord blood cells with mouse stromal cell lines in the absence of exogenous IL-2 or other cytokines. HOZOT were characterized and compared with CD4(+)CD25(+) Treg cells in terms of the CD phenotype, FOXP3 expression, suppressor activity against allogeneic MLR, anergy property, and IL-10 production. RESULTS: HOZOT were generated and expanded as normal lymphoblastoid cells with cytotoxic activity against the cocultured stromal cells. HOZOT consisted of three subpopulations as defined by phenotype: CD4(+)CD8(+), CD4(+)CD8(dim), and CD4(-)CD8(+). All three subpopulations showed both suppressor and cytotoxic activities. While HOZOT's expression of FOXP3, CD25, GITR, and cytoplasmic CTLA-4 implied a similarity to naturally occurring CD4(+)CD25(+) Treg cells, these two Treg cells differed in IL-2 responsiveness and IL-10 production. CONCLUSIONS: Our studies introduce a new method of generating Treg cells in an IL-2-independent manner and highlight a unique Treg cell type with cytotoxic activity and a phenotype of FOXP3(+)CD4(+)CD8(+)CD25(+).

Erythropoietin induces sustained phosphorylation of STAT5 in primitive but not definitive erythrocytes generated from mouse embryonic stem cells.

OBJECTIVE: During embryonic development murine erythropoiesis occurs in two waves by producing first primitive erythroid cells (EryPs) and then definitive erythroid cells (EryDs). Erythropoietin (EPO) signaling is compared between EryPs and EryDs. METHODS: We studied the EPO signaling in EryPs and EryDs using an embryonic stem-derived culture system, which can recapitulate this in vivo development process and has thus been used as a convenient in vitro model system of erythropoiesis. RESULTS: We found that EPO induced sustained phosphorylation and nuclear translocation of signal transducer and activator of transcription 5 (STAT5) in EryPs but not EryDs. EryPs expressed dramatically higher amounts of EPO receptor compared with EryDs, indicating there was excessive signaling from the receptor upon EPO stimulation. In addition, reduced expression of tyrosine phosphatase, Src homology region 2 domain-containing phosphatase-1, and decreased total phosphatase activity in EryPs partly explain the persistent activation of STAT5. Nevertheless, Janus kinase 2 (JAK2) phosphorylation, which is essential for transduction of EPO signaling from the EPO receptor to STAT5, was observed in a transient but not a persistent manner. Inhibition of JAK activity resulted in partial suppression of transient phosphorylation of STAT5 and no suppression of sustained phosphorylation of STAT5. CONCLUSION: This study presents a unique feature of EryPs, as this is the first known example of sustained activation of STAT5 in normal cells. Our results also imply the existence of a JAK2-independent pathway of EPO signaling to induce STAT5 activation.

Progenitor analysis of primitive erythropoiesis generated from in vitro culture of embryonic stem cells.

OBJECTIVE: A variety of hematopoietic lineage cells have been produced from embryonic stem (ES) cells, but their differentiation processes have not been elucidated well, especially from the point of view of progenitor analysis. In this study, we utilized our coculture system, in which ES-derived Flk-1+ cells differentiated into TER-119+ primitive erythroid (EryP) cells on OP9 cells, and looked for progenitors in primitive erythropoiesis. MATERIALS AND METHODS: We studied the kinetics of TER-119+ erythroblast generation from Flk-1+ cells by monitoring the expression of TER-119, CD41, VE-cadherin, CD34, and c-kit antigens. Multicolor analysis was performed to detect CD41+TER-119+ cells and the stained cells were sorted to examine their morphology and EryP-producing potential in colony formation. RESULTS: Kinetic studies showed that the CD41+ population appeared early in the coculture and its expression pattern implied a role as an immediate progenitor of TER-119+ EryP cells. Multicolor analysis and colony-formation study supported this notion. Other progenitor markers such as VE-cadherin, CD34, and c-kit did not seem to define an immediate progenitor of EryP cells. One interesting observation is the detection of unique populations, CD41dim and CD41bright, detectable after 48 hours of the coculture. Majority of the CD41dim population progressed to the EryP lineage, whereas the CD41bright population seemingly advanced on a pathway distinct from the CD41dim population. CONCLUSIONS: CD41 expression was a useful marker to trace hematopoietic progenitors in ES-derived differentiation system. In particular, the CD41dim but not CD41bright population could serve as immediate precursors of EryP cells.

Erythroblasts derived in vitro from embryonic stem cells in the presence of erythropoietin do not express the TER-119 antigen.

OBJECTIVE: In this study, we analyzed murine primitive erythropoiesis by coculturing Flk-1+ ES-derived cells with OP9 to find efficient culture conditions for erythroid cell induction. We utilized a nonserum culture system and EPO (erythropoietin) and found that this cytokine had unique properties. MATERIALS AND METHODS: ES cells (E14.1) were first differentiated to Flk-1+ cells and then cocultured with OP9 stromal cells. BIT9500 was used as a serum replacement. The erythroid morphology, hemoglobin types, and TER-119 expression levels were analyzed. RESULTS: Primitive erythroid cells with embryonic hemoglobin were generated very efficiently when the serum-containing culture was converted to the nonserum system. In this serum-free culture, TER-119+ erythroblasts appeared first on day 2 and maturation proceeded until day 7. When EPO was added to this coculture, the number of induced floating cells increased twofold to threefold. Unexpectedly, the erythroid-specific antigen TER-119 expression of these cells was drastically reduced. Since reduced TER-119 expression is usually interpreted as maturation arrest, we examined the phenotypic features of the EPO-treated cells. We found, however, no evidence of maturation arrest in the aspects of morphology and hemoglobin content. EPO did not suppress TER-119 expression of erythroblasts derived from fetal liver or adult bone marrow. CONCLUSIONS: Our results showed that EPO had the unusual property of inducing TER-119- erythroblasts in ES-derived primitive erythropoiesis. It is likely that this effect is unique to primitive erythropoiesis.

Relevance of nuclear receptor expression in a Tchreg cell line, HOZOT: RXRα and PPARγ negatively regulate IFN-γ production.

Nuclear receptors (NRs) have recently received much attention for their newly discovered roles in T cell development, as exemplified by RARα (Treg cells) and RORγt (Th17 cells). In previous studies, we characterized a new type of T cell subset, designated as Tchreg (cytotoxic, helper, and regulatory T) cells, in terms of its cytokine signature. In this study, we investigated the expression and functional relevance of NRs in Tchreg cells by performing mRNA profiling of HOZOT, a cord blood-derived Tchreg cell line. We identified eleven inducible and eight constitutively expressed NRs in HOZOT. Among these NRs, RXRα and PPARγ showed features of signature NRs of Tchreg cells because they were selectively expressed in HOZOT compared with other T cell subsets. These NRs exhibited contrasting expression patterns, as RXRα was independent of anti-CD3/28 antibody stimulation while PPARγ was stimulated-dependent. Upon agonist treatment, both proteins translocated to the nucleus and inhibited IFN-γ production through binding to the promoter region of the IFN-γ gene. These results provide new insight into the roles of RXRα and PPARγ in T cell biology, especially in their biological relevance in Tchreg cells.

miR-155, a Modulator of FOXO3a Protein Expression, Is Underexpressed and Cannot Be Upregulated by Stimulation of HOZOT, a Line of Multifunctional Treg.

MicroRNAs (miRNAs) play important roles in regulating post-transcriptional gene repression in a variety of immunological processes. In particular, much attention has been focused on their roles in regulatory T (Treg) cells which are crucial for maintaining peripheral tolerance and controlling T cell responses. Recently, we established a novel type of human Treg cell line, termed HOZOT, multifunctional cells exhibiting a CD4(+)CD8(+) phenotype. In this study, we performed miRNA profiling to identify signature miRNAs of HOZOT, and therein identified miR-155. Although miR-155 has also been characterized as a signature miRNA for FOXP3(+) natural Treg (nTreg) cells, it was expressed quite differently in HOZOT cells. Under both stimulatory and non-stimulatory conditions, miR-155 expression remained at low levels in HOZOT, while its expression in nTreg and conventional T cells remarkably increased after stimulation. We next searched candidate target genes of miR-155 through bioinformatics, and identified FOXO3a, a negative regulator of Akt signaling, as a miR-155 target gene. Further studies by gain- and loss-of-function experiments supported a role for miR-155 in the regulation of FOXO3a protein expression in conventional T and HOZOT cells.

Potent anti-tumor killing activity of the multifunctional Treg cell line HOZOT against human tumors with diverse origins.

The T cell line HOZOT has a unique FOXP3+CD4+ CD8+CD25+ phenotype, exhibits suppressive activity in allogeneic mixed lymphocyte reactions (MLR), and produces IL-10, defining HOZOT as regulatory T cells (Tregs). Interestingly, in addition to possessing a suppressive Treg ability, HOZOT was also found to show cytotoxicity against certain representative human cancer cell types. In order to disclose the range of anti-tumor activity by HOZOT, we screened it by using a panel of twenty human tumor cell lines with different origins. Consequently, HOZOT showed potent cytocidal effects against a wide spectrum of neoplastic cells including carcinomas, sarcomas, mesotheliomas and glioblastomas except for hematopoietic malignancies. Its anti-tumor activity was strong enough with an E:T ratio of 4:1, which is considered to be more effective than that by conventional CTLs. Furthermore, an in vivo representative mouse tumor model by implanting human colon adenocarcinoma cells revealed that adoptive transfer of HOZOT almost completely eradicated disseminated lesions on peritoneum, markedly reduced metastases in lung and liver, and dramatically decreased bloody ascites caused by peritoneal carcinomatosis. Treatment of the tumor model mice by HOZOT with an E:T ratio of 2:1 even indicated the prolongation of their survival, although not reaching obvious statistical significance. In vitro blocking experiments using antibodies and inhibitors suggested that the cytotoxic mechanism of HOZOT against tumors is different from conventional cytotoxic cells such as CTL, NK or NKT cells. Altogether, our studies demonstrated the potent killing activity of HOZOT against a broad range of human malignancies, which indicates that HOZOT is a powerful tool in immunotherapy for advanced stage tumors.

Interleukin-8 and RANTES are signature cytokines made by HOZOT, a new type of regulatory T cells.

Distinct cytokine production profiles define the effector functions of both helper and regulatory T cells. Recently, we established novel cytotoxic regulatory T (Treg) cell lines, HOZOT, which have been characterized as IL-10-producing T cells. In this study, we further characterized HOZOT by performing comprehensive analyses of cytokines produced by HOZOTs in order to identify a signature cytokine profile. Using DNA microarrays, we compared the gene expression profiles of HOZOT-4, a representative HOZOT cell line, under three different conditions. Seven genes, including IL-8, IL-10, IL-13, MIP-1alpha, and MIP-1beta, were identified as inducible cytokines when stimulated with stromal cells or anti-CD3/CD28 antibodies. Twelve genes, including IL-2, IL-3, IL-4, IL-22, CCL1, and lymphotactin, were categorized as antibody stimulation-responsive but stromal cell-non-responsive. Three genes, IL-32, RANTES, and CCL23, were constitutively expressed irrespective of stimulation condition. Among these cytokines, we focused on two chemokines, IL-8 and RANTES for further studies, and found that only HOZOT produced both of them at considerable levels whereas other T cell subsets, including Tregs and helper T cells, did not. Kinetic and inhibition experiments revealed contrasting properties for the two chemokines. IL-8 was induced only after stimulation, whereas RANTES mRNA and protein accumulated to high levels even before stimulation. Interestingly, IL-8 mRNA was induced by cycloheximide treatment and RANTES showed reduced mRNA but increased protein expression by antibody stimulation. As a whole, the unique cytokine signature profile consisting of Th1, Th2, and cytolytic T cell cytokines as well as Treg cytokines reflect the multifunctional nature of HOZOT. In particular, the dual production of IL-8 and RANTES by distinct mechanisms is a hallmark of HOZOT.

Demethylating agent, 5-azacytidine, reverses differentiation of embryonic stem cells.

The de novo methylation activity is essential for embryonic development as well as embryonic stem (ES) cell differentiation, where the intensive and extensive DNA methylation was detected. In this study, we investigated the effects of a demethylating agent, 5-azacytidine (5-AzaC), on differentiated ES cells in order to study the possibility of reversing the differentiation process. We first induced differentiation of ES cells by forming embryoid bodies, and then the cells were treated with 5-AzaC. The cells showed some undifferentiated features such as stem cell-like morphology with unclear cell-to-cell boundary and proliferative responsiveness to LIF. Moreover, 5-AzaC increased the expressions of ES specific markers, SSEA-1, and alkaline phosphatase activity as well as ES specific genes, Oct4, Nanog, and Sox2. We also found that 5-AzaC demethylated the promoter region of H19 gene, a typical methylated gene during embryonic differentiation. These results indicate that 5-AzaC reverses differentiation state of ES cells through its DNA demethylating activity to differentiation related genes.