Osteopontin-integrin interaction as a novel molecular target for antibody-mediated immunotherapy in adult T-cell leukemia

Aberrant stem cell and developmental programs in pediatric leukemia

Hematopoiesis is a finely orchestrated process, whereby hematopoietic stem cells give rise to all mature blood cells. Crucially, they maintain the ability to self-renew and/or differentiate to replenish downstream progeny. This process starts at an embryonic stage and continues throughout the human lifespan. Blood cancers such as leukemia occur when normal hematopoiesis is disrupted, leading to uncontrolled proliferation and a block in differentiation of progenitors of a particular lineage (myeloid or lymphoid). Although normal stem cell programs are crucial for tissue homeostasis, these can be co-opted in many cancers, including leukemia. Myeloid or lymphoid leukemias often display stem cell-like properties that not only allow proliferation and survival of leukemic blasts but also enable them to escape treatments currently employed to treat patients. In addition, some leukemias, especially in children, have a fetal stem cell profile, which may reflect the developmental origins of the disease. Aberrant fetal stem cell programs necessary for leukemia maintenance are particularly attractive therapeutic targets. Understanding how hijacked stem cell programs lead to aberrant gene expression in place and time, and drive the biology of leukemia, will help us develop the best treatment strategies for patients.

Targeting integrins in drug-resistant acute myeloid leukaemia

Acute myeloid leukaemia (AML) continues to have a poor prognosis, warranting new therapeutic strategies. The bone marrow (BM) microenvironment consists of niches that interact with not only normal haematopoietic stem cells (HSC) but also leukaemia cells like AML. There are many adhesion molecules in the BM microenvironment; therein, integrins have been of central interest. AML cells express integrins that bind to ligands in the microenvironment, enabling adhesion of leukaemia cells in the microenvironment, thereby initiating intracellular signalling pathways that are associated with cell migration, cell proliferation, survival, and drug resistance that has been described to mediate cell adhesion-mediated drug resistance (CAM-DR). Identifying and targeting integrins in AML to interrupt interactions with the microenvironment have been pursued as a strategy to overcome CAM-DR. Here, we focus on the BM microenvironment and review the role of integrins in CAM-DR of AML and discuss integrin-targeting strategies. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Thrombin Cleavage of Osteopontin and the Host Anti-Tumor Immune Response

Osteopontin (OPN) is a multi-functional protein that is involved in various cellular processes such as cell adhesion, migration, and signaling. There is a single conserved thrombin cleavage site in OPN that, when cleaved, yields two fragments with different properties from full-length OPN. In cancer, OPN has tumor-promoting activity and plays a role in tumor growth and metastasis. High levels of OPN expression in cancer cells and tumor tissue are found in various types of cancer, including breast, lung, prostate, ovarian, colorectal, and pancreatic cancer, and are associated with poor prognosis and decreased survival rates. OPN promotes tumor progression and invasion by stimulating cell proliferation and angiogenesis and also facilitates the metastasis of cancer cells to other parts of the body by promoting cell adhesion and migration. Furthermore, OPN contributes to immune evasion by inhibiting the activity of immune cells. Thrombin cleavage of OPN initiates OPN's tumor-promoting activity, and thrombin cleavage fragments of OPN down-regulate the host immune anti-tumor response.

The Interplay between Integrins and Immune Cells as a Regulator in Cancer Immunology

Integrins are a group of heterodimers consisting of α and β subunits that mediate a variety of physiological activities of immune cells, including cell migration, adhesion, proliferation, survival, and immunotolerance. Multiple types of integrins act differently on the same immune cells, while the same integrin may exert various effects on different immune cells. In the development of cancer, integrins are involved in the regulation of cancer cell proliferation, invasion, migration, and angiogenesis; conversely, integrins promote immune cell aggregation to mediate the elimination of tumors. The important roles of integrins in cancer progression have provided valuable clues for the diagnosis and targeted treatment of cancer. Furthermore, many integrin inhibitors have been investigated in clinical trials to explore effective regimens and reduce side effects. Due to the complexity of the mechanism of integrin-mediated cancer progression, challenges remain in the research and development of cancer immunotherapies (CITs). This review enumerates the effects of integrins on four types of immune cells and the potential mechanisms involved in the progression of cancer, which will provide ideas for more optimal CIT in the future.

Both Full-Length and Protease-Cleaved Products of Osteopontin Are Elevated in Infectious Diseases

Circulating full-length osteopontin (FL-OPN) is elevated in plasma from patients with various infectious diseases, such as adult T-cell leukemia, Mycobacterium tuberculosis (TB), hepatitis virus infection, leptospirosis, acquired immune deficiency syndrome (AIDS), AIDS/TB, and coronavirus disease 2019 (COVID-19). Proteolysis of OPN by thrombin, matrix metalloproteases, caspase 8/3, cathepsin D, plasmin, and enterokinase generates various cleaved OPNs with a variety of bioactivities by binding to different target cells. Moreover, OPN is susceptible to gradual proteolysis. During inflammation, one of the cleaved fragments, N-terminal thrombin-cleaved OPN (trOPN or OPN-Arg¹⁶⁸ [OPN-R]), induces dendritic cell (DC) adhesion. Further cleavage by carboxypeptidase B2 or carboxypeptidase N removes Arg¹⁶⁸ from OPN-R to OPN-Leu¹⁶⁷ (OPN-L). Consequently, OPN-L decreases DC adhesion. In particular, the differences in plasma level over time are observed between FL-OPN and its cleaved OPNs during inflammation. We found that the undefined OPN levels (mixture of FL-OPN and cleaved OPN) were elevated in plasma and reflected the pathology of TB and COVID-19 rather than FL-OPN. These infections are associated with elevated levels of various proteases. Inhibition of the cleavage or the activities of cleaved products may improve the outcome of the therapy. Research on the metabolism of OPN is expected to create new therapies against infectious diseases.

HTLV-1 Infection and Pathogenesis: New Insights from Cellular and Animal Models

Since the discovery of the human T-cell leukemia virus-1 (HTLV-1), cellular and animal models have provided invaluable contributions in the knowledge of viral infection, transmission and progression of HTLV-associated diseases. HTLV-1 is the causative agent of the aggressive adult T-cell leukemia/lymphoma and inflammatory diseases such as the HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). Cell models contribute to defining the role of HTLV proteins, as well as the mechanisms of cell-to-cell transmission of the virus. Otherwise, selected and engineered animal models are currently applied to recapitulate in vivo the HTLV-1 associated pathogenesis and to verify the effectiveness of viral therapy and host immune response. Here we review the current cell models for studying virus–host interaction, cellular restriction factors and cell pathway deregulation mediated by HTLV products. We recapitulate the most effective animal models applied to investigate the pathogenesis of HTLV-1-associated diseases such as transgenic and humanized mice, rabbit and monkey models. Finally, we summarize the studies on STLV and BLV, two closely related HTLV-1 viruses in animals. The most recent anticancer and HAM/TSP therapies are also discussed in view of the most reliable experimental models that may accelerate the translation from the experimental findings to effective therapies in infected patients.

Silencing Osteopontin Expression Inhibits Proliferation, Invasion and Induce Altered Protein Expression in Melanoma Cells

Osteopontin (OPN) is a multifunctional phosphoprotein that is expressed in different types of cancers, including melanoma. OPN overexpression is associated with tumor progression and metastasis formation; however, the role of OPN in cell invasion and metastasis formation is not completely understood. In this study we aimed to define OPN expression in melanoma tissues and cell lines and investigate the effect of OPN expression on cell proliferation and invasion after inhibiting OPN expression with small interfering RNA (siRNA). OPN gene expression was determined by qRT-PCR, while protein expression was examined using a Proteome Profiler Oncology Array. siRNA-mediated OPN knockdown led to decreased OPN expression in melanoma cell lines, which was associated with decreased cell proliferation and invasion. Proteome profile analysis revealed significantly different protein expression between the original and transfected cell lines. The altered expression of the differently expressed proteins was validated at the mRNA level. Furthermore, OPN-specific siRNA was able to reduce OPN expression and inhibit the invasiveness of melanoma cells. Our results revealed for the first time that silencing the OPN gene influences proliferation and invasion of melanoma cells by effecting EGFR, tenascin C, survivin, galectin-3 and enolase 2 expression. To predict protein-protein interactions along with putative pathways we used STRING analysis for the differentially expressed proteins. These proteins formed multiple clusters, including extracellular matrix organization, regulation of angiogenesis, cell death and cell migration, PI3K-Akt, MAPK and focal adhesion signaling pathways. Taken together these data suggest that OPN might be an ideal target for drug development and therapies.

Osteopontin Blockade Immunotherapy Increases Cytotoxic T Lymphocyte Lytic Activity and Suppresses Colon Tumor Progression

Simple Summary

Despite the breakthrough in human cancer immunotherapy, colorectal cancer, except for the small subset of microsatellite instable colorectal cancer (MSI, ~4% total cases), is one of the few human cancers that does not respond to current immune checkpoint inhibitor (ICI) immunotherapy. CTLs are present in both MSI and microsatellite stable (MSS) human colon carcinoma, suggesting that PD-L1-independent mechanisms may exist and suppress CTL activation in the colon tumor microenvironment. We determined that osteopontin (OPN) inhibits tumor-specific cytotoxic T lymphocyte (CTL) lytic activity to promote colon tumor growth in vivo. Accordingly, OPN blockade immunotherapy using OPN neutralization monoclonal antibodies 100D3 and 103D6 suppressed colon tumor growth in vivo. Our findings indicate that 100D3 and 103D6 has the potential to be further developed for colorectal cancer immunotherapy.

Abstract

Human colorectal cancers are mostly microsatellite-stable with no response to anti-PD-1 blockade immunotherapy, necessitating the development of a new immunotherapy. Osteopontin (OPN) is elevated in human colorectal cancer and may function as an immune checkpoint. We aimed at elucidating the mechanism of action of OPN and determining the efficacy of OPN blockade immunotherapy in suppression of colon cancer. We report here that OPN is primarily expressed in tumor cells, myeloid cells, and innate lymphoid cells in human colorectal carcinoma. Spp1 knock out mice exhibit a high incidence and fast growth rate of carcinogen-induced tumors. Knocking out Spp1 in colon tumor cells increased tumor-specific CTL cytotoxicity in vitro and resulted in decreased tumor growth in vivo. The OPN protein level is elevated in the peripheral blood of tumor-bearing mice. We developed four OPN neutralization monoclonal antibodies based on their efficacy in blocking OPN inhibition of T cell activation. OPN clones 100D3 and 103D6 increased the efficacy of tumor-specific CTLs in killing colon tumor cells in vitro and suppressed colon tumor growth in tumor-bearing mice in vivo. Our data indicate that OPN blockade immunotherapy with 100D3 and 103D6 has great potential to be further developed for colorectal cancer immunotherapy and for rendering a colorectal cancer response to anti-PD-1 immunotherapy.

The extracellular matrix: A key player in the pathogenesis of hematologic malignancies

Hematopoietic stem and progenitor cells located in the bone marrow lay the foundation for multiple lineages of mature hematologic cells. Bone marrow niches are architecturally complex with specific cellular, physiochemical, and biomechanical factors. Increasing evidence suggests that the bone marrow microenvironment contributes to the pathogenesis of hematological neoplasms. Numerous studies have deciphered the role of genetic mutations and chromosomal translocations in the development hematologic malignancies. Significant progress has also been made in understanding how the cellular components and cytokine interactions within the bone marrow microenvironment promote the evolution of hematologic cancers. Although the extracellular matrix is known to be a key player in the pathogenesis of various diseases, it's role in the progression of hematologic malignancies is less understood. In this review, we discuss the interactions between the extracellular matrix and malignant cells, and provide an overview of the role of extracellular matrix remodeling in sustaining hematologic malignancies.

Osteopontin: A Key Regulator of Tumor Progression and Immunomodulation

Simple Summary

Anti-PD-1/PD-L1 and anti-CTLA-4-based immune checkpoint blockade (ICB) immunotherapy have recently emerged as a breakthrough in human cancer treatment. Durable efficacy has been achieved in many types of human cancers. However, not all human cancers respond to current ICB immunotherapy and only a fraction of the responsive cancers exhibit efficacy. Osteopontin (OPN) expression is highly elevated in human cancers and functions as a tumor promoter. Emerging data suggest that OPN may also regulate immune cell function in the tumor microenvironment. This review aims at OPN function in human cancer progression and new findings of OPN as a new immune checkpoint. We propose that OPN compensates PD-L1 function to promote tumor immune evasion, which may underlie human cancer non-response to current ICB immunotherapy.

Abstract

OPN is a multifunctional phosphoglycoprotein expressed in a wide range of cells, including osteoclasts, osteoblasts, neurons, epithelial cells, T, B, NK, NK T, myeloid, and innate lymphoid cells. OPN plays an important role in diverse biological processes and is implicated in multiple diseases such as cardiovascular, diabetes, kidney, proinflammatory, fibrosis, nephrolithiasis, wound healing, and cancer. In cancer patients, overexpressed OPN is often detected in the tumor microenvironment and elevated serum OPN level is correlated with poor prognosis. Initially identified in activated T cells and termed as early T cell activation gene, OPN links innate cells to adaptive cells in immune response to infection and cancer. Recent single cell RNA sequencing revealed that OPN is primarily expressed in tumor cells and tumor-infiltrating myeloid cells in human cancer patients. Emerging experimental data reveal a key role of OPN is tumor immune evasion through regulating macrophage polarization, recruitment, and inhibition of T cell activation in the tumor microenvironment. Therefore, in addition to its well-established direct tumor cell promotion function, OPN also acts as an immune checkpoint to negatively regulate T cell activation. The OPN protein level is highly elevated in peripheral blood of human cancer patients. OPN blockade immunotherapy with OPN neutralization monoclonal antibodies (mAbs) thus represents an attractive approach in human cancer immunotherapy.

Successful Amplified-Natural-Killer Cell (ANK) Therapy Administered to a Patient with Smoldering Adult T-Cell Leukemia in Acute Crisis

Adult T-cell leukemia (ATL) is an indolent leukemia caused by type 1 human T-cell leukemia virus (HTLV-1). A variety of therapeutic interventions via immunological approaches have been attempted. ATL cells express costimulatory molecules of natural killer (NK) cells, and a new modality—amplified NK (ANK) cell treatment—was administered here to a patient with ATL. A 70-year-old female presenting with ringworm infection received a diagnosis of smoldering ATL in 2004. Monitoring of soluble IL-2 receptors (sIL-2Rs) in the serum showed disease exacerbation in 2007, associated with the enlargement of lymph nodes and formation of a skin tumor. NK cells were amplified by in vitro cell culture methods. To avoid cytokine release syndrome, 2–5 × 108 cells were administered with each injection. A total of 15 injections from 12 November 2007 to 15 February 2008 were administered to this patient. This case showed drastic downregulation of sIL-2R, resulting in the induction of complete remission, which lasted for >5 years. This is the first report of treatment of a patient with ATL using ANK cell therapy. More attempts of this therapy will enhance our insight into the appropriate application of this new therapy to clinically diverse patients.

Assessing the Feasibility of Neutralizing Osteopontin with Various Therapeutic Antibody Modalities

Osteopontin is a secreted glycophosphoprotein that is highly implicated in many physiological and pathological processes such as biomineralization, cell-mediated immunity, inflammation, fibrosis, cell survival, tumorigenesis and metastasis. Antibodies against osteopontin have been actively pursued as potential therapeutics for various diseases by pharmaceutical companies and academic laboratories. Many studies have demonstrated the efficacy of osteopontin inhibition in a variety of preclinical models of diseases such as rheumatoid arthritis, cancer, nonalcoholic steatohepatitis, but clinical utility has not yet been demonstrated. To evaluate the feasibility of osteopontin neutralization with antibodies in a clinical setting, we measured its physiological turnover rate in humans, a sensitive parameter required for mechanistic pharmacokinetic and pharmacodynamic (PK/PD) modeling of biotherapeutics. Results from a stable isotope-labelled amino acid pulse-chase study in healthy human subjects followed by mass spectrometry showed that osteopontin undergoes very rapid turnover. PK/PD modeling and simulation of different theoretical scenarios reveal that achieving sufficient target coverage using antibodies can be very challenging mostly due to osteopontin’s fast turnover, as well as its relatively high plasma concentrations in human. Therapeutic antibodies against osteopontin would need to be engineered to have much extended PK than conventional antibodies, and be administered at high doses and with short dosing intervals.

Mouse Models That Enhanced Our Understanding of Adult T Cell Leukemia

Adult T cell Leukemia (ATL) is an aggressive lymphoproliferative malignancy secondary to infection by the human T-cell leukemia virus type I (HTLV-I) and is associated with a dismal prognosis. ATL leukemogenesis remains enigmatic. In the era of precision medicine in oncology, mouse models offer one of the most efficient in vivo tools for the understanding of the disease biology and developing novel targeted therapies. This review provides an up-to-date and comprehensive account of mouse models developed in the context of ATL and HTLV-I infection. Murine ATL models include transgenic animals for the viral proteins Tax and HBZ, knock-outs for key cellular regulators, xenografts and humanized immune-deficient mice. The first two groups provide a key understanding of the role of viral and host genes in the development of ATL, as well as their relationship with the immunopathogenic processes. The third group represents a valuable platform to test new targeted therapies against ATL.

The Roles of Matricellular Proteins in Oncogenic Virus-Induced Cancers and Their Potential Utilities as Therapeutic Targets

Matricellular proteins differ from other classical extracellular matrix proteins; for instance, they are transiently expressed as soluble proteins rather than being constitutively expressed in pathological conditions, such as acute viral infections. Accumulating studies have revealed that matricellular proteins, including osteopontin and tenascin-C, both of which interact with integrin heterodimers, are involved in inflammatory diseases, autoimmune disorders, and cancers. The concentrations of these matricellular proteins are elevated in the plasma of patients with certain types of cancers, indicating that they play important roles in oncogenesis. Chronic viral infections are associated with certain cancers, which are distinct from non-viral cancers. Viral oncogenes play critical roles in the development and progression of such cancers. It is vital to investigate the mechanisms of tumorigenesis and, particularly, the mechanism by which viral proteins induce tumor progression. Viral proteins have been shown to influence not only the viral-infected cancer cells, but also the stromal cells and matricellular proteins that constitute the extracellular matrix that surrounds tumor tissues. In this review, we summarize the recent progress on the involvement of matricellular proteins in oncogenic virus-induced cancers to elucidate the mechanism of oncogenesis and consider the possible role of matricellular proteins as therapeutic targets in virus-induced cancers.

Elevated levels of circulating osteopontin are associated with a poor survival after resection of cholangiocarcinoma

BACKGROUND & AIMS

Cholangiocarcinoma (CCA) represents a primary hepatic malignancy with incidence and mortality rising globally. Surgical treatment has remained the only potentially curative treatment option, but it is still unclear which patients benefit most from extended liver surgery, highlighting the need for new pre-operative stratification strategies. Osteopontin is a secreted extracellular glyco-phosphoprotein that has been associated with inflammation, metabolic disorders and cancer. Here, we examined the potential of circulating osteopontin serum levels as a diagnostic or prognostic biomarker in patients with CCA undergoing extended liver surgery.

METHODS

Osteopontin expression levels were analysed in human and murine CCA tumour samples, using semi-quantitative reverse transcriptase PCR and immunohistochemistry. Osteopontin serum concentrations were measured by enzyme-linked immunosorbent assay in 107 patients with CCA undergoing elective tumour resection as well as 55 healthy controls. Results were correlated with clinical data.

RESULTS

Correlating with an upregulation in CCA tumour cells and the tumour stroma, serum levels of osteopontin were elevated in patients with cholangiocarcinoma compared to healthy controls and patients with primary sclerosing cholangitis. Importantly, pre- and postoperative elevations of osteopontin showed a striking association with poor postoperative survival.

CONCLUSIONS

Serum osteopontin concentrations represent a promising prognostic biomarker in patients resectable CCA which could help to guide preoperative treatment decisions and to identify patients that will particularly benefit from extended liver surgery. Lay summary: Extended liver surgery is the only potentially curative treatment for patients with cholangiocarcinoma (CCA/biliary cancer), but it is currently unclear which patients benefit most from surgery. Detecting serum levels of osteopontin - a specific secreted glycoprotein involved in multiple human diseases - in CCA patients might help to identify those patients that particularly benefit from tumour resection.

Osteopontin and their roles in hematological malignancies: Splice variants on the new avenues

Osteopontin (OPN) is a protein expressed in several tissues, including bone marrow, in which it performs distinct roles, such as modulating hematopoietic stem cell niche and bone remodeling. Most data in hematological malignancies (HMs) refers to total OPN (tOPN), comprehending the sum of distinct OPN splicing isoforms (OPN-SI), while reports describing the expression and roles of each OPN-SI are scarce. This review aims to summarize tOPN roles in HMs and provide evidence that OPN-SIs can also modulate specific functions in HMs biology. We summarize that upregulated tOPN can modulate HMs (leukemia, lymphoma and myeloma) progression, inducing cell adhesion, invasion, angiogenesis, cell differentiation and extramedullary and/or central nervous system infiltration. Based on this expression pattern, tOPN has been pointed out as a biomarker in those HMs, thus providing potential targets for therapeutic approaches. Our group found that OPN-SIs are expressed in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cell lines (unpublished data), providing early evidence that OPN-SIs are also expressed in BCP-ALL. Further studies should investigate whether these OPN-SIs can differently modulate HMs biology and their putative application as auxiliary biomarkers for HMs.

Adult T-cell leukemia: molecular basis for clonal expansion and transformation of HTLV-1-infected T cells

Adult T-cell leukemia (ATL) is an aggressive T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1) that develops through a multistep carcinogenesis process involving 5 or more genetic events. We provide a comprehensive overview of recently uncovered information on the molecular basis of leukemogenesis in ATL. Broadly, the landscape of genetic abnormalities in ATL that include alterations highly enriched in genes for T-cell receptor-NF-κB signaling such as PLCG1, PRKCB, and CARD11 and gain-of function mutations in CCR4 and CCR7 Conversely, the epigenetic landscape of ATL can be summarized as polycomb repressive complex 2 hyperactivation with genome-wide H3K27 me3 accumulation as the basis of the unique transcriptome of ATL cells. Expression of H3K27 methyltransferase enhancer of zeste 2 was shown to be induced by HTLV-1 Tax and NF-κB. Furthermore, provirus integration site analysis with high-throughput sequencing enabled the analysis of clonal composition and cell number of each clone in vivo, whereas multicolor flow cytometric analysis with CD7 and cell adhesion molecule 1 enabled the identification of HTLV-1-infected CD4+ T cells in vivo. Sorted immortalized but untransformed cells displayed epigenetic changes closely overlapping those observed in terminally transformed ATL cells, suggesting that epigenetic abnormalities are likely earlier events in leukemogenesis. These new findings broaden the scope of conceptualization of the molecular mechanisms of leukemogenesis, dissecting them into immortalization and clonal progression. These recent findings also open a new direction of drug development for ATL prevention and treatment because epigenetic marks can be reprogrammed. Mechanisms underlying initial immortalization and progressive accumulation of these abnormalities remain to be elucidated.