Phosphatase inhibitor, sodium stibogluconate, in combination with interferon (IFN) alpha 2b: phase I trials to identify pharmacodynamic and clinical effects

Targeting small GTPases: emerging grasps on previously untamable targets, pioneered by KRAS

Small GTPases including Ras, Rho, Rab, Arf, and Ran are omnipresent molecular switches in regulating key cellular functions. Their dysregulation is a therapeutic target for tumors, neurodegeneration, cardiomyopathies, and infection. However, small GTPases have been historically recognized as "undruggable". Targeting KRAS, one of the most frequently mutated oncogenes, has only come into reality in the last decade due to the development of breakthrough strategies such as fragment-based screening, covalent ligands, macromolecule inhibitors, and PROTACs. Two KRAS^G12C covalent inhibitors have obtained accelerated approval for treating KRAS^G12C mutant lung cancer, and allele-specific hotspot mutations on G12D/S/R have been demonstrated as viable targets. New methods of targeting KRAS are quickly evolving, including transcription, immunogenic neoepitopes, and combinatory targeting with immunotherapy. Nevertheless, the vast majority of small GTPases and hotspot mutations remain elusive, and clinical resistance to G12C inhibitors poses new challenges. In this article, we summarize diversified biological functions, shared structural properties, and complex regulatory mechanisms of small GTPases and their relationships with human diseases. Furthermore, we review the status of drug discovery for targeting small GTPases and the most recent strategic progress focused on targeting KRAS. The discovery of new regulatory mechanisms and development of targeting approaches will together promote drug discovery for small GTPases.

Identification of Candidate Biomarker and Drug Targets for Improving Endometrial Cancer Racial Disparities

Racial disparities in incidence and survival exist for many human cancers. Racial disparities are undoubtedly multifactorial and due in part to differences in socioeconomic factors, access to care, and comorbidities. Within the U.S., fundamental causes of health inequalities, including socio-economic factors, insurance status, access to healthcare and screening and treatment biases, are issues that contribute to cancer disparities. Yet even these epidemiologic differences do not fully account for survival disparities, as for nearly every stage, grade and histologic subtype, survival among Black women is significantly lower than their White counterparts. To address this, we sought to investigate the proteomic profiling molecular features of endometrial cancer in order to detect modifiable and targetable elements of endometrial cancer in different racial groups, which could be essential for treatment planning. The majority of proteins identified to be significantly altered among the racial groups and that can be regulated by existing drugs or investigational agents are enzymes that regulate metabolism and protein synthesis. These drugs have the potential to improve the worse outcomes of endometrial cancer patients based on race.

Biomimetic and Materials-Potentiated Cell Engineering for Cancer Immunotherapy

In cancer immunotherapy, immune cells are the main force for tumor eradication. However, they appear to be dysfunctional due to the taming of the tumor immunosuppressive microenvironment. Recently, many materials-engineered strategies are proposed to enhance the anti-tumor effect of immune cells. These strategies either utilize biomimetic materials, as building blocks to construct inanimate entities whose functions are similar to natural living cells, or engineer immune cells with functional materials, to potentiate their anti-tumor effects. In this review, we will summarize these advanced strategies in different cell types, as well as discussing the prospects of this field.

Toward a Treatment of Cancer: Design and In Vitro/In Vivo Evaluation of Uncharged Pyrazoline Derivatives as a Series of Novel SHP2 Inhibitors

Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP2) is a non-receptor protein tyrosine phosphatase (PTP) encoded by the PTPN11 gene, which is involved in the RAS/MAPK cell signaling transduction process. SHP2 has been shown to contribute to the progression of various cancers and is emerging as an important target for anti-tumor drug research. However, past efforts to develop SHP2 inhibitors into drugs have been unsuccessful owing to the positively charged nature of the active site pocket tending to bind negatively charged groups that are usually non-drug-like. Here, a series of uncharged pyrazoline derivatives were designed and developed as new SHP2 inhibitors using a structure-based strategy. Compound 4o, which exhibited the strongest SHP2 inhibitory activity, bound directly to the catalytic domain of SHP2 in a competitive manner through multiple hydrogen bonds. Compound 4o affected the RAS/MAPK signaling pathway by inhibiting SHP2, and subsequently induced apoptosis and growth inhibition of HCT116 cells in vitro and in vivo. Notably, the oral administration of compound 4o in large doses showed no obvious toxicity. In summary, our findings provide a basis for the further development of compound 4o as a safe, effective and anti-tumor SHP2 inhibitor.

Sodium stibogluconate and CD47-SIRPα blockade overcome resistance of anti-CD20-opsonized B cells to neutrophil killing

SSG turns neutrophil trogocytosis of rituximab-opsonized malignant B cells into cell killing.

Neutrophil antibody–dependent killing of malignant B cells occurs primarily through FcγRI (CD64).

Anti-CD20 antibodies such as rituximab are broadly used to treat B-cell malignancies. These antibodies can induce various effector functions, including immune cell-mediated antibody-dependent cellular cytotoxicity (ADCC). Neutrophils can induce ADCC toward solid cancer cells by trogoptosis, a cytotoxic mechanism known to be dependent on trogocytosis. However, neutrophils seem to be incapable of killing rituximab-opsonized B-cell lymphoma cells. Nevertheless, neutrophils do trogocytose rituximab-opsonized B-cell lymphoma cells, but this only reduces CD20 surface expression and is thought to render tumor cells therapeutically resistant to further rituximab-dependent destruction. Here, we demonstrate that resistance of B-cell lymphoma cells toward neutrophil killing can be overcome by a combination of CD47-SIRPα checkpoint blockade and sodium stibogluconate (SSG), an anti-leishmaniasis drug and documented inhibitor of the tyrosine phosphatase SHP-1. SSG enhanced neutrophil-mediated ADCC of solid tumor cells but enabled trogoptotic killing of B-cell lymphoma cells by turning trogocytosis from a mechanism that contributes to resistance into a cytotoxic anti-cancer mechanism. Tumor cell killing in the presence of SSG required both antibody opsonization of the target cells and disruption of CD47-SIRPα interactions. These results provide a more detailed understanding of the role of neutrophil trogocytosis in antibody-mediated destruction of B cells and clues on how to further optimize antibody therapy of B-cell malignancies.

If small molecules immunotherapy comes, can the prime be far behind?

Anti-cancer immunotherapy, which includes cellular immunotherapy, immune checkpoint inhibitors and cancer vaccines, has transformed the treatment strategies of several malignancies in the past decades. Immune checkpoints blockade (ICB) is the most commonly tested therapy and has the potential to induce a durable immune response in different types of cancers. However, all approved immune checkpoint inhibitors (ICIs) are monoclonal antibodies (mAbs), which are fraught with disadvantages including lack of oral bioavailability, prolonged tissue retention and poor membrane permeability. Therefore, the research focus has shifted to developing small molecule inhibitors to obviate the limitations of mAbs. Given the complexity of the tumor micro-environment (TME), the combination of ICIs with various small molecule agonists/inhibitors are currently being tested in clinical trials to improve treatment outcomes and prevent tumor recurrence. In this review, we have summarized the mechanisms and therapeutic potential of several molecular targets, along with the current status of small molecule inhibitors.

Modulation of TCR Signaling by Tyrosine Phosphatases: From Autoimmunity to Immunotherapy

Early TCR signaling is dependent on rapid phosphorylation and dephosphorylation of multiple signaling and adaptor proteins, leading to T cell activation. This process is tightly regulated by an intricate web of interactions between kinases and phosphatases. A number of tyrosine phosphatases have been shown to modulate T cell responses and thus alter T cell fate by negatively regulating early TCR signaling. Mutations in some of these enzymes are associated with enhanced predisposition to autoimmunity in humans, and mouse models deficient in orthologous genes often show T cell hyper-activation. Therefore, phosphatases are emerging as potential targets in situations where it is desirable to enhance T cell responses, such as immune responses to tumors. In this review, we summarize the current knowledge about tyrosine phosphatases that regulate early TCR signaling and discuss their involvement in autoimmunity and their potential as targets for tumor immunotherapy.

CpG ODN D35 improves the response to abbreviated low-dose pentavalent antimonial treatment in non-human primate model of cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) affects the lives of 0.7–1 million people every year causing lesions that take months to heal. These lesions can result in disfiguring scars with psychological, social and economic consequences. Antimonials are the first line of therapy for CL, however the treatment is lengthy and linked to significant toxicities; further, its efficacy is variable and resistant parasites are emerging. Shorter or lower dose antimonial treatment regimens, which would decrease the risk of adverse events and improve patient compliance, have shown reduced efficacy and further increase the risk emergence of antimonial-resistant strains. The progression of lesions in CL is partly determined by the immune response it elicits, and previous studies showed that administration of immunomodulatory type D CpG ODNs, magnifies the immune response to Leishmania and reduces lesion severity in nonhuman primates (NHP) challenged with Leishmania major or Leishmania amazonensis. Here we explored whether the addition of a single dose of immunomodulating CpG ODN D35 augments the efficacy of a short-course, low-dose pentavalent antimonial treatment regimen. Results show that macaques treated with D35 plus 5mg/kg sodium stibogluconate (Sb^V) for 10 days had smaller lesions and reduced time to re-epithelization after infection with Leishmania major. No toxicities were evident during the studies, even at doses of D35 10 times higher than those used in treatment. Critically, pentavalent antimonial treatment did not modify the ability of D35 to induce type I IFNs. The findings support the efficacy of D35 as adjuvant therapy for shorter, low dose pentavalent antimonial treatment.

Cutaneous leishmaniasis is a devastating disease that affects close to a million people every year. Its clinical presentation ranges from small uncomplicated lesions that heal over a few months to debilitating large chronic or recurring lesions that result in disfigurement, stigma, and economic loss. Antimonials are the first line treatment for cutaneous leishmaniasis in most countries, but the lengthy treatment schedules, significant associated toxicities, and the emergence of resistant strains, require the development of alternative strategies. As the immune response is a key determinant of disease course, immunomodulatory therapies could be harnessed to act in concert with antimonials to improve the safety and efficacy of CL treatment. Synthetic oligonucleotide D35 selectively activates plasmacytoid dendritic cells and was previously shown to reduce the severity of L. major and L. amazonensis lesions in rhesus macaques, but its activity in combination with antimonials was unknown. Our studies show that a single subcutaneous dose of innate immune modulator D35 improved the response to a low-dose abbreviated antimonial course, reducing the severity of the lesions and accelerating healing in primates. No toxicities were evident with D35 at doses ten-fold higher than the effective dose. The studies suggest that the combined therapy strategy shows clinical promise.

Targeting SHP2 as a promising strategy for cancer immunotherapy

Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) is a major phosphatase involved in several cellular processes. In recent years, SHP2 has been the focus of significant attention in human diseases, particular in cancer. Several studies have shown that SHP2 plays an important role in regulating immune cell functions in tumor microenvironment. A few clinical trials conducted using SHP2 allosteric inhibitors have shown remarkable anti-tumor benefits and good safety profiles. This review focuses on the current understanding of the regulation of SHP2 and highlights the vital roles of SHP2 in T lymphocytes, macrophages and cancer cells. It also summarizes the current development of SHP2 inhibitors as a promising strategy for cancer immunotherapy.

Protein tyrosine phosphatase SHP-1: resurgence as new drug target for human autoimmune disorders

Recognition of self-antigen and its destruction by the immune system is the hallmark of autoimmune diseases. During the developmental stages, immune cells are introduced to the self-antigen, for which tolerance develops. The inflammatory insults that break the immune tolerance provoke immune system against self-antigen, progressively leading to autoimmune diseases. SH2 domain containing protein tyrosine phosphatase (PTP), SHP-1, was identified as hematopoietic cell-specific PTP that regulates immune function from developing immune tolerance to mediating cell signaling post-immunoreceptor activation. The extensive research on SHP-1-deficient mice elucidated the diversified role of SHP-1 in immune regulation, and inflammatory process and related disorders such as cancer, autoimmunity, and neurodegenerative diseases. The present review focalizes upon the implication of SHP-1 in the pathogenesis of autoimmune disorders, such as allergic asthma, neutrophilic dermatosis, atopic dermatitis, rheumatoid arthritis, and multiple sclerosis, so as to lay the background in pursuance of developing therapeutic strategies targeting SHP-1. Also, new SHP-1 molecular targets have been suggested like SIRP-α, PIPKIγ, and RIP-1 that may prove to be the focal point for the development of therapeutic strategies.

Role of SHP2 in hematopoiesis and leukemogenesis

PURPOSE OF REVIEW

SH2 domain-containing tyrosine phosphatase 2 (SHP2), encoded by PTPN11 plays an important role in regulating signaling from cell surface receptor tyrosine kinases during normal development as well as oncogenesis. Herein we review recently discovered roles of SHP2 in normal and aberrant hematopoiesis along with novel strategies to target it.

RECENT FINDINGS

Cell autonomous role of SHP2 in normal hematopoiesis and leukemogenesis has long been recognized. The review will discuss the newly discovered role of SHP2 in lineage specific differentiation. Recently, a noncell autonomous role of oncogenic SHP2 has been reported in which activated SHP2 was shown to alter the bone marrow microenvironment resulting in transformation of donor derived normal hematopoietic cells and development of myeloid malignancy. From being considered as an 'undruggable' target, recent development of allosteric inhibitor has made it possible to specifically target SHP2 in receptor tyrosine kinase driven malignancies.

SUMMARY

SHP2 has emerged as an attractive target for therapeutic targeting in hematological malignancies for its cell autonomous and microenvironmental effects. However a better understanding of the role of SHP2 in different hematopoietic lineages and its crosstalk with signaling pathways activated by other genetic lesions is required before the promise is realized in the clinic.

Molecular Pathways: Targeting Protein Tyrosine Phosphatases in Cancer

The aberrant activation of oncogenic signaling pathways is a universal phenomenon in cancer and drives tumorigenesis and malignant transformation. This abnormal activation of signaling pathways in cancer is due to the altered expression of protein kinases and phosphatases. In response to extracellular signals, protein kinases activate downstream signaling pathways through a series of protein phosphorylation events, ultimately producing a signal response. Protein tyrosine phosphatases (PTP) are a family of enzymes that hydrolytically remove phosphate groups from proteins. Initially, PTPs were shown to act as tumor suppressor genes by terminating signal responses through the dephosphorylation of oncogenic kinases. More recently, it has become clear that several PTPs overexpressed in human cancers do not suppress tumor growth; instead, they positively regulate signaling pathways and promote tumor development and progression. In this review, we discuss both types of PTPs: those that have tumor suppressor activities as well as those that act as oncogenes. We also discuss the potential of PTP inhibitors for cancer therapy. Clin Cancer Res; 23(9); 2136-42. ©2017 AACR.

Preclinical evaluation of a nanoformulated antihelminthic, niclosamide, in ovarian cancer

Ovarian cancer treatment remains a challenge and targeting cancer stem cells presents a promising strategy. Niclosamide is an “old” antihelminthic drug that uncouples mitochondria of intestinal parasites. Although recent studies demonstrated that niclosamide could be a potential anticancer agent, its poor water solubility needs to be overcome before further preclinical and clinical investigations can be conducted. Therefore, we evaluated a novel nanosuspension of niclosamide (nano-NI) for its effect against ovarian cancer. Nano-NI effectively inhibited the growth of ovarian cancer cells in which it induced a metabolic shift to glycolysis at a concentration of less than 3 μM in vitro and suppressed tumor growth without obvious toxicity at an oral dose of 100 mg/kg in vivo. In a pharmacokinetic study after oral administration, nano-NI showed rapid absorption (reaching the maximum plasma concentration within 5 min) and improved the bioavailability (the estimated bioavailability for oral nano-NI was 25%). In conclusion, nano-NI has the potential to be a new treatment modality for ovarian cancer and, therefore, further clinical trials are warranted.

Breaking Free of Control: How Conventional T Cells Overcome Regulatory T Cell Suppression

Conventional T (Tcon) cells are crucial in shaping the immune response, whether it is protection against a pathogen, a cytotoxic attack on tumor cells, or an unwanted response to self-antigens in the context of autoimmunity. In each of these immune settings, regulatory T cells (Tregs) can potentially exert control over the Tcon cell response, resulting in either suppression or activation of the Tcon cells. Under physiological conditions, Tcon cells are able to transiently overcome Treg-imposed restraints to mount a protective response against an infectious threat, achieving clonal expansion, differentiation, and effector function. However, evidence has accumulated in recent years to suggest that Tcon cell resistance to Treg-mediated suppression centrally contributes to the pathogenesis of autoimmune disease. Tipping the balance too far in the other direction, cancerous tumors utilize Tregs to establish an overly suppressive microenvironment, preventing antitumor Tcon cell responses. Given the wide-ranging clinical importance of the Tcon/Treg interaction, this review aims to provide a better understanding of what determines whether a Tcon cell is susceptible to Treg-mediated suppression and how perturbations to this finely tuned balance play a role in pathological conditions. Here, we focus in detail on the complex array of factors that confer Tcon cells with resistance to Treg suppression, which we have divided into two categories: (1) extracellular factor-mediated signaling and (2) intracellular signaling molecules. Further, we explore the therapeutic implications of manipulating the phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway, which is proposed to be the convergence point of signaling pathways that mediate Tcon resistance to suppression. Finally, we address important unresolved questions on the timing and location of acquisition of resistance, and the stability of the “Treg-resistant” phenotype.

Inhibition of Src homology 2 domain-containing phosphatase 1 increases insulin sensitivity in high-fat diet-induced insulin-resistant mice

Insulin resistance plays a crucial role in the development of type 2 diabetes. Insulin receptor signalling is antagonized and tightly controlled by protein tyrosine phosphatases (PTPs). However, the precise role of the PTP src homology 2 domain‐containing phosphatase 1 (SHP‐1) in insulin resistance has not been explored. Male C57BL/6J mice were fed a high‐fat diet (HFD, 60% kcal from fat), to induce insulin resistance, or a low‐fat diet (LFD, 10% kcal from fat) for 10 weeks. Afterwards, HFD‐fed mice were pharmacologically treated with the SHP‐1 (Ptpn6) inhibitor sodium stibogluconate and the broad spectrum pan‐PTP inhibitor bis(maltolato)oxovanadium(IV) (BMOV). Both inhibitors ameliorated the metabolic phenotype, as evidenced by reduced body weight, improved insulin sensitivity and glucose tolerance, which was not due to altered PTP gene expression. In parallel, phosphorylation of the insulin receptor and of the insulin signalling key intermediate Akt was enhanced, and both PTP inhibitors and siRNA‐mediated SHP‐1 downregulation resulted in an increased glucose uptake in vitro. Finally, recombinant SHP‐1 was capable of dephosphorylating the ligand‐induced tyrosine‐phosphorylated insulin receptor. These results indicate a central role of SHP‐1 in insulin signalling during obesity, and SHP‐1 inhibition as a potential therapeutic approach in metabolic diseases.

Mutations in tyrosine kinase and tyrosine phosphatase and their relevance to the target therapy in hematologic malignancies

Protein tyrosine kinases and protein tyrosine phosphatases play pivotal roles in regulation of cellular phosphorylation and signal transduction with opposite functions. Accumulating evidences have uncovered the relevance of genetic alterations in these two family members to hematologic malignancies. This review underlines progress in understanding the pathogenesis of these genetic alterations including mutations and aberrant expression and the evolving protein tyrosine kinases and protein tyrosine phosphatases targeted therapeutic strategies in hematologic neoplasms.

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.

Targeting protein tyrosine phosphatase SHP2 for therapeutic intervention

Protein tyrosine phosphatases have been the focus of considerable research efforts aimed at developing novel therapeutics; however, these targets are often characterized as being ‘undruggable’ due to the challenge of achieving selectivity, potency and cell permeability. More recently, there has been renewed interest in developing inhibitors of the tyrosine phosphatase SHP2 (PTPN11) in the light of its broad role in cancer, specifically juvenile myelomonocytic leukemia, and recent studies that implicate SHP2 as a key factor in breast cancer progression. Recent significant advances in the field of SHP2 inhibitor development raise the question: are we on the verge of a new era of protein tyrosine phosphatase-directed therapeutics? This article critically appraises recent developments, assesses ongoing challenges and presents a perspective on possible future directions.

Common drugs and treatments for cancer and age-related diseases: revitalizing answers to NCI's provocative questions

In 2011, The National Cancer Institute (NCI) has announced 24 provocative questions on cancer. Some of these questions have been already answered in “NCI's provocative questions on cancer: some answers to ignite discussion” (published in Oncotarget, 2011, 2: 1352.) The questions included “Why do many cancer cells die when suddenly deprived of a protein encoded by an oncogene?” “Can we extend patient survival by using approaches that keep tumors static?” “Why are some disseminated cancers cured by chemotherapy alone?” “Can we develop methods to rapidly test interventions for cancer treatment or prevention?” “Can we use our knowledge of aging to enhance prevention or treatment of cancer?” “What is the mechanism by which some drugs commonly and chronically used for other indications protect against cancer?” “How does obesity contribute to cancer risk?” I devoted a single subchapter to each the answer. As expected, the provocative questions were very diverse and numerous. Now I choose and combine, as a single problem, only three last questions, all related to common mechanisms and treatment of age-related diseases including obesity and cancer. Can we use common existing drugs for cancer prevention and treatment? Can we use some targeted “cancer-selective” agents for other diseases and … aging itself.

Recent discoveries in the cycling, growing and aging of the p53 field

The P53 gene and it product p53 protein is the most studied tumor suppressor, which was considered as oncogene for two decades until 1990. More than 60 thousand papers on the topic of p53 has been abstracted in Pubmed. What yet could be discovered about its role in cell death, growth arrest and apoptosis, as well as a mediator of the therapeutic effect of anticancer drugs. Still during recent few years even more amazing discoveries have been done. Here we review such topics as suppression of epigenetic silencing of a large number of non-coding RNAs, role of p53 in suppression of the senescence phenotype, inhibition of oncogenic metabolism, protection of normal cells from chemotherapy and even tumor suppression without apoptosis and cell cycle arrest.

Protein tyrosine phosphatases as novel targets in breast cancer therapy

Breast cancer is linked to hyperactivation of protein tyrosine kinases (PTKs), and recent studies have unveiled that selective tyrosine dephosphorylation by protein tyrosine phosphatases (PTPs) of specific substrates, including PTKs, may activate or inactivate oncogenic pathways in human breast cancer cell growth-related processes. Here, we review the current knowledge on the involvement of PTPs in breast cancer, as major regulators of breast cancer therapy-targeted PTKs, such as HER1/EGFR, HER2/Neu, and Src. The functional interplay between PTKs and PTK-activating or -inactivating PTPs, and its implications in novel breast cancer therapies based on targeting of specific PTPs, are discussed.

SHP-1 phosphatase activity counteracts increased T cell receptor affinity

Anti-self/tumor T cell function can be improved by increasing TCR-peptide MHC (pMHC) affinity within physiological limits, but paradoxically further increases (K(d) < 1 μM) lead to drastic functional declines. Using human CD8(+) T cells engineered with TCRs of incremental affinity for the tumor antigen HLA-A2/NY-ESO-1, we investigated the molecular mechanisms underlying this high-affinity-associated loss of function. As compared with cells expressing TCR affinities generating optimal function (K(d) = 5 to 1 μM), those with supraphysiological affinity (K(d) = 1 μM to 15 nM) showed impaired gene expression, signaling, and surface expression of activatory/costimulatory receptors. Preferential expression of the inhibitory receptor programmed cell death-1 (PD-1) was limited to T cells with the highest TCR affinity, correlating with full functional recovery upon PD-1 ligand 1 (PD-L1) blockade. In contrast, upregulation of the Src homology 2 domain-containing phosphatase 1 (SHP-1/PTPN6) was broad, with gradually enhanced expression in CD8(+) T cells with increasing TCR affinities. Consequently, pharmacological inhibition of SHP-1 with sodium stibogluconate augmented the function of all engineered T cells, and this correlated with the TCR affinity-dependent levels of SHP-1. These data highlight an unexpected and global role of SHP-1 in regulating CD8(+) T cell activation and responsiveness and support the development of therapies inhibiting protein tyrosine phosphatases to enhance T cell-mediated immunity.

Synapse-directed delivery of immunomodulators using T-cell-conjugated nanoparticles

Regulating molecular interactions in the T-cell synapse to prevent autoimmunity or, conversely, to boost anti-tumor immunity has long been a goal in immunotherapy. However, delivering therapeutically meaningful doses of immune-modulating compounds into the synapse represents a major challenge. Here, we report that covalent coupling of maleimide-functionlized nanoparticles (NPs) to free thiol groups on T-cell membrane proteins enables efficient delivery of compounds into the T-cell synapse. We demonstrate that surface-linked NPs are rapidly polarized toward the nascent immunological synapse (IS) at the T-cell/APC contact zone during antigen recognition. To translate these findings into a therapeutic application we tested the NP delivery of NSC-87877, a dual inhibitor of Shp1 and Shp2, key phosphatases that downregulate T-cell receptor activation in the synapse, in the context of adoptive T cell therapy of cancer. Conjugating NSC-87877-loaded NPs to the surface of tumor-specific T cells just prior to adoptive transfer into mice with advanced prostate cancer promoted a much greater T-cell expansion at the tumor site, relative to co-infusing the same drug dose systemically, leading to enhanced survival of treated animals. In summary, our studies support the application of T-cell-linked synthetic NPs as efficient drug delivery vehicles into the IS, as well as the broad applicability of this new paradigm for therapeutically modulating signaling events at the T-cell/APC interface.