Interferon-gamma is induced in human peripheral blood immune cells in vitro by sodium stibogluconate/interleukin-2 and mediates its antitumor activity in vivo

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.

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.

Potential Use of Gluconate in Cancer Therapy

We have recently discovered that cancer cells take up extracellular citrate through plasma membrane citrate transporter (pmCiC) and advantageously use citrate for their metabolism. Citrate uptake can be blocked with gluconate and this results in decreased tumor growth and altered metabolic characteristics of tumor tissue. Interestingly, gluconate, considered to be physiologically neutral, is incidentally used in medicine as a cation carrier, but not as a therapeutically active substance. In this review we discuss the results of our recent research with available literature and suggest that gluconate may be useful in the treatment of cancer.

Ex vivo host and parasite response to antileishmanial drugs and immunomodulators

Background

Therapeutic response in infectious disease involves host as well as microbial determinants. Because the immune and inflammatory response to Leishmania (Viannia) species defines the outcome of infection and efficacy of treatment, immunomodulation is considered a promising therapeutic strategy. However, since Leishmania infection and antileishmanial drugs can themselves modulate drug transport, metabolism and/or immune responses, immunotherapeutic approaches require integrated assessment of host and parasite responses.

Methodology

To achieve an integrated assessment of current and innovative therapeutic strategies, we determined host and parasite responses to miltefosine and meglumine antimoniate alone and in combination with pentoxifylline or CpG 2006 in peripheral blood mononuclear cells (PBMCs) of cutaneous leishmaniasis patients. Parasite survival and secretion of TNF-α, IFN-γ, IL-10 and IL-13 were evaluated concomitantly in PBMCs infected with Luc-L. (V.) panamensis exposed to meglumine antimoniate (4, 8, 16, 32 and 64 μg Sb^V/mL) or miltefosine (2, 4, 8, 16 and 32 μM HePC). Concentrations of 4 μM of miltefosine and 8 μg Sb^V/mL were selected for evaluation in combination with immunomodulators based on the high but partial reduction of parasite burden by these antileishmanial concentrations without affecting cytokine secretion of infected PBMCs. Intracellular parasite survival was determined by luminometry and cytokine secretion measured by ELISA and multiplex assays.

Principal Findings

Anti- and pro-inflammatory cytokines characteristic of L. (V.) panamensis infection were evaluable concomitantly with viability of Leishmania within monocyte-derived macrophages present in PBMC cultures. Both antileishmanial drugs reduced the parasite load of macrophages; miltefosine also suppressed IL-10 and IL-13 secretion in a dose dependent manner. Pentoxifylline did not affect parasite survival or alter antileishmanial effects of miltefosine or meglumine antimoniate. However, pentoxifylline diminished secretion of TNF-α, IFN-γ and IL-13, cytokines associated with the outcome of infection by species of the Viannia subgenus. Exposure to CpG diminished the leishmanicidal effect of meglumine antimoniate, but not miltefosine, and significantly reduced secretion of IL -10, alone and in combination with either antileishmanial drug. IL-13 increased in response to CpG plus miltefosine.

Conclusions and Significance

Human PBMCs allow integrated ex vivo assessment of antileishmanial treatments, providing information on host and parasite determinants of therapeutic response that may be used to tailor therapeutic strategies to optimize clinical resolution.

Host determinants of the response to infection have increasingly been recognized as therapeutically relevant targets. Despite the pathogenesis of dermal leishmaniasis being mediated by the immune and inflammatory response, in vitro anti-leishmanial drug screening has been based on antimicrobial effect without consideration of effects on the host response. The results of this study show that peripheral blood mononuclear cells from patients allow an integrated evaluation of both antimicrobial efficacy and host response to drugs, immunomodulatory agents, and their combinations. This integrated approach to defining treatment strategies based on host and parasite responses opens the way for the optimization and tailoring of treatment to different clinical circumstances.

The protein tyrosine phosphatase SHP-1 modulates the suppressive activity of regulatory T cells

The importance of regulatory T cells (Tregs) for immune tolerance is well recognized, yet the signaling molecules influencing their suppressive activity are relatively poorly understood. In this article, through in vivo studies and complementary ex vivo studies, we make several important observations. First, we identify the cytoplasmic tyrosine phosphatase Src homology region 2 domain-containing phosphatase 1 (SHP-1) as an endogenous brake and modifier of the suppressive ability of Tregs; consistent with this notion, loss of SHP-1 expression strongly augments the ability of Tregs to suppress inflammation in a mouse model. Second, specific pharmacological inhibition of SHP-1 enzymatic activity via the cancer drug sodium stibogluconate potently augmented Treg suppressor activity both in vivo and ex vivo. Finally, through a quantitative imaging approach, we directly demonstrate that Tregs prevent the activation of conventional T cells and that SHP-1-deficient Tregs are more efficient suppressors. Collectively, our data reveal SHP-1 as a critical modifier of Treg function and a potential therapeutic target for augmenting Treg-mediated suppression in certain disease states.

Tyrosine phosphatase inhibitor-3 sensitizes melanoma and colon cancer to biotherapeutics and chemotherapeutics

Drug resistance is a major obstacle in cancer treatments and diminishes the clinical efficacy of biological, cytotoxic, or targeted therapeutics. Being an antiapoptotic mediator of chemoresistance in breast and lung cancer cells, MKP1 phosphatase might be targeted for overcoming chemoresistance and improving therapeutic efficacy. In this work, tyrosine phosphatase inhibitor-3 (TPI-3) was identified as a novel small molecule inhibitor of MKP1 and was capable of sensitizing tumors to bio- and chemotherapeutics in mice as a tolerated oral agent. Effective against recombinant MKP1, TPI-3 selectively increased MKP1 phosphosubstrates in Jurkat cells and induced cell death via apoptosis at nanomolar concentrations. TPI-3 also increased MKP1 phosphosubstrates in WM9 human melanoma cells and synergized with biotherapeutic IFN alpha 2b in the growth inhibition of melanoma cells in vitro (combination index, <1). WM9 xenografts unresponsive to individual agents were significantly inhibited (62%, P = 0.001) in mice by a tolerated combination of oral TPI-3 (10 mg/kg, 5 d/wk) and IFN alpha 2b. MKP1 expression was detected in human melanoma cell lines and tissue samples at levels up to six times higher than those in normal or nonmalignant melanocytes. TPI-3 also interacted positively with chemotherapeutics, 5-fluorouracil/leucovorin, against MC-26 colon cancer cells in vitro and in mice. Altogether, our data show the preclinical activities of TPI-3 in overcoming cancer resistance to bio- and chemotherapeutics, implicate MKP1 as a drug-resistant molecule in melanoma, and support the targeting of MKP1 for improving cancer therapeutic efficacy.

Novel SHP-1 inhibitors tyrosine phosphatase inhibitor-1 and analogs with preclinical anti-tumor activities as tolerated oral agents

Src homology region 2 domain-containing phosphatase 1 (SHP-1) has been implicated as a potential cancer therapeutic target by its negative regulation of immune cell activation and the activity of the SHP-1 inhibitor sodium stibogluconate that induced IFN-gamma(+) cells for anti-tumor action. To develop more potent SHP-1-targeted anti-cancer agents, inhibitory leads were identified from a library of 34,000 drug-like compounds. Among the leads and active at low nM for recombinant SHP-1, tyrosine phosphatase inhibitor-1 (TPI-1) selectively increased SHP-1 phospho-substrates (pLck-pY394, pZap70, and pSlp76) in Jurkat T cells but had little effects on pERK1/2 or pLck-pY505 regulated by phosphatases SHP-2 or CD45, respectively. TPI-1 induced mouse splenic-IFN-gamma(+) cells in vitro, approximately 58-fold more effective than sodium stibogluconate, and increased mouse splenic-pLck-pY394 and -IFN-gamma(+) cells in vivo. TPI-1 also induced IFN-gamma(+) cells in human peripheral blood in vitro. Significantly, TPI-1 inhibited ( approximately 83%, p < 0.002) the growth of B16 melanoma tumors in mice at a tolerated oral dose in a T cell-dependent manner but had little effects on B16 cell growth in culture. TPI-1 also inhibited B16 tumor growth and prolonged tumor mice survival as a tolerated s.c. agent. TPI-1 analogs were identified with improved activities in IFN-gamma(+) cell induction and in anti-tumor actions. In particular, analog TPI-1a4 as a tolerated oral agent completely inhibited the growth of K1735 melanoma tumors and was more effective than the parental lead against MC-26 colon cancer tumors in mice. These results designate TPI-1 and the analogs as novel SHP-1 inhibitors with anti-tumor activity likely via an immune mechanism, supporting SHP-1 as a novel target for cancer treatment.

An overview of cytokines and cytokine antagonists as therapeutic agents

Cytokine-based therapies have the potential to provide novel treatments for cancer, autoimmune diseases, and many types of infectious disease. However, to date, the full clinical potential of cytokines as drugs has been limited by a number of factors. To discuss these limitations and explore ways to overcome them, the FDA partnered with the New York Academy of Sciences in March 2009 to host a two-day forum to discuss more effective ways to harness the clinical potential of cytokines and cytokine antagonists as therapeutic agents. The first day was focused primarily on the use of recombinant cytokines as therapeutic agents for treatment of human diseases. The second day focused largely on the use of cytokine antagonists as therapeutic agents for treatment of human diseases. This issue of the Annals includes more than a dozen papers that summarize much of the information that was presented during this very informative two-day conference.