SHIP1 intrinsically regulates NK cell signaling and education, resulting in tolerance of an MHC class I-mismatched bone marrow graft in mice.

NK cells are an important component of host immune defense against malignancy and infection. NK cells are educated by MHC class I ligands to ensure self-tolerance while also promoting lytic competency against altered self and damaged self targets. However, the intracellular molecular events that culminate in tolerance and functional competency of educated NK cells remain undefined. Mice with germline deficiency in SHIP1 were shown to have a defective NK cell compartment. However, SHIP1 is expressed in all hematopoietic lineages, and consequently several hematolymphoid phenotypes have already been identified in certain cell types that are the result of SHIP1 deficiency in cells in separate and distinct lineages, that is, cell-extrinsic phenotypes. Thus, it was previously impossible to determine the NK cell-intrinsic role of SHIP1. In the present study, through the creation of an NK cell-specific deletion mouse model of SHIP1, we show that SHIP1 plays a profound NK lineage-intrinsic role in NK cell homeostasis, development, education, and cytokine production. Moreover, we show SHIP1 expression by NK cells is required for in vivo-mismatched bone marrow allograft rejection as well as for NK memory responses to hapten.

A phase I open-label study of the safety and efficacy of apatinib (rivoceranib) administered to patients with advanced malignancies to improve sensitivity to pembrolizumab in the second- or later-line setting (APPEASE).

OBJECTIVE: APPEASE is a phase I study to assess the safety, dosing, and efficacy of rivoceranib (a selective, small-molecule inhibitor of VEGFR2) in combination with pembrolizumab. We aimed to treat patients with metastatic malignancies who have progressed through at least first-line therapy, with pembrolizumab 200 mg every 3 weeks, as well as escalating doses of rivoceranib until disease progression or unacceptable toxicity. RESULTS: Five patients were enrolled on the starting dose of rivoceranib 300 mg once daily. There were no dose-limiting toxicities observed in combination with pembrolizumab. The dose of rivoceranib was not escalated due to study closure. We note a treatment related grade 3 adverse event (AE) rate of 40%, predominantly in urothelial cancer patients, with no deaths related to treatment related AEs. The disease control rate was 75% (3 of 4) and the median progression free survival (PFS) was 3.6 months. Tumor shrinkage was noted in patients who were previously progressing on pembrolizumab alone. Apatinib 300 mg is safe and demonstrates anti-tumor activity in advanced solid tumors in combination with pembrolizumab. Further dose escalation and efficacy need to be investigated in larger disease-specific patient populations. TRIAL REGISTRATION NUMBER: Clinical trial registration number: NCT03407976. Date of registration: January 17, 2018.

Therapeutic potential of SH2 domain-containing inositol-5'-phosphatase 1 (SHIP1) and SHIP2 inhibition in cancer.

Many tumors present with increased activation of the phosphatidylinositol 3-kinase (PI3K)-PtdIns(3,4,5)P(3)-protein kinase B (PKB/Akt) signaling pathway. It has long been thought that the lipid phosphatases SH2 domain-containing inositol-5'-phosphatase 1 (SHIP1) and SHIP2 act as tumor suppressors by counteracting with the survival signal induced by this pathway through hydrolysis or PtdIns(3,4,5)P(3) to PtdIns(3,4)P(2). However, a growing body of evidence suggests that PtdInd(3,4)P(2) is capable of, and essential for, Akt activation, thus suggesting a potential role for SHIP1/2 enzymes as proto-oncogenes. We recently described a novel SHIP1-selective chemical inhibitor (3α-aminocholestane [3AC]) that is capable of killing malignant hematologic cells. In this study, we further investigate the biochemical consequences of 3AC treatment in multiple myeloma (MM) and demonstrate that SHIP1 inhibition arrests MM cell lines in either G0/G1 or G2/M stages of the cell cycle, leading to caspase activation and apoptosis. In addition, we show that in vivo growth of MM cells is blocked by treatment of mice with the SHIP1 inhibitor 3AC. Furthermore, we identify three novel pan-SHIP1/2 inhibitors that efficiently kill MM cells through G2/M arrest, caspase activation and apoptosis induction. Interestingly, in SHIP2-expressing breast cancer cells that lack SHIP1 expression, pan-SHIP1/2 inhibition also reduces viable cell numbers, which can be rescued by addition of exogenous PtdIns(3,4)P(2). In conclusion, this study shows that inhibition of SHIP1 and SHIP2 may have broad clinical application in the treatment of multiple tumor types.

Dual enhancement of T and NK cell function by pulsatile inhibition of SHIP1 improves antitumor immunity and survival.

The success of immunotherapy in some cancer patients has revealed the profound capacity for cytotoxic lymphocytes to eradicate malignancies. Various immunotherapies work by blocking key checkpoint proteins that suppress immune cell activity. The phosphatase SHIP1 (SH2-containing inositol polyphosphate 5-phosphatase) limits signaling from receptors that activate natural killer (NK) cells and T cells. However, unexpectedly, genetic ablation studies have shown that the effector functions of SHIP1-deficient NK and T cells are compromised in vivo. Because chronic activation of immune cells renders them less responsive to activating signals (a host mechanism to avoid autoimmunity), we hypothesized that the failure of SHIP1 inhibition to induce antitumor immunity in those studies was caused by the permanence of genetic ablation. Accordingly, we found that reversible and pulsatile inhibition of SHIP1 with 3-α-aminocholestane (3AC; "SHIPi") increased the antitumor response of NK and CD8+ T cells in vitro and in vivo. Transient SHIP1 inhibition in mouse models of lymphoma and colon cancer improved the median and long-term tumor-free survival rates. Adoptive transfer assays showed evidence of immunological memory to the tumor in hematolymphoid cells from SHIPi-treated, long-term surviving mice. The findings suggest that a pulsatile regimen of SHIP1 inhibition might be an effective immunotherapy in some cancer patients.

SHIP1-expressing mesenchymal stem cells regulate hematopoietic stem cell homeostasis and lineage commitment during aging.

Hematopoietic stem cell (HSC) self-renewal and lineage choice are subject to intrinsic control. However, this intrinsic regulation is also impacted by external cues provided by niche cells. There are multiple cellular components that participate in HSC support with the mesenchymal stem cell (MSC) playing a pivotal role. We had previously identified a role for SH2 domain-containing inositol 5'-phosphatase-1 (SHIP1) in HSC niche function through analysis of mice with germline or induced SHIP1 deficiency. In this study, we show that the HSC compartment expands significantly when aged in a niche that contains SHIP1-deficient MSC; however, this expanded HSC compartment exhibits a strong bias toward myeloid differentiation. In addition, we show that SHIP1 prevents chronic G-CSF production by the aging MSC compartment. These findings demonstrate that intracellular signaling by SHIP1 in MSC is critical for the control of HSC output and lineage commitment during aging. These studies increase our understanding of how myeloid bias occurs in aging and thus could have implications for the development of myeloproliferative disease in aging.

SHIPi Enhances Autologous and Allogeneic Hematolymphoid Stem Cell Transplantation.

Hematopoietic stem cell transplantation (HSCT) is a highly effective procedure enabling long-term survival for patients with hematologic malignancy or heritable defects. Although there has been a dramatic increase in the success rate of HSCT over the last two decades, HSCT can result in serious, sometime untreatable, disease due to toxic conditioning regimens, graft vs. host disease and required use of mismatched bone marrow in some cases. Studies utilizing germline knockout mice have discovered several candidate genes that could be targeted pharmacologically to create a more favorable environment for transplant success. SHIP1 deficiency permits improved engraftment of hematopoietic stem-progenitor cells (HS-PC) and produces a suppressive microenvironment ideal for incoming grafts. The recent development of small molecule SHIP1 inhibitors has opened a different therapeutic approach to creating transient SHIP1-deficiency. Here we show that SHIP1 inhibition (SHIPi) can mobilize functional HS-PC, accelerate hematologic recovery, and enhance donor HS-PC engraftment in both allogeneic and autologous transplant settings. We also observed the expansion of key cell populations known to suppress host-reactive cells formed during engraftment. Therefore, SHIPi represents a non-toxic, new therapeutic that has significant potential to improve the success and safety of therapies that utilize HSCT.

Role of inositol phospholipid signaling in natural killer cell biology.

Natural killer (NK) cells are important for host defense against malignancy and infection. At a cellular level NK cells are activated when signals from activating receptors exceed signaling from inhibitory receptors. At a molecular level NK cells undergo an education process to both prevent autoimmunity and acquire lytic capacity. Mouse models have shown important roles for inositol phospholipid signaling in lymphocytes. NK cells from mice with deletion in different members of the inositol phospholipid signaling pathway exhibit defects in development, NK cell repertoire expression and effector function. Here we review the current state of knowledge concerning the function of inositol phospholipid signaling components in NK cell biology.

Chronic mucocutaneous candidiasis in humans with inborn errors of interleukin-17 immunity.

Chronic mucocutaneous candidiasis disease (CMCD) is characterized by recurrent or persistent infections of the skin, nails, and oral and genital mucosae caused by Candida albicans and, to a lesser extent, Staphylococcus aureus, in patients with no other infectious or autoimmune manifestations. We report two genetic etiologies of CMCD: autosomal recessive deficiency in the cytokine receptor, interleukin-17 receptor A (IL-17RA), and autosomal dominant deficiency of the cytokine interleukin-17F (IL-17F). IL-17RA deficiency is complete, abolishing cellular responses to IL-17A and IL-17F homo- and heterodimers. By contrast, IL-17F deficiency is partial, with mutant IL-17F-containing homo- and heterodimers displaying impaired, but not abolished, activity. These experiments of nature indicate that human IL-17A and IL-17F are essential for mucocutaneous immunity against C. albicans, but otherwise largely redundant.