Matthew Gumbleton

Chronic Mucocutaneous Candidiasis in Humans with Inborn Errors of Interleukin-17 Immunity

Chronic yeast infections in the absence of other infections result from genetic deficiencies in proinflammatory host responses. 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.

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)P3-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)P3 to PtdIns(3,4)P2. However, a growing body of evidence suggests that PtdInd(3,4)P2 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)P2. In conclusion, this study shows that inhibition of SHIP1 and SHIP2 may have broad clinical application in the treatment of multiple tumor types.

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.

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.

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

Intermittent inhibition of the phosphatase SHIP1 promotes antitumor immunity and memory in mouse models of lymphoma and colon cancer. Finding the right balance in immunotherapy To stimulate the immune system’s activity against tumors, therapies often inhibit the regulatory pathways that suppress or counteract stimulatory signaling in immune cells. The phosphatase SHIP1 is one such target; however, chronic inhibition or genetic ablation of SHIP1 in mouse models of cancer fails to induce effective antitumor immunity, perhaps because chronic activation causes immune cell exhaustion. Gumbleton et al. found that, instead, a pulsatile regimen of SHIP1 inhibition not only enhanced the antitumor activity of critical populations of immune cells and extended the survival of mice with lymphoma and colon cancer but also induced immunological memory against the tumor cells. This treatment strategy may thus be effective at killing various types of tumors and preventing relapse in cancer patients. 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.

Abstract C81: Therapeutic potential of SHIP1 and SHIP2 inhibitors in cancer.

Many tumors present with increased activation of the phosphatidylinositol 3-kinase (PI3K)-PtdIns (3,4,5) P3- protein kinase B (PKB/AKT) signaling pathway. The lipid phosphatases SHIP1 and SHIP2 have long been thought to act as tumor-suppressors by counteracting the survival signal induced by this pathway through hydrolysis or PtdIns (3,4,5) P3 to PtdIns (3,4) P2. However, a growing body of evidence suggests that PtdInd (3,4) P2 is capable of, and essential for, AKT activation, thus opening up a potential role for SHIP1/2 enzymes as proto-oncogenes. We have recently described a novel SHIP1 selective chemical inhibitor (3AC), which was capable of killing malignant hematological cells. In this study, we further investigate the biochemical consequences of 3AC treatment in multiple myeloma (MM) cells, 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 (1PIE, 2PIQ, 6PTQ), which efficiently kill MM cells through G2/M arrest, caspase activation and apoptosis induction. Interestingly, in SHIP2-expressing breast cancer cells, pan-SHIP1/2 inhibition also reduces viable cell numbers, which can be rescued by addition of exogenous PtdIns (3,4) P2. In conclusion, this study shows that inhibition of SHIP1 and SHIP2 may have broad clinical application in the treatment of multiple tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C81.