sirolimus and idelalisib

Obinutuzumab is a glycoengineered tumor-targeting anti-CD20 mAb with a modified crystallizable fragment (Fc) domain designed to increase the affinity for the FcγRIIIA/CD16 receptor, which was recently approved for clinical use in CLL and follicular lymphoma. Here we extend our previous observation that, in human NK cells, the sustained CD16 ligation by obinutuzumab-opsonized targets leads to a markedly enhanced IFN-γ production upon a subsequent cytokine re-stimulation. The increased IFN-γ competence in response to IL-2 or IL-15 is attributable to post-transcriptional regulation, as it does not correlate with the upregulation of IFN-γ mRNA levels. Different from the reference molecule rituximab, we observe that the stimulation with obinutuzumab promotes the upregulation of microRNA (miR)-155 expression. A similar trend was also observed in NK cells from untreated CLL patients stimulated with obinutuzumab-opsonized autologous leukemia. miR-155 upregulation associates with reduced levels of SHIP-1 inositol phosphatase, which acts in constraining PI3K-dependent signals, by virtue of its ability to mediate phosphatidylinositol 3,4,5-trisphosphate (PIP3) de-phosphorylation. Downstream of PI3K, the phosphorylation status of mammalian target of rapamycin (mTOR) effector molecule, S6, results in amplified response to IL-2 or IL-15 stimulation in obinutuzumab-experienced cells. Importantly, NK cell treatment with the PI3K or mTOR inhibitors, idelalisib and rapamycin, respectively, prevents the enhanced cytokine responsiveness, thus, highlighting the relevance of the PI3K/mTOR axis in CD16-dependent priming. The enhanced IFN-γ competence may be envisaged to potentiate the immunoregulatory role of NK cells in a therapeutic setting.

Topics: Antibodies, Monoclonal, Humanized; Antineoplastic Agents, Immunological; Cell Line, Tumor; Cells, Cultured; Enzyme Inhibitors; Gene Expression; Humans; Interferon-gamma; Interleukin-12; Killer Cells, Natural; Leukemia, Lymphocytic, Chronic, B-Cell; MicroRNAs; Phosphatidylinositol 3-Kinases; Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; Purines; Quinazolinones; Receptors, IgG; Sirolimus; TOR Serine-Threonine Kinases

Topics: Allografts; Animals; B-Lymphocytes; Epstein-Barr Virus Infections; Female; Graft Rejection; Graft Survival; Heart Transplantation; Heterocyclic Compounds, 3-Ring; Humans; Inhibitory Concentration 50; Lymphoma, B-Cell; Lymphoproliferative Disorders; Male; Mice; Mice, Inbred C57BL; Mice, Inbred NOD; Mice, SCID; Neoplasm Transplantation; Organ Transplantation; Phosphoinositide-3 Kinase Inhibitors; Postoperative Complications; Proto-Oncogene Proteins c-akt; Purines; Quinazolinones; Sirolimus; TOR Serine-Threonine Kinases

Lately, mTOR inhibitors have gained clinical relevance in malignant lymphoma. Still, rapamycin derivatives may activate a pro-survival feedback loop through PI3K-Akt. In this current study, temsirolimus effectively reduced cell growth in GCB and ABC diffuse large cell B-cell lymphoma (GCB=30-66%, ABC=45-57%). Combination treatment with the PI3K-δ inhibitor idelalisib additively effected ABC and GCB lymphoma (GCB=16-38%, ABC=25-50%). Since Bruton's Tyrosine Kinase (BTK) plays a significant role for the survival of ABC lymphoma, this study also combined the BTK inhibitor ibrutinib with temsirolimus, which resulted in additive cell growth reduction (ibrutinib 50%, temsirolimus 44%, combination 25%) in ABC lymphoma. In contrast, bortezomib, which has been shown previously to be efficient in ABC lymphoma, revealed an antagonistic effect with temsirolimus in some GCB lymphoma (temsirolimus 53%, temsirolimus+bortezomib 63%). Western blot analysis identified the increase of phosphorylated pro-survival kinases Akt and PDK as a possible underlying mechanism of this interaction.

Topics: Adenine; Antineoplastic Agents; Bortezomib; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drug Antagonism; Drug Synergism; Humans; Lymphoma, Large B-Cell, Diffuse; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Purines; Pyrazoles; Pyrimidines; Quinazolinones; Receptors, Antigen, B-Cell; Signal Transduction; Sirolimus