ULBPs, Novel MHC Class I–Related Molecules, Bind to CMV Glycoprotein UL16 and Stimulate NK Cytotoxicity through the NKG2D Receptor

AbstractThe human cytomegalovirus glycoprotein, UL16, binds to two members of a novel family of molecules, the ULBPs, and to the MHC class I homolog, MICB. The ULBPs are GPI-linked glycoproteins belonging to the extended MHC class I family but are only distantly related to MICB. The ULBP and MICB molecules are ligands for the activating receptor, NKG2D/DAP10, and this interaction is blocked by a soluble form of UL16. The ULBPs stimulate cytokine and chemokine production from NK cells, and expression of ULBPs in NK cell–resistant target cells confers susceptibility to NK cell cytotoxicity. Masking of NK cell recognition of ULBP or MIC antigens by UL16 provides a potential mechanism by which human cytomegalovirus–infected cells might evade attack by the immune system

Immunologic and Hematopoietic Effects of CD40 Stimulation after Syngeneic Bone Marrow Transplantation in Mice

CD40 is a molecule present on multiple cell types including B lymphocyte lineage cells. CD40 has been shown to play an important role in B cell differentiation and activation in vitro, although little is known concerning the effects of CD40 stimulation in vivo. We therefore examined the effects of CD40 stimulation in mice using a syngeneic bone marrow transplantation (BMT) model in an effort to augment B cell recovery after high dose therapy with hematopoietic reconstitution. After the BMT, mice were treated with or without 2-6 μg of a soluble recombinant murine CD40 ligand (srmCD40L) given intraperitoneally twice a week. A significant increase in B cell progenitors (B220 +/surface IgM -) was observed in the bone marrow of mice receiving the srmCD40L. The treated recipients also demonstrated improved B-cell function with increases in total serum immunoglobulin and increased splenic mitogen responsiveness to LPS being noted. Additionally, srmCD40L treatment promoted secondary lymphoid organ repopulation, accelerating germinal center formation in the lymph nodes. Total B cell numbers in the periphery were not significantly affected even with continuous srmCD40L administration. Lymphocytes obtained from mice treated with the ligand also had increases in T cell mitogen and anti-CD3 mAb responsiveness and acquired the capability to produce IL-4. Surprisingly, treatment with srmCD40L also produced hematopoietic effects in mice, resulting in an increase of BM and splenic hematopoietic progenitor cells in the mice after BMT. Treatment with srmCD40L significantly increased granulocyte and platelet recovery in the peripheral blood. Incubation of BMC with srmCD40L in vitro also resulted in increased progenitor proliferation, demonstrating that the hematopoietic effects of the ligand may be direct. Thus, stimulation of CD40 by its ligand may he beneficial in accelerating both immune and hematopoietic recovery in the setting of bone marrow transplantation

Dietary nucleotide restriction and supplementation in mice: Influence on lymphocyte function, maturation and nucleotide metabolism

An observed phenomenon of cell mediated immunosuppression in mice caused by the lack of preformed purine and pyrimidines in the diet was characterized and the mechanism of action explored utilizing three different approaches. The three approaches employed were as follows: (1) measurement of T cell mediated immune response in vitro and in vivo; (2) analysis of lymphocyte phenotype involving surface marker immunofluorescence, measurement of the levels of purine and pyrimidine enzymes as predictors of lymphocyte maturation and evaluation of putative G\sb1 phase characteristics; and (3) examination of diet fed host effects on the in vivo out growth of syngeneic lymphoid tumors. Balb/c mice fed a nucleotide free (NF) diet exhibited significantly decreased T helper/inducer cell function and number relative to mice fed normal rodent chow (F) or NF plus RNA (NFR). Lymphoproliferative response in vitro and in vivo was significantly lower in mice fed the NF diet than the response exhibited by mice fed the control diets or NF plus uracil (NFU). This lack of proliferative response was accompanied by decreased induction of two purine enzymes important to the immune response: adenosine deaminase and purine nucleoside phosphorylase. Bone marrow, thymus and spleen obtained from NF diet fed mice contained significantly more T cells of an immature phenotype with high terminal deoxynucleotidyl transferase and adenosine deaminase levels and low purine nucleoside phosphorylase level enzyme profiles relative to that of similar lymphoid tissues obtained from mice fed the control diets. Levels of ecto 5\sp\prime nucleotidase, another enzyme linked to optimal B cell function were not affected by the NF diet. Lymphocyte nucleotide pools were altered and the number of putative G\sb1 phase T lymphocytes were increased in mice fed the NF diet relative to mice fed the purine and pyrimidine supplemented diets. In vivo outgrowth of the syngeneic T cell lymphoma, 5F4, in Balb/c hosts fed the NF diet was significantly decreased compared to the 5F4 tumor growth observed in mice fed the NF diet supplemented with RNA, adenine or uracil. (Abstract shortened with permission of author.

Intracellular Catabolism of an Antibody Drug Conjugate with a Non-Cleavable Linker

Abstract words: 56 Introduction words: 78

Tumor penetration and epidermal growth factor receptor saturation by panitumumab correlate with antitumor activity in a preclinical model of human cancer

Abstract Background Successful treatment of solid tumors relies on the ability of drugs to penetrate into the tumor tissue. Methods We examined the correlation of panitumumab (an anti-epidermal growth factor [EGFR] antibody) tumor penetration and EGFR saturation, a potential obstacle in large molecule drug delivery, using pharmacokinetics, pharmacodynamics, and tumor growth rate in an A431 epidermoid carcinoma xenograft model of human cancer. To determine receptor saturation, receptor occupancy, and levels of proliferation markers, immunohistochemical and flow cytometric methods were used. Pharmacokinetic data and modeling were used to calculate growth characteristics of panitumumab-treated tumors. Results Treatment with panitumumab in vivo inhibited pEGFR, Ki67 and pMAPK levels vs control. Tumor penetration and receptor saturation were dose- and time-dependent, reaching 100% and 78%, respectively. Significant tumor inhibition and eradication (p  Conclusions These data demonstrate that the antitumor activity of panitumumab correlates with its ability to penetrate into tumor tissue, occupy and inhibit activation of EGFR, and inhibit markers of proliferation and MAPK signaling.</p

Inhibition of VEGF-Dependent Multistage Carcinogenesis by Soluble EphA Receptors

Elevated expression of Eph receptors has long been correlated with the growth of solid tumors. However, the functional role of this family of receptor tyrosine kinases in carcinogenesis and tumor angiogenesis has not been well characterized. Here we report that soluble EphA receptors inhibit tumor angiogenesis and tumor progression in vivo in the RIP-Tag transgenic model of vascular endothelial growth factor (VEGF)-dependent multistage pancreatic islet cell carcinoma. Soluble EphA receptors delivered either by a transgene or an osmotic minipump inhibited the formation of angiogenic islet, a premalignant lesion, and reduced tumor volume of solid islet cell carcinoma. EphA2-Fc or EphA3-Fc treatment resulted in decreased tumor volume but increased tumor and endothelial cell apoptosis in vivo. In addition, soluble EphA receptors inhibited VEGF and βTC tumor cell-conditioned medium-induced endothelial cell migration in vitro and VEGF-induced cornea angiogenesis in vivo. A dominant negative EphA2 mutant inhibited—whereas a gain-of-function EphA2 mutant enhanced—tumor cell-induced endothelial cell migration, suggesting that EphA2 receptor activation is required for tumor cell-endothelial cell interaction. These data provide functional evidence for EphA class receptor regulation of VEGF-dependent tumor angiogenesis, suggesting that the EphA signaling pathway may represent an attractive novel target for antiangiogenic therapy in cancer