S40 Abstracts

OR.97. Immunotherapy of Breast and ProstateCancer Patients with Gc Protein-DerivedMacrophage Activating Factor, GcMAF or Its ClonedDerivative, GcMAFcNobuto Yamamoto1, Masumi Ueda1, Kazuya Hashinaka1,Theodore Sery1, Charles Benson2. 1Socrates Institute forTherapeutic Immunology, Philadelphia, PA; 2University ofPennsylvania, Philadelphia, PA

Serum Gc protein (known as vitamin D-binding protein) isthe precursor for the macrophage activating factor (MAF).The MAF precursor activity of serum Gc protein of cancerpatients was lost or reduced because Gc protein isdeglycosylated by serum α-N-acetylgalactosaminidase(Nagalase) secreted from cancerous cells but not fromhealthy cells. Thus, serum Nagalase activity is proportionalto tumor burden and serves as a prognostic index. Deglyco-sylated serum Gc protein can not be converted to MAF,leading to immunosuppression. Stepwise treatment ofpurified serum Gc protein or cloned Gc protein withimmobilized β-galactosidase and sialidase generates themost potent MAF (termed GcMAF or GcMAFc, respectively)that produces no side effect in humans. Intramuscularadministration of 100 ng GcMAF, or GcMAFc, activatedsystemic macrophages to develop an enormous variation ofreceptors that recognize cell surface abnormality of a varietyof cancer cells and to become tumoricidal. GcMAF also has apotent mitogenic activity on myeloid progenitor cells thatgenerate systemically a 40-fold increase in the activatedmacrophages in 4 days. When adenocarcinoma (breast andprostate cancer) patients (n=38) were intramuscularlyadministered with 100 ng GcMAF or GcMAFc/week, theirtumors were eradicated in16-25 weeks. These patients weretumor free for more than 8 years after the therapy. Sinceintravenous administration of GcMAFc allows rapid interac-tion of GcMAFc with myeloid progenitor cells in bone marrow,the systemic cell counts of the activated macrophagesincreased to 220-fold in 2 days. Weekly intravenous admin-istration of 100 ng GcMAFc to adenocarcinoma patientseradicated tumors in 11-16 weeks.

doi:10.1016/j.clim.2009.03.112

OR.98. GARP (LRRC32) is Essential for the SurfaceExpression of Latent TGFβ on Platelets andActivated FOXP3+Regulatory T Cells by Anchoringit to the MembraneDat Tran, Ethan Shevach. NIAID/NIH, Bethesda, MD

TGFβ are multipotent cytokines that modulate cellgrowth, inflammation, matrix synthesis and apoptosis.Dysregulation in TGFβ are associated with multiple patho-logical conditions including tumor cell growth, fibrosis,emphysema and autoimmunity. TGFβ is expressed in latentform consisting of a latency-associated peptide (LAP) thatnoncovalently associates with the mature TGFβ to preventits activity. This complex is known as latent TGFβ. It isexpressed on the membrane of many cell types, includingmegakaryocytes, platelets, immature dendritic cells and

activated FOXP3+regulatory T cells (Tregs), and has impor-tant functions such as tissue healing and immune regulation.It is unknown how latent TGFβ is anchored to the surface.We show that GARP (LRRC32) is the molecule that anchorslatent TGFβ to the surface. By silencing GARP mRNAexpression with siRNA, neither GARP nor LAP protein isexpressed on the surface of activated Tregs. If TGFbeta1mRNA is silenced, GARP is still expressed on the surface inthe absence of LAP. LAP expression can be detected on thesurface of GARP+but not GARP-Tregs when they areincubated with recombinant latent TGFβ1 or LAP plusTGFβ1, but not with TGFβ1 or LAP alone, indicating thatlatent TGFbeta1 interacts with GARP. Immunoprecipitationand confocal colocalization imaging studies also reveal thedirect association of GARP with latent TGFβ1. Transfectionof GARP into nonTregs was sufficient to permit these cells toexpress latent TGFβ on their surface. In conclusion, GARPplays an essential role in the function of latent TGFβ byanchoring it to the cell surface. This finding gives importantinsights into the potential expression of GARP and utilizationof TGFβ by cancerous cells to escape anti-tumor immunity.Research was supported by the Intramural Research Programof the NIH, NIAID.

doi:10.1016/j.clim.2009.03.113

OR.99. Epstein-Barr Virus Latent Membrane Protein1 Modulates Host MicroRNAs in B Cell LymphomasAleishia Harris, Stacie Lambert, Sheri Krams, OliviaMartinez. Stanford University School of Medicine,Stanford, CA

Epstein-Barr Virus (EBV) infection is usually benign butimmunosuppression can promote post-transplant lymphopro-liferative disease (PTLD) and B cell lymphomas in organ andbone marrow transplant recipients. Latent membrane pro-tein 1 (LMP1) is an important EBV-encoded oncogene thatusurps cellular pathways to drive B cell transformation.MicroRNAs are tiny, non-coding RNAs that regulate cellulargene expression. Since aberrant expression of microRNAs hasbeen observed in a variety of malignancies, we hypothesizedthat modulation of cellular microRNA expression by EBV mayplay a role in the development of EBV+B cell lymphomas.Infection of B cell lymphoma lines with EBV significantlymodulated expression of microRNA-7,-15b,-221, and-222.Importantly, a similar pattern of microRNA expression wasobserved in an EBV+B lymphoma cell line derived from apatient with PTLD. Activation of a chimeric LMP1 signalingsystem in EBV negative B lymphoma cell lines also inducedmicroRNA-221 and-222 expression. These microRNAs targetthe cell cycle regulators p27 and p57. Thus, LMP1 canpromote cell cycle progression in B cells through microRNAexpression. Modulation of microRNAs may be a novelmechanism by which EBV drives lymphomagenesis. Under-standing how EBV infection alters microRNA expression maylead to new therapies to treat EBV-associated malignancies,including PTLD.

doi:10.1016/j.clim.2009.03.114