Low-dose combretastatin A4 phosphate enhances the immune response of tumor hosts to experimental colon carcinoma

Purpose: Although there is a need to enhance the therapeutic efficiency in cancer by combining immunotherapeutic procedures with other therapy, combination with chemotherapy is complicated due to immunosuppressive effects of most chemotherapeutic drugs. The purpose of this investigation was to study whether combining tumor cell immunization with the vascular targeting drug combretastatin A4 phosphate (CA4P) would enhance tumor retardation and/or affect the antitumor immune response. Experimental Design: Rats with intrahepatic colon carcinoma were immunized weekly with IL-18/IFN gamma-transfected tumor cells, starting day 9, and were treated with a low-dose CA4P (2 mg/kg, 5 days a week starting day 7). The effect of CA4P was studied on tumor growth and on immune reactivity in vitro. Results: Rats with preexisting tumor, immunized and treated with low-dose CA4P, had a significantly retarded tumor growth compared with rats receiving CA4P or immunization alone. Splenocytes from rats treated with this combination had a significantly enhanced antitumor immune response compared with splenocytes from control rats. Exposure of nonadherent splenocytes to CA4P in vitro did not enhance their proliferation. However, 3-hour pretreatment of adherent splenocytes with 0.3 mu g/mL CA4P significantly enhanced proliferation and IFN gamma production of admixed nonadherent splenocytes, partly due to nitric oxide reduction. Combining the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester with CA4P and immunization further retarded tumor growth. Conclusion: Concomitant treatment of rats with progressively growing tumor with immunization and low-dose CA4P significantly enhances the therapeutic effect as compared with either treatment alone and results in an enhanced antitumor immune reactivity

Chemokine-directed migration of tumor-inhibitory neural progenitor cells towards an intracranially growing glioma.

We have earlier shown that the rat neural progenitor cell line HiB5 is capable of suppressing intracranial growth of glioma cells in Fisher rats. Unlike some neural progenitor cells, HiB5 cells have not shown homing capacity towards glioma cells growing intracranially. In this study, we have genetically modified HiB5 progenitor cells to over-express the chemokine receptor CXCR3. We show that the introduced receptor is functionally responding to ligand stimulation with increased phosphorylation levels of ERK and SAPK/JNK and a transcriptional response of an AP-1 reporter system introduced into HIB5 cells. These transfected progenitor cells migrate in vitro in response to IP-10 and I-TAC. Further, we show an enhanced in vivo migration of the CXCR3 transfected HiB5 cells over the corpus callosum towards an IP-10 and I-TAC expressing glioma, as compared to wild type HiB5 cells. Our data indicate that it is possible to take advantage of chemokines natural capacity to initiate migratory responses, and to use this ability to enhance tumor-inhibitory neural progenitor cells to target an intracranially growing glioma

Human peripheral blood lymphocytes transplanted into SCID mice constitute an in vivo culture system exhibiting several parameters found in a normal humoral immune response and are a source of immunocytes for the production of human monoclonal antibodies.

Human PBL from vaccinated healthy blood donors, which was transplanted i.p. into mice with severe combined immunodeficiency (SCID), exhibited an Ag-dependent humoral Ir against tetanus toxoid. This Ir was dose dependent and was completely abrogated by immunizing with large amounts of Ag, suggesting a high dose tolerization of the B cells. A dose-dependent selection of specific, high affinity B clonotypes was also suggested, since immunization with low concentrations of tetanus toxoid produced antisera with higher avidity than immunizations using a high dose of Ag. The production of human Ig and the clonal outgrowth of normal human B cells in the SCID mouse was strongly down-regulated by human NK cells. Human immune B lymphocytes were also recovered from immunized SCID mice and transformed with EBV, yielding lymphoblastoid cell lines producing high affinity antitetanus human IgG antibodies. These results suggest that SCID mice, repopulated with human PBL, can constitute a functional model of several parameters of a normal human humoral Ir and can provide a source of immune B cells for the production of human mAb

Carnitine palmitoyltransferase 1C promotes cell survival and tumor growth under conditions of metabolic stress

Tumor cells gain a survival/growth advantage by adapting their metabolism to respond to environmental stress, a process known as metabolic transformation. The best-known aspect of metabolic transformation is the Warburg effect, whereby cancer cells up-regulate glycolysis under aerobic conditions. However, other mechanisms mediating metabolic transformation remain undefined. Here we report that carnitine palmitoyltransferase 1C (CPT1C), a brain-specific metabolic enzyme, may participate in metabolic transformation. CPT1C expression correlates inversely with mammalian target of rapamycin (mTOR) pathway activation, contributes to rapamycin resistance in murine primary tumors, and is frequently up-regulated in human lung tumors. Tumor cells constitutively expressing CPT1C show increased fatty acid (FA) oxidation, ATP production, and resistance to glucose deprivation or hypoxia. Conversely, cancer cells lacking CPT1C produce less ATP and are more sensitive to metabolic stress. CPT1C depletion via siRNA suppresses xenograft tumor growth and metformin responsiveness in vivo. CPT1C can be induced by hypoxia or glucose deprivation and is regulated by AMPKα. Cpt1c-deficient murine embryonic stem (ES) cells show sensitivity to hypoxia and glucose deprivation and altered FA homeostasis. Our results indicate that cells can use a novel mechanism involving CPT1C and FA metabolism to protect against metabolic stress. CPT1C may thus be a new therapeutic target for the treatment of hypoxic tumors