Antineoplastic chemotherapeutic agents may indirectly activate dendritic cells (DCs) by inducing the release of “danger” signals from dying tumor cells. Whereas the direct cytotoxic or inhibitory effect of conventional chemotherapy on DCs has been reported, modulation of DC function by chemotherapeutic agents in low noncytotoxic concentrations has not yet been investigated. We have tested the effects of different classes of antineoplastic chemotherapeutic agents used in low noncytotoxic concentrations on the Ag-presenting function of DCs. We revealed that paclitaxel, doxorubicin, mitomycin C, and methotrexate up-regulated the ability of DCs to present Ags to Ag-specific T cells. Stimulation of DC function was associated with the up-regulation of expression of Ag-processing machinery components and costimulatory molecules on DCs, as well as increased IL-12p70 expression. However, the ability of DCs treated with paclitaxel, methotrexate, doxorubicin, and vinblastine to increase Ag presentation to Ag-specific T cells was abolished in DCs generated from IL-12 knockout mice, indicating that up-regulation of Ag presentation by DCs is IL-12-dependent and mediated by the autocrine or paracrine mechanisms. At the same time, IL-12 knockout and wild-type DCs demonstrated similar capacity to up-regulate OVA presentation after their pretreatment with low concentrations of mitomycin C and vincristine, suggesting that these agents do not utilize IL-12-mediated pathways in DCs for stimulating Ag presentation. These findings reveal a new mechanism of immunopotentiating activity of chemotherapeutic agents—a direct immunostimulatory effect on DCs (chemomodulation)—and thus provide a strong rationale for further assessment of low-dose chemotherapy given with DC vaccines for cancer treatment.

The dose-delivery schedule of conventional chemotherapy, which determines its efficacy and toxicity, is based on the maximum tolerated dose. This strategy has lead to cure and disease control in a significant number of patients but is associated with significant short-term and long-term toxicity. Recent data demonstrate that moderately low-dose chemotherapy may be efficiently combined with immunotherapy, particularly with dendritic cell (DC) vaccines, to improve the overall therapeutic efficacy. However, the direct effects of low and ultra-low concentrations on DCs are still unknown. Here we characterized the effects of low noncytotoxic concentrations of different classes of chemotherapeutic agents on human DCs in vitro. DCs treated with antimicrotubule agents vincristine, vinblastine, and paclitaxel or with antimetabolites 5-aza-2-deoxycytidine and methotrexate, showed increased expression of CD83 and CD40 molecules. Expression of CD80 on DCs was also stimulated by vinblastine, paclitaxel, azacytidine, methotrexate, and mitomycin C used in low nontoxic concentrations. Furthermore, 5-aza-2-deoxycytidine, methotrexate, and mitomycin C increased the ability of human DCs to stimulate proliferation of allogeneic T lymphocytes. Thus, our data demonstrate for the first time that in low noncytotoxic concentrations chemotherapeutic agents do not induce apoptosis of DCs, but directly enhance DC maturation and function. This suggests that modulation of human DCs by noncytotoxic concentrations of antineoplastic drugs, i.e. chemomodulation, might represent a novel approach for up-regulation of functional activity of resident DCs in the tumor microenvironment or improving the efficacy of DCs prepared ex vivo for subsequent vaccinations.

Given that cancer is one of the main causes of death worldwide, many efforts have been directed toward discovering new treatments and approaches to cure or control this group of diseases. Chemotherapy is the main treatment for cancer; however, a conventional schedule based on maximum tolerated dose (MTD) shows several side effects and frequently allows the development of drug resistance. On the other side, low dose chemotherapy involves antiangiogenic and immunomodulatory processes that help host to fight against tumor cells, with lower grade of side effects. In this review, we present evidence that metronomic chemotherapy, based on the frequent administration of low or intermediate doses of chemotherapeutics, can be better than or as efficient as MTD. Finally, we present some data indicating that noncytotoxic concentrations of antineoplastic agents are able to both up-regulate the immune system and increase the susceptibility of tumor cells to cytotoxic T lymphocytes. Taken together, data from the literature provides us with sufficient evidence that low concentrations of selected chemotherapeutic agents, rather than conventional high doses, should be evaluated in combination with immunotherapy.

Salmonella, one of the most important pathogens transmitted by food, especially poultry, has the ability to form biofilms on surfaces. Its adhesion can be influenced by different physicochemical properties of these surfaces, while Salmonella uses fimbriae and produces cellulose as the main matrix components of biofilms. Their synthesis is co-regulated by a LuxR-type regulator, the agfD (aggregative fimbriae, curli), and adrA genes, respectively. Thus, this study investigated the production of biofilm by Salmonella spp. isolated from raw poultry (breast fillet), purchased in Botucatu, Sao Paulo, Brazil, on glass, polyvinyl chloride, and stainless steel at different temperatures (16°, 20°, 28°, and 35°C). We analyzed the frequency of the agfD and adrA genes and the rdar morphotype at 28°C and 35°C in isolated strains. We found Salmonella in 112 of 240 poultry samples (46.7%), and 62 strains previously isolated from the same kind of food were included in the study on biofilm development, gene expression, and rdar morphotype. All of them were positive for both genes, and 98.3% were able to produce biofilm in at least one temperature. The rates of rdar morphotype at 28°C and at 35°C were 55.2% (96 strains) and 2.3% (4 strains), respectively. Glass was the best material to avoid biofilm production, while Salmonella grew even at 16°C on stainless steel. These results point out the need for more effective sanitizing processes in the slaughter plants in order to avoid the permanence of these bacteria in food and eventual human foodborne diseases.

These results demonstrate that chemomodulation of human tumor cells with noncytotoxic concentrations of chemotherapeutic agents increases tumor immunogenicity and results in the generation of more efficient DC vaccines and CTLs, which can be used for cell-based anticancer immunotherapies.

Propolis, a beehive product widely used in folk medicine as an antiinflammatory agent, has been attracting researchers' attention to scientifically elucidate its biological properties and therapeutic activities. The aim of this paper was to study the possible effect of propolis on natural killer activity, since propolis immunomodulatory action has been suggested, especially on non-specific immunity. Propolis was produced by africanized honeybees (Apis mellifera L.), collected throughout a whole year, and pooled by season. Hydroalcoholic solutions of propolis were prepared with each pool and administered to rats by gavage over three days. Natural killer activity of non-adherent spleen cells was evaluated by the 51Cr-release cytotoxicity assay against Yac-1 target cells. Our results indicated that the natural killer activity was increased in spleen cells from propolis-treated animals. There were no significant differences related to the seasonal effect on the immunomodulatory action of propolis

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BackgroundThe injection of mesenchymal stem cells (MSCs) directly into the bone of osteoporotic (OP) patients for rapid recovery has been studied worldwide. Scaffolds associated with MSCs are used to maintain and avoid cell loss after application. A unique heterologous fibrin sealant (HFS) derived from snake venom was evaluated for the cytotoxicity of its main components and as a three-dimensional biological scaffold for MSCs to repair a critical femur defect in osteoporotic rats.MethodsThe cytotoxicity of HFS was assessed using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT) assay and transmission electron microscopy. The cells were cultured, characterized by flow cytometry and differentiated into the osteogenic lineage. Two-month-old rats underwent ovariectomy to induce OP. After 3 months, a 5 mm critical bone defect was made in the distal end of the rat femurs and filled with HFS; HFS + MSCs; and HFS + MSCs D (differentiated into the osteogenic lineage) to evaluate the effects. An injury control group (injury and no treatment) and blank control group (no injury and no treatment) were also included. The animals were observed at days 14 and 28 by microtomographic (micro-CT) analyses, histologic and biochemical analysis, as well as scanning electron microscopy.ResultsThe results revealed that one of the compounds of HFS, the thrombin-like enzyme extracted from snake venom, had no cytotoxic effects on the MSCs. OP was successfully induced, as demonstrated by the significant differences in the levels of 17β-estradiol, Micro-CT analyses and alkaline phosphatase between the ovariectomized (OVX) and non-ovariectomized (NOVX) groups. The histological data revealed that at 14 days after surgery in both the OVX and NOVX animals, the HFS + CTMs and HFS + CTMsD showed a higher formation of bone cells at the site in relation to the control group (without treatment). Collagen formation was evidenced through bone neoformation in all treated and control groups. No morphological differences in the femurs of the NOVX and OVX animals were observed after the surgical procedure. Scanning electron microscopy (SEM) confirmed the histological analysis.ConclusionsThe new HFS composed of two non-toxic components for MSCs showed capacity to promote the recovery of the bone lesions in OVX and NOVX animals at 14 days after surgery. In addition, the HFS enabled the differentiation of MSCs into MSCs D in the group treated with HFS + MSCs. Using the MSCs and/or MSCs D together with this biopharmaceutical could potentially enable significant advances in the treatment of osteoporotic fractures. Future clinical trials will be necessary to confirm these results.