Macrophages, IL-10, and nitric oxide increase, induced by hyperglycemic conditions, impact the development of murine melanoma B16F10-Nex2.

Epidemiological studies show a strong correlation between diabetes and the increased risk of developing different cancers, including melanoma. In the present study, we investigated the impact of a streptozotocin (STZ)-induced hyperglycemic environment on B16F10-Nex2 murine melanoma development. Hyperglycemic male C57Bl/6 mice showed increased subcutaneous tumor development, partially inhibited by metformin. Tumors showed increased infiltrating macrophages, and augmented IL-10 and nitric oxide (NO) concentrations. In vivo neutralization of IL-10, NO synthase inhibition, and depletion of macrophages reduced tumor development. STZ-treated TLR4 KO animals showed delayed tumor development; the transfer of hyperglycemic C57Bl/6 macrophages to TLR4 KO reversed this effect. Increased concentrations of IL-10 present in tumor homogenates of hyperglycemic mice induced a higher number of pre-angiogenic structures in vitro, and B16F10-Nex2 cells incubated with different glucose concentrations in vitro produced increased levels of IL-10. In summary, our findings show that a hyperglycemic environment stimulates murine melanoma B16F10-Nex2 primary tumor growth, and this effect is dependent on tumor cell stimulation, increased numbers of macrophages, and augmented IL-10 and NO concentrations. These findings show the involvement of tumor cells and other components of the tumor microenvironment in the development of subcutaneous melanoma under hyperglycemic conditions, defining novel targets for melanoma control in diabetic patients.

Killed Propionibacterium acnes enhances immunogenicity and tumor growth control of a dendritic-tumor cell hybrid vaccine in a murine melanoma model.

Hybrid vaccines have been investigated in clinical and experimental studies once expresses total antigens of a tumor cell combined with the ability of a dendritic cell (DC) to stimulate immune responses. However, the response triggered by these vaccines is often weak, requiring the use of adjuvants to increase vaccine immunogenicity. Killed Propionibacterium acnes (P. acnes) exerts immunomodulatory effects by increasing the phagocytic and tumoricidal activities of macrophages, promoting DC maturation, inducing pro-inflammatory cytokines production and increasing the humoral response to different antigens. Here, we evaluated the effect of P. acnes on a specific antitumor immune response elicited by a hybrid vaccine in a mouse melanoma model. Hybrid vaccine associated with P. acnes increased the absolute number of memory T cells, the IFN-γ secretion by these cells and the IgG-specific titers to B16F10 antigens, polarizing the immune response to a T helper 1 pattern. Furthermore, the addition of P. acnes to a hybrid vaccine increased the cytotoxic activity of splenocytes toward B16F10 in vitro and avoided late tumor progression in a pulmonary colonization model. These results revealed the adjuvant effect of a killed P. acnes suspension, as it improved specific humoral and cellular immune responses elicited by DC-tumor cell hybrid vaccines.

Propionibacterium acnes induces an adjuvant effect in B-1 cells and affects their phagocyte differentiation via a TLR2-mediated mechanism.

B-1 lymphocytes are present in large numbers in the mouse peritoneal cavity, as are macrophages, and are responsible for natural IgM production. These lymphocytes migrate to inflammatory foci and are also involved in innate immunity. It was also demonstrated that B-1 cells are able to differentiated into phagocytes (B-1CDP), which is characterized by expression of F4/80 and increased phagocytic activity. B-1 cell responses to antigens and adjuvants are poorly characterized. It has been shown that Propionibacterium acnes suspensions induce immunomodulatory effects in both macrophages and B-2 lymphocytes. We recently demonstrated that this bacterium has the ability to increase B-1 cell populations both in vitro and in vivo. P. acnes induces B-1CDP differentiation, increases the expression of TLR2, TLR4 and TLR9 and augments the expression of CD80, CD86 and CD40 in B-1 and B-1CDP cells. Because P. acnes has been shown to modulate TLR expression, in this study, we investigated the role of TLR2 and TLR4 in B-1 cell population, including B-1CDP differentiation and phagocytic activity in vitro and in vivo. Interestingly, we have demonstrated that TLR2 signaling could be involved in the increase in the B-1 cell population induced by P. acnes. Furthermore, the early differentiation of B-1CDP is also dependent of TLR2. It was also observed that TLR signals also interfere in the phagocytic ability of B-1 cells and their phagocytes. According to these data, it is clear that P. acnes promotes an important adjuvant effect in B-1 cells by inducing them to differentiate into B-1CDP cells and modulates their phagocytic functions both in vivo and in vitro. Moreover, most of these effects are mediated primarily via TLR2. These data reinforce the findings that such bacterial suspensions have powerful adjuvant properties. The responses of B-1 cells to exogenous stimulation indicate that these cells are important to the innate immune response.