To verify whether the mifamurtide ineffectiveness in aggressive HOS and 143B relied on the blockade of IL-6 signaling caused by a high IL-10 secretion by these tumor cells, we first analyzed the expression of IL-6 in macrophages co-cultured with the three different OS cell lines and treated with an anti-IL-10 blocking antibody alone or in combination with mifamurtide (Figure 5A,B). Here, IL10 is linked to neoplasm.