They are considered to be important targets for see more tumor immunotherapy not only because of their different expression

patterns in healthy and transformed human tissues, but also because of their suppressive effect on immune system functions [2, 3]. In particular, N-glycolylated gangliosides are attractive targets for tumor immunotherapy because they are not normally synthesized in human tissues. This is due to a 92 bp deletion in the gene that encodes the cytidine-monophosphate-N-acetyl-neuraminc acid hydroxylase (CMAH) enzyme that catalyzes the conversion of N-acetyl to N-glycolyl sialic acid (NeuGc) [4-6]. Although humans lack this catalytic enzyme, studies have reported the presence of NeuGc in human tumors [7-10] and, in smaller amounts, in healthy adult human tissues [11]. Since an alternative pathway for NeuGc biosynthesis has not been described, the most accepted explanation for this phenomenon is the incorporation of NeuGc from dietary sources such as red meats and milk products. This incorporation occurs preferentially in tumor cells and may be due to the high division rate characteristic of tumor cells [11]. An additional proposed mechanism is that hypoxia present in the tumor microenvironment induces the Navitoclax ic50 expression of a sialin transporter in tumor cells resulting in enhanced incorporation

of (N-glycolylneuraminyl)-lactosylceramide (NeuGcGM3) [12, 13]. We have previously reported the induction of a high-titer antibody response against NeuGc-gangliosides in melanoma, breast, small, and non-small cell lung cancer (NSCLC) patients vaccinated with the mimetic anti-idiotypic antibody 1E10 [14-17]. One of these studies, performed in NSCLC patients, showed that the anti-NeuGcGM3 antibodies actively elicited by 1E10 vaccination were able aminophylline not only to recognize NeuGcGM3-expressing tumor cells but also to induce their death by an oncotic necrosis mechanism, independent of complement activation [18]. Furthermore, there was a correlation between the induction of antibodies against NeuGcGM3 and longer survival times [17]. Surprisingly, this

idiotypic vaccination also elicited a “parallel set” of antibodies that recognize NeuGcGM3 and share the cytotoxic capacity against tumor cell lines but do not recognize 1E10 mAb. This suggested that this vaccination was activating a natural response against NeuGcGM3 ganglioside [15, 17]. Taking this into account, we wondered whether this cytotoxic anti-NeuGcGM3 response was present in healthy individuals. We show here that healthy humans possess antibodies against NeuGcGM3 ganglioside able to recognize and kill tumor cells expressing this antigen. These antibodies induce tumor cell death not only by complement activation, but also by a complement independent, oncotic necrosis mechanism, similar to the one observed in cancer patients treated with 1E10 mAb.