An established hallmark of tumorigenesis is the biosynthesis of aberrant glycan chains due to changes in the expression of glycoprocessing enzymes in tumor tissue. These aberrations become more marked as the tumor acquires a more aggressive phenotype. Tumor cell-surface carbohydrates play important roles in the motility and metastasis of many different cancer cells. In addition, many of these aberrant glycans are tumor-associated carbohydrate antigens (TACA) and have been used in the development of tumor vaccines. Since most of the cellular interactions with TACAs are not well understood, there is an urgent need to better characterize the specific molecular interactions that occur during these events. One feature of carbohydrate binding to macromolecules that is well understood is the concept of multivalency: Monomer carbohydrates bind to proteins very weakly while clustering of a monomer raises this affinity as much as a million-fold. We have prepared the important Thomsen-Friedenreich (Tf) antigen (Gal(beta)1-3GalNAc(alpha)-O-Ser/Thr) on very specific templates to take advantage of this so-called cluster glycoside effect. As mentioned in the last report, we have prepared gold self-assembled nanospheres and quantum dots containing sugar derivative and reported preliminary details on their function. The in vivo experiments with our gold nanospheres in mice were conflicting, so we retreated to basics and performed more rigorous characterization and explored a host of new syntheses that allowed for production of more uniform particles. We proceeded to systematically study the optimum procedure, from several related methods, that offered the highest quality particles with regards to stability and uniformity. We are still examining these data in various media to test for stability. We have prepared the TF antigen in different contexts (attached to both serine and threonine) and linked them to particles. As mentioned, our TF particles have now been shown in pull down experiments to bind to Galectin-3 and integrin complexes related to metastasis. We put a heavy emphasis on preparing particles that encompassed what we consider the best antigen, a glycopeptide from tumor associated cell-surface mucins, and combined that with various concentrations of linker and T-helper epitope to construct particles that may act as novel immunogens. We prepared at least seven separate particles with various placements of the disaccharide on the peptide, and along with linker and a 28-residue portion of C3d, a domain of complement component 3 and a ligand of CD21, a B-cell surface protein that, when engaged, lowers the threshold of B-cell activation.. These particles were injected into mice and the sera were analyzed for immune responses. A statistically significant immune response was observed in at least two test groups, and animals we boosted a second time with fresh particles. Tumors were implanted and survival was followed. Although one specific antigen group did better than the others, they did not do better than the group that received only PBS. There are several parameters that could have led to a lower than desired response, and we are looking into these now. Further work in this area this cycle has been to take the aforementioned best construct, called MUC4-5TF, and prepare polyclonal antibody sera. This construct as prepared by us was conjugated to KLH and mice were vaccinated by Precision Antibodies Inc. Titers against our specific glycopeptides antigen are in the tens-of-thousand range and the sera was given to our new collaborator, Professor Pinku Mukherjee, at the University of North Carolina at Charlotte. She has a mouse model of pancreatic cancer in which she has been testing our antisera for protection against this tumor. Results are ongoing and will be reported soon. The new study started in collaboration with Howard Young mentioned in the last annual report, continues to explore the modulation in cytokine profiles that is elicited by particles with varying antigens in different chemical guises. Initial data showed that levels of several cytokines from activated murine macrophages are either potentiated or attenuated with particles containing different surface chemistries. This was reexamined and refined to show that specifically, TNF-alpha expression was turned on much more with very specific glycopeptide constructs than others. We have prepared three new sets of particles of various sizes coated with our important antigens. These were examined in the macrophage system and showed a dramatic increase in cytokine expression with particle size. Thus particles from sizes of 3, 16, 25 and 40 nm have dramatically different effects on cytokine gene expression, which is also dependent on the ligand for activity. In addition, we tested al the constructs in a mutant MyD88 knockout macrophage cell line. MyD88 is an adapter protein involved in the signal transduction cascade for the expression of toll-like receptor proteins. The cytokine expression induced by the nanoparticles was greatly reduced in the knockout cell line, suggesting that toll-like receptors are involved in the process of cytokine gene expression by the nanoparticles. A manuscript on the evaluation of the optimum precursors for the preparation gold nanoparticles with a variety of ligands is in the final stages before submission to Journal of Colloid and Interface Science .
