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 TACA's 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 repeated twice with varying results. However, these were caused by the use of a tumor cells that had had a different genetic makeup than the original and an error in the amount of tumor used. We have done further in vitro characterization of the gold particles and found them to act differently than monovalent sugar molecules. A large in vivo study has yielded conflicting but highly provocative results with varying concentrations of particles being tested against control (linker-only) nanoparticles. We seem to be able to inhibit primary tumor growth in vivo, but we possibly promote metastasis with particles of larger hydrodynamic volume. In the last report we reported synthesis of mucin glycopeptides and developed new linker technology to attach these to gold particles. Synthesis of gold particles with 2 glycopeptides has been achieved and characterization is in full swing. Preliminary in vitro testing showed funcytional sugar untis on the gold particles. In our quantum dots (qdots) work, we showed that contain Tf antigen-containing Qdots are functional but we needed to develop technology that removed the negative charge on our original design. WE now feel that our qdots may be more stable than commercial qdots since ours do not precipitate on size exclusion membranes during concentration experiments. We are scaling up our process and will supply several collaborators with material for labeling studies. We are very excited about the prospects for both families of particles that are being developed.
| Sundgren, Andreas; Barchi Jr, Joseph J (2008) Varied presentation of the Thomsen-Friedenreich disaccharide tumor-associated carbohydrate antigen on gold nanoparticles. Carbohydr Res 343:1594-604 |
