Glycoconjugates: Novel Non-toxic Therapies for Breast Cancer

Institution: Sidney Kimmel Cancer Center
Investigator(s): Margaret Huflejt, Ph.D. -
Award Cycle: 2003 (Cycle IX) Grant #: 9IB-0032 Award: $191,278
Award Type: IDEA
Research Priorities
Detection, Prognosis and Treatment>Innovative Treatment Modalities: search for a cure

Initial Award Abstract (2003)
Our research is focused on biology of risk factors for breast cancer. We have found that certain carbohydrate-binding proteins, called galectins, are present in breast cancers and even in pre-malignant lesions with a high-risk of progression. Research has shown that galectins are tumor-promoting proteins, and support tumor growth in many ways. One of their activities is immunosuppression, which is achieved by inhibiting cytotoxic T-cell functions or by inducing their apoptosis. We intend to test small non-toxic, non-hormonal lactulosamines, which are galectin inhibitors, to evaluate their effects on the activity of the immune system using breast tumor models. We have already shown that these compounds can slow down the growth of human-like cancers in mice, and nearly eradicate cancers when used as a complement to immunotherapy.

In this study, we will investigate the mechanisms by which an immune response can be restored by galectin inhibitors. The results will tell us whether these compounds should be considered as potential novel non-toxic therapeutics that could be used to protect and maintain active immune systems in breast cancer and in high-risk patients. First, we plan to assess the impact of galectins on the suppression of both CD4 and CD8 T-cell functions in a murine transgenic model system. Then, we plan to study of anti-cancer activity of galectin-inhibiting lactulosamines in a murine system transgenic for the rat Her-2/neu protein. We hope to optimize anti-cancer treatment protocols, and to assess the effects of inhibitors on the immune response by isolating CD4 and CD8 T-cells from freshly excised tumors and testing their activation status. Finally, we plan to determine whether inhibitors enable animals to develop protective immune responses, by re-challenging mice having rejected the initial tumor burden.

This research aims to test novel potential therapies targeting tumor-promoting proteins in the animal model of human breast cancer, and assess the benefits of these therapies by modulation of the immune system. If the tested lactulosamine compounds yield expected results, then they will become candidates for consideration as novel therapies for human breast cancer.

Final Report (2005)
Our research is focused on early detection of breast cancer, and development of non- or low toxicity preventive and anti-cancer treatments based on inhibitors of tumor-promoting, carbohydrate-binding proteins called galectins. We have earlier found that galectins -1 and -4 are induced in breast cancers and even in pre-malignant lesions with a high-risk of progression to malignancy. Others and we have shown that galectins support tumor growth in many ways. Immunosuppressive galectin-1 promotes tumors by blocking or killing cytotoxic T cells, and appearance of galectin-4 in early benign breast tumors signals high risk of progression of these benign breast diseases into full-blown malignant cancers. We have later demonstrated that galectin-4 promotes progression to malignancy by allowing aging breast epithelial cells to live longer, while continuing to multiply and accumulating genetic errors. These activities of galectins depend on the ability of these proteins to interact with abnormal sugars called Tumor Associated Carbohydrate Antigens, TACAs, present on tumor cells and tissues. We have therefore hypothesized that (1) galectins provide benign and cancer breast cells with several means of evading immune system and continuing malignant transformation, and (2) by inhibiting the activities of galectins using their non-toxic and non-hormonal carbohydrate-based inhibitors, we will be able to block breast tumor progression and growth. Therefore, the anti-cancer activities of carbohydrate-based galectin inhibitors are expected to: (a) reverse the immunosuppression, allowing increased activation and infiltration immune cells into the tumor site and thereby the tumor rejection, and (b) reduce the life-time of premalignant and malignant breast cells.

In this study, we have proposed to investigate the mechanisms by which an immune response and normal growth rates of breast epithelial cells can be restored by galectin inhibitors. Inhibitor of immunosuppressive galectin-1 has been already identified and tested in T-cell assays. However, this inhibitor had very week activity against galectin-4. Therefore, in this project, to identify active galectin-4 inhibitors, we have established cellular model of breast malignant transformation in which galectin-4 has been transfected into non-cancer epithelial cells and allowed these cells to survive in cancer-like conditions of serum starvation. To our knowledge this is the first cellular model in which normal cells acquire properties of cells in early breast tumors by being able to survive and multiply in conditions of early tumors such as lack of nutrients and growth factors due to competition for nutrients by abnormal cellular masses. We have then used this cellular model to screen for their activities a series of synthetic carbohydrate-based galectin-4 inhibitors. These inhibitors have been identified using printed glycan array (PGA) recently developed by the Consortium for Functional Glycomics at Scripps, thus also validating this new technology as a drug discovery tool. Preliminary testing using our cellular model has shown that two of these compounds in the monovalent form were able to lower abnormal cell proliferation and resistance to serum starvation. However, polyvalent galectin-4 inhibitor induced the apoptosis in galectin-4-expressing cells, and completely blocked growth and proliferation of these cells. Finally, using PGA, we have also screened sera of breast cancer patients and healthy individuals, and identified a subset of anti-glycan autoantibodies specifically associated with breast malignancy. We are currently testing PGA for its application as a screening method for the risk of breast cancer and breast malignancy status. We have also found that most significant breast-cancer specific autoantibodies target TACAs, which are ligands for galectins-4 and -1

Thus we have confirmed our hypothesis that galectin-4 inhibitors are potential anti-cancer drugs. Therefore, antibodies targeting galectin ligands have a great therapeutic potential.

Galectin-4 in normal tissues and cancer
Periodical:Glycoconjugate Journal
Index Medicus: Glycoconj J
Authors: Huflejt ME, Leffler H
Yr: 2004 Vol: 20 Nbr: 4 Abs: Pg:247-55

Galectin-4 in normal tissues and cancer
Periodical:Glycoconjugate Journal
Index Medicus: Glycoconj J
Authors: Huflejt ME, Leffler H
Yr: 2004 Vol: 20 Nbr: 4 Abs: Pg:247-55

Printed covalent glycan array for ligand profiling of diverse glycan binding proteins
Periodical:Proceedings of the National Academy of Sciences of the United States of America
Index Medicus: Proc Nat Acad Sci, U S A
Authors: Blixt O, Head S, Mondala T, Scanlan C, Huflejt ME, et al.
Yr: 2004 Vol: 101 Nbr: 49 Abs: Pg:17033-8

Detection of neoplasia-specific clusters of anti-glycan antibodies in sera of breast cancer patients using a novel glycan array
Periodical:American Association for Cancer Research
Index Medicus: AACR
Authors: Heflejt ME, etal.
Yr: 2005 Vol: Nbr: Abs: Pg: