NKT cell immunotherapy for breast cancer

Breast cancer is the most common type of cancer in Canadian women and the second leading cause of cancer deaths. Despite advances in screening and treatments, 15-20% of patients do not survive past the first five years, and 25-35% of patients will experience local recurrence or spread of their cancer to other organs. This highlights the continued need for new therapeutic strategies to combat this disease. One approach is to enhance tumour control by manipulating the function of the immune system. Dr. Johnston’s laboratory has been examining the anti-tumour properties of a rare population of white blood cells called natural killer T (NKT) cells. Activation of NKT cells in mice can induce potent anti-tumor responses that prevent metastasis (the spread of cancer cells). However, the potential benefits of NKT cell activation in breast cancer have not been established. In this project, Dr. Johnston’s group will determine whether NKT cell activation following surgical removal of established breast tumours can enhance the immune system to control breast cancer metastasis and increase survival in mice. As NKT cell numbers are reduced in many cancer patients, Dr. Johnston’s group will also determine whether transferring additional NKT cells or optimizing their activation will enhance the control of metastatic breast disease. This work will help establish the rationale and design for future clinical trials with breast cancer patients. Aim #1: Role of NKT cell activation in the clearance of breast cancer metastases.Following resection of primary mammary tumour masses, endogenous NKT cells will be activated with the glycolipid antigens a-GalCer or a-C-GalCer. We will examine the impact of NKT cell activation on metastatic tumour burden and survival time. The effects of NKT cell activation on myeloid derived suppressor cell (MDSC) number and activity will be assessed by flow cytometry and in vitro suppression assays. The in vivo generation of tumour-specific memory and effector T cells will be examined by measuring IFN-? recall responses to tumour antigens and lysis of 4T1 and EO771 target cells ex vivo.Aim #2: Role of NKT cell adoptive transfer in control of breast cancer metastasis.As NKT cell numbers and function are reduced in many breast cancer patients, the effectiveness of endogenous NKT activation could be limited. Therefore, we will examine the role of adoptive NKT cell transfer in the control of mammary tumour metastasis. In vitro expanded NKT cells will be transferred into tumour resected mice prior to glycolipid activation. This may overcome NKT cell defects or a requirement for a higher threshold of NKT cell effector activity to enhance anti-tumour immunity and clearance of tumour metastases.Aim #3: Control of breast cancer metastasis with a-GalCer-loaded dendritic cells (DCs).Glycolipid presentation to NKT cells occurs in the context of the MHC-like molecule CD1d expressed on antigen presenting cells. Adoptive transfer of DCs loaded with glycolipid antigens induces more efficient NKT cell activation in vivo than treatment with free glycolipids. a-GalCer-loaded DCs can also be used to deliver multiple NKT cell stimulations as they do not induce NKT cell anergy like treatments with free glycolipids. We will test the anti-tumour response induced by adoptive transfer of a-GalCer-loaded DCs alone or in combination with expanded NKT cells. a-GalCer-loaded DCs will allow us to determine whether multiple NKT cell stimulations are required to mediate long term tumour control.