Breast cancer is the most common malignancy effecting women worldwide. Whilst most women present with early breast cancer, potentially curable with a combination of surgery, chemotherapy and radiotherapy a substantial proportion present with or develop metastatic disease, no longer curable with conventional treatment. Immunotherapy is emerging as a valuable treatment strategy for metastatic cancer. Tumour infiltrating lymphocytes (TILs) have been investigated as a therapy in cancers such as melanoma with some success. TILs in breast cancer have been evaluated in the prognostic setting are found to be more prevalent in cancers that have poor prognostic characteristics and they have been independently correlated with improved overall survival and decreased distant recurrence. This therefore suggests that immunotherapeutic approaches may be relevant and that enhancing the anti-tumour activity of TILs may improve outcome in metastatic breast cancer. Furthermore, recent work has suggested that T cell migration into the tumour is regulated by the tumour endothelium. This novel work and the mechanisms underlying it have yet to be investigated in the human tumour situation.
It is therefore proposed that breast cancer TIL activity is modulated by the tumour and
immune microenvironment and can be enhanced to induce improved anti tumour
Materials and Methods
A balb/c mouse model using the 4T1 cell line was employed to investigate the hypothesis in an in vivo setting. In vitro work was carried out following isolation and expansion of T cells from human breast tumour samples using the GentleMACS system. Expanded T cells were assessed by flow cytometry for differentiation and phenotypic markers. Expression of immune checkpoint molecules were included in this panel. Comparison to healthy donor PBMCs was also carried out.
The 4T1 mouse model is a rapidly growing animal tumour model prone to ulceration and thus animal culling within a small number of days. Expansion of breast TIL is difficult and only one sample has been successfully expanded. Expression of multiple immune checkpoint molecules occurs only in a minority of T cells.
The 4T1 tumour model is unlikely to give meaningful results when considering the time necessary to establish a complete tumour microenvironment and competent host
immune response. As a result further animal work has been suspended. Human breast
TIL prove difficult to expand and therefore further optimisation of the expansion protocol is required. Once optimised methods to release TILs from immunosubversion can be investigated. Work is currently underway to establish an in vitro human tumour
endothelium and T cell migration model.