The Treatment of Solid Tumours with Complete Freund's Adjuvant

Abstract

Cancer immunotherapy, although being established over a century ago, is an emerging field in cancer treatment. The immune system contains multiple immune cell types which have been demonstrated to play complex roles in cancer development, progression, and elimination of tumour masses. This thesis describes the assessment of a novel potential cancer treatment, Complete Freund’s Adjuvant (CFA), which is injected intratumourally in an attempt to induce an anti-tumour immune response, leading to tumour regression. CFA has been used in research for decades, primarily to produce research antibodies. CFA is composed of heat-killed mycobacteria in mineral oil and surfactant, which when emulsified with an aqueous solution creates a thick water-in-oil emulsion, which persists at the injection site. This thesis proposed that a single intra-tumoural injection of CFA would induce inflammation within a tumour, recruit immune cells to the tumour site, which would be activated by mycobacterial components and produce an anti-tumour immune response. The potential therapeutic effects of CFA were investigated in four tumour models, and found to increase survival in both the P815 mastocytoma and 4T1 mammary cancer models. CFA treatment was not, however, found to be effective in the CT26 colorectal carcinoma and the DEN-induced Hepatocellular carcinoma. Combination therapy with CFA and anti-CTLA-4, which blocks the inhibitory effects of CTLA-4 on T cells, did not improve CFA treatment efficacy in either the P815 or 4T1 models, but was found to be effective against CT26 cancers. This thesis presents a novel technique for identifying tumour-infiltrating immune cells in subcutaneous cancers over time, while also allowing those infiltrates to be correlated with survival and metastasis by the combination of repeated fine needle aspiration (FNA) and flow cytometry. Using this technique, the tumour-infiltrating immune cells in tumours after CFA treatment were identified. In the P815 model, tumour-infiltrating neutrophils were identified as the primary infiltrating cell type, and high frequencies within the tumours early after treatment was associated with improved survival and reduced metastasis. The selective depletion of neutrophils using anti-GR-1 antibody abrogated the therapeutic benefit of CFA treatment and worsened overall tumour progression and metastasis. This thesis describes the use of an inexpensive and simple cancer treatment successfully in two solid tumour types, the P815 mastocytoma and 4T1 mammary cancer models. The efficacy of this treatment was found to be mediated by neutrophils in the P815 model. This work provides the first demonstration of the potential anti-cancer effects of CFA and furthers the current knowledge regarding the controversial role of neutrophils in tumours and their potential as immune effector cells which can be targeted therapeutically. Show more