Enhancing the efficacy of anti-CD20 monoclonal antibody therapy through manipulation of the tumour microenvironment

Abstract

Anti-CD20 monoclonal antibodies have significantly improved outcomes in a wide range of B-cell malignancies over the last two decades. However, many patients still relapse, and develop progressive and refractory disease, ultimately dying of their disease. Such resistance to therapy is mainly caused by the ability of malignant B cells to migrate towards the bone marrow and home in the stromal layer. In the bone marrow, the tumour micro-environment components, namely stromal cells, extracellular matrices and soluble growth factors, promote the onset of tumour-stromal-tumour interactions, which ultimately mediate tumour cell survival and protection from therapies. The abrogation of such stroma-mediated increased survival could lead to higher responses to therapy. Therefore, the project aims to characterise the stroma-mediated tumour cell protection from the novel type-II antibody GA101 (obinutuzumab) and to develop strategies to block tumour-stromal interactions, in order to improve therapeutic efficacy. Firstly, a stromal-tumour co-culture system has been established in vitro which was able to protect tumour cells from GA101-mediated programmed cell death (PCD), antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC). The basis of this protection was investigated, to understand whether such increased survival was due to direct contact between tumour cells and stromal layer, or to soluble components of the microenvironment. Some of the main pathways known to mediate interaction and migration of B cells towards the micro-environment were analysed, to investigate whether their inhibition could have led to the abrogation of stroma-mediated tumour cell protection. A mass spectrometry-based proteomic analysis was then performed to gain insights into pathways in tumour cells which were altered after co-culture with stromal cells. It was shown that the presence of stromal cells was able to protect tumour cells from type-II antibody-induced PCD, ADCP and ADCC in vitro, and such protection seemed to require the contact between stroma and tumour cells. Stromal cells appeared to interfere with the GA101-mediated B cell homotypic adhesion that leads to PCD. The proteomic analysis of tumour cells after contact with stroma led to the identification of a number of altered pathways, some of which have been further explored in vitro to validate their role in mediating protection of tumour cells from type-II antibody GA101. Characterisation of the stroma-mediated protection of malignant B cells and a deeper understanding of tumour-stroma interactions could prove a useful tool to define better strategies to target the micro-environment, ultimately improving therapeutic outcomes in B-cell lymphoma patients.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Eleanor Cheadle (Supervisor) & Timothy Illidge (Supervisor)