Tumours crate environment in which all cells are involved in supporting tumour progression. The formation of tumour cell takes many years during which the cell generate transformation that will allow uncontrolled division. All these changes allow the tumour cells to survive on expense of the surrounding normal tissues. Common cells supporting the tumour growth are cells of the haematopoietic system, lymphocytes, macrophages and granulocytes. Interestingly the immune system is not visible involved in the initial tumour growth. According to one of the hypothesis the tumour is detected but develops resistance to the immune response. It is observed that not all tumours are infiltrated by the immune system cells and this vary by tumour type. In majority of the cases the tumours are able to avoid the immune system and continue their growth.
What is observed in oncology patients is that T lymphocytes are destroyed at higher level and according to the hypothesis this is tumour induced mechanism. There are evidences that the tumours do not affect only specific cells but the whole immune system and its functions.
Interestingly tumours not only stimulate the immune system, but they suppress it as well. Tumours produce cytokines which suppress the anti-immune response.
Potential therapies and their implications:
- Inhibition of IL-10 (interleukin 10) – Inhibition of IL-10 generally improve the immune system anti-tumour response but this is not true for all cases. One of the theories that inhibition of IL-10 leads to increased production of anti-tumour T cells. A low dose of Cyclophosphamide which inhibits IL-10 and other factors has shown to reduce the tumour size and metastasis in treated animals.
- Macrophages Migration Inhibitory Factor (MIF) – It is shown to have significant role in inflammation process. It was observed that MIF is expressed in higher levels in tumour cells than normal cells. According to one of the theories this is due to tumour cells producing MIF to inhibit the natural killers induced lysis in the cells. Studies have shown that inhibition of MIF delays tumour growth.
- Prostaglandin (PG)E2 – is a lipid that mediates tumour growth and supress the host immune system. The synthesis of prostaglandin is regulated by cyclooxygenase (COX). Studies have shown that the inhibition of COX enzymes leads to reduction in tumour growth and metastasis.
There are number of other mechanisms that supress tumour growth and support the immune system, however more research is required to investigate the roles of different components and mechanisms of action.
Author: Olga Peycheva
Olga is a clinical research professional who has been working in clinical research since 2005. She has extensive experience in clinical research in Eastern and Western Europe.
Originally published on 5 Oct 2020