Cell-based immune therapy is a type of immunotherapy that works by direct transfer of activated cancer-fighting immune cells to the patient in order to seek and destroy the cancer. The cells transferred can originate from the patient’s own immune cells isolated from the blood or from a donor, engineered in the laboratory to become super activated then injected into the patient.
The most common type of this treatment is the chimeric antigen receptor T cells (CAR-T cells) where the immune cells (here called T cells) are equipped with a new version of a cell surface protein (T cell receptor) that enhances the stimulation of the immune cells once they come into contact with a pre-defined target on the cancer cells.
This approach works very well for blood cancers but its success in solid tumors is yet to be realized, for a variety of reasons, including difficult to penetrate tumor structure, harsh local conditions preventing CAR-T cell expansion and survival, and the heterogeneity of the targets on cancer cells.
Ensuring the delivery and continued presence/activation of adequate numbers of immune cells in tumors remains a major goal of cell therapy and for this reason, many clinical trials are exploring the value of injecting cells straight into the tumor site.
Direct delivery of CAR-T cells into the site of the cancer could work very well for localized disease (where there is no metastasis, for example in some cases of brain cancer). This is because it can deliver a high load of therapeutic cells which can persist and mount an effective attack on tumors more effectively, potentially leading to better disease control. This also avoids unnecessary presence of activated immune cells in (and potential for immune attack on) normal tissues, and as a consequence limits the side effects in other parts of the body.
Systemic delivery (injection of therapeutic CAR-T cells into the patient’s blood stream) is however the preferred method for disease that has spread to other parts of the body (and blood cancers of course). However the amount of cells delivered locally to each disease site and their chances of persistence and expansion remain problematic, not to mention the side effects likely to occur as a result of the presence of activated immune cells in normal tissues.
It is however just the beginning of the road for cell therapy with many clinical studies looking at ways to increase the effectiveness as well as safety of this very promising type of anti-cancer treatment.
