Focus On: Cancer Vaccines

After decades of research, therapeutic cancer vaccines are finally beginning to show promise in clinical trials. We look at why earlier efforts failed and how the latest approaches work

The Biologist 65(4) p26-29

Therapeutic cancer vaccines aim to ‘teach’ the immune system to attack and break down cancerous cells and tumours.

First, an antigen must be found that is expressed exclusively by the cancer cells, then the body’s T cells must be encouraged to attack any cell found to have that target molecule.

The antigen might be a complete surface protein found on cells in the tumour, or the peptide fragments of any protein expressed by the cancer cells. To be effective, the vaccine must stimulate cytotoxic T cells (such as CD8+ T cells) to attack any cell expressing the target antigen. Helper T cells (such as CD4+ T cells), which modulate the immune response to pathogens and tumours, are known to be recruited in successful vaccines, although the exact response of the two types of T cell is complex and depends on the antigen.

In early efforts to develop cancer vaccines, many of the target antigens failed to trigger a strong enough immune response to halt the cancer’s progress. After all, for cancer cells to have progressed into a tumour, they must already be successfully evading or suppressing the body’s immune response. Many early trials were also often conducted on patients with advanced cancer whose immune systems were severely compromised.

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