The Herpes simplex virus is a widespread virus that often causes cold sores, and most people carry it. By removing a virulence gene, i.e. a gene that makes the virus harmful to humans, the herpes virus can be repurposed as a cancer vaccine. This modification prevents the virus from harming healthy tissue while allowing it to target cancer cells, which function differently from normal cells. These findings are presented in a new doctoral thesis at Åbo Akademi University, Finland.
The new cancer vaccine includes a gene that encodes the protein decorin. Decorin is a proteoglycan—a protein with attached sugar chains—crucial for connective tissue, where it regulates wound healing and the formation of new blood vessels.
"Ample evidence shows that decorin is absent in most human cancers, even in tissues where it is normally present. Tumour angiogenesis—the formation of new blood vessels during tumour growth—leads to the development of disorganised vessels around the tumour. These disorganised blood vessels hinder drug delivery to the tumour and shield it from various therapies. They also contribute to more aggressive cancer," says PhD Fanny Frejborg, who is completing her doctoral thesis in pharmacy at Åbo Akademi University.
In the first part of her thesis, Frejborg demonstrated that decorin enhanced the vaccine's cancer-killing effect on lung cancer cells. In the second part of the study, the research showed that these cancer vaccines can be administered intranasally to the lungs of mice. In the third part of the study, the cancer vaccine was shown to reduce tumour angiogenesis by 40% in liver cancer in chicken embryos, with treated tumours developing normal blood vessels compared to untreated ones. This effect was observed even when tumours were treated after blood vessel formation and appeared just a few days after a single vaccine dose. The chicken embryos showed no side effects from the treatment, indicating that the vaccine's action is specific to the tumour.
"These results could pave the way for new cancer vaccines that not only treat cancer without side effects, but also enhance the effectiveness of existing therapies, since regulating blood vessel growth around tumours can improve drug delivery," says Frejborg.
PhD Fanny Frejborg defended her doctoral thesis in pharmacy, titled Decorin-expressing oncolytic herpes simplex virus vector for novel cancer therapy on Friday, 19 September 2025. The thesis is available to read online: https://www.doria.fi/handle/10024/193197
