Researchers from Kumamoto University in Japan studied the effects of a natural onion compound, onionin A (ONA), on a preclinical model of epithelial ovarian cancer (EOC) both in vivo and in vitro.
Previously, researchers found that ONA suppressed pro-tumour activation of host myeloid cells.
According to a 2014 review of cancer medicines from the World Health Organisation, EOC is the most common type of ovarian cancer and has a five-year survival rate of about 40 per cent, researchers said.
It has a relatively low lifetime risk that is less than one per cent, but that can increase up to 40 per cent if there is a family history of the disease.
A majority of patients (80 per cent) experience a relapse after their initial treatment with chemotherapy; therefore, a more effective line of treatment is needed.
The group's in vitro experiments showed that EOCs, which usually proliferate in the presence of pro-tumour M2 macrophages, showed inhibited growth after introduction of ONA.
This was thought to be due to ONA influence on STAT3, a transcription factor known to be involved in both M2 polarisation and cancer cell proliferation.
The team also found that ONA inhibited the pro-tumour functions of myeloid-derived suppressor cells (MDSC), which are associated with the suppression of the anti-tumour immune response of host lymphocytes, by using preclinical sarcoma model.
Moreover, experiments on an ovarian cancer murine model that investigated the effects of orally administered ONA resulted in longer lifespans and inhibited ovarian cancer tumour development.
This was considered to be a result of ONA's suppression of M2 polarised macrophages, researchers said.
The study shows that ONA reduces the progression of malignant ovarian cancer tumours by interfering with the pro-tumour function of myeloid cells.
ONA appears to activate anti-tumour immune responses by nullifying the immunosuppressive function of myeloid cells. It has the potential to enhance existing anti-cancer drugs while also having little to no cytotoxic effects on normal cells, researchers said.
No side effects in animals have been observed. With a little more testing, an oral ONA supplement could greatly benefit cancer patients, they said.
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