Vaginal Microbiota and Ovarian Cancer: A New Frontier in Immunomodulation and Diagnosis.

Ovarian cancer remains one of the deadliest gynaecological cancers due to its often-late diagnosis and the absence of specific symptoms in the early stages. Beyond genetic alterations, the tumour microenvironment, including the vaginal microbiota, plays a decisive role in tumour progression. Recent studies have highlighted the involvement of microbial imbalance 'dysbiosis' in ovarian carcinogenesis, particularly through interactions with the immune system and the modulation of local inflammatory pathways such as Th17-related pathways. In a state of 'eubiosis,' the vaginal microbiota, dominated by Lactobacillus species, plays a protective role by producing lactic acid, maintaining an acidic pH, and preventing infections. Conversely, dysbiosis, characterised by a decrease in lactobacilli and an increase in opportunistic bacteria such as Gardnerella, Atopobium and Prevotella, promotes chronic inflammation through Toll-like receptor signalling, stimulates the production of IL-6, IL-8 and TNF-α, thereby creating a pro-tumour immune microenvironment conducive to tumour development. The complex interactions of the microbial flora, mucosal immunity, and tumour cells could explain the association between vaginal microbiota and ovarian cancer. This review highlights these mechanisms and emphasises the potential of vaginal microbiota as a tool for early detection and improved diagnosis of ovarian cancer. A better understanding of this microbe-host dialogue could pave the way for new prevention and detection strategies.