Research progress on the association between vaginal Lactobacillus iners and cervical cancer

Persistent infection with high-risk Human Papillomavirus (hrHPV) is the central etiological factor in cervical cancer, while the host vaginal microenvironment plays a critical role in disease progression. Lactobacillus iners is one of the most widely distributed lactobacilli in the vagina. Because of its unique biological features, including exclusive production of L-lactic acid and a small genome, it occupies a transitional state within the vaginal ecosystem. Recent studies have shown that Lactobacillus iners (L. iners) plays dual and paradoxical roles in cervical carcinogenesis and progression. In the vaginal microenvironment, L. iners is associated with persistent hrHPV infection and an increased risk of Cervical Intraepithelial Neoplasia (CIN) progression; its protective effects are limited and often coexist with unfavorable inflammatory states. In contrast, within the tumor microenvironment, intratumoral colonization by L. iners can markedly increase L-lactate production, induce chemoradiotherapy resistance in tumor cells, and serve as an independent risk factor for poor prognosis. This review systematically summarizes the biological characteristics of L. iners, its roles and mechanisms in cervical cancer initiation, progression, and treatment resistance, and its translational value as a novel biomarker and potential therapeutic target. Current controversies, limitations, and future directions are also discussed.