Postbiotics as Adjuvant Therapy in Cancer Care

Abstract

Postbiotics are defined as a preparation of inanimate microorganisms and/or their components that confers a health benefit to the host. They range from cell wall fragments to metabolites, bacterial lysates, extracellular vesicles, and short-chain fatty acids (SCFAs). Postbiotics may influence carcinogenesis via a variety of mechanisms. They can promote homeostatic immune responses, reduce inflammation, induce selective cytotoxicity against tumor cells, as well as the enabling the control of tumor cell proliferation and enhancing intestinal epithelial barrier function. Therefore, probiotics can serve as an adjunct strategy in anticancer treatment together with chemotherapy and immunotherapy. Up to now, the only relevant postbiotics used as interventions in oncological patients remain vitamin K molecules, with few phase-II and III trials available. In fact, postbiotics' levels are strictly dependent on the gut microbiota's composition, which may vary between individuals and can be altered under different physiological and pathological conditions. Therefore, the lack of consistent clinical evidence supporting postbiotics' efficacy is due to their poor bioavailability, short half-life, and fluctuating levels. Synbiotics, a mixture of prebiotics and probiotics, are expected to have a more homogeneous bioavailability with respect to postbiotics and may have greater potential for future development. In this review, we focus on the role of postbiotics as an adjuvant therapy in cancer treatment.

Keywords: cancer; gut microbiome; immunity; inflammation; postbiotics.

Figure 1

Factors that modify the gut microbiome, including the various types of postbiotics. Our own elaboration based on the data in [8,11,12,13]. This figure was created using Biorender.com (accessed on 1 July 2024).

Figure 2

Mechanisms by which postbiotics enhance the effectiveness of chemotherapy and immunotherapy in cancer care. This figure illustrates several actions of postbiotics: (1) increasing tumor cell cytotoxicity by enhancing caspase activity, thereby promoting apoptosis in cancer cells; (2) immune modulation by reducing proinflammatory cytokines, contributing to a more balanced immune response; (3) controlling tumor proliferation by inducing apoptosis through the production of reactive oxygen species (ROS); (4) strengthening barrier function by increasing mucin production and tight junction protein expression, reducing the passage of potential carcinogens into the systemic circulation; and (5) increasing the effectiveness of standard chemotherapy and immunotherapy by sensitizing cancer cells to these treatments or by regulating immune responses to enhance antitumor activity. These complex mechanisms highlight the potential of postbiotics as adjuncts in cancer therapies.