Targeting Melanoma Hypoxia with the Food-Grade Lactic Acid Bacterium Lactococcus Lactis

Abstract

Melanoma is the most aggressive form of skin cancer. Hypoxia is a feature of the tumor microenvironment that reduces efficacy of immuno- and chemotherapies, resulting in poor clinical outcomes. Lactococcus lactis is a facultative anaerobic gram-positive lactic acid bacterium (LAB) that is Generally Recognized as Safe (GRAS). Recently, the use of LAB as a delivery vehicle has emerged as an alternative strategy to deliver therapeutic molecules; therefore, we investigated whether L. lactis can target and localize within melanoma hypoxic niches. To simulate hypoxic conditions in vitro, melanoma cells A2058, A375 and MeWo were cultured in a chamber with a gas mixture of 5% CO2, 94% N2 and 1% O2. Among the cell lines tested, MeWo cells displayed greater survival rates when compared to A2058 and A375 cells. Co-cultures of L. lactis expressing GFP or mCherry and MeWo cells revealed that L. lactis efficiently express the transgenes under hypoxic conditions. Moreover, multispectral optoacoustic tomography (MSOT), and near infrared (NIR) imaging of tumor-bearing BALB/c mice revealed that the intravenous injection of either L. lactis expressing β-galactosidase (β-gal) or infrared fluorescent protein (IRFP713) results in the establishment of the recombinant bacteria within tumor hypoxic niches. Overall, our data suggest that L. lactis represents an alternative strategy to target and deliver therapeutic molecules into the tumor hypoxic microenvironment.

Skin Barriers in Dermal Drug Delivery: Which Barriers Have to Be Overcome and How Can We Measure Them?

“…Therefore, optoacoustic imaging allows to differentiate between single skin layers (SC, viable epidermis and dermis) and enables visualization of the blood capillary loops and the vascular plexus (impact of the vascular barrier on drug delivery). Addressing cancer-induced morphologic (e.g., angiogenesis) or metabolic changes (e.g., tissue glycation) within the skin, several studies already document the applicability of optoacoustic imaging for diagnostic purposes [ 190 , 191 , 192 ] or potentially cancer-related changes of tissue glycation [ 193 ].…”

Engineered live bacteria as disease detection and diagnosis tools

“…Current therapeutic approaches are unable to target tumor cells due to increased stiffness resulting from abnormal extracellular matrix structural changes and a hypoxic tumor environment [ 200 ]. In this regard, the ability of L. lactis to detect melanoma using Multispectral Optoacoustic Tomography (MSOT) was investigated [ 156 ]. L. lactis was engineered to express β-galactosidase, a well-characterized MSOT contrast agent [ 201 ], under the Stress-Inducible Controlled Expression (SICE) system.…”

Recent advances in bacteria-mediated cancer therapy

“… Stritzker et al (2007 ) showed that some facultative anaerobes (e.g., Escherichia and Salmonella ) are able to sense the nutrient-rich region in and around the tumor center, which results in enhanced accumulation in tumors. Actually, these mechanisms are neither mutually exclusive nor completely independent, and bacteria might activate multiple pathways to specifically target tumors ( Garza-Morales et al, 2020 ). Certainly, different strains may exhibit distinct mechanisms lead to different tumor-targeting abilities.…”