Molecularly engineered biosurfactants and their biological activities against breast cancer

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Miceli, Rebecca
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Microbially produced surfactants offer fertile ground for the discovery and development of low-cost alternative cancer specific biologics to treat breast cancer. Naturally derived through simple fermentations in high titers, biosurfactants have good biodegradability, low-cost input, and natural therapeutic properties which include anti-cancer and immunomodulating. Furthermore, natural biosurfactants provide rich scaffolds for molecular engineering. Herein, the lipopeptide surfactin and the glycolipid sophorolipid (SL) are molecularly engineered for enhanced biological activity against breast cancer. Breast cancer is the second leading cause of death among women in the US and, by the year 2040, an estimated 3 million new cases of breast cancer will be diagnosed per year due to population growth and ageing. Four different breast tumorigenic cell lines have been utilized in this study, ranging in aggressiveness, differing plasma membrane compositions, and hormonal receptor presence to elucidate the effects of molecularly engineered analogues on a range of breast cancer subtypes. Non-tumorigenic fibroblasts and erythrocytes were used to determine selectivity. Additionally, select engineered analogues were tested as monolayers and three-dimensional tumor spheroids. The later better addresses diffusional gradients, tight cell-cell junctions, and the complex tumor microenvironment found in vivo. In addition, we explore how molecular engineering of surfactin by amidation of the glutamate and aspartate carboxyl moieties affects the structural physiochemical characteristics and biological activity against tumorigenic and non-tumorigenic breast cells. We determined that overall charge of the resulting analogues induced key differences in cytotoxicity and selectivity, where anionic analogues were more selective and cationic analogues were more cytotoxic. We also explore the effects of molecularly engineered SL-esters on three different in vitro model morphologies of MDA-MB-231, triple negative breast cancer. A follow up study was completed to investigate if natural SL and a modified SL-ester induce differing cell death mechanisms using a combination of cell-based assays and exploratory RNA sequencing transcriptomics. Finally, we explore the use of synergy in the combined treatment of SL-hexyl ester and Piscidin 3, an antimicrobial peptide with biological activity against breast cancer. Studies were conducted to determine the synergistic anti-cancer effects of the drug combination and its effects in producing multiple programmed cell death pathways in BT-474 and MDA-MB-231 tumorigenic breast cells. In summary, microbial surfactants represent a broad family of alterative, low-cost novel chemotherapeutics. Their unique molecular skeletons provide a rich platform for structural regulation. Future work on further engineering microbial surfactant structure and corresponding in vitro and in vivo mechanistic studies on an extended range of breast cancer lines holds great potential for the development of therapeutics that, due to simple and scalable synthetic routes, can also provide urgently needed therapeutics to cost challenged patients worldwide.
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Rensselaer Polytechnic Institute, Troy, NY
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