Development of targeted lipid nanoparticles enclosing miRNA for the treatment of HER2-positive breast cancer (MICROTARGET).

Francis Crick’s central idea in molecular biology explains how genetic information moves from DNA (the blueprint of all life) to proteins (which do much of the work in our bodies) through an intermediary called RNA. We now know that this RNA molecule first popularized as a simple messenger can take many different forms including that a powerful molecular switch, now defined as microRNA. microRNA can tell a cell to stop growing or even to die and could therefore become an important weapon in the fight against cancer. But there are challenges. First, it is difficult to get microRNA into cancer cells. Second, we need to make sure they only target cancer cells and not healthy cells. That is where our research comes in. We are developing tiny “delivery vehicles” called nanocarriers that can transport microRNA directly to cancer cells. These nanocarriers have a special “address tag” that ensures they only deliver their target to the right cells, like a GPS system for medicine. In our case we will work with a specific subtype of breast cancer that is defined as epidermal growth factor receptor 2 (HER2) positive. We will test our nanocarriers on cells grown in the lab and in an animal model – zebrafish – a tiny fish that allows us to see exactly where the nanocarriers go and how they affect cancer cells. This research could lead to new, targeted cancer therapies with fewer side effects, offering hope to patients with HER2-positive breast cancer.

MicroRNA (miRNA) is a class of non-coding RNA made of a short single strand of nucleotides that can selectively bind specific messenger RNAs and inhibiting translation. While every cell in the body utilizes hundreds of miRNA for gene regulation, cancers modify the expression of some miRNAs by upregulating those that promote tumor growth and inhibit tumor suppressor miRNA. Different groups have recently attempted to treat cancer by restoring the normal pattern of miRNA. They did so by administering therapeutic miRNA made of synthetic nucleotides that block oncogenic miRNA or provide the missing tumor suppressor miRNA. This strategy has been hampered by miRNA off-target effects leading to toxicity. Here we aim to overcome this problem by delivering therapeutic miRNA via targeted lipid nanoparticles (LNP). These can encapsulate large amounts of miRNA, enter cells via endocytosis and deliver miRNA to the cytoplasm via endosomal escape. We will engineer these LNP with a targeting ligand on their surface to selectively enter a specific cell type. We have chosen as target Human epidermal growth factor receptor 2 (HER2) which is upregulated in 20% of breast cancers, the most common malignancy worldwide. After preparation of LNP, we will assess them in vitro and in vivo. For the in vitro system we are establishing a cell co-culture that mixes HER2-positive and negative cells; this allows us to select LNP that selectively bind, enter and kill HER2-positive cells. For in vivo analysis we will take advantage of the transparency of the zebrafish embryo to quantitate the amount of targeted LNP that can selectively enter and kill target HER2-positive but not-negative cells. These basic experiments will lay the foundation for using patient-derived cancer cells to assess whether our findings could be applied in a personalized approach.