Investigation of nanobody-decorated albumin nanoparticles for tumor targeting

Abstract

Cancer is still the worldwide leading cause of death. Cancer cells are similar to and different from healthy cells and this makes the eradication of these cells difficult without harming the healthy ones. They are similar in the sense that they share the same cellular machinery with the healthy cells (such as cell division) and different from healthy cells where the feedback mechanisms of controlled cell division and proliferation cease to exist. Conventional cancer chemotherapy aims at blocking the cell division by interfering with the cell cycle, provided that tumor cells divide faster than healthy cells. However the chances of harming fast dividing healthy cells and fast dividing tumor cells are equal. Indeed, the common toxicities observed for cytotoxic drugs are observed mostly in healthy cells that divide fast, such as cells of the gastrointestinal tract and hair follicles. Mutations in tumor cells that lead to higher expression levels of growth factor receptors, for instance, enable those cells to survive as they are more capable of proliferating and are more resistant to apoptosis. The tumor pathophysiology (at a tissue level) is characterized by leaky vasculature and impaired lymphatic drainage. The combination of these two lead to the enhanced permeation and retention at the tumor site, commonly referred to as the EPR effect. The field of “nanomedicine” exploits this EPR effect in order to treat or diagnose cancer. Nanomedicine, in simple terms, refers to nano-sized carriers that can retain a drug throughout its circulation in the blood stream and limit its whole body distribution as opposed to systemic intravenous injection of drugs. Drug carrying nanoparticles cannot easily cross the endothelial barrier and therefore avoid most healthy tissues. In contrast, these nano-sized carriers can pass through the leaky tumor blood vessels, provided that they can circulate long and are small enough to pass through the endothelial gaps. Nanoparticulate carriers will eventually accumulate at the tumor site, Lastly, since the lymphatic drainage at the tumor site is impaired, they are usually retained in the tumor. The initial part of this thesis describes the reformulation of alternative drugs used in the treatment of cancer in addition to conventional cell cycle inhibitors, such as molecularly targeted small molecule drugs into albumin nanoparticles. Overexpressed growth factor receptors (i.e EGFR and c-MET) are good druggable proteins. They can both be targeted with small molecule receptor kinase inhibitors that can inhibit the intracellular part of the protein and antibodies/nanobodies that can block the extracellular epitopes, resulting in the inhibition of signaling cascades. The nanobody-decorated albumin nanoparticles loaded with kinase inhibitors are evaluated for their cellular binding, uptake, trafficking and eventually efficacy on tumor cells. They are shown to be taken up only by the tumor cells where it exerts its effect. The second part deals with understanding the haemacompatibility and biodistribution of these nanoparticles. Nanoparticles showed haemacompatible properties whereas the tumor accumulation was dominated by liver uptake as is commonly observed for nanoparticulate drug carriers.