טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBar-Zeev Maya
SubjectCasein Based Nano-vehicles for Oral Delivery of
Chemotherapeutic Combinations to Overcome
Multidrug Resistance in Gastric Cancer
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisors Professor Yoav Livney
Professor Yehuda Assaraf


Abstract

Gastrointestinal cancers are the third leading cause of cancer-related mortality worldwide. The vast majority of chemotherapeutic drugs are administered intravenously (IV). IV drug administration causes discomfort and stress to patients and incurs high costs due to multiple hospitalizations required to complete the series of IV sessions. Moreover, chemotherapy is dangerous for immunocompromized cancer patients, due to antibiotic-resistant pathogens widespread in hospitals.

Oral drug administration is a highly preferred route of drug delivery, promoting patient’s satisfaction and compliance; it does not require medical equipment and thereby does not necessitate hospitalization. The availability of suitable and effective oral chemotherapeutics would significantly contribute to patients’ quality of life, allowing less painful treatment at the comfort of their home, circumvent infection with antibiotic-resistant bacteria, and reduce costs.

Bovine milk is mainly comprised of phosphoproteins known as caseins. Their pronounced amphiphilic structure promotes their self-assembly into stable micellar structures in aqueous solution. Casein (CN) micelles (CM) are composed of four caseins: αs1-, αs2-, β- and κ-CN supported by calcium-phosphate bridging. The open tertiary structure of CM, resulting from their proline-rich sequence, facilitates enhanced gastric proteases accessibility. Previous studies from our lab have demonstrated the ability of β-casein (β-CN) micelles (β-CM) and re-assembled casein micelles (rCM) to serve as nano-vehicles for oral delivery and target-activated release of hydrophobic bioactives including chemotherapeutics locally in the stomach. In this respect, many of the current cancer chemotherapeutics are hydrophobic.

Multidrug resistance (MDR), mediated by ATP-dependent efflux of multiple hydrophobic cytotoxic drugs, continues to be a dominant hindrance towards curative cancer therapy. Compounds that reverse MDR by inhibition of efflux transporters and hence re-sensitize MDR cells to chemotherapy are known as chemosensitizers or MDR modulators.

Herein we characterized, optimized and explored the possibility to use different combinations of hydrophobic synergistic drug pairs, each comprising a chemotherapeutic drug (e.g. Paclitaxel, SN-38) and a corresponding chemosensitizer (e.g. Tariquidar, Elacridar, respectively), which block MDR efflux pumps (e.g. P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), respectively). The drugs were individually encapsulated within CN-based micelles, in particular, either rCM or β-CM. Hence, the rationally designed novel oral drug delivery platform encapsulating these paired drugs is expected to display enhanced efficacy and synergy in the treatment of gastric cancer and overcoming both P-gp- and BCRP-mediated MDR.

Spectrophotometry, light microscopy, dynamic light scattering and zeta potential analyses revealed drug solubilization by the CN nano-vehicles and suppression of drug crystal growth. These nano-vehicles demonstrated high drug-loading capacity and good encapsulation efficiency. Furthermore, spectrofluorimetry and spectrophotometry revealed high binding affinities of each of the drugs to either CN or β-CN. Importantly, following simulated gastric digestion, in vitro cytotoxicity assays against human MDR gastric carcinoma cells with P-gp or BCRP overexpression, exhibited remarkable antitumor activity and synergistic efficacy by complete MDR reversal. Hence, our findings highlight that CN-based nano-vehicles carrying synergistic drug combinations constitute an efficacious therapeutic regimen for oral delivery and local target-activated release in the stomach that may overcome chemoresistance in gastric cancer and for possible treatment of non-malignant gastric disorders.