Date of Award


Document Type


Degree Name

Master of Science (MS)



Committee Member

Dr. Jeoung Soo Lee, Committee Chair

Committee Member

Dr. Wendy Cornett

Committee Member

Dr. Richard Pace


Despite tremendous progress within the field of oncology, highly metastatic forms of breast cancer remain particularly challenging to effectively treat. Systemically delivered chemotherapy with cytotoxic agents typically requires some convalescence time between treatments – allowing rapidly growing cancer types to develop resistance. Multidrug resistance, also known as pump-dependent, is particularly difficult to treat as it functions through overexpression of P-glycoprotein, an efflux pump which can produce resistance to a range of chemotherapeutics. We have previously developed the cationic micellar copolymer poly(lactide-co-glycolide)-g-poly(ethylenimine) (PgP) and demonstrated its capacity as a vector for gene therapy. Here, we examine the capacity of PgP in mediating co-delivery of siRNA targeting P-glycoprotein (siMDR1) and the anthracycline class drug doxorubicin to mitigate multidrug resistance in drug resistant triple-negative human cancer cells in vitro. The results of this project have shown that PgP can be used to successfully bind siRNA into a complex that protects from interaction with charged particles through heparin competition assay, and remains stable in serum conditions. Results of MTT assay assessing metabolic activity have shown PgP/siMDR1 complexes to exhibit minimal cytotoxicity in vitro in comparison to untreated human MDA-MB-435 cancer cells. Assessment of silencing following treatment with PgP/siMDR1 complexes formed at various nitrogen:phosphate (N/P) ratios has shown significant knockdown of MDR1 mRNA up 67%, in comparison to untreated groups of drug resistant MDA-MB-435 cells. PgP has also been shown to successfully load the hydrophobic chemotherapeutic doxorubicin, improving the toxicity of the drug in vitro. These results show the efficacy of PgP as a vehicle for delivery of both doxorubicin and siMDR1 to drug resistant cancer cells, and may have potential for use in co-delivery of siMDR1 and chemotherapeutics in metastatic cancer treatment. Future studies will include in vivo toxicity and antitumor studies in athymic mouse breast cancer models.



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