Drug combination nanoparticles targeted to ICAM-1 on breast cancer cells enhance cellular drug exposure in vitro and in mouse model

Abstract

Triple-negative breast cancer (TNBC) is a subtype of breast cancer that lacks the expression of 3 cell receptors--the estrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor-2 (Her2) --that cancer cells use for uncontrolled growth. A number of drugs that interfere with the aforementioned receptors are available to control breast cancer growth. However, cells that have lost these receptors are difficult to treat, and typically lead to aggressive metastatic cancer cell spread with progressive disease. Due to the lack of druggable cell-specific targets, there are limited therapeutic options, leading to higher metastasis rates and poor treatment outcomes. To address these limitations in breast cancer treatment, this thesis research leverages on a nanoparticle technology which has been previously proven to enable the assembly of potent drugs in combination to provide long-acting effects in the body. Specifically, this research assembled a highly potent two-drug combination of gemcitabine (G) and paclitaxel (T) into drug combination nanoparticles or DcNP. We then determined whether a cell receptor that over-expressed in breast cancer cells, called Intercellular Adhesion Molecule 1 (ICAM-1), can be used to enhance uptake and localization of a highly potent, but non-selective gemcitabine and paclitaxel (GT) cancer drug combination assembled in a small nano-size particle. The two drugs—gemcitabine (G) and paclitaxel (T)—are currently used in clinic with some effectiveness, but exhibit dose-limiting toxicity. Our overarching goal is determining whether ICAM-1 targeted drug combination particles could provide higher drug potency and increase the margin of safety. We found that incorporating two anti-cancer drugs—gemcitabine (G) and paclitaxel (T)—into nanoparticles and targeting them to ICAM-1 overexpressed on breast cancer 4T1 cells enhanced drug uptake and retention in the cells and tumor laden tissues. Targeting to ICAM-1 is achieved by coating GT-DcNP with an ICAM binding peptide fragment sequence (ITDGEATDSG) derived from its endogenous binding ligand lymphocyte function-associated antigen 1 (LFA-1) [referred to as LFA1-P]. We found that coating LFA1-P on DcNP provides preferential localization of G and T to breast cancer cells 4T1 and MDA-MB231. This novel anti-cancer drug combination nanoparticle (GT-DcNP-LFA1-P) can enhance the effects of two parent anti-cancer drugs (in solution) and enable sustained drug concentrations in target cells both in vitro and in vivo. In this thesis, the target selectivity of different ligand incorporated DcNPs was designed, prepared, characterized and finally evaluated in an MDA-MB-231 breast cancer cell line. ICAM-1 ligand (LFA1-P) showed the best target ability. We found that compared to a non-targeted GT-DcNP counterpart (when given a high dose to 4T1 metastatic breast cancer mice), incorporation of LAF1-P in DcNP targeted to ICAM-1 on breast cancer cells enhanced the accumulation of G and T in lung tissue by 2.2 and 1.7 fold (P ≤ 0.05), respectively. In an aggressive 4T1 breast metastatic tumor model, we found that inclusion of LFA1-P enhanced GT-DcNP mediated tumor inhibitory effects at a low single GT (5/0.5 mg/kg, IV) dose. While ICAM-1 targeted and non-targeted GT-DcNP exhibited significant tumor suppression compared to an untreated control, targeted LAF-1-P-GT-DcNP exhibited a higher degree of significance over that of free GT treated mice. Collectively, based on the ICAM-1 overexpression on TNBC breast cancer GT-DcNP- LFA1-P, mimicking LFA-1, the ICAM-1 ligand was designed and verified to enable the targeting of GT in drug-combination particles to breast cancer cells leading to enhanced tumor tissue accumulation and suppression of 4T1 tumor growth in the lung. This approach may be applicable for developing other potent cancer chemotherapeutic combinations to provide targeted and synchronized drug combination delivery to advancing and metastatic cancer cells for increasing efficacy and safety.