Polymeric delivery of siRNA for dual silencing of Mcl-1 and P-glycoprotein and apoptosis induction in drug-resistant breast cancer cells

Abstract

Enhanced survival mechanisms of malignant cells in combination with elevated levels of drug transporters can sustain an undesirable resistance against drug therapy. Short interfering RNA (siRNA) delivery against targets involved in aberrant mechanisms is a promising approach and we hypothesize that simultaneous silencing of multiple targets could prove more advantageous than common approach to silence individual targets. To explore this approach, we targeted anti-apoptotic proteins myeloid cell leukemia 1 (Mcl-1) and survivin along with the efflux pump P-glycoprotein (P-gp) in drug-resistant breast cancer cells. Polymeric siRNA delivery was employed for this purpose by using small polyethylenimine (PEI) substituted with lipids. While silencing Mcl-1 caused ∼90% cell death in wild-type cells, this effect was less significant in P-gp over-expressing cells. An additive effect for Mcl-1 and P-gp silencing was evident in the latter cells, where simultaneous silencing of these targets created a significantly higher effect compared with silencing each individual target. Prolonged exposure of wild-type cells to doxorubicin (DOX) resulted in upregulation of P-gp, breast cancer resistance protein, survivin and Mcl-1. Dual silencing of P-gp and Mcl-1 again resulted in an additive effect in resistance-induced cells, which displayed an increased dependency on Mcl-1 for survival. Cytotoxic effect of DOX was also enhanced in resistance-induced cells after silencing Mcl-1. We conclude that polymer-mediated siRNA delivery can silence multiple targets simultaneously and reverse drug resistance.

Cholesterol grafted cationic lipopolymers: Potential siRNA carriers for selective chronic myeloid leukemia therapy

“…We have successfully delivered different siRNAs (including KSP) to breast cancer cells using aliphatic lipid-grafted PEIs (Aliabadi et al, 2013), but these polymers were typically derived from PEI2 and not smaller PEIs. We have successfully delivered different siRNAs (including KSP) to breast cancer cells using aliphatic lipid-grafted PEIs (Aliabadi et al, 2013), but these polymers were typically derived from PEI2 and not smaller PEIs.…”

“…Low-MW PEIs are more biocompatible with sensitive human cells and could be cleared easier in body due to smaller size, but they are also less effective in delivery of nucleic acids. We have been grafting aliphatic lipids onto PEI for this purpose and such modifications enhanced the efficacy of parent polymers via increased membrane interaction and intracellular uptake (Aliabadi, Mahdipoor, & Uludag, 2013;Bahadur, Landry, Aliabadi, Lavasanifar, & Uludag, 2011;Linder & Deschenes, 2003). We have been grafting aliphatic lipids onto PEI for this purpose and such modifications enhanced the efficacy of parent polymers via increased membrane interaction and intracellular uptake (Aliabadi, Mahdipoor, & Uludag, 2013;Bahadur, Landry, Aliabadi, Lavasanifar, & Uludag, 2011;Linder & Deschenes, 2003).…”

Multi-Target Inhibition of Cancer Cell Growth by SiRNA Cocktails and 5-Fluorouracil Using Effective Piperidine-Terminated Phosphorus Dendrimers

“…Being overexpressed in many types of cancer, these genes allow malignant cells to survive and grow by impairing essential signaling processes that lead to programmed cell death [23]. RNAi-based downregulation of the aforementioned genes triggers cell death in ovarian cancers [24], breast cancers [25,26], pancreatic cancers [27], acute myeloid leukemia [28] and skin cancers [29]. Silencing of BCL-2 family genes is also known to increase the sensitization of various cancer cells types to drugs commonly used in chemotherapy such as cisplatin [24], doxorubicin [26], etoposide [28] and 5-fluorouracil [30].…”

Polymeric nanoparticle-mediated silencing of CD44 receptor in CD34+ acute myeloid leukemia cells

“…In fact, siRNA silencing in LSPC has been shown to be the most challenging [38], making siRNA-mediated anti-CD44 approaches a difficult therapeutic modality. To overcome this limitation, we recently developed functional lipid-substituted polymeric materials that could efficiently deliver siRNA in both adherent breast cancer cells and leukemic cells grown in suspension [25][26][27]34,39]. We pursued silencing of various model (e.g., GFP) and targets (e.g., CXCR4, BCR-ABL) in differentiated types of AML and CML cell lines [34,39].…”

“…Although this could be achieved using anti-CD44-moAb-based approaches or small molecule inhibitors [17], strategic alternatives are continually being sought to overcome the low efficacy/safety ratio, toxicity and immunogenicity of moAbs and the toxicity and short half-life of inhibitors [18][19][20][21]. Non-viral lipid or polymer-based gene silencing with RNA interference (RNAi) is a promising therapeutic approach for treatment of various diseases including cancer [22][23][24][25][26][27]. Synthetic small interfering RNAs (siRNAs) promote mRNA degradation in the process of RNAi and prevent the translation of proteins.…”