siRNA Delivery Using a Cationic-Lipid-Based Highly Selective Human DNA Ligase I Inhibitor

Permanently Charged Cationic Lipids-Evolution from Excipients to Therapeutic Lipids

Cationic lipids are crucial in medical and biotechnological applications including cellular transfection and gene delivery. Ionizable cationic lipids are critical components of the mRNA-based COVID vaccines while permanently charged cationic lipids have shown promise in cancer treatment. Despite significant research progress over the past few decades in designing improved, biocompatible cationic lipids, their transfection efficiency remains lower than that of viral vectors. Cationic lipids with additional functionalities like fusogenicity, stimuli-responsiveness, targeting capabilities, and therapeutic activity have been engineered to improve their performance. This review highlights the importance of molecular hybridization toward the design of biocompatible cationic lipids having fusogenic, stimuli-responsive, targeting, or therapeutic properties. This review mainly focuses on cationic lipids, having a permanent positive charge in the headgroup region, as these are typically employed to both increase cellular interactions and for improved loading, particularly for anionic nucleic acid-based therapeutics and vaccines. Structure-activity relationships between the lipid chemical structure (headgroup, spacer, hydrocarbon chain) and, to a lesser extent, the self-assembled nanostructure and the intrinsic biological activity of the multi-functional cationic lipids are described. Finally, the challenges involved in developing smart lipids without affecting their inherent capacity to self-assemble into structured nano-carriers are discussed.

A systematic study of the effect of lipid architecture on cytotoxicity and cellular uptake of cationic cubosomes

HYPOTHESIS

Lipid nanoparticles containing a cationic lipid are increasingly used in drug and gene delivery as they can display improved cellular uptake, enhanced loading for anionic cargo such as siRNA and mRNA or exhibit additional functionality such as cytotoxicity against cancer cells. This research study tests the hypothesis that the molecular structure of the cationic lipid influences the structure of the lipid nanoparticle, the cellular uptake, and the resultant cytotoxicity.

EXPERIMENTS

Three potentially cytotoxic cationic lipids, with systematic variations to the hydrophobic moiety, were designed and synthesised. All the three cationic lipids synthesised contain pharmacophores such as the bicyclic coumarin group (CCA12), the tricyclic etodolac moiety (ETD12), or the large pentacyclic triterpenoid "ursolic" group (U12) conjugated to a quaternary ammonium cationic lipid containing twin C12 chains. The cationic lipids were doped into monoolein cubosomes at a range of concentrations from 0.1 mol% to 5 mol% and the effect of the lipid molecular architecture on the cubosome phase behaviour was assessed using a combination of Small Angle X-Ray Scattering (SAXS), Dynamic Light Scattering (DLS), zeta-potential and cryo-Transmission Electron Microscopy (Cryo-TEM). The resulting cytotoxicity of these particles against a range of cancerous and non-cancerous cell-lines was assessed, along with their cellular uptake.

FINDINGS

The molecular architecture of the cationic lipid was linked to the internal nanostructure of the resulting cationic cubosomes with a transition to more curved cubic and hexagonal phases generally observed. Cubosomes formed from the cationic lipid CCA12 were found to have improved cellular uptake and significantly higher cytotoxicity than the cationic lipids ETD12 and U12 against the gastric cancer cell-line (AGS) at lipid concentrations ≥ 75 µg/mL. CCA12 cationic cubosomes also displayed reasonable cytotoxicity against the prostate cancer PC-3 cell-line at lipid concentrations ≥ 100 µg/mL. In contrast, 2.5 mol% ETD12 and 2.5 mol% U12 cubosomes were generally non-toxic against both cancerous and non-cancerous cell lines over the entire concentration range tested. The molecular architecture of the cationic lipid was found to influence the cubosome phase behaviour, the cellular uptake and the toxicity although further studies are necessary to determine the exact relationship between structure and cellular uptake across a range of cell lines.

Synthesis and Characterization of a New Cationic Lipid: Efficient siRNA Delivery and Anticancer Activity of Survivin-siRNA Lipoplexes for the Treatment of Lung and Breast Cancers

Survivin has been shown to be widely expressed in most tumor cells, including lung and breast cancers. Due to limited siRNA delivery, it is more challenging to target survivin using knockdown-based techniques. Designing and developing new, bifunctional chemical molecules with both selective anti-proliferative activity and effective siRNA transfection capabilities by targeting a particular gene is important to treat aggressive tumors like triple-negative breast tumors (TNBC). The cationic lipids deliver small interfering RNA (siRNA) and also display inherent anti-cancer activities; therefore, cationic lipid therapies have become very popular for treating malignant cancers. In the current study, we attempted to synthesize a series of acid-containing cationic lipids, anthranilic acid-containing mef lipids, and indoleacetic acid-containing etodo lipids etc. Further, we elucidated their bi-functional activity for their anticancer activity and survivin siRNA-mediated anti-cancer activity. Our results showed that lipoplexes with siRNA-Etodo: Dotap (ED) and siRNA-Mef: Dotap (MD) exhibited homogeneous particle size and positive zeta potential. Further, biological investigations resulted in enhanced survivin siRNA delivery with high stability, improved transfection efficiency, and anti-cancer activity. Additionally, our findings showed that survivin siRNA lipoplexes (ED and MD) in A549 cells and 4T1 cells exhibited stronger survivin knockdown, enhanced apoptosis, and G1 or G2/M phase arrest in both cell types. In vivo results revealed that treatment with survivin complexed lipoplexes significantly reduced tumor growth and tumor weight compared to control. Thus, our novel quaternary amine-based liposome formulations are predicted to open up new possibilities in the development of a simple and widely utilized platform for siRNA delivery and anti-cancer activities.

Novel bioactive cationic cubosomes enhance the cytotoxic effect of paclitaxel against a paclitaxel resistant prostate cancer cell-line

Hypothesis The study aimed to use molecular hybridization of a cationic lipid with a known pharmacophore to produce a bifunctional lipid having a cationic charge to enhance fusion with the cancer cell surface and biological activity via the pharmacophoric head group. Experiments The novel cationic lipid DMP12 [N-(2-(3-(3,4-dimethoxyphenyl) propanamido) ethyl)-N-dodecyl-N-methyldodecan-1-aminium iodide] was synthesised by conjugating 3-(3,4-dimethoxyphenyl) propanoic acid (or 3,4-dimethoxyhydrocinnamic acid) to twin 12 carbon chains bearing a quaternary ammonium group [N-(2-aminoethyl)-N-dodecyl-N-methyldodecan-1-aminium iodide]. The physicochemical and biological properties of DMP12 were investigated. Cubosome particles consisting of monoolein (MO) doped with DMP12 and paclitaxel were characterized using Small-angle X-ray Scattering (SAXS), Dynamic Light Scattering (DLS), and Cryo-Transmission Electron Microscopy (Cryo-TEM). Combination therapy using these cubosomes was assessed in vitro against the gastric (AGS) and prostate (DU-145 and PC-3) cancer cell lines using cytotoxicity assay. Findings Monoolein (MO) cubosomes doped with DMP12 were observed to be toxic against the AGS and DU-145 cell-lines at higher cubosome concentrations (≥100 µg/ml) but had limited activity against the PC-3 cell-line. However, combination therapy consisting of 5 mol% DMP12 and 0.5 mol% paclitaxel (PTX) significantly increased the cytotoxicity against the PC-3 cell-line which was resistant to either DMP12 or PTX individually. The results demonstrate that DMP12 has a prospective role as a bioactive excipient in cancer therapy.

Biomedical potentialities of cationic geminis as modulating agents of liposome in drug delivery across biological barriers and cellular uptake

Hydroxyethyl bearing gemini surfactants, alkanediyl-α,ω-bis(N-hexadecyl-N-2-hydroxyethyl-N-methylammonium bromide), 16-s-16(OH), were used to augment phosphatidylcholine based liposomes to achieve higher stability and enhanced cellular uptake and penetration. The developed liposomes were loaded with rhodamine B, doxorubicin hydrochloride, pralidoxime chloride to investigate release properties, cytotoxicity in vitro, as well as ability to cross the blood-brain barrier. At molar ratio of 35:1 (lipid:surfactant) the formulation was found to be of low toxicity, stable for two months, and able to deliver rhodamine B beyond the blood-brain barrier in rats. In vivo, pharmacokinetics of free and formulated 2-PAM in plasma and brain were evaluated, liposomal 2-PAM was found to reactivate 27% of brain acetylcholinesterase, which is, to our knowledge, the first example of such high degree of reactivation after intravenous administration of liposomal drug.

Nucleic acid nanotechnology for cancer treatment

Cancer is one of the most prevalent potentially lethal diseases. With the increase in the number of investigations into the uses of nanotechnology, many nucleic acid (NA)-based nanostructures such as small interfering RNA, microRNA, aptamers, and immune adjuvant NA have been applied to treat cancer. Here, we discuss studies on the applications of NA in cancer treatment, recent research trends, and the limitations and prospects of specific NA-mediated gene therapy and immunotherapy for cancer treatment. The NA structures used for cancer therapy consist only of NA or hybrids comprising organic or inorganic substances integrated with functional NA. We also discuss delivery vehicles for therapeutic NA and anti-cancer agents, and recent trends in NA-based gene therapy and immunotherapy against cancer.

Recent advances in the targeting of human DNA ligase I as a potential new strategy for cancer treatment

The emergence of drug resistance, coupled with the issue of low tumor selectivity and toxicity is a major pitfall in cancer chemotherapy. It has necessitated the urgent need for the discovery of less toxic and more potent new anti-cancer pharmaceuticals, which target the interactive mechanisms involved in division and metastasis of cancer cells. Human DNA ligase I (hligI) plays an important role in DNA replication by linking Okazaki fragments on the lagging strand of DNA, and also participates in DNA damage repair processes. Dysregulation of the functioning of such ligases can severely impact DNA replication and repair pathways events that are generally targeted in cancer treatment. Although, several human DNA ligase inhibitors have been reported in the literature but unfortunately not a single inhibitor is currently being used in cancer chemotherapy. Results of pre-clinical studies also support the fact that human DNA ligases are an attractive target for the development of new anticancer agents which work by the selective inhibition of rapidly proliferating cancer cells. In this manuscript, we discuss, in brief, the structure, synthesis, structure-activity-relationship (SAR) and anticancer activity of recently reported hLigI inhibitors.

Au-CGKRK Nanoconjugates for Combating Cancer through T-Cell-Driven Therapeutic RNA Interference

Numerous prior studies on fighting cancer have been based on using inhibitors of JAK-STAT pathway (signal transducer and activator of transcription 3 (STAT3) inhibitor in particular), a signaling pathway responsible for progression of many types of cancer cells. However, recent studies have shown that STAT3 activation leads to upregulation of program death receptor-ligand 1 (PD-L1, an immune checkpoint protein that plays a major role behind evasion of immune systems by growing tumors) expression levels in tumor cells, leading to enhanced immune suppression. This is why global efforts are being witnessed in combating cancer through use of immune checkpoint inhibitors. Herein, we report on the design, synthesis, physicochemical characterizations, and bioactivity evaluation of novel tumor- and tumor-vasculature-targeting noncytotoxic Au-CGKRK nanoconjugates (17-80 nm) for combating tumor. Using a syngeneic mouse tumor model, we show that intraperitoneal (i.p.) administration of the Au-CGKRK nanoparticles (NPs) complexed with both PD-L1siRNA (the immune checkpoint inhibitor) and STAT3siRNA (the JAK-STAT pathway inhibitor) results in significant (>70%) enhancement in overall survivability (OS) in melanoma-bearing mice (n = 5) when compared to the OS in the untreated mice group. The expression levels of CD8 and CD4 proteins in the tumor lysates of differently treated mice groups (by Western blotting) are consistent with the observed OS enhancement being a T-cell-driven process. Biodistribution study using near-infrared dye-loaded Au-CGKRK nanoconjugates revealed selective accumulation of the dye in mouse tumor. Notably, the overall survival benefits were significantly less (∼35%) when melanoma-bearing mice were treated (i.p.) with Au-CGKRK NPs complexed with only PD-L1siRNA or with STAT3siRNA alone. The presently described Au-CGKRK nanoconjugates are expected to find future use in therapeutic RNA-interference-based cancer immunotherapy.