Examples of Tumor Growth Inhibition Properties of Liposomal Formulations of pH-Sensitive Histidinylated Cationic Amphiphiles

Aptamer-conjugated nanoliposomes containing COL1A1 siRNA sensitize CRC cells to conventional chemotherapeutic drugs

COL1A1 is an important extracellular matrix component that is associated with poor prognosis in cancers. In this study, As1411 aptamer-conjugated liposomes were used for targeted siRNA delivery against the COL1A1 gene in colorectal cancer (CRC) cells. Cationic liposomes were synthesized and siRNA loading and conjugation of aptamer were confirmed by gel shift assay and spectrophotometry method. Release of siRNA from liposomes was assessed using dialysis method. Binding and uptake of aptamer-conjugated liposomes to and into cancer cells was assessed by fluorescence microscopy and flowcytometry. Gene expression was evaluated using qRT-PCR. Cell viability, chemosensitivity and apoptosis were determined by MTT assay and Annexin/PI kit. Cellular studies showed that liposomal transfer of COL1A1 siRNA into HCT116 and HEK293 cells significantly reduced the expression level of corresponding gen and cell viability, and significantly increased the sensitivity to chemotherapy drugs while free siRNA had no such effects. Aptamer conjugation was associated with increased cellular effects in HCT116 cells, but not in HEK293 cells. Our study revealed that delivery of COL1A1 siRNA via AS1411-targeted liposomes is a promising therapeutic approach to overcome treatment resistance in CRC.

Novel Suberoylanilide Hydroxamic Acid Analogs Inhibit Angiogenesis and Induce Apoptosis in Breast Cancer Cells

BACKGROUND

Histone deacetylases (HDACs) are the enzymes that catalyze the removal of the acetyl group from lysine residues and regulate several biological processes. Suberoylanilide hydroxamic acid (SAHA) is a notable HDAC inhibitor that exhibited remarkable anti-proliferative efficiency by alleviating gene regulation against solid and hematologic cancers.

AIM

The aim of this study was to develop new chemotherapeutic agents for breast cancer treatment, therefore, a novel series of Suberoylanilide hydroxamic acid (SAHA) analogs were investigated as anticancer agents.

METHODS

We designed and synthesized a novel series of analogs derived from SAHA by substituting alkyl, alkoxy, halo, and benzyl groups at different positions of the phenyl ring. The newly synthesized analogs were assessed for their cytotoxic potential against four human cancer cell lines in comparison with healthy cell lines, using several biological assays.

RESULTS

SAHA analogs displayed significant cytotoxic potential with IC50 values ranging from 1.6 to 19.2 µM in various tumor cell lines. Among these analogs, 2d (containing 3-chloro, 4-floro substitutions on phenyl moiety), 2h (containing 3,4-di chloro substitutions on phenyl moiety), and 2j (containing 4-chloro, 3-methyl substitutions on phenyl moiety) showed significant cytotoxic potential with IC50 values ranging from 1.6 to 1.8 µM in MCF-7 (breast carcinoma) cell line. More importantly, these analogs were found to be non-toxic towards healthy primary human hepatocytes (PHH) and mouse fibroblast cells (NIH3T3), which represent their tumor selectivity. These analogs were further analyzed for their effect on cell migration, BrdU incorporation, Annexin V-FITC and cell cycle arrest (Sub-G1 phase). Remarkably, analogs 2d, 2h, and 2j displayed significant HDAC inhibition than the parent SAHA molecule. Further studies also confirmed that these SAHA analogs are efficient in inducing apoptosis, as they regulated the expression of several proteins involved in mitochondrial or intrinsic apoptosis pathways. Findings in the Chick Chorioallantoic Membrane (CAM) assay studies revealed anti-angiogenic properties of the currently described SAHA analogs.

CONCLUSION

From anti-proliferative study results, it is clearly evident that 3,4-substitution at the SAHA phenyl ring improves the anti-proliferative activity of SAHA. Based on these findings, we presume that the synthesized novel SAHA analogs could be potential therapeutic agents in treating breast cancer.

Innovative lipoplexes formulations with enhanced siRNA efficacy for cancer treatment: Where are we now?

Over the past two decades, RNA interference has become an extensively studied mechanism to silence gene and treat diseases including cancer. siRNA appears as a promising strategy that could avoid some side effects related to traditional chemotherapy. Considering the weak stability of naked siRNA in blood, vectors like cationic liposomes or Lipid Nanoparticles (LNPs) are widely used to carry and protect siRNA until it reaches the tumor targeted. Despite extensive research, only three RNAi drugs are currently approved by the Food and Drug Administration, including only one LNP formulation of siRNA to treat hereditary ATTR amyloidosis. This shows the difficulty of lipoplexes clinical translation, in particular in cancer therapy. To overcome the lipoplexes limitations, searches are made on innovative lipoplexes formulations with enhanced siRNA efficacy. The present review is focusing on the recent use of pH-sensitive lipids, peptides and cell-penetrating peptides or polymers. The incorporation of some of these components in the lipoplex formulation induces a fusogenic property or an enhanced endosomal escape, an enhanced cellular uptake, an enhanced tumor targeting, an improved stability in the blood stream …These innovations appear critical to obtain an efficient siRNA accumulation in tumor cells with effective antitumor effect considering the complex tumor environment.

pH-triggered solubility and cytotoxicity changes of malachite green derivatives incorporated in liposomes for killing cancer cells

Three different malachite green leuco derivatives (MG-Xs) are incorporated in liposomes. In all three cases, a substituent (X) is covalently linked to the central carbon atom, abbreviated as MG-OH, MG-OCH3, and MG-CN. The three MG-X compounds are solubilized separately in liposome membranes and become cationic (MG+) and water soluble under acidic conditions. MG+ is consequently released from the liposome to the aqueous exterior. Their release behavior corresponds to their ionization ability: MG-OH > MG-OCH3 > MG-CN. The cellular uptake of the liposomes, the cytotoxic effect, and the location of MG+ in cancer cells are investigated using murine cells derived from colon cancer (Colon 26 cells) and human embryonic kidney cells (HEK 293 cells). The toxic effect on cancer cells is correlated to the ionization ability of MG-Xs. The liposomes effectively deliver MG+via the endocytic pathway, resulting in the cytotoxicity of liposomes containing MG-OH which is higher than that of free MG-OH and MG+. The difference in the phospholipids constituting the liposome membranes barely had an effect on the ionization ratio and the cytotoxicity of MG-OH. Confocal fluorescence microscopic observations revealed that MG+ is ultimately transported into the nuclei after being released in acidic cellular compartments.

Pleiotropic Properties of Amphiphilic Dihydropyridines, Dihydropyridones, and Aminovinylcarbonyl Compounds

Three groups of synthetic lipids are chosen for studies: (1) 1,4-dihydropyridines (1,4-DHPs) containing two cationic moieties and their analogues; (2) 3,4-dihydro-2(1H)-pyridones containing a cationic moiety; and (3) acyclic, open-chain analogues, i.e., 2-amino-3-alkoxycarbonylalkylammonium derivatives. 1,4-DHPs possessing dodecyl alkyl chains in the ester groups in positions 3 and 5 and cationic nitrogen-containing groups in positions 2 and 6 have high cytotoxicity in cancer cells HT-1080 (human lung fibrosarcoma) and MH-22A (mouse hepatoma), but low cytotoxicity in the noncancerous NIH3T3 cells (mouse embryonic fibroblast). On the contrary, similar compounds having short (methyl, ethyl, or propoxyethyl) chains in the ester groups in positions 3 and 5 lack cytotoxicity in the cancer cells HT-1080 and MH-22A even at high doses. Inclusion of fluorine atoms in the alkyl chains in positions 3 and 5 of the DHP cycle decreases the cytotoxicity of the mentioned compounds. Structurally related dihydropyridones with a polar head group are substantially more toxic to normal and cancerous cells than the DHP analogues. Open-chain analogues of DHP lipids comprise the same conjugated aminovinylcarbonyl moiety and possess anticancer activity, but they also have high basal cytotoxicity. Electrochemical oxidation data demonstrate that oxidation potentials of selected compounds are in the range of 1.6-1.7 V for cationic 1,4-DHP, 2.0-2.4 V for cationic 3,4-dihydropyridones, and 1.2-1.5 V for 2-amino-3-alkoxycarbonylalkylammonium derivatives. Furthermore, the tested cationic 1,4-DHP amphiphiles possess antiradical activity. Molecular topological polar surface area values for the tested compounds were defined in accordance with the main fragments of compound structures. The determined logP values were highest for dodecyl ester groups in positions 3 and 5 of the 1,4-DHP and lowest for short alkyl chain-containing amphiphiles.

Specific On-site Assembly of Multifunctional Magnetic Nanocargos Based on Highly Efficient and Parallelized Bioconjugation: Toward Personalized Cancer Targeting Therapy

The rational design of particle-based cancer theranostic agents, combining diagnostic and therapeutic features in a single entity, has emerged as an effective approach toward personalized cancer therapy; however, creating a flexible assembly of specific targeting ligands with regard to a broad range of tumor tissues and cells is still challenging. Here, we present a convenient and highly variable on-site assembly strategy for the preparation of multifunctional doxorubicin (DOX)-loaded nanocargos with magnetic supraparticles (MSPs) as a core and redox-degradable poly(methylacrylic acid-co-N,N-bis(acryloyl) cystamine) (P(MAA-co-Cy) as the shell, which could be simultaneously modified with multiple targeting ligands through parallelized bioconjugation on the basis of a streptavidin-biotin (SA-BT) interaction. Under physiological conditions similar to those of the cytoplasm of tumor cells, DOX could be released in a controlled manner from these nanocargos to specific tumor sites, while dual-ligand modified nanocargos showed remarkable proliferation inhibition for the HeLa cells and the SK-OV-3 cells that overexpressed both folate as well as integrin receptors. The experimental results demonstrated that the on-site assembly strategy described herein opens access to highly efficient targeting drug delivery systems toward personalized cancer targeting therapy by incorporating functional diversity, which can be easily achieved through highly efficient and parallelized one-step bioconjugation.

Simultaneous delivery of Paclitaxel and Bcl-2 siRNA via pH-Sensitive liposomal nanocarrier for the synergistic treatment of melanoma

pH-sensitive drug carriers that are sensitive to the acidic (pH = ~6.5) microenvironments of tumor tissues have been primarily used as effective drug/gene/siRNA/microRNA carriers for releasing their payloads to tumor cells/tissues. Resistance to various drugs has become a big hurdle in systemic chemotherapy in cancer. Therefore delivery of chemotherapeutic agents and siRNA's targeting anti apoptotic genes possess advantages to overcome the efflux pump mediated and anti apoptosis-related drug resistance. Here, we report the development of nanocarrier system prepared from kojic acid backbone-based cationic amphiphile containing endosomal pH-sensitive imidazole ring. This pH-sensitive liposomal nanocarrier effectively delivers anti-cancer drug (Paclitaxel; PTX) and siRNA (Bcl-2), and significantly inhibits cell proliferation and reduces tumor growth. Tumor inhibition response attributes to the synergistic effect of PTX potency and MDR reversing ability of Bcl-2 siRNA in the tumor supporting that kojic acid based liposomal pH-sensitive nanocarrier as efficient vehicle for systemic co-delivery of drugs and siRNA.

Delivering anti-cancer drugs with endosomal pH-sensitive anti-cancer liposomes

Numerous prior studies have been reported on the use of pH-sensitive drug carriers such as micelles, liposomes, peptides, polymers, nanoparticles,etc. that are sensitive to the acidic (pH = ∼6.5) microenvironments of tumor tissues.

Incorporation of Amphipathic Diblock Copolymer in Lipid Bilayer for Improving pH Responsiveness

Diblock copolymers (mPEG-b-PDPA), which were designed to possess pH-sensitivity as well as amphipathy, were used as an intelligent lock in the liposomal membrane. The so-called pH-sensitive liposomes were prepared by simple mixing of the synthesized mPEG-b-PDPA with phospholipids and cholesterol. Fluorescence polarization at pH 7.4 showed that the membrane stability of the hybrid liposome was significantly increased compared with the pure liposome. Therefore, in the neutral environment, the leakage of doxorubicin (DOX) was inhibited. However, when pH decreased to 6.0, DOX release rate increased by 60% due to the escape of copolymer. The effects of the membrane composition and the PDPA segment length on bilayer membrane functions were investigated. These results revealed that the synthesized copolymers increased the difference in DOX cumulative release between pH 7.4 and 6.0, that is, improved the pH-controllability of the drug release from hybrid liposomes.