Targeted downregulation of MYC mediated by a highly efficient lactobionic acid-based glycoplex to enhance chemosensitivity in human hepatocellular carcinoma cells

The chemosensitization of tumor cells by gene therapy represents a promising strategy for hepatocellular carcinoma (HCC) treatment. In this regard, HCC-specific and highly efficient gene delivery nanocarriers are urgently needed. For this purpose, novel lactobionic acid-based gene delivery nanosystems were developed to downregulate c-MYC expression and sensitize tumor cells to low concentration of sorafenib (SF). A library of tailor-made cationic glycopolymers, based on poly(2-aminoethyl methacrylate hydrochloride) (PAMA) and poly(2-lactobionamidoethyl methacrylate) (PLAMA) were synthesized by a straightforward activators regenerated by electron transfer atom transfer radical polymerization. The nanocarriers prepared with PAMA₁₁₄-co-PLAMA₂₀ glycopolymer were the most efficient for gene delivery. These glycoplexes specifically bound to the asialoglycoprotein receptor and were internalized through the clathrin-coated pit endocytic pathway. c-MYC expression was significantly downregulated by MYC short-hairpin RNA (MYC shRNA), resulting in efficient inhibition of tumor cells proliferation and a high levels apoptosis in 2D and 3D HCC-tumor models. Moreover, c-MYC silencing increased the sensitivity of HCC cells to SF (IC₅₀ for MYC shRNA+ SF 1.9 μM compared to 6.9 μM for control shRNA + SF). Overall, the data obtained demonstrated the great potential of PAMA₁₁₄-co-PLAMA₂₀/MYC shRNA nanosystems combined with low doses of SF for the treatment of HCC.

Glycopolymers Mediate Suicide Gene Therapy in ASGPR-Expressing Hepatocellular Carcinoma Cells in Tandem with Docetaxel

Cationic glycopolymers stand out as gene delivery nanosystems due to their inherent biocompatibility and high binding affinity to the asialoglycoprotein receptor (ASGPR), a target receptor overexpressed in hepatocellular carcinoma (HCC) cells. However, their synthesis procedure remains laborious and complex, with problems of solubilization and the need for protection/deprotection steps. Here, a mini-library of well-defined poly(2-aminoethyl methacrylate hydrochloride-co-poly(2-lactobionamidoethyl methacrylate) (PAMA-co-PLAMA) glycopolymers was synthesized by activators regenerated by electron transfer (ARGET) ATRP to develop an efficient gene delivery nanosystem. The glycoplexes generated had suitable physicochemical properties and showed high ASGPR specificity and high transfection efficiency. Moreover, the HSV-TK/GCV suicide gene therapy strategy, mediated by PAMA₁₄₄-co-PLAMA₁₉-based nanocarriers, resulted in high antitumor activity in 2D and 3D culture models of HCC, which was significantly enhanced by the combination with small amounts of docetaxel. Overall, our results demonstrated the potential of primary-amine polymethacrylate-containing-glycopolymers as HCC-targeted suicide gene delivery nanosystems and highlight the importance of combined strategies for HCC treatment.

Poly(ethylene glycol)- block-poly(2-aminoethyl methacrylate hydrochloride)-Based Polyplexes as Serum-Tolerant Nanosystems for Enhanced Gene Delivery

Incorporation of poly(ethylene glycol) (PEG) into polyplexes has been used as a promising approach to enhance their stability and reduce unwanted interactions with biomolecules. However, this strategy generally has a negative influence on cellular uptake and, consequently, on transfection of target cells. In this work, we explore the effect of PEGylation on biological and physicochemical properties of poly(2-aminoethyl methacrylate) (PAMA)-based polyplexes. For this purpose, different tailor-made PEG- b-PAMA block copolymers, and the respective homopolymers, were synthesized using the controlled/"living" radical polymerization method based on activators regenerated by electron transfer atom transfer radical polymerization. The obtained data show that PEG- b-PAMA-based polyplexes exhibited a much better transfection activity/cytotoxicity relationship than the corresponding non-PEGylated nanocarriers. The best formulation, prepared with the largest block copolymer (PEG₄₅- b-PAMA₁₆₈) at a 25:1 N/P ratio, presented a 350-fold higher transfection activity in the presence of serum than that obtained with polyplexes generated with the gold standard bPEI. This higher transfection activity was associated to an improved capability to overcome the intracellular barriers, namely the release from the endolysosomal pathway and the vector unpacking and consequent DNA release from the nanosystem inside cells. Moreover, these nanocarriers exhibit suitable physicochemical properties for gene delivery, namely reduced sizes, high DNA protection, and colloidal stability. Overall, these findings demonstrate the high potential of the PEG₄₅- b-PAMA₁₆₈ block copolymer as a gene delivery system.

High transfection efficiency promoted by tailor-made cationic tri-block copolymer-based nanoparticles

Cationic polymer-based vectors have been considered a promising strategy in gene therapy area due to their inherent ability to condense genetic material and successfully transfect cells. However, they usually exhibit high cytotoxicity. In this work, it is proposed the use of a tailor-made gene carrier based on a tri-block copolymer of poly[2-(dimethylamino)ethyl methacrylate] and poly(β-amino ester) (PDMAEMA-b-PβAE-b-PDMAEMA), the influence of the PβAE length being assessed. For this purpose, three different block copolymers were prepared varying the molecular weight of this segment. The obtained materials were characterized by NMR and SEC analyzes. Different polyplexes formulations were prepared and evaluated in terms of physicochemical characterization (ethidium bromide intercalation assay, agarose gel electrophoresis assay, dynamic light scattering, zeta potential analyzes and atomic force microscopy) and biological activity (cytotoxicity, and luciferase and green fluorescent protein expression in Hela and COS-7 cell lines). Among the developed nanosystems, the best polyplex formulation revealed between 40- and 60-fold higher transgene expression, in HeLa and COS-7 cell lines, and much lower cytotoxicity than that observed with branched PEI and TurboFect™. Moreover, these nanosystems present suitable physicochemical properties for gene delivery namely reduced mean diameter and high DNA protection. The results reported here show the enormous potential of this block copolymer as gene carrier.

STATEMENT OF SIGNIFICANCE

Syntheses of PDMAEMA-b-PβAE-b-PDMAEMA block copolymers for an extremely effective non-viral vector. The block copolymer PDMAEMA₃₀₀₀-b-PβAE₁₂₀₀₀-b-PDMAEMA₃₀₀₀-based polyplexes at 100/1N/P ratio exhibits between 40- and 60-fold higher transgene expression in HeLa and COS-7 cell lines than commonly used polymeric non-viral vectors, namely branched PEI (known as the gold standard) and TurboFect™ (commercial available).

Ischemic mitral regurgitation: intraventricular papillary muscle imbrication without mitral ring during left ventricular restoration

OBJECTIVES

Functional mitral regurgitation in ischemic cardiomyopathy carries a poor prognosis, and its surgical management remains problematic and controversial. The aim of this study was to report the results of our surgical approach to patients who have had myocardial infarctions and have ventricular dilatation, mitral regurgitation, reduced pump function, pulmonary hypertension and coronary artery disease. This surgical approach consists of endoventricular mitral repair without prosthetic ring, ventricular reconstruction with or without patch, and coronary artery bypass grafting.

PATIENTS

Forty-six patients (aged 64 +/- 10 years) with previous anterior transmural myocardial infarction and mitral regurgitation comprised the study group. Indication for surgery was heart failure in 93% of cases; 25 patients were in New York Heart Association functional class IV and 17 were in class III. Mitral regurgitation was moderate to severe in 32 cases (69%).

RESULTS

All patients underwent coronary artery bypass grafting, with a mean of 3.2 +/- 1.3 grafts. Associated aortic valve replacement was performed in 4 cases. Global operative mortality rate was 15.2%. End-diastolic and end-systolic volumes significantly decreased after surgery (from 140 +/- 40 to 98 +/- 36 mL/m(2) and from 98 +/- 32 to 63 +/- 22 mL/m(2), respectively, P =.001). Systolic pulmonary pressure decreased significantly (from 55 +/- 13 to 43 +/- 16 mm Hg, P =.001). Ejection fraction did not change significantly. Postoperative mitral regurgitation was absent or minimal in 84% of cases; 1 patient had severe mitral regurgitation necessitating valve replacement. New York Heart Association functional class significantly improved. The mean preoperative functional class was 3.4 +/- 0.6 (median 3, range 2-4); after the operation, this decreased to 1.9 +/- 0.7 (median 2, range 1-3, P <.001). Cumulative survival at a 30-month follow-up was 63%.

CONCLUSIONS

Our aggressive, combined surgical approach is aimed at correcting the three components of ischemic cardiomyopathy: relieving ischemia, reducing left ventricular wall tension by decreasing left ventricular volumes, and reducing volume overload and pulmonary hypertension by repairing the mitral valve. Despite a relatively high perioperative mortality rate, surviving patients benefitted from the operation, with improved clinical functional class and thus quality of life.