Nonsense suppression therapy is an approach to treat genetic diseases caused by nonsense mutations. This therapeutic strategy pharmacologically suppresses translation termination at Premature Termination Codons (PTCs) in order to restore expression of functional protein. However, the process of Nonsense-Mediated mRNA Decay (NMD), which reduces the abundance of mRNAs containing PTCs, frequently limits this approach. Here, we used a mouse model of the lysosomal storage disease mucopolysaccharidosis I-Hurler (MPS I-H) that carries a PTC in the Idua locus to test whether NMD attenuation can enhance PTC suppression in vivo. Idua encodes alpha-L-iduronidase, an enzyme required for degradation of the glycosaminoglycans (GAGs) heparan sulfate and dermatan sulfate. We found that the NMD attenuator NMDI-1 increased the abundance of the PTC-containing Idua transcript. Furthermore, co-administration of NMDI-1 with the PTC suppression drug gentamicin enhanced alpha-L-iduronidase activity compared to gentamicin alone, leading to a greater reduction of GAG storage in mouse tissues, including the brain. These results demonstrate that NMD attenuation significantly enhances suppression therapy in vivo.

Purpose The present study was designed to determine biological structure-activity relationships (SAR) for four newly synthesized analogs of natural compounds (makaluvamines). The compounds, 7-(4-fluorobenzylamino)-1,3,4,8-tetrahydropyrrolo[4,3,2-de]quinolin-8(1H)-one (FBA-TPQ); 7-(phenethylamino)-1,3,4,8-tetrahydro-pyrrolo[4,3,2-de]-quinolin-8(1H)-one (PEA-TPQ); 7-(3,4-methylenedioxyphenethylamino)-1,3,4,8-tetrahydropyrrolo[4,3,2-de]quinolin-8(1H)-one (MPA-TPQ); 7-(3,4-dimethoxyphenethylamino)-1,3,4,8-tetrahydropyrrolo[4,3,2-de]quinolin-8(1H)-one (DPA-TPQ), were synthesized and purified, and their chemical structures were elucidated on the basis of physicochemical constants and nuclear magnetic resonance spectra. Experimental Design The structure-activity relationship of the compounds was initially evaluated by comparing their in vitro cytotoxicity against 14 human cell lines. Detailed in vitro and in vivo studies were then done in MCF-7 and MDA-MB-468 breast cancer cell lines. Results The in vitro cytotoxicity was compound-, dose-, and cell line dependent. Whereas all of the compounds exerted some activity, FBA-TPQ was the most potent inducer of apoptosis and the most effective inhibitor of cell growth and proliferation, with half maximal inhibitory concentration values for most cell lines in the range of 0.097-2.297 μmol/L. In MCF-7 cells, FBA-TPQ exposure led to an increase in p53/p-p53, Bax, ATM/p-ATM, p-chk1 and p-chk2, p-H2AX, and cleavage of poly (ADP)ribose polymerase, caspases -3, -8, and -9. It also decreased the levels of MDM2, E2F1, Bcl-2, chk1/2 and proteins associated with cell proliferation [cyclin-dependent kinase (Cdk)2, Cdk4, Cdk6, cyclin D1, etc). Moreover, FBA-TPQ inhibited the growth of breast cancer xenograft tumors in nude mice in a dose-dependent manner. Western blot analysis of the xenograft tumors indicated that similar changes in protein expression also occur in vivo. Conclusion Our preclinical data indicate that FBA-TPQ is a potential therapeutic agent for breast cancer, providing a basis for development of the compound as a novel anticancer agent.

Herein we report our examination of the anti-breast cancer activity of a novel synthetic compound, 7-(benzylamino)-1, 3, 4, 8-tetrahydropyrrolo [4, 3, 2-de]quinolin-8(1H)-one (BA-TPQ). This agent is an analog of a naturally-occurring marine compound, and was found to be the most active out of more than 40 related compounds. We investigated the in vitro activity of BA-TPQ on the survival, proliferation, and apoptosis of breast cancer cells using the MTT and BrdUrd assays, and Annexin/Annexin-PI staining and flow cytometry. The in vivo anti-cancer effects of BA-TPQ were evaluated in xenograft models of breast cancer. Finally, the mechanisms of action of the compound were also assessed by cDNA microarrays, RT-PCR and Western blotting. In a dose-dependent manner, BA-TPQ inhibited cell growth and induced apoptosis and cell cycle arrest in human MCF-7 and MDA-MB-468 breast cancer cells in vitro, and showed in vivo efficacy in mice bearing MCF-7 or MDA-MB-468 xenograft tumors. We demonstrated that BA-TPQ modifies the expression of numerous molecules involved in cell cycle progression and apoptosis. Similar changes in protein expression were observed in vitro and in vivo, as determined by examination of cells and excised xenograft tumors. Our preclinical data indicate that BA-TPQ is a potential therapeutic agent for breast cancer that has multiple hormone-, Her2- and p53-independent mechanisms of action, providing a basis for further development of the compound as a novel anticancer agent.

We report a novel delivery platform for a highly potent anticancer drug, 7-(benzylamino)-3,4-dihydro-pyrrolo[4,3,2-de]quinolin-8(1H)-one (BA-TPQ), using pH- and redox-sensitive poly(methacrylic acid) (PMAA) hydrogel cubes of micrometer size as the encapsulating matrix. The hydrogels are obtained upon cross-linking PMAA with cystamine in PMAA/poly(N-vinylpyrrolidone) multilayers assembled within mesoporous sacrificial templates. The BA-TPQ-loaded hydrogels maintain their cubical shape and pH-sensitivity after lyophilization, which is advantageous for long-term storage. Conversely, the particles degrade in vitro in the presence of glutathione (5 mM) providing 80% drug release within 24 h. Encapsulating BA-TPQ into hydrogels significantly increases its transport via Caco-2 cell monolayers used as a model for oral delivery where the apparent permeability of BA-TPQ-hydrogel cubes was ~2-fold higher than that of BA-TPQ. BA-TPQ-hydrogel cubes exhibit better anticancer activity against HepG2 (IC50=0.52 μg/mL) and Huh7 (IC50=0.29 μg/mL) hepatoma cells with a 40% decrease in the IC50 compared to the non-encapsulated drug. Remarkably, non-malignant liver cells have a lower sensitivity to BA-TPQ-hydrogel cubes with 2-fold increased IC50 values compared to those of cancer cells. In addition, encapsulating BA-TPQ in the hydrogels amplifies the potency of the drug via down-regulation of MDM2 oncogenic protein and upregulation of p53 (a tumor suppressor) and p21 (cell proliferation suppressor) expression in HepG2 liver cancer cells. Moreover, enhanced inhibition of MDM2 protein expression by BA-TPQ-hydrogel cubes is independent of p53-status in Huh7 cells. This drug delivery platform of non-spherical shape provides a facile method for encapsulation of hydrophobic drugs and can facilitate the enhanced efficacy of BA-TPQ for liver cancer therapy.

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