An In-House-Built and Light-Emitting-Diode-Based Photodynamic Therapy Device for Enhancing Verteporfin Cytotoxicity in a 2D Cell Culture Model

This paper describes a novel, simple, and low-cost device to perform in vitro photodynamic therapy (PDT) assays, named the PhotoACT. The device was built ...

Federal University of Parana

Herbaspirillum rubrisubalbicans decreases growth of rice. Inoculation of rice with H. rubrisubalbicans increased the ACCO mRNA levels and ethylene production. The H. rubrisubalbicans rice interactions were further characterized by proteomic approach. Herbaspirillum rubrisubalbicans is a well-known growth-promoting rhizobacteria that can also act as a mild phyto-pathogen. During colonisation of rice, RT-qPCR analyses showed that H. rubrisubalbicans up-regulates the methionine recycling pathway as well as phyto-siderophore synthesis genes. mRNA levels of ACC oxidase and ethylene levels also increased in rice roots but inoculation with H. rubrisubalbicans impaired growth of the rice plant. A proteomic approach was used to identify proteins specifically modulated by H. rubrisubalbicans in rice and amongst the differentially expressed proteins a V-ATPase and a 14-3-3 protein were down-regulated. Several proteins of H. rubrisubalbicans were identified, including the type VI secretion system effector Hcp1, suggesting that protein secretion play a role colonisation in rice. Finally, the alkyl hydroperoxide reductase, a primary scavenger of endogenous hydrogen peroxide was also identified. Monitoring the levels of reactive oxygen species in the epiphytic bacteria by flow cytometry revealed that H. rubrisubalbicans is subjected to oxidative stress, suggesting that the alkyl hydroperoxide reductase is an important regulator of redox homeostasis in plant-bacteria interactions.

Herbaspirillum rubrisubalbicans, a mild pathogen impairs growth of rice by augmenting ethylene levels.

The ATP-binding cassette transporter ABCG2 mediates the efflux of several chemotherapeutic drugs, contributing to the development of multidrug resistance (MDR) in many cancers. The most promising strategy to overcome ABCG2-mediated MDR is the use of specific inhibitors. Despite many efforts, the identification of new potent and specific ABCG2 inhibitors remains urgent. In this study, a structural optimization of indeno[1,2-b]indole was performed and a new generation of 18 compounds was synthesized and tested as ABCG2 inhibitors. Most compounds showed ABCG2 inhibition with IC values below 0.5 µM. The ratio between cytotoxicity (IG) and ABCG2 inhibition potency (IC) was used to identify the best inhibitors. In addition, it was observed that some indeno[1,2-b]indole derivatives produced complete inhibition, while others only partially inhibited the transport function of ABCG2. All indeno[1,2-b]indole derivatives are not transported by ABCG2, and even the partial inhibitors are able to fully chemosensitize cancer cells overexpressing ABCG2. The high affinity of these indeno[1,2-b]indole derivatives was confirmed by the strong stimulatory effect on ABCG2 ATPase activity. These compounds did not affect the binding of conformation-sensitive antibody 5D3 binding, but stabilized the protein structure, as revealed by the thermostabilization assay. Finally, a docking study showed the indeno[1,2-b]indole derivatives share the same binding site as the substrate estrone-3-sulfate.

Mechanistic basis of breast cancer resistance protein inhibition by new indeno[1,2-b]indoles.

The ABCG2 transporter plays a pivotal role in multidrug resistance, however, no clinical trial using specific ABCG2 inhibitors have been successful. Although ABC transporters actively extrude a wide variety of substrates, photodynamic therapeutic agents with porphyrinic scaffolds are exclusively transported by ABCG2. In this work, we describe for the first time a porphyrin derivative (4B) inhibitor of ABCG2 and capable to overcome multidrug resistance in vitro. The inhibition was time-dependent and 4B was not itself transported by ABCG2. Independently of the substrate, the porphyrin 4B showed an IC value of 1.6 μM and a mixed type of inhibition. This compound inhibited the ATPase activity and increased the binding of the conformational-sensitive antibody 5D3. A thermostability assay confirmed allosteric protein changes triggered by the porphyrin. Long-timescale molecular dynamics simulations revealed a different behavior between the ABCG2 porphyrinic substrate pheophorbide a and the porphyrin 4B. Pheophorbide a was able to bind in three different protein sites but 4B showed one binding conformation with a strong ionic interaction with GLU446. The inhibition was selective toward ABCG2, since no inhibition was observed for P-glycoprotein and MRP1. Finally, this compound successfully chemosensitized cells that overexpress ABCG2. These findings reinforce that substrates may be a privileged source of chemical scaffolds for identification of new inhibitors of multidrug resistance-linked ABC transporters.

A new porphyrin as selective substrate-based inhibitor of breast cancer resistance protein (BCRP/ABCG2).

A promising strategy to overcome multidrug resistance is the use of inhibitors of ABC drug transporters. For this reason, we evaluated the polyoxovanadates (POVs) [V O ] (V ), [H V O (PO )] (V ), [V O Cl] (V ) and [V O I] (V ) as inhibitors of three major multidrug resistance-linked ABC transporters: P-glycoprotein (P-gp), ABCG2 and MRP1. All of the POVs selectively inhibited P-gp. V and V were the two most promising compounds, with IC values of transport inhibition of 25.4 and 22.7 µm, respectively. Both compounds inhibited P-gp ATPase activity, with the same IC value of 1.26 µm. V and V triggered different conformational changes in the P-gp protein with time-dependent inhibition, which was confirmed using the synthesized salt of V with rhodamine B, RhoB-V . The hydrophilic nature of POVs supports the hypothesis that these compounds target an unusual ligand-binding site, opening new possibilities in the development of potent modulators of ABC transporters.

Polyoxovanadates as new P-glycoprotein inhibitors: insights into the mechanism of inhibition.

The primary source of failure of cancer therapies is multidrug resistance (MDR), which can be caused by different mechanisms, including the overexpression of ABC transporters in cancer cells. Among the 48 human ABC proteins, the breast cancer resistance protein (BCRP/ABCG2) has been described as a pivotal player in cancer resistance. The use of functional inhibitors and expression modulators is a promising strategy to overcome the MDR caused by ABCG2. Despite the lack of clinical trials using ABCG2 inhibitors, many compounds have already been discovered. This review presents an overview about various ABCG2 inhibitors that have been identified, discussing some chemical aspects and the main experimental methods used to identify and characterize the mechanisms of new inhibitors. In addition, some biological requirements to pursue preclinical tests are described. Finally, we discuss the potential use of ABCG2 inhibitors in cancer stem cells (CSC) for improving the objective response rate and the mechanism of ABCG2 modulators at transcriptional and protein expression levels.

Vivian Rotuno Moure

Graduate Program in Pharmaceutical Sciences,
Laboratory of Cancer Drug Resistance,
Graduate Program in Pharmaceutical Sciences, Laboratory of Cancer Drug Resistance

Federal University of Parana

An In-House-Built and Light-Emitting-Diode-Based Photodynamic Therapy Device for Enhancing Verteporfin Cytotoxicity in a 2D Cell Culture Model

Vivian Rotuno Moure

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Graduate Program in Pharmaceutical Sciences,Laboratory of Cancer Drug Resistance,Graduate Program in Pharmaceutical Sciences, Laboratory of Cancer Drug Resistance

Federal University of Parana

An In-House-Built and Light-Emitting-Diode-Based Photodynamic Therapy Device for Enhancing Verteporfin Cytotoxicity in a 2D Cell Culture Model

Graduate Program in Pharmaceutical Sciences,
Laboratory of Cancer Drug Resistance,
Graduate Program in Pharmaceutical Sciences, Laboratory of Cancer Drug Resistance