Editorial: multidrug resistance in cancer: pharmacological strategies from basic research to clinical issues.

More than 40 years ago, the observation that doxorubicin-resistant tumor cells were cross-resistant to several structurally different anticancer agents was the first step in the discovery of P-glycoprotein (P-gp). P-gp belongs to the superfamily of ATP-binding cassette (ABC) transporters;its overexpression has become a therapeutic target for overcoming multidrug resistance in tumors. However, P-gp is also expressed in cells of normal tissues where it plays a physiological role, by protecting them from the toxic effects of xenobiotics. Also, ABCB1 gene polymorphisms may influence the response to anticancer drugs substrate of P-gp. Several strategies to overcome P-gp tumor drug resistance have been suggested. P-gp 'circumvention’ is the most explored and is based on the coadministration of anticancer agents and pump inhibitors (P-gp modulators). Despite the positive findings obtained in preclinical studies, results of clinical trials are not yet successful and clinical research is still ongoing. Other investigational approaches have been studied (e.g. P-gp targeting antibodies, use of antisense strategies or transcriptional regulators targeting ABCB1 gene expression) but their use is still circumscribed to the preclinical setting. A further approach is represented by the encapsulation of P-gp substrate anticancer drugs into liposomes or nanoparticles. This strategy has shown higher efficacy in tumor previously treated with the free drug. The reasons explaining the increased efficacy of liposomal/nanoparticle-based drugs in Pgp-overexpressing tumors include the coating with specific surfactants, the composition changes in the plasma membrane microdomains where P-gp is embedded, the direct impairment of P-gp catalytic mechanisms exerted by specific component of the liposomal shell, but are not yet fully understood. A second strategy to overcome P-gp tumor drug resistance is represented by exploiting the P-gp presence. Actually, P-gp-overexpressing cells show increased sensitivity (collateral sensitivity) to some drugs (e.g. verapamil, narcotic analgesics) and to some investigational compounds (e.g. NSC73306). P-gp-overexpressing cell are hypersensitive to reactive oxygen species, to agents perturbing the energetic metabolic pathways, changing the membrane compositions, reducing the efflux of endogenous toxic catabolites. However, the mechanisms explaining collateral sensitivity have not been fully elucidated. Another approach to exploit P-gp is represented by ABCB1 gene transfer to transform bone marrow progenitor cells into a drug resistant state which may allow conventional or higher doses of anticancer drug substrates of P-gp to be administered safely after transplantation. More recently the development and introduction in the clinics of anticancer drugs which are not substrates of P-gp (e.g. new microtubule modulators, topoisomerase inhibitors) has provided a new and promising strategy to overcome P-gp tumor drug resistance (P-gp 'evasion'). This ‘research topic’ issue aims at exploding the above mentioned matters, in particular by: -retracing the history of the first researches on P-gp - describing the physiological role of P-gp - describing the molecular basis, structural features and mechanism of action of P-gp - describing diagnostic laboratory methods useful to determine the expression of P-gp and its transporter function - describing strategies to overcome tumor drug resistance due to P-gp and other ABC transporters - indicating novel approaches to overcome P-gp multidrug resistance, ranging from basic research studies to pre-clinical/clinical studies

Migration and public finances in the EU

We provide novel and comprehensive evidence on the net fiscal contributions of natives and migrants to the governmental budgets of EU countries. We account for income taxes and cash benefits, along with indirect taxes and in-kind benefits, which are often missing in standard datasets. We find that on average, migrants were net contributors to public finances over the period of 2014–2018 in the EU and, moreover, that they contribute approximately €1.5 thousand more per capita each year than natives. We also show that this difference is partly due to the selection on characteristics that make migrants net fiscal contributors, such as demographic factors and employment probability

Impact of ABC transporters in osteosarcoma and ewing’s sarcoma: Which are involved in chemoresistance and which are not?

The ATP-binding cassette (ABC) transporter superfamily consists of several proteins with a wide repertoire of functions. Under physiological conditions, ABC transporters are involved in cellular trafficking of hormones, lipids, ions, xenobiotics, and several other molecules, including a broad spectrum of chemical substrates and chemotherapeutic drugs. In cancers, ABC transporters have been intensely studied over the past decades, mostly for their involvement in the multidrug resistance (MDR) phenotype. This review provides an overview of ABC transporters, both related and unrelated to MDR, which have been studied in osteosarcoma and Ewing’s sarcoma. Since different backbone drugs used in first-line or rescue chemotherapy for these two rare bone sarcomas are substrates of ABC transporters, this review particularly focused on studies that have provided findings that have been either translated to clinical practice or have indicated new candidate therapeutic targets; however, findings obtained from ABC transporters that were not directly involved in drug resistance were also discussed, in order to provide a more complete overview of the biological impacts of these molecules in osteosarcoma and Ewing’s sarcoma. Finally, therapeutic strategies and agents aimed to circumvent ABC-mediated chemoresistance were discussed to provide future perspectives about possible treatment improvements of these neoplasms

Multifunctional thiosemicarbazones targeting sigma receptors: in vitro and in vivo antitumor activities in pancreatic cancer models

Purpose: Association of the metal chelating portion of thiosemicarbazone with the cytotoxic activity of sigma-2 receptors appears a promising strategy for the treatment of pancreatic tumors. Here, we developed a novel sigma-2 receptor targeting thiosemicarbazone (FA4) that incorporates a moiety associated with lysosome destabilization and ROS increase in order to design more efficient antitumor agents. Methods: The density of sigma receptors in pancreatic cancer cells was evaluated by flow cytometry. In these cells, cytotoxicity (MTT assay) and activation of ER- and mitochondria-dependent cell death pathways (mRNA expression of GRP78, ATF6, IRE1, PERK; ROS levels by MitoSOX and DCFDA-AM; JC-1 staining) induced by the thiosemicarbazones FA4, MLP44, PS3 and ACthio-1, were evaluated. The expression of autophagic proteins (ATG5, ATG7, ATG12, beclin, p62 and LC3-I) was also studied. In addition, the in vivo effect of FA4 in xenograft models with and without gemcitabine challenge was investigated. Results: We found that FA4 exerted a more potent cytotoxicity than previously studied thiosemicarbazones (MLP44, PS3 and ACthio-1), which were found to display variable effects on the ER or the mitochondria-dependent pro-apoptotic axis. By contrast, FA4 activated pro-apoptotic pathways and decreased autophagy, except in MiaPaCa2 cells, in which autophagic proteins were expressed at lower levels and remained unmodified by FA4. FA4 treatment of PANC-1 xenografted mouse models, poorly responsive to conventional chemotherapy, significantly reduced tumor volumes and increased intratumor apoptosis compared to gemcitabine, with no signs of toxicity. Conclusions: Our data indicate that FA4 exhibits encouraging activity in pancreatic cancer cells unresponsive to gemcitabine. These results warrant further investigation in patient-derived pancreatic cancers, and hold promise for the development of therapies that can more efficiently target the specific characteristics of individual tumor types