A Selective ALDH1A3 Inhibitor Impairs Mesothelioma 3-D Multicellular Spheroid Growth and Neutrophil Recruitment.

Aldehyde dehydrogenase 1A3 (ALDH1A3), one of the three members of the aldehyde dehydrogenase 1A subfamily, has been associated with increased progression and drug resistance in various types of solid tumours. Recently, it has been reported that high ALDH1A3 expression is prognostic of poor survival in patients with malignant pleural mesothelioma (MPM), an asbestos-associated chemoresistant cancer. We treated MPM cells, cultured as multicellular spheroids, with NR6, a potent and highly selective ALDH1A3 inhibitor. Here we report that NR6 treatment caused the accumulation of toxic aldehydes, induced DNA damage, CDKN2A expression and cell growth arrest. We observed that, in CDKN2A proficient cells, NR6 treatment induced IL6 expression, but abolished CXCL8 expression and IL-8 release, preventing both neutrophil recruitment and generation of neutrophil extracellular traps (NETs). Furthermore, we demonstrate that in response to ALDH1A3 inhibition, CDKN2A loss skewed cell fate from senescence to apoptosis. Dissecting the role of ALDH1A3 isoform in MPM cells and tumour microenvironment can open new fronts in the treatment of this cancer.

A nicotinamide phosphoribosyltransferase-GAPDH interaction sustains the stress-induced NMN/NAD+ salvage pathway in the nucleus.

All cells require sustained intracellular energy flux, which is driven by redox chemistry at the subcellular level. NAD+, its phosphorylated variant NAD(P)+, and its reduced forms NAD(P)/NAD(P)H are all redox cofactors with key roles in energy metabolism and are substrates for several NAD-consuming enzymes (e.g. poly(ADP-ribose) polymerases, sirtuins, and others). The nicotinamide salvage pathway, constituted by nicotinamide mononucleotide adenylyltransferase (NMNAT) and nicotinamide phosphoribosyltransferase (NAMPT), mainly replenishes NAD+ in eukaryotes. However, unlike NMNAT1, NAMPT is not known to be a nuclear protein, prompting the question of how the nuclear NAD+ pool is maintained and how it is replenished upon NAD+ consumption. In the present work, using human and murine cells; immunoprecipitation, pulldown, and surface plasmon resonance assays; and immunofluorescence, small-angle X-ray scattering, and MS-based analyses, we report that GAPDH and NAMPT form a stable complex that is essential for nuclear translocation of NAMPT. This translocation furnishes NMN to replenish NAD+ to compensate for the activation of NAD-consuming enzymes by stressful stimuli induced by exposure to H2O2 or S-nitrosoglutathione and DNA damage inducers. These results indicate that by forming a complex with GAPDH, NAMPT can translocate to the nucleus and thereby sustain the stress-induced NMN/NAD+ salvage pathway.

Unsymmetric Cisplatin-Based Pt(IV) Conjugates Containing a PARP-1 Inhibitor Pharmacophore Tested on Malignant Pleural Mesothelioma Cell Lines.

Cisplatin is widely employed as a first-line chemotherapeutic agent for many solid tumors, including malignant pleural mesothelioma (MPM). However, its clinical use is limited by heavy side effects and acquired resistance, the latter being mainly related to enhanced DNA repair. Many clinical trials using combinations of platinum drugs and PARP-1 inhibitors (PARPis) have been carried out, with the hope that such combinations might lead to improved therapeutic efficacy against tumors. Here, the synthesis and efficacy in reducing MPM cell viability of four cisplatin-based Pt(IV) prodrugs containing the PARPi 3-aminobenzamide (3-ABA) fragment are described. The most promising conjugate is more effective than cisplatin or cisplatin/3-ABA combination, administered in equimolar doses, in inhibiting PARP-1 activity and inducing apoptosis in BRCA1/2 wild type MPM cells, grown as monolayer or as multicellular spheroids.

Epigenetic Insights on PARP-1 Activity in Cancer Therapy.

The regulation of chromatin state and histone protein eviction have been proven essential during transcription and DNA repair. Poly(ADP-ribose) (PAR) polymerase 1 (PARP-1) and poly(ADP-ribosyl)ation (PARylation) are crucial mediators of these processes by affecting DNA/histone epigenetic events. DNA methylation/hydroxymethylation patterns and histone modifications are established by mutual coordination between all epigenetic modifiers. This review will focus on histones and DNA/histone epigenetic machinery that are direct targets of PARP-1 activity by covalent and non-covalent PARylation. The effects of these modifications on the activity/recruitment of epigenetic enzymes at DNA damage sites or gene regulatory regions will be outlined. Furthermore, based on the achievements made to the present, we will discuss the potential application of epigenetic-based therapy as a novel strategy for boosting the success of PARP inhibitors, improving cell sensitivity or overcoming drug resistance.

The Cytokine Nicotinamide Phosphoribosyltransferase (eNAMPT; PBEF; Visfatin) Acts as a Natural Antagonist of C-C Chemokine Receptor Type 5 (CCR5).

(1) Background: Extracellular nicotinamide phosphoribosyltrasferase (eNAMPT) is released by various cell types with pro-tumoral and pro-inflammatory properties. In cancer, eNAMPT regulates tumor growth through the activation of intracellular pathways, suggesting that it acts through a putative receptor, although its nature is still elusive. It has been shown, using surface plasma resonance, that eNAMPT binds to the C-C chemokine receptor type 5 (CCR5), although the physiological meaning of this finding is unknown. The aim of the present work was to characterize the pharmacodynamics of eNAMPT on CCR5. (2) Methods: HeLa CCR5-overexpressing stable cell line and B16 melanoma cells were used. We focused on some phenotypic effects of CCR5 activation, such as calcium release and migration, to evaluate eNAMPT actions on this receptor. (3) Results: eNAMPT did not induce ERK activation or cytosolic Ca2+-rises alone. Furthermore, eNAMPT prevents CCR5 internalization mediated by Rantes. eNAMPT pretreatment inhibits CCR5-mediated PKC activation and Rantes-dependent calcium signaling. The effect of eNAMPT on CCR5 was specific, as the responses to ATP and carbachol were unaffected. This was strengthened by the observation that eNAMPT inhibited Rantes-induced Ca2+-rises and Rantes-induced migration in a melanoma cell line. (4) Conclusions: Our work shows that eNAMPT binds to CCR5 and acts as a natural antagonist of this receptor.