Separation and determination of cysteine enantiomers in plasma after derivatization with 4-fluoro-7-nitrobenzofurazan.

The importance of D-amino acids in mammals associated with enantio-dependent biological functions has been increasingly highlighted. In addition to naturally occurring, D-amino acid supplementation could have a positive biological impact, including cytoprotective implications. In this context, supplementation with D-cysteine has revealed beneficial effects. Quantification of cysteine enantiomers in rodent plasma has been achieved by using 4-fluoro-7-nitrobenzofurazan derivatization of the target analytes. Cystine, the main form of cysteine in the plasma, was initially reduced to cysteine using DL-dithiothreitol. Baseline enantioseparation was then achieved in less than 3 min using a (R,R)-Whelk-O 1 stationary phase and isocratic elution using CH3OH-H2O 90:10 (v/v) with 15 mM ammonium formate (apparent pH 6.0) at 0.5 mL/min. The derivatives were then detected using negative ESI-MS in SRM mode. An external calibration was employed for D-cysteine, while L-cysteine quantification, as an endogenous analyte, was addressed using a background subtraction strategy. The method was validated. Response functions were obtained from 0 to 300 µM and from 0 to 125 µM for D-cysteine and L-cysteine, respectively. The trueness ranged from 96% to 105% for both enantiomers with repeatability and intermediate precision lower than 8% and 15% for the D-form and the endogenous L-form, respectively. The method was successfully applied for determining D- and L-cysteine in mouse plasma after D-cysteine administration.

The Multifaceted Pyruvate Metabolism: Role of the Mitochondrial Pyruvate Carrier.

Pyruvate, the end product of glycolysis, plays a major role in cell metabolism. Produced in the cytosol, it is oxidized in the mitochondria where it fuels the citric acid cycle and boosts oxidative phosphorylation. Its sole entry point into mitochondria is through the recently identified mitochondrial pyruvate carrier (MPC). In this review, we report the latest findings on the physiology of the MPC and we discuss how a dysfunctional MPC can lead to diverse pathologies, including neurodegenerative diseases, metabolic disorders, and cancer.

Development and validation of a chiral UHPLC-MS method for the analysis of cysteine enantiomers in biological samples.

For years, d-amino acids were thought to have a minor function in biological processes compared to that of l-enantiomers. Recently, many studies have shown that d-amino acids are present in high concentrations in microorganisms, plants, mammals and humans and execute specific biological functions. One relevant example is that of d-cysteine, whose hydrogen sulfide-producing properties have been found to protect neurons against oxidative stress and to promote dendritic development. Herein, we introduce a chiral LCMS method for the rapid determination of cysteine enantiomers under polar ionic elution conditions (MeOH/MeCN/H2O 49/49/2 v/v/v, containing 50 mM formic acid and 50 mM ammonium formate) developed on a Chiralpak® ZWIX(+) chiral stationary phase. Cysteine enantiomers were analysed in biological samples after efficient reduction of the disulfide bond in cystine; the latter was achieved with the use of 1,4-dithio-dl-threitol as a reducing agent. A baseline resolution (RS = 2.7) was obtained, and the d-enantiomer eluted before the l-enantiomer. For the enantioselective analysis, cysteine was labelled with AccQ-Tag reagent, resulting in improved chromatographic behaviour and MS detection sensitivity. The method was validated according to the Food and Drug Administration guidelines. Good linearity was determined in the ranges of 0.05-0.50 mg/L for d-cysteine and 0.11-0.56 mg/L for l-cysteine. The repeatability and intermediate precision were found to be lower than 4.0%, with trueness ranging from 95.6 to 100.2% for both enantiomers. The LOD and LOQ values were 0.02 and 0.05 mg/L for d-cysteine and 0.04 and 0.11 mg/L for l-cysteine, respectively. The method was successfully applied to cell culture samples treated with d-cysteine.

E2F1 inhibition mediates cell death of metastatic melanoma.

Melanoma is one of the most lethal cancers when it reaches a metastatic stage. Despite advancements in targeted therapies (BRAF inhibitors) or immunotherapies (anti-CTLA-4 or anti-PD1), most patients with melanoma will need additional treatment. Thus, there is an urgent need to develop new therapeutical approaches to bypass resistance and achieve more prolonged responses. In this context, we were interested in E2F1, a transcription factor that plays a major role in the control of cell cycle under physiological and pathological conditions. Here we confirmed that E2F1 is highly expressed in melanoma cells. Inhibition of E2F1 activity further increased melanoma cell death and senescence, both in vitro and in vivo. Moreover, blocking E2F1 also induced death of melanoma cells resistant to BRAF inhibitors. In conclusion, our studies suggest that targeting the E2F1 signaling pathway may be therapeutically relevant for melanoma.

MiR-223-3p inhibits angiogenesis and promotes resistance to cetuximab in head and neck squamous cell carcinoma.

MicroRNAs (miRs) participate in tumor growth and dissemination by regulating expression of various target genes. MiR-223-3p is suspected of being involved in head and neck squamous cell carcinoma (HNSCC) growth although its precise role has not been elucidated. In this study, we showed that miR-223-3p is present in biopsies of HNSCC patients and that its presence is correlated with high neutrophil infiltrate. We found that overexpression of miR-223-3p slightly increased proliferation of the CAL27 squamous carcinoma cell line both in vitro and in vivo. Moreover, miR-223-3p induced CAL27 apoptosis in an orthotopic xenograft mouse model, counteracting the proliferative effect and resulting in no impact on overall tumor growth. We analyzed the effect of miR-223-3p overexpression on signaling pathways and showed that it induced pERK2, pAKT and AKT, consistent with an increase in cell proliferation. In addition, we found that miR-223-3p reduced the STAT3 level correlating with increased cell apoptosis and inhibited vasculature formation. In HNSCC tissues, miR-223-3p expression was inversely correlated to CD31, highlighting the relationship between miR-223 and vessel formation. Finally, we studied the effect of miR-223-3p on response to selected anticancer agents and showed that cells expressing miR-223-3p are more resistant to drugs, notably cetuximab. In conclusion, our study is the first to show the antiangiogenic properties of miR-223-3p in HNSCC patients and to question whether expression levels of miR-223-3p can be evaluated as an indicator of eligibility for non-treatment of HNSCC patients with cetuximab.

Characterizing isomiR variants within the microRNA-34/449 family.

miR-34/449 microRNAs are conserved regulators of multiciliated cell differentiation. Here, we evidence and characterize expression of two isomiR variant sequences from the miR-34/449 family in human airway epithelial cells. These isomiRs differ from their canonical counterparts miR-34b and miR-449c by one supplemental uridine at their 5'-end, leading to a one-base shift in their seed region. Overexpression of canonical miR-34/449 or 5'-isomiR-34/449 induces distinct gene expression profiles and biological effects. However, some target transcripts and functional activities are shared by both canonical microRNAs and isomiRs. Indeed, both repress important targets that result in cell cycle blockage and Notch pathway inhibition. Our findings suggest that 5'-isomiR-34/449 may represent additional mechanisms by which miR-34/449 family finely controls several pathways to drive multiciliogenesis.

Rapid decay of engulfed extracellular miRNA by XRN1 exonuclease promotes transient epithelial-mesenchymal transition.

Extracellular vesicles (EVs) have been shown to play an important role in intercellular communication as carriers of DNA, RNA and proteins. While the intercellular transfer of miRNA through EVs has been extensively studied, the stability of extracellular miRNA (ex-miRNA) once engulfed by a recipient cell remains to be determined. Here, we identify the ex-miRNA-directed phenotype to be transient due to the rapid decay of ex-miRNA. We demonstrate that the ex-miR-223-3p transferred from polymorphonuclear leukocytes to cancer cells were functional, as demonstrated by the decreased expression of its target FOXO1 and the occurrence of epithelial-mesenchymal transition reprogramming. We showed that the engulfed ex-miRNA, unlike endogenous miRNA, was unstable, enabling dynamic regulation and a return to a non-invasive phenotype within 8 h. This transient phenotype could be modulated by targeting XRN1/PACMAN exonuclease. Indeed, its silencing was associated with slower decay of ex-miR-223-3p and subsequently prolonged the invasive properties. In conclusion, we showed that the 'steady step' level of engulfed miRNA and its subsequent activity was dependent on the presence of a donor cell in the surroundings to constantly fuel the recipient cell with ex-miRNAs and of XRN1 exonuclease, which is involved in the decay of these imported miRNA.

MicroRNA-375/SEC23A as biomarkers of the in vitro efficacy of vandetanib.

In this study, we performed microRNA (miRNA) expression profiling on a large series of sporadic and hereditary forms of medullary thyroid carcinomas (MTC). More than 60 miRNAs were significantly deregulated in tumor vs adjacent non-tumor tissues, partially overlapping with results of previous studies. We focused our attention on the strongest up-regulated miRNA in MTC samples, miR-375, the deregulation of which has been previously observed in a variety of human malignancies including MTC. We identified miR-375 targets by combining gene expression signatures from human MTC (TT) and normal follicular (Nthy-ori 3-1) cell lines transfected with an antagomiR-375 inhibitor or a miR-375 mimic, respectively, and from an in silico analysis of thyroid cell lines of Cancer Cell Line Encyclopedia datasets. This approach identified SEC23A as a bona fide miR-375 target, which we validated by immunoblotting and immunohistochemistry of non-tumor and pathological thyroid tissue. Furthermore, we observed that miR-375 overexpression was associated with decreased cell proliferation and synergistically increased sensitivity to vandetanib, the clinically relevant treatment of metastatic MTC. We found that miR-375 increased PARP cleavage and decreased AKT phosphorylation, affecting both cell proliferation and viability. We confirmed these results through SEC23A direct silencing in combination with vandetanib, highlighting the importance of SEC23A in the miR-375-associated increased sensitivity to vandetanib.Since the combination of increased expression of miR-375 and decreased expression of SEC23A point to sensitivity to vandetanib, we question if the expression levels of miR-375 and SEC23A should be evaluated as an indicator of eligibility for treatment of MTC patients with vandetanib.

EFA6B antagonizes breast cancer.

One of the earliest events in epithelial carcinogenesis is the dissolution of tight junctions and cell polarity signals that are essential for normal epithelial barrier function. Here, we report that EFA6B, a guanine nucleotide exchange factor for the Ras superfamily protein Arf6 that helps assemble and stabilize tight junction, is required to maintain apico-basal cell polarity and mesenchymal phenotypes in mammary epithelial cells. In organotypic three-dimensional cell cultures, endogenous levels of EFA6B were critical to determine epithelial-mesenchymal status. EFA6B downregulation correlated with a mesenchymal phenotype and ectopic expression of EFA6B hampered TGFß-induced epithelial-to-mesenchymal transition (EMT). Transcriptomic and immunohistochemical analyses of human breast tumors revealed that the reduced expression of EFA6B was associated with loss of tight junction components and with increased signatures of EMT, cancer stemness, and poor prognosis. Accordingly, tumors with low levels of EFA6B were enriched in the aggressive triple-negative and claudin-low breast cancer subtypes. Our results identify EFA6B as a novel antagonist in breast cancer and they point to its regulatory and signaling pathways as rational therapeutic targets in aggressive forms of this disease.

Response of CAIX and CAXII to in vitro re-oxygenation and clinical significance of the combined expression in NSCLC patients.

The disorganized neo-vasculature in tumours causes fluctuations in the concentration of oxygen, which contributes to tumour development and metastatic potential. Although hypoxic regulation of the expression of the carbonic anhydrases CAIX and CAXII is well established, the effect of re-oxygenation on these proteins remains to be elucidated. A549 and H1975 human lung cancer cell lines were exposed to hypoxia for 24 h and then re-oxygenated. CAIX or CAXII expression and cell cycle progression at different time-points were monitored. A549-shCA9 cells were analyzed for cell cycle progression in the same conditions. We demonstrate for the first time an association between the stability of CAIX and restoration of the S/G2 phase of hypoxia-arrested cells subjected to re-oxygenation. In exchange, we have found that the loss of CA9 did not cause a decreased progression into S/G2 phase during re-oxygenation, but rather affected the hypoxic growth arrest. We previously demonstrated that CAIX expression is a poor prognostic factor and that CAXII expression is a good prognostic factor in non-small cell lung cancer (NSCLC) patients. We further detail the relevance of the combined expression of these proteins for predicting outcome in a large population of NSCLC patients after long-term follow-up. The high CAIX/low CAXII expression sub-group was associated with a high cumulative incidence of relapse and with poor overall survival of NSCLC patients (P < 0.0001). Our results demonstrate a critical role for re-oxygenation on CAIX and CAXII levels that may select for an aggressive lung cancer phenotype. These findings suggest that CAIX and CAXII play dual roles in tumour progression and emphasize their significant prognostic and potential therapeutic value.

In papillary thyroid carcinoma, TIMP-1 expression correlates with BRAF (V600E) mutation status and together with hypoxia-related proteins predicts aggressive behavior.

BRAF (V600E) causes upregulation of tissue inhibitor of metalloproteinase-1 (TIMP-1), which promotes cell invasion in papillary thyroid carcinoma (PTC). Hypoxia-inducible factor-1α (HIF- α) is regulated by hypoxia and also by the BRAF-mediated signaling pathway in PTC. We assessed the association of expression of TIMP-1, HIF-1α, and hypoxia-inducible carbonic anhydrase IX (CAIX) and XII (CAXII) with clinical parameters in PTC. TPC-1/BRAF (WT) wild-type and BcPAP/BRAF (V600E) -mutated PTC cell lines were selected to study the effects of the BRAF (V600E) mutation and hypoxia on expression in vitro of TIMP-1, CAIX, and CAXII proteins by immunoblotting. Higher expression of all proteins was detected in BcPAP cells exposed to hypoxia. Tissue microarray immunohistochemistry analysis was performed to study protein expression in 114 BRAF-genotyped PTC samples. Expression data on tumor tissue were compared with clinicopathological variables. TIMP-1 expression had a sensitivity of 87 % and a specificity of 83 % in identifying a BRAF mutation (P < 0.001) and was associated with pT stage (P = 0.001), pN stage (P = 0.02), and multifocality (P = 0.03). HIF-1α expression correlated with pT stage (P = 0.05). CAIX expression was associated with pN stage (P = 0.02), and both CAIX (P = 0.004) and CAXII (P = 0.05) were strongly associated with vascular invasion. We conclude that TIMP-1 protein expression is a reliable surrogate marker for BRAF-mutated status in PTC. TIMP-1 and hypoxia-regulated proteins are promising as predictors of aggressiveness in PTC and warrant further investigation as new therapeutic targets for the treatment of highly aggressive forms of PTC.

Senescent cells develop a PARP-1 and nuclear factor-{kappa}B-associated secretome (PNAS).

Melanoma cells can enter the process of senescence, but whether they express a secretory phenotype, as reported for other cells, is undetermined. This is of paramount importance, because this secretome can alter the tumor microenvironment and the response to chemotherapeutic drugs. More generally, the molecular events involved in formation of the senescent-associated secretome have yet to be determined. We reveal here that melanoma cells experiencing senescence in response to diverse stimuli, including anti-melanoma drugs, produce an inflammatory secretory profile, where the chemokine ligand-2 (CCL2) acts as a critical effector. Thus, we reveal how senescence induction might be involved in therapeutic failure in melanoma. We further provide a molecular relationship between senescence induction and secretome formation by revealing that the poly(ADP-ribose) polymerase-1 (PARP-1)/nuclear factor-κB (NF-κB) signaling cascade, activated during senescence, drives the formation of a secretome endowed with protumoral and prometastatic properties. Our findings also point to the existence of the PARP-1 and NF-κB-associated secretome, termed the PNAS, in nonmelanoma cells. Most importantly, inhibition of PARP-1 or NF-κB prevents the proinvasive properties of the secretome. Collectively, identification of the PARP-1/NF-κB axis in secretome formation opens new avenues for therapeutic intervention against cancers.