Iron-(Fe3+) dependent reactivation of telomerase drives colorectal cancers.

Over-consumption of iron-rich red meat and hereditary or genetic iron overload are associated with increased risk of colorectal carcinogenesis, yet the mechanistic basis of how metal-mediated signaling leads to oncogenesis remains enigmatic. Using fresh colorectal cancer (CRC) samples we identify Pirin, an iron sensor, that overcomes a rate-limiting step in oncogenesis, by re-activating the dormant human-reverse-transcriptase (hTERT) subunit of telomerase holoenzyme in an iron-(Fe3+)-dependent-manner and thereby drives CRCs. Chemical genetic screens combined with isothermal-dose response fingerprinting and mass-spectrometry identified a small molecule SP2509, that specifically inhibits Pirin-mediated hTERT reactivation in CRCs by competing with iron-(Fe3+) binding. Our findings, first to document how metal ions reactivate telomerase, provide a molecular mechanism for the well-known association between red meat, and increased incidence of CRCs. Small molecules like SP2509 represent a novel modality to target telomerase that acts as driver of 90% human cancers and is yet to be targeted in clinic.

Establishment of HPLC-ESI-MS method for the determination of eplerenone in human plasma and its pharmacokinetics / 药学学报

A sensitive high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method was established for the determination of eplerenone (EP) in human plasma. The plasma samples of EP were extracted with ethyl acetate and separated by HPLC on a reversed phase C18 column with a mobile phase of 10 mmol x L(-1) ammonium acetate water solution-methanol (30 : 70, v/v). EP was determined with electrospray ionization-mass spectrometry (ESI-MS) in the selected ion monitoring (SIM) mode. The calibration curves were linear over the range of 2-4 000 ng x mL(-1) for EP. The lower limit of quantification was 2 ng x mL(-1). The method has been successfully applied in the pharmacokinetic study of the EP tablets. The main pharmacokinetic parameters of EP after oral administration of 25 mg, 50 mg, 100 mg were as follows, t1/2: (4.9 +/- 2.1), (4.7 +/- 1.5), (5.9 +/- 1.2) h; AUC(0-infinity): (4 402 +/- 1 735), (8 150 +/- 2 509), (13 783 +/- 4 102) microg x h x L(-1); and MRT: (6.2 +/- 2.1), (6.6 +/- 1.3), and (7.2 +/- 1.6) h. Parameters of EP after oral administration of multiple doses of 50 mg were as follows, t1/2: (6.1 +/- 1.7) h; AUC(ss): (10 071 +/- 4220) microg x h x L(-1); MRT: (8.1 +/- 2.3) h; and DF: (3.2 +/- 1.0).