1.
NS1643 enhances ionic currents in a G604S-WT hERG co-expression system associated with long QT syndrome 2.
Huo, J, Guo, X, Lu, Q, Qiang, H, Liu, P, Bai, L, Huang, CL, Zhang, Y, Ma, A
Clinical and experimental pharmacology & physiology. 2017;(11):1125-1133
Abstract
Loss of function mutations in the human ether-a-go-go-related gene (hERG) cause long QT syndrome type 2 (LQT2). Most LQT2 patients are heterozygous mutation carriers in which the mutant hERG exerts potent dominant-negative effects. 1, 3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea (NS1643) is known to enhance IKr in WT-hERG. We investigated its actions following lipofectamine-induced expression of both mutant G604S- and WT-hERG in the heterologous HEK293 expression system. Cells transfected with pcDNA3-G604S-hERG did not lead to any expression of detectable currents whether before or following NS1643 challenge. Cells transfected with both pcDNA3-WT-hERG and pcDNA3-G604S-hERG showed reduced hERG currents compared to those transfected with pcDNA3-G604S-hERG consistent with the reduced trafficking and formation of modified heteromeric WT-G604S channels reported on earlier occasions. Nevertheless, NS1643 then continued to produce concentration- and voltage-dependent increases in hERG current amplitude. It did not affect the voltage dependence of activation, recovery from inactivation and deactivation. However, NS1643 (30 μmol/L) slowed steady state inactivation and shifted the steady state half maximal activation voltage (V1/2 ) of the inactivation curve by +10 mV, and significantly increased the time constants of inactivation. Our present experimental results suggest that NS1643 significantly increases ion current and attenuates its inactivation in cells co-expressing G604S-hERG and WT-hERG. These findings raise the possibility that hERG channel activators offer potential treatment strategies for inherited LQT2.
2.
Pharmacological rescue of hERG currents carried out by G604S and wide type hERG co-expression.
Huo, J, Zhang, A, Guo, X, Qiang, H, Liu, P, Bai, L, Ma, A
Clinical and experimental pharmacology & physiology. 2016;(9):851-61
Abstract
Mutations in human ether-a-go-go-related gene (hERG) can lead to type 2 long-QT syndrome (LQT2). The authors previously identified the hERG mutation G604S results in a loss of function and obviously decreased current amplitude and impaired channel protein trafficking when co-expressed with WT-hERG. The present study further investigates the biological and electrophysiological consequences of pharmacologic chaperones in HEK293 cells expressing G604S-hERG or co-expressing G604S-hERG and WT-hERG. It was found that a low temperature (27°C), thapsigargin, NS1643 and E-4031 fail to rescue the G604S mutation. Interestingly, only E-4031 treatment resulted in a significant increase in hERG currents in cells co-expressing G604S-hERG and WT-hERG, correspondingly more mature protein band at 155 kDa by Western blotting and an increased membrane staining by confocal microscopy. In addition, E-4031 treatment shifted the steady-state half maximal activation voltage (V1/2 ) of the inactivation curve by +8 mV in cells co-expressing G604S-hERG and WT-hERG. The present experimental results suggest that a G604S mutation is resistant to pharmacological rescue. E-4031 treatment resulted in a significant increase in hERG currents by promoting the hERG channel processing and trafficking in cells co-expressing G604S-hERG and WT-hERG.
3.
Randomized controlled trial of the prophylactic effect of urea-based cream on sorafenib-associated hand-foot skin reactions in patients with advanced hepatocellular carcinoma.
Ren, Z, Zhu, K, Kang, H, Lu, M, Qu, Z, Lu, L, Song, T, Zhou, W, Wang, H, Yang, W, et al
Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2015;(8):894-900
Abstract
PURPOSE To assess whether urea-based cream (UBC) has prophylactic benefits on sorafenib-induced hand-foot skin reaction (HFSR) in patients with advanced hepatocellular carcinoma (HCC). PATIENTS AND METHODS In this randomized, open-label trial, 871 patients with advanced HCC throughout China were treated with 10% UBC three times per day plus best supportive care (BSC; n = 439) or BSC alone excluding all creams (n = 432), starting on day 1 of sorafenib treatment, for up to 12 weeks. HFSR was assessed every 2 weeks and at 14 weeks for patients completing the study. Once HFSR occurred, patients were allowed any cream, including a UBC. RESULTS The 12-week incidence of any grade HFSR was significantly lower in the UBC group versus the BSC-alone group (56.0% v 73.6%, respectively; odds ratio [OR], 0.457; 95% CI, 0.344 to 0.608; P < .001), as was the incidence of grade ≥ 2 HFSR (20.7% v 29.2%, respectively; OR, 0.635; 95% CI, 0.466 to 0.866; P = .004). Median time to first occurrence of HFSR was significantly longer in the UBC group than the BSC-alone group (84 v 34 days, respectively; hazard ratio, 0.658; 95% CI, 0.541 to 0.799; P < .001). Elevated AST was associated with increased risk of HFSR but did not alter the treatment effect of UBC. UBC plus BSC, compared with BSC alone, did not affect the sorafenib dose reduction or interruption rate (9.1% v 11.8%, respectively; P = .1937), response rate (11.1% v 10.1%, respectively; P = .6674), or disease control rate (98.8% v 98.2%, respectively; P = .5350) at week 12. CONCLUSION UBC prophylaxis in patients with advanced HCC starting sorafenib reduced HFSR rates, extended the time to first occurrence of HFSR, and improved patient quality of life compared with BSC. Blinded, randomized, placebo-controlled trials to determine the role of UBC on the incidence and severity of HFSR are warranted.