Evolutionarily conserved DDB1‐and CUL4‐associated factor 13 (DCAF13) is a recently discovered substrate receptor for the cullin RING‐finger ubiquitin ligase 4 (CRL4) E3 ubiquitin ligase that regulates cell cycle progression. DCAF13 is overexpressed in many cancers, although its role in breast cancer is currently elusive. In this study we demonstrate that DCAF13 is overexpressed in human breast cancer and that its overexpression closely correlates with poor prognosis, suggesting that DCAF13 may serve as a diagnostic marker and therapeutic target. We knocked down DCAF13 in breast cancer cell lines using CRISPR/Cas9 and found that DCAF13 deletion markedly reduced breast cancer cell proliferation, clone formation, and migration both in vitro and in vivo. In addition, DCAF13 deletion promoted breast cancer cell apoptosis and senescence, and induced cell cycle arrest in the G1/S phase. Genome‐wide RNAseq analysis and western blotting revealed that loss of DCAF13 resulted in both mRNA and protein accumulation of p53 apoptosis effector related to PMP22 (PERP). Knockdown of PERP partially reversed the hampered cell proliferation induced by DCAF13 knockdown. Co‐immunoprecipitation assays revealed that DCAF13 and DNA damage‐binding protein 1 (DDB1) directly interact with PERP. Overexpression of DDB1 significantly increased PERP polyubiquitination, suggesting that CRL4DCAF13 E3 ligase targets PERP for ubiquitination and proteasomal degradation. In conclusion, DCAF13 and the downstream effector PERP occupy key roles in breast cancer proliferation and potentially serve as prognostics and therapeutic targets.

Background: Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder, and its specific pathogenesis is still unclear. We have previously reported that TTX-resistant (TTX-R) sodium channels in colon-specific dorsal root ganglion (DRG) neurons were sensitized in a rat model of visceral hypersensitivity induced by neonatal colonic inflammation (NCI). However, the detailed molecular mechanism for activation of sodium channels remains unknown. This study was designed to examine roles for Melatonin (MT) in sensitization of sodium channels in NCI rats. Methods: Colorectal distention (CRD) in adult male rats as a measure of visceral hypersensitivity. Colon-specific dorsal root ganglion (DRG) neurons were labeled with DiI and acutely dissociated for measuring excitability and sodium channel current under whole-cell patch clamp configurations. Western blot and Immunofluorescence were employed to detect changes in expression of Na_v1.8 and MT2. Results: The results showed that rats exhibited visceral hypersensitivity after NCI treatment. Intrathecal application of melatonin significantly increased the threshold of CRD in NCI rats with a dose-dependent manner, but has no role in the control group. Whole-cell patch clamp recording showed that melatonin remarkably decreased the excitability and the density of TTX-R sodium channel in DRG neurons from NCI rats. The expression of MT2 receptor at the protein level was markedly lower in NCI rats. 8-MP, an agonist of MT2 receptor, enhanced the distention threshold in NCI rats. Application of 8-MP reversed the enhanced hypersensitivity of DRG neurons from NCI rats. 8-MP also reduced TTX-R sodium current density and modulated dynamics of TTX-R sodium current activation. Conclusions: These data suggest that sensitization of sodium channels of colon DRG neurons in NCI rats is most likely mediated by MT2 receptor, thus identifying a potential target for treatment for chronic visceral pain in patients with IBS.

BackgroundIt was reported that epidural volume extension could decrease the ED50 of intrathecal plain bupivacaine. In this study, we investigated the ED50 of intrathecal hyperbaric ropivacaine followed by epidural normal saline bolus for cesarean section.MethodsSixty parturients were allocated into two groups in this prospective study. About 10 mL of epidural normal saline was given after the intrathecal dose of hyperbaric ropivacaine in the Group S (normal saline group), and no epidural injection of normal saline was given after the intrathecal ropivacainve injection in the Group C (control group). The dose of intrathecal ropivacaine for each parturient was decided by up-down allocation method. The initial dose was set as 10 mg. Effective anesthesia was defined as the level of T6 or above achieved within 10 minutes after intrathecal injection and no additional epidural drug to complete operation. The Massey formula was applied to calculate the ED50 of intrathecal ropivacaine.ResultsThe ED50 of intrathecal ropivacaine for cesarean section determined by up-and-down method was 7.51 mg (95% CI, 7.09–7.93 mg) in the Group S and 8.29 mg (95% CI, 7.73–8.85 mg) in the Group C, and there was a significant difference in ED50 of ropivacaine between the two groups (P<0.05). Compared with the Group C, the ED50 of intrathecal ropivacaine decreased when followed by epidural normal saline bolus.ConclusionThe ED50 of intrathecal hyperbaric ropivacaine for cesarean section is 8.29 mg, and it is reduced when followed by epidural normal saline bolus (www.chictr.org.cn, registration number: ChiCTR-ROC-17013382).