Glucocorticoids (GCs) are commonly co-administered with cisplatin in the treatment of patients with carcinomas to prevent drug-induced allergic reaction, nausea and vomiting. Although GC receptor (GR) is ubiquitous in carcinoma cells and has been linked to signal transduction pathways pertinent to cell growth and apoptosis, little is known regarding the possible effect of GC on the chemosensitivity of carcinomas. Our previous study demonstrated that dexamethasone (DEX) enhances the cytotoxicity to cisplatin in a GR-rich human cervical carcinoma cell line, SiHa. In this study, we found that this cisplatin cytotoxicity-enhancing effect of DEX correlated well with its effect on abrogating the cisplatin-induced activation of nuclear factor kappa B (NF-κB). RU486, a structural homologue of DEX, partially reversed this cytotoxicity-enhancing effect of DEX, a finding consistent with the well-known partial reversing effect of RU486 on DEX-induced NF-κB suppression. Furthermore, expression of a dominant-negative truncated IκBα gene in SiHa cells completely abolished the cisplatin cytotoxicity-enhancing effect of DEX. Our data suggest that the specific action of DEX on GR may enhance the cytotoxicity of cisplatin in selected GR-rich cancer cells by suppressing NF-κB activation.
Yen-Shen Lu, Pei-Yen Yeh, Shuang-En Chuang, Ming Gao, Min-Liang Kuo, and Ann-Lii Cheng
Hai-Fan Yu, Zhan-Peng Yue, Kai Wang, Zhan-Qing Yang, Hong-Liang Zhang, Shuang Geng, and Bin Guo
Although Gja1 has been proved to play an important role in uterine decidualization, its regulatory mechanism remains largely unknown. Here, we showed that Gja1 was highly expressed in the decidual cells and promoted the proliferation of uterine stromal cells and expression of Prl8a2 and Prl3c1, which were two well-known differentiation markers for decidualization. Further analysis revealed that Gja1 might act downstream of Acvr1 and cAMP to regulate the differentiation of uterine stromal cells. Administration of cAMP analog 8-Br-cAMP to Acvr1 siRNA-transfected stromal cells resulted in an obvious increase of Gja1 expression, whereas PKA inhibitor H89 impeded the induction of Gja1 elicited by Acvr1 overexpression, indicating that cAMP–PKA signal mediates the regulation of Acvr1 on Gja1 expression. In uterine stromal cells, knockdown of Gja1 blocked the cAMP induction of Hand2. Moreover, siRNA-mediated downregulation of Hand2 impaired the stimulatory effects of Gja1 overexpression on the expression of Prl8a2 and Prl3c1, whereas constitutive expression of Hand2 reversed the inhibitory effects of Gja1 siRNA on stromal differentiation. Meanwhile, Gja1 might play a vital role in the crosstalk between Acvr1 and Hand2. Collectively, Gja1 may act downstream of cAMP–PKA signal to mediate the effects of Acvr1 on the differentiation of uterine stromal cells through targeting Hand2.