Compound C, a well-known inhibitor of AMP-activated protein kinase (AMPK), has been reported to exert antitumor activities in some types of cells. Whether compound C can exert antitumor effects in human cholangiocarcinoma (CCA) remains unknown. Here, we demonstrated that compound C is a potent inducer of cell death and autophagy in human CCA cells. Autophagy inhibitors increased the cytotoxicity of compound C towards human CCA cells, as confirmed by increased LDH release, and PARP cleavage. It is notable that compound C treatment increased phosphorylated Akt, sustained high levels of phosphorylated p70S6K, and decreased mTOR regulated p-ULK1 (ser757). Based on the data that blocking PI3K/Akt or mTOR had no apparent influence on autophagic response, we suggest that compound C induces autophagy independent of Akt/mTOR signaling in human CCA cells. Further study demonstrated that compound C inhibited the phosphorylation of JNK and its target c-Jun. Blocking JNK by SP600125 or siRNA suppressed autophagy induction upon compound C treatment. Moreover, compound C induced p38 MAPK activation, and its inhibition promoted autophagy induction via JNK activation. In addition, compound C induced p53 expression, and its inhibition attenuated compound C-induced autophagic response. Thus, compound C triggers autophagy, at least in part, via the JNK and p53 pathways in human CCA cells. In conclusion, suppresses autophagy could increase compound C sensitivity in human CCA.

The search for biomarkers is important for providing more targeted treatments for osteosarcoma patients with chemoresistance. In this study, differentially expressed microRNAs (miRNAs) were identified from miRNA expression profiles. And the target messenger RNAs (mRNAs) of miRNA were obtained from two websites in public domains. Analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway by these miRNA targets suggests that they may have potential links to osteosarcoma chemoresistance. In the protein‐protein interaction (PPI) network, we screened three subnetworks and 10 hub RNAs, and analyzed through KEGG pathway and searched the PubMed database, indicating that they were significantly associated with drug resistance. Then we found 12 key mRNAs by analyzing the mRNA expression profile. Survival analyses showed that most of the 10 hub mRNAs and 12 key mRNAs had a significant influence on the prognosis of patients with chemoresistance osteosarcoma. A miRNA‐mRNA network is constructed by integrating mRNAs and miRNAs information. The network biomarkers in this study have an advantage over traditional single‐molecule biomarkers in terms of predictive power. And the mRNAs in this network biomarkers are supported by survival analysis or by existing theories. These results will contribute to the choice of chemotherapy before treatment and the prediction of patient prognosis.

The loss of contact inhibition is a hallmark of a wide range of human cancer cells. Yet, the precise mechanism behind this process is not fully understood. c‑Myc plays a pivotal role in carcinogenesis, but its involvement in regulating contact inhibition has not been explored to date. Here, we report that c‑Myc plays an important role in abrogating contact inhibition in human cholangiocarcinoma (CCA) cells. Our data show that the protein level of c‑Myc obviously decreased in contact-inhibited normal biliary epithelial cells. However, CCA cells sustain high protein levels of c‑Myc and keep strong proliferation ability in confluent conditions. Importantly, the suppression of c‑Myc by inhibitor or siRNA induced G0/G1 phase cell cycle arrest in confluent CCA cells. We demonstrate that the inhibition of c‑Myc suppressed the activity of mammalian target of rapamycin (mTOR) in confluent CCA cells, and mTOR inhibition induced G0/G1 phase cell cycle arrest in confluent CCA cells. In confluent CCA cells, the activity of Merlin is downregulated, and Yes-associated protein (YAP) sustains high levels of activity. Furthermore, YAP inhibition not only induced G0/G1 phase cell cycle arrest, but also decreased c‑Myc expression in confluent CCA cells. These results indicate that Merlin/YAP/c‑Myc/mTOR signaling axis promotes human CCA cell proliferation by overriding contact inhibition. We propose that overriding c‑Myc‑mediated contact inhibition is implicated in the development of CCA.

Cholangiocarcinoma (CCA) is a highly malignant and aggressive tumor of the bile duct that arises from epithelial cells. Chemotherapy is an important treatment strategy for CCA patients, but its efficacy remains limited due to drug resistance. Salubrinal, an inhibitor of eukaryotic translation initiation factor 2 alpha (eIF2α), has been reported to affect antitumor activities in cancer chemotherapy. In this study, the authors investigated the effect of salubrinal on the chemosensitivity of doxorubicin in CCA cells. They showed that doxorubicin induces CCA cell death in a dose- and time-dependent manner. Doxorubicin triggers reactive oxygen species (ROS) generation and induces DNA damage in CCA cells. In addition, ROS inhibitor N-acetylcysteine (NAC) pretreatment inhibits doxorubicin-induced CCA cell death. Importantly, these data demonstrate a synergistic death induction effect contributed by the combination of salubrinal and doxorubicin in CCA cells. It is notable that salubrinal promotes doxorubicin-induced ROS production and DNA damage in CCA cells. Taken together, these data suggest that salubrinal enhances the sensitivity of doxorubicin in CCA cells through promoting ROS-mediated DNA damage.