Effect of enhanced expression of connexin 43 on sunitinib-induced cytotoxicity in mesothelioma cells

AbstractConnexin (Cx) makes up a type of intercellular channel called gap junction (GJ). GJ plays a regulatory role in cellular physiology. The Cx expression level is often decreased in cancer cells compared to that in healthy ones, and the restoration of its expression has been shown to exert antiproliferative effects. This work aims to evaluate the effect of the restoration of connexin 43 (Cx43) (the most ubiquitous Cx subtype) expression on sunitinib (SU)-induced cytotoxicity in malignant mesothelioma (MM) cells. Increased Cx43 expression in an MM cell line (H28) improved the ability of SU to inhibit receptor tyrosine kinase (RTK) signaling. Moreover, higher Cx43 expression promoted SU-induced apoptosis. The cell viability test revealed that Cx43 enhanced the cytotoxic effect of SU in a GJ-independent manner. The effect of Cx43 on a proapoptotic factor, Bax, was then investigated. The interaction between Cx43 and Bax was confirmed by immunoprecipitation. Furthermore, higher Cx43 expression increased the production of a cleaved (active) form of Bax during SU-induced apoptosis with no alteration in total Bax expression. These findings indicate that Cx43 most likely increases sensitivity to SU in H28 through direct interaction with Bax. In conclusion, we found that Cx43 overcame the chemoresistance of MM cells

Conflicting Roles of Connexin43 in Tumor Invasion and Growth in the Central Nervous System

The tumor microenvironment is known to have increased levels of cytokines and metabolites, such as glutamate, due to their release from the surrounding cells. A normal cell around the tumor that responds to the inflammatory environment is likely to be subsequently altered. We discuss how these abnormalities will support tumor survival via the actions of gap junctions (GJs) and hemichannels (HCs) which are composed of hexamer of connexin43 (Cx43) protein. In particular, we discuss how GJ intercellular communication (GJIC) in glioma cells, the primary brain tumor, is a regulatory factor and its attenuation leads to tumor invasion. In contrast, the astrocytes, which are normal cells around the glioma, are “hijacked” by tumor cells, either by receiving the transmission of malignant substances from the cancer cells via GJIC, or perhaps via astrocytic HC activity through the paracrine signaling which enable the delivery of these substances to the distal astrocytes. This astrocytic signaling would promote tumor expansion in the brain. In addition, brain metastasis from peripheral tissues has also been known to be facilitated by GJs formed between cerebral vascular endothelial cells and cancer cells. Astrocytes and microglia are generally thought to eliminate cancer cells at the blood–brain barrier. In contrast, some reports suggest they facilitate tumor progression as tumor cells take advantage of the normal functions of astrocytes that support the survival of the neurons by exchanging nutrients and metabolites. In summary, GJIC is essential for the normal physiological function of growth and allowing the diffusion of physiological substances. Therefore, whether GJIC is cancer promoting or suppressing may be dependent on what permeates through GJs, when it is active, and to which cells. The nature of GJs, which has been ambiguous in brain tumor progression, needs to be revisited and understood together with new findings on Cx proteins and HC activities.Medicine, Faculty ofOther UBCNon UBCCellular and Physiological Sciences, Department ofReviewedFacult

Connexin 43 enhances Bax activation via JNK activation in sunitinib-induced apoptosis in mesothelioma cells

The constituent protein of gap junctions, connexin (Cx), interacts with various proteins via its C-terminus region, including kinases, cell-adhesion proteins, and a pro-apoptotic protein, Bax. This molecular interaction may affect expression and functioning of the interacting proteins and modulate the cellular physiology. In our previous work, Cx43 was found to interact directly with Bax and in the presence of sunitinib, lead to the Bax-mediated apoptosis in mesothelioma cells. In this study, we investigated the mechanism of how Cx43 promotes Bax-mediated apoptosis using the same cell line. Treatment with sunitinib increased the expression of the active conformation of the Bax protein, which was predominantly localized at the mitochondria, only in Cx43-transfected cells. Bax oligomerization and decrease in the mitochondrial membrane potential were also observed. The involvement of c-Jun N-terminal kinase (JNK) in the interaction of Cx43 and Bax was further examined. Treatment with sunitinib increased the expression of phosphorylated (active) form of JNK only in the Cx43-transfected cells. Phosphorylated JNK and active Bax were co-localized, and the co-localization was suppressed by the knockdown of Cx43. Moreover, JNK inhibition clearly suppressed Bax activation. In conclusion, we identified a novel Cx43-JNK-Bax axis regulating the process of apoptosis for the first time

Antiretroviral therapy alone versus antiretroviral therapy with a kick and kill approach, on measures of the HIV reservoir in participants with recent HIV infection (the RIVER trial): a phase 2, randomised trial

Background: Antiretroviral therapy (ART) cannot cure HIV infection because of a persistent reservoir of latently infected cells. Approaches that force HIV transcription from these cells, making them susceptible to killing—termed kick and kill regimens—have been explored as a strategy towards an HIV cure. RIVER is the first randomised trial to determine the effect of ART-only versus ART plus kick and kill on markers of the HIV reservoir. Methods: This phase 2, open-label, multicentre, randomised, controlled trial was undertaken at six clinical sites in the UK. Patients aged 18–60 years who were confirmed as HIV-positive within a maximum of the past 6 months and started ART within 1 month from confirmed diagnosis were randomly assigned by a computer generated randomisation list to receive ART-only (control) or ART plus the histone deacetylase inhibitor vorinostat (the kick) and replication-deficient viral vector T-cell inducing vaccines encoding conserved HIV sequences ChAdV63. HIVconsv-prime and MVA.HIVconsv-boost (the kill; ART + V + V; intervention). The primary endpoint was total HIV DNA isolated from peripheral blood CD4+ T-cells at weeks 16 and 18 after randomisation. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, NCT02336074. Findings: Between June 14, 2015 and Jul 11, 2017, 60 men with HIV were randomly assigned to receive either an ART-only (n=30) or an ART + V + V (n=30) regimen; all 60 participants completed the study, with no loss-to-follow-up. Mean total HIV DNA at weeks 16 and 18 after randomisation was 3·02 log10 copies HIV DNA per 106 CD4+ T-cells in the ART-only group versus 3·06 log10 copies HIV DNA per 106 CD4+ T-cells in ART + V + V group, with no statistically significant difference between the two groups (mean difference of 0·04 log10 copies HIV DNA per 106 CD4+ T-cells [95% CI −0·03 to 0·11; p=0·26]). There were no intervention-related serious adverse events. Interpretation: This kick and kill approach conferred no significant benefit compared with ART alone on measures of the HIV reservoir. Although this does not disprove the efficacy kick and kill strategy, for future trials enhancement of both kick and kill agents will be required. Funding: Medical Research Council (MR/L00528X/1)