Adiponectin Promotes VEGF Expression in Rheumatoid Arthritis Synovial Fibroblasts and Induces Endothelial Progenitor Cell Angiogenesis by Inhibiting miR-106a-5p.

Rheumatoid arthritis (RA) is an erosive polyarthritis that can lead to severe joint destruction and painful disability if left untreated. Angiogenesis, a critical pathogenic mechanism in RA, attracts inflammatory leukocytes into the synovium, which promotes production of proinflammatory cytokines and destructive proteases. Adipokines, inflammatory mediators secreted by adipose tissue, also contribute to the pathophysiology of RA. The most abundant serum adipokine is adiponectin, which demonstrates proinflammatory effects in RA, although the mechanisms linking adiponectin and angiogenic manifestations of RA are not well understood. Our investigations with the human MH7A synovial cell line have revealed that adiponectin dose- and time-dependently increases vascular endothelial growth factor (VEGF) expression, stimulating endothelial progenitor cell (EPC) tube formation and migration. These adiponectin-induced angiogenic activities were facilitated by MEK/ERK signaling. In vivo experiments confirmed adiponectin-induced downregulation of microRNA-106a-5p (miR-106a-5p). Inhibiting adiponectin reduced joint swelling, bone destruction, and angiogenic marker expression in collagen-induced arthritis (CIA) mice. Our evidence suggests that targeting adiponectin has therapeutic potential for patients with RA. Clinical investigations are needed.

CXCL13/CXCR5 axis facilitates endothelial progenitor cell homing and angiogenesis during rheumatoid arthritis progression.

Angiogenesis is a critical process in the formation of new capillaries and a key participant in rheumatoid arthritis (RA) pathogenesis. The chemokine (C-X-C motif) ligand 13 (CXCL13) plays important roles in several cellular functions such as infiltration, migration, and motility. We report significantly higher levels of CXCL13 expression in collagen-induced arthritis (CIA) mice compared with controls and also in synovial fluid from RA patients compared with human osteoarthritis (OA) samples. RA synovial fluid increased endothelial progenitor cell (EPC) homing and angiogenesis, which was blocked by the CXCL13 antibody. By interacting with the CXCR5 receptor, CXCL13 facilitated vascular endothelial growth factor (VEGF) expression and angiogenesis in EPC through the PLC, MEK, and AP-1 signaling pathways. Importantly, infection with CXCL13 short hairpin RNA (shRNA) mitigated EPC homing and angiogenesis, articular swelling, and cartilage erosion in ankle joints of mice with CIA. CXCL13 is therefore a novel therapeutic target for RA.

MERTK Inhibition: Potential as a Treatment Strategy in EGFR Tyrosine Kinase Inhibitor-Resistant Non-Small Cell Lung Cancer.

Epidermal growth factor tyrosine kinase inhibitors (EGFR-TKIs) are currently the most effective treatment for non-small cell lung cancer (NSCLC) patients, who carry primary EGFR mutations. However, the patients eventually develop drug resistance to EGFR-TKIs after approximately one year. In addition to the acquisition of the EGFR T790M mutation, the activation of alternative receptor-mediated signaling pathways is a common mechanism for conferring the insensitivity of EGFR-TKI in NSCLC. Upregulation of the Mer receptor tyrosine kinase (MERTK), which is a member of the Tyro3-Axl-MERTK (TAM) family, is associated with a poor prognosis of many cancers. The binding of specific ligands, such as Gas6 and PROS1, to MERTK activates phosphoinositide 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK) cascades, which are the signaling pathways shared by EGFR. Therefore, the inhibition of MERTK can be considered a new therapeutic strategy for overcoming the resistance of NSCLC to EGFR-targeted agents. Although several small molecules and monoclonal antibodies targeting the TAM family are being developed and have been described to enhance the chemosensitivity and converse the resistance of EGFR-TKI, few have specifically been developed as MERTK inhibitors. The further development and investigation of biomarkers which can accurately predict MERTK activity and the response to MERTK inhibitors and MERTK-specific drugs are vitally important for obtaining appropriate patient stratification and increased benefits in clinical applications.

The MyoD family inhibitor domain-containing protein enhances the chemoresistance of cancer stem cells in the epithelial state by increasing ß-catenin activity.

Cancer cells with mesenchymal attributes potentially display chemoresistance. Cancer stem cells (CSCs), which are intrinsically resistant to most chemotherapy agents, exhibit considerable phenotypic heterogeneity in their epithelial versus mesenchymal states. However, the drug response of CSCs in the epithelial and mesenchymal states has not been completely investigated. In this study, we found that epithelial-type (E-cadherinhigh/CD133high) CSCs displayed a higher sphere formation ability and chemoresistance than mesenchymal-type (E-cadherinlowCD133high) CSCs. Gene expression profiling of the CSC and non-CSC subpopulations with distinct epithelial-to-mesenchymal transition (EMT) states showed that MyoD family inhibitor domain-containing (MDFIC) was selectively upregulated in epithelial-type CSCs. Knockdown of MDFIC sensitized epithelial-type CSCs to chemotherapy agents. Ectopic expression of MDFIC increased the chemoresistance of mesenchymal-type CSCs. In a tissue microarray, high MDFIC expression was associated with poor prognosis of non-small cell lung cancer (NSCLC) patients. A mechanistic study showed that the MDFIC p32 isoform, which is located in the cytoplasm, interacted with the destruction complex, Axin/GSK-3/ß-catenin. This interaction stabilized ß-catenin by inhibiting ß-catenin phosphorylation at S33/37 and increased the nuclear translocation and transcriptional activity of ß-catenin. Knockdown of ß-catenin decreased MDFIC-enhanced chemoresistance. These results suggested that the upregulation of MDFIC enhanced the chemoresistance of epithelial-type CSCs by elevating ß-catenin activity. Thus, targeting MDFIC-regulated ß-catenin signaling of epithelial-type CSCs may be a potential strategy to overcome chemoresistance in NSCLC.

Low TIP30 Protein Expression is Associated with a High Risk of Metastasis and Poor Prognosis for Non-Small-Cell Lung Cancer.

Non-small-cell lung cancer (NSCLC) is a deadly malignancy with a high prevalence worldwide. A reliable biomarker that can predict the prognosis is required to determine the therapeutic strategy. TIP30 was first identified as a tumor suppressor. A number of mechanistic studies indicated that the downregulation of TIP30 enhances the stemness, migration and survival of NSCLC cells. However, the clinical relevance of TIP30 for the prognosis of NSCLC is unknown. From a meta-analysis of public microarray datasets, we showed the upregulation of TIP30 mRNA expression was associated with worse overall survival of NSCLC patients, which contradicted the tumor suppressive role of TIP30. It is worth noting that the TIP30 mRNA expression was not correlated with its protein expression in 15 NSCLC cell lines. The results from the immunohistochemistry of a tissue microarray showed the downregulation of the TIP30 protein expression was associated with a higher risk of metastasis. In addition, the decrease in TIP30 protein was correlated with worse overall and progression-free survival of the NSCLC patients. Multivariate analysis suggested the loss of TIP30 protein was an independent factor to predict the poor prognosis of NSCLC. Our data indicated that TIP30 protein, not mRNA, would be a potential prognostic biomarker of NSCLC.

Human immunodeficiency virus Tat-TIP30 interaction promotes metastasis by enhancing the nuclear translocation of Snail in lung cancer cell lines.

Lung cancer patients with human immunodeficiency virus (HIV) have a poorer prognosis than do patients without HIV infection. HIV1 Tat is a secreted viral protein that penetrates the plasma membrane and interacts with a number of proteins in non-HIV-infected cells. The loss of function of Tat-interacting protein 30 (TIP30) has been linked to metastasis in non-small cell lung cancer (NSCLC). However, it is unknown how the interaction of HIV1 Tat with TIP30 regulates the metastasis of NSCLC cells. In this study, the overexpression of TIP30 decreased tumor growth factor-ß-induced epithelial-to-mesenchymal transition (EMT) and invasion of NSCLC cells, whereas the knockdown of TIP30 promoted EMT, invasion and stemness. Exposure to recombinant HIV1 Tat proteins promoted EMT and invasion. A mechanistic study showed that the interaction of HIV1 Tat with TIP30 blocked the binding of TIP30 to importin-ß, which is required for the nuclear translocation of Snail. Indeed, the loss of TIP30 promoted the nuclear translocation of Snail. In vivo studies demonstrated that the overexpression of TIP30 inhibited the metastasis of NSCLC cells. In contrast, the coexpression of HIV1 Tat and TIP30 diminished the inhibitory effect of TIP30 on metastasis. Immunohistochemistry confirmed that TIP30 overexpression reduced the nuclear localization of Snail, whereas the coexpression of HIV1 Tat and TIP30 increased nuclear Snail in metastatic tumors. In conclusion, the binding of HIV1 Tat to TIP30 enhanced EMT and metastasis by regulating the nuclear translocation of Snail. Targeting Tat-interacting proteins may be a potential therapeutic strategy to prevent metastasis in NSCLC patients with HIV infection.

Reverse epithelial-mesenchymal transition contributes to the regain of drug sensitivity in tyrosine kinase inhibitor-resistant non-small cell lung cancer cells.

Tyrosine kinase inhibitors (TKIs) are currently the first-line treatment for non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations. These patients receive platinum-based chemotherapy as the second-line treatment after they develop resistance to TKIs. Many patients regain sensitivity to the TKIs used in the first-line treatment after the failure of chemotherapy. However, the molecular mechanism for the regain of TKI sensitivity is largely unknown. In this study, we established gefitinib-resistant PC9 and HCC827 cell lines, which did not harbor the EGFR T790M mutation and MET amplification but exhibited the epithelial-mesenchymal transition (EMT) phenotype. Overexpression of EMT inducers, Snail or Slug, in the parental lines promoted their resistance to gefitinib. The gefitinib-resistant cell lines regained their sensitivity to gefitinib and displayed reverse EMT phenotypes after long-term culture in gefitinib-free culture medium. Blockage of reverse EMT by stable expression of Snail or Slug prevented the regain of TKI sensitivity. In conclusion, reverse EMT is one of the major mechanisms for the regain of TKI sensitivity in TKI-resistant NSCLC cells, suggesting that the development of small molecules targeting the EMT process may prolong the efficacy of TKIs in NSCLC patients with EGFR mutations.