No abstract

Radiotherapy is a frequent mode of cancer treatment, although the development of radioresistance limits its effectiveness. Extensive investigations indicate the diversity of the mechanisms underlying radioresistance. Here, we aimed to explore the effects of extracellular signal-regulated kinase 5 (ERK5) on lung cancer radioresistance and the associated mechanisms. Our data showed that ERK5 is activated during solid lung cancer development, and ectopic expression of ERK5 promoted cell proliferation and G2/M cell cycle transition. In addition, we found that ERK5 is a potential regulator of radiosensitivity in lung cancer cells. Mechanistic investigations revealed that ERK5 could trigger IR-induced activation of Chk1, which has been implicated in DNA repair and cell cycle arrest in response to DNA double-strand breaks (DSBs). Subsequently, ERK5 knockdown or pharmacological inhibition selectively inhibited colony formation of lung cancer cells and enhanced IR-induced G2/M arrest and apoptosis. In vivo, ERK5 knockdown strongly radiosensitized A549 and LLC tumor xenografts to inhibition, with a higher apoptotic response and reduced tumor neovascularization. Taken together, our data indicate that ERK5 is a novel potential target for the treatment of lung cancer, and its expression might be used as a biomarker to predict radiosensitivity in NSCLC patients.

Combinatorial therapies that target multiple signaling pathways may provide improved therapeutic responses over monotherapies. Celecoxib and curcumol are two highly hydrophobic drugs which show bioavailability problems due to their poor aqueous solubility. In the present study, we evaluated the effects of celecoxib and curcumol alone and in combination on cell proliferation, invasion, migration, cell cycle and apoptosis induction in non-small cell lung cancer (NSCLC) cells using in vitro and in vivo experiments. Our data showed that the sensitivity of a combined therapy using low concentration of celecoxib and curcumol was higher than that of celecoxib or curcumol alone. Suppression of NF-κB transcriptional activity, activation of caspase-9/caspase-3, cell cycle G1 arrest, and inhibition of survival MAPK and PI3K/AKT signaling pathway contributed to the synergistic effects of this combination therapy for induction of apoptosis. Additionally, either celecoxib alone or in combination with curcumol inhibited NSCLC cell migration and invasion by suppressing FAK and matrix metalloproteinase-9 activities. Furthermore, the combined treatment reduced tumor volume and weight in xenograft mouse model, and significantly decreased tumor metastasis nodules in lung tissues by tail vein injection. Our results confirm and provide mechanistic insights into the prominent anti-proliferative activities of celecoxib and/or curcumol on NSCLC cells, which provide a rationale for further detailed preclinical and potentially clinical studies of this combination for the therapy of lung cancer.

This study was designed to evaluate ERK5 expression in lung cancer and malignant melanoma progression and to ascertain the involvement of ERK5 signaling in lung cancer and melanoma. We show that ERK5 expression is abundant in human lung cancer samples, and elevated ERK5 expression in lung cancer was linked to the acquisition of increased metastatic and invasive potential. Importantly, we observed a significant correlation between ERK5 activity and FAK expression and its phosphorylation at the Ser 910 site. Mechanistically, ERK5 increased the expression of the transcription factor USF1, which could transcriptionally upregulate FAK expression, resulting in FAK signaling activation to promote cell migration. We also provided evidence that the phosphorylation of FAK at Ser 910 was due to ERK5 but not ERK1/2, and we then suggested a role for Ser 910 in the control of cell motility. In addition, ERK5 had targets in addition to FAK that regulate epithelial-to-mesenchymal transition and cell motility in cancer cells. Taken together, our findings uncover a cancer metastasis-promoting role for ERK5 and provide the rationale for targeting ERK5 as a potential therapeutic approach.

Hydrogen sulfide (H2S) is now widely considered the third endogenous gasotransmitter and plays critical roles in cancer biological processes. In this study, we demonstrate that 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (ADT-OH), the most widely used moiety for synthesising slow-releasing H2S donors, induces melanoma cell death in vitro and in vivo. Consistent with previous reports, ADT-OH inhibited IκBɑ degradation, resulting in reduced NF-κB activation and subsequent downregulation of the NF-κB-targeted anti-apoptotic proteins XIAP and Bcl-2. More importantly, we found that ADT-OH suppressed the ubiquitin-induced degradation of FADD by downregulating the expression of MKRN1, an E3 ubiquitin ligase of FADD. In addition, ADT-OH had no significant therapeutic effect on FADD-knockout B16F0 cells or FADD-knockdown A375 cells. Based on these findings, we evaluated the combined effects of ADT-OH treatment and FADD overexpression on melanoma cell death in vivo using a mouse xenograft model. As expected, tumour-specific delivery of FADD through a recombinant Salmonella strain, VNP-FADD, combined with low-dose ADT-OH treatment significantly inhibited tumour growth and induced cancer cell apoptosis. Taken together, our data suggest that ADT-OH is a promising cancer therapeutic drug that warrants further investigation into its potential clinical applications.