Preedakorn Chunhacha

Caveolin-1 regulates Mcl-1 stability and anoikis in lung carcinoma cells

Both caveolin-1 (Cav-1) and Mcl-1 have been implicated in the regulation of cancer cell anoikis, but their relationship and underlying mechanisms of regulation are not known. The present study demonstrated for the first time that Cav-1 regulates Mcl-1 through protein-protein interaction and inhibits its downregulation during cell anoikis in human lung cancer cells. Immunoprecipitation and immunocytochemistry studies showed that Cav-1 interacted with Mcl-1 and prevented it from degradation via the ubiquitin-proteasome pathway. Mcl-1 and Mcl-1-Cav-1 complex were highly elevated in Cav-1-overexpressing cells but were greatly reduced in Cav-1 knockdown cells. Consistent with this finding, we found that Mcl-1 ubiquitination was significantly attenuated by Cav-1 overexpression but increased by Cav-1 knockdown. Together, our results indicate a novel role of Cav-1 in anoikis regulation through Mcl-1 interaction and stabilization, which provides a new insight to the pathogenesis of metastatic lung cancer and its potential treatment.

Long-term nitric oxide exposure enhances lung cancer cell migration.

Nitric oxide (NO) found in the vicinity of lung cancer cells may play a role in the regulation of cancer cell behaviors. To explore the possible effects of NO on cell motility, human lung cancer cells were exposed to nontoxic concentrations of NO for 0–14 days, and the migratory characteristics of the cells were determined. The present study found that long-term treatment with NO significantly enhanced cell migration in a dose- and time-dependent manner. Furthermore, we found that the increased migratory action was associated with the increased expression of caveolin-1 (Cav-1), which in turn activated the focal adhesion kinase (FAK) and ATP-dependent tyrosine kinase (Akt) pathways. Notably, the NO-treated cells exhibited an increased number of filopodia per cell, as well as an increase in the levels of cell division cycle 42 (Cdc42) protein. Together, these results indicate that extended NO exposure has a novel effect on cell migration through a Cav-1-dependent mechanism, a finding that strengthens our understanding of cancer biology.

Epithelial‑mesenchymal transition mediates anoikis resistance and enhances invasion in pleural effusion‑derived human lung cancer cells

Epithelial-mesenchymal transition (EMT) is implicated in cancer pathological processes, particularly cancer invasion and metastasis. The present study demonstrated that EMT was critical for the metastasic potential of lung cancer cells isolated from a patient. P1 primary lung cancer cells were found to exhibit increased anoikis resistance compared with established A549, H23 and H460 lung cancer cells. Results of migration and invasion assays revealed that the invasion capability of P1 and A549 cells was higher than that of H23 and H460 cells. However, the migration of P1 cells was similar to that of H23 and H460 cells while A549 demonstrated a superior migrating ability. Western blot analysis indicated that while E-cadherin levels in all lung cancer cells were identified as comparable, P1 cells expressed the highest levels of N-cadherin. In the present study, detachment of cells was demonstrated for the first time to stimulate further transition of E-cadherin to N-cadherin. In addition, this obervation was more pronounced in P1 cells. These observations highlight the importance of EMT in cancer metastasis. In order to study the effect of ethnicity on cancer cell behavior, in the future a large number of Thai patient-derived cell lines must be analyzed.

Ouabain Suppresses the Migratory Behavior of Lung Cancer Cells

The migratory capability of cancer cells is one of the most important hallmarks reflecting metastatic potential. Ouabain, an endogenous cardiac glycoside produced by the adrenal gland, has been previously reported to have anti-tumor activities; however, its role in the regulation of cancer cell migration remains unknown. The present study has revealed that treatment with ouabain at physiological concentrations is able to inhibit the migratory activities of human lung cancer H292 cells. The negative effects of ouabain were found to be mediated through the suppression of migration regulatory proteins, such as focal adhesion kinase (FAK), ATP-dependent tyrosine kinase (Akt), and cell division cycle 42 (Cdc42). We found that the observed actions of ouabain were mediated via a reactive oxygen species (ROS)-dependent mechanism because the addition of ROS scavengers (N-acetylcysteine and glutathione) could reverse the effect of ouabain on cell migration. Furthermore, ouabain was shown to inhibit the spheroidal tumor growth and decrease the cancer cell adhesion to endothelial cells. However, the compound had no significant effect on anoikis of the cells. Together, these findings shed light on the understanding of cancer cell biology by exploring the novel function of this endogenous human substance.

Caveolin-1 regulates endothelial adhesion of lung cancer cells via reactive oxygen species-dependent mechanism.

The knowledge regarding the role of caveolin-1 (Cav-1) protein on endothelium adhesion of cancer cells is unclear. The present study revealed that Cav-1 plays a negative regulatory role on cancer-endothelium interaction. Endogenous Cav-1 was shown to down-regulate during cell detachment and the level of such a protein was conversely associated with tumor-endothelial adhesion. Furthermore, the ectopic overexpression of Cav-1 attenuated the ability of the cancer cells to adhere to endothelium while shRNA-mediated Cav-1 knock-down exhibited the opposite effect. We found that cell detachment increased cellular hydrogen peroxide and hydroxyl radical generation and such reactive oxygen species (ROS) were responsible for the increasing interaction between cancer cells and endothelial cells through vascular endothelial cell adhesion molecule-1 (VCAM-1). Importantly, Cav-1 was shown to suppress hydrogen peroxide and hydroxyl radical formation by sustaining the level of activated Akt which was critical for the role of Cav-1 in attenuating the cell adhesion. Together, the present study revealed the novel role of Cav-1 and underlying mechanism on tumor adhesion which explain and highlight an important role of Cav-1 on lung cancer cell metastasis.

Imperatorin sensitizes anoikis and inhibits anchorage-independent growth of lung cancer cells

The anoikis-sensitization activity of imperatorin, an active furanocoumarin component of Angelica dahurica root, is reported herein for the first time. The present study demonstrated that the imperatorin treatment at sub-toxic concentrations enhanced human lung cancer H23 cell apoptosis after detachment. A Western blot analysis showed that imperatorin significantly enhanced the p53 protein level, which subsequently down-regulated Mcl-1 protein and up-regulated Bax, while it had a minimal effect on Bcl-2 expression. In addition, an anchorage-independent growth assay was performed to support the anti-metastasis potential of imperatorin. Consistent with anoikis assay, imperatorin exhibited a strong inhibitory effect on the anchorage-independent growth of the cells. Further, this study demonstrated that imperatorin sensitizes anoikis in other lung cancer cells, namely, H292 and A549. Because anoikis was shown to be a critical hindrance in preventing cancer cell metastasis, the knowledge regarding such an activity and an underlying mechanism may lead to the development of this compound for a cancer therapy.

Caveolin-1 induces lamellipodia formation via an Akt-dependent pathway

BackgroundThe enhancement of migration is critical for facilitating cancer cell metastasis.MethodLung cancer H23 cells were transfected with either a caveolin-1 (Cav-1) overexpression or shCav-1 plasmid and further subjected to cell migration assays and lamellipodia characterization. The regulation of Cav-1 via an ATP-dependent tyrosine kinase (Akt) pathway was further examined by Akt knockdown in Cav-1 overexpressing cells and migratory behavior investigations.ResultsHere, we demonstrate for the first time that overexpression of Cav-1 in human lung cancer H23 cells significantly increased the formation of lamellipodia, whereas the suppression of Cav-1 using shRNA transfection had the opposite effect. Consistent with an increase in lamellipodia, Cav-1 overexpressing cells exhibited increased migratory activity in comparison to their parental, control-transfected, H23 cells. The induction of lamellipodia was demonstrated to occur via the Akt pathway because the addition of the Akt inhibitor LY294002 inhibited lamellipodia in both Cav-1-overexpressing and H23 cells. Additionally, transient transfection with Akt-siRNA significantly inhibited the formation of lamellipodia and the migration of Cav-1-overexpressing H23 cells. In addition, Cav-1 levels and the migratory action of other lung cancer cells, namely, H460 and A549, were assessed, and the migration of these cells was found to be correlated with the basal Cav-1 level.ConclusionThese data showed that Cav-1 enhances cancer cell migration through Akt-mediated lamellipodia formation. Our results provide novel insights regarding the molecular mechanism controlling cancer cell migration, leading to a better understanding of cancer cell biology.

Prolonged Nitric Oxide Exposure Enhances Anoikis Resistance and Migration through Epithelial-Mesenchymal Transition and Caveolin-1 Upregulation

Nitric oxide (NO) in tumor microenvironment may have a significant impact on metastatic behaviors of cancer. Noncytotoxic doses of NO enhanced anoikis resistance and migration in lung cancer H23 cells via an increase in lamellipodia, epithelial-mesenchymal transition (EMT) markers including vimentin and snail, and caveolin-1 (Cav-1). However, the induction of EMT was found in Cav-1-knock down cells treated with NO, suggesting that EMT was through Cav-1-independent pathway. These effects of NO were consistently observed in other lung cancer cells including H292 and H460 cells. These findings highlight the novel role of NO on EMT and metastatic behaviors of cancer cells.

Lung Cancer Metastasis

Lung cancer is one of leading cancer-related causes of mortality worldwide. The propensity for metastasis in this disease undoubtedly contributes to the low survival rate and final poor outcome of patients. Lung cancer metastasis involves specific molecular pathways that confer the cancer cells abilities to survive in circulation, be motile, and form new tumors. Recent evidences have widened the understanding of cancer disseminating basis and emphasized the role of genetic and epigenetic imperfections, epithelial to mesenchymal transition, and cancer stem cells. The present chapter aims to illustrate metastatic processes of lung cancer, shedding more light on such key molecular paradigms. A deeper understanding of the mechanisms of lung cancer metastasis may lead to novel strategies in cancer preventive and therapeutic approaches.

Corrigendum to "Long-term nitric oxide exposure enhances lung cancer cell migration".

In the paper titled “Long-Term Nitric Oxide Exposure Enhances Lung Cancer Cell Migration,” the Acknowledgments is corrected as follows. This work was supported by grants from the Thailand Research Fund (P. Chanvorachote) and the 90th Anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot Endowment Fund). The authors would like to thank Mr. Krich Rajprasit for his assistance in proofreading.