Palbociclib Induces the Apoptosis of Lung Squamous Cell Carcinoma Cells via RB-Independent STAT3 Phosphorylation.

Lung squamous cell carcinoma (LUSC) treatment response is poor and treatment alternatives are limited. Palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, has recently been approved for hormone receptor-positive breast cancer patients and applied in multiple preclinical models, but its use for LUSC therapy remains elusive. Here, we investigated whether palbociclib induced cell apoptosis and dissected the underlying mechanism in LUSC. We found that palbociclib induced LUSC cell apoptosis through inhibition of Src tyrosine kinase/signal transducers and activators of transcription 3 (STAT3). Interestingly, palbociclib reduced STAT3 signaling in LUSC cells interfered by retinoblastoma tumor-suppressor gene (RB), suggesting that pro-apoptosis effect of palbociclib was independent of classic CDK4/6-RB signaling. Furthermore, palbociclib could suppress IL-1ß and IL-6 expression, and therefore blocked Src/STAT3 signaling, which were rescued by either recombinant human IL-1ß or IL-6. Moreover, Myc mediated the sensitivity of LUSC cells to palbociclib. Our discoveries demonstrated that palbociclib induces apoptosis of LUSC cells through the Src/STAT3 axis in an RB-independent manner, and provided a reliable experimental basis of clinical studies in LUSC patients.

Correction: Qi, W., et al. (+)-Usnic Acid Induces ROS-dependent Apoptosis via Inhibition of Mitochondria Respiratory Chain Complexes and Nrf2 Expression in Lung Squamous Cell Carcinoma. Int. J. Mol. Sci. 2020, 21, 876.

The authors wish to make the following corrections to this paper [1]:[...].

(+)-Usnic Acid Induces ROS-dependent Apoptosis via Inhibition of Mitochondria Respiratory Chain Complexes and Nrf2 Expression in Lung Squamous Cell Carcinoma.

Lung squamous cell carcinoma (LUSC) has a poor prognosis, in part due to poor therapeutic response and limited therapeutic alternatives. Lichens are symbiotic organisms, producing a variety of substances with multiple biological activities. (+)-Usnic acid, an important biologically active metabolite of lichens, has been shown to have high anti-cancer activity at low doses. However, there have been no reports regarding the effect of (+)-usnic acid on LUSC cells. This study found that (+)-usnic acid reduced viability and induced apoptosis in LUSC cells by reactive oxygen species (ROS) accumulation. (+)-Usnic acid induced mitochondria-derived ROS production via inhibition of complex I and complex III of the mitochondrial respiratory chain (MRC). Interestingly, the elimination of mitochondrial ROS by Mito-TEMPOL only partially reversed the effect of (+)-usnic acid on cellular ROS production. Further study showed that (+)-usnic acid also induced ROS production via reducing Nrf2 stability through disruption of the PI3K/Akt pathway. The in vitro and in vivo xenograft studies showed that combined treatment of (+)-usnic acid and paclitaxel synergistically suppressed LUSC cells. In conclusion, this study indicates that (+)-usnic acid induces apoptosis of LUSC cells through ROS accumulation, probably via disrupting the mitochondrial respiratory chain (MRC) and the PI3K/Akt/Nrf2 pathway. Therefore, although clinical use of (+)-usnic acid will be limited due to toxicity issues, derivatives thereof may turn out as promising anticancer candidates for adjuvant treatment of LUSC.

Sesamin suppresses NSCLC cell proliferation and induces apoptosis via Akt/p53 pathway.

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer with a disappointing prognosis. The aim of this study was to investigate the anticancer effect of sesamin and the underlying mechanism. The MTT assay was used to detect the proliferation of NSCLC cells. The cell cycle and apoptosis were analyzed by flow cytometry. The protein levels of Akt, p-Akt (Ser473), p53, cyclin D1, CDK2, MDM2, p-MDM2 (Ser166) were detected by western blotting. The expression of p-Akt (Ser473), p53 and Ki67 in vivo was analyzed by IHC. Histopathologic analyses of major organs (heart, liver, spleen, lung and kidney) were performed by H&E staining. The results show that sesamin suppressed cell proliferation and induced apoptosis of NSCLC cells (A549 and H1792) in a dose-dependent manner. Treatment with sesamin caused cell cycle arrest at G1 phase and inhibited cyclin D1 and CDK2 expression. In addition, sesamin inhibited Akt activity and upregulated p53 expression both in vivo and in vitro. When Akt and p53 were suppressed by LY294002 and PFTα, respectively, sesamin exerted no additional effects. The in vivo results mostly matched the in vitro findings. Specifically, sesamin exerted little damage to major organs. Taken together, this study demonstrates that sesamin suppresses NSCLC cell proliferation by induction of G1 phase cell cycle arrest and apoptosis via Akt/p53 pathway. Therefore, sesamin may be a promising adjuvant treatment for NSCLC therapy.