Kaempferide Enhances Chemosensitivity of Human Lung Adenocarcinoma A549 Cells Mediated by the Decrease in Phosphorylation of Akt and Claudin-2 Expression.

Hiroaki Eguchi,Satoshi Endo,Akira Ikari,Toshiyuki Matsunaga,Kenji Ichihara

doi:10.3390/nu12041190

Abstract

Claudins (CLDNs) play crucial roles in the formation of tight junctions. We have reported that abnormal expression of CLDN2 confers chemoresistance in the spheroids of human lung adenocarcinoma A549 cells. A food composition, which can reduce CLDN2 expression, may function to prevent the malignant progression. Here, we found that ethanol extract of Brazilian green propolis (EBGP) and kaempferide, a major component of EBGP, decrease CLDN2 expression. In the two-dimensional culture model, EBGP decreased the tight junctional localization of CLDN2 without affecting that of zonula occludens-1, an adaptor protein, and enhanced paracellular permeability to doxorubicin, a cytotoxic anticancer drug. EBGP reduced hypoxic stress, and enhanced the accumulation and sensitivity of doxorubicin in the spheroid of A549 cells. Kaempferide dose-dependently decreased CLDN2 expression, although dihydrokaempferide and pinocembrin did not. The phosphorylation of Akt, a regulatory factor of CLDN2 expression, was inhibited by kaempferide but not by dihydrokaempferide. The 2,3-double bond in the C ring may be important to inhibit Akt. Kaempferide decreased the mRNA level and promoter activity of CLDN2, indicating that it inhibits the transcription of CLDN2. In accordance with EBGP, kaempferide decreased the tight junctional localization of CLDN2 and increased a paracellular permeability to doxorubicin, suggesting that it diminished the paracellular barrier to small molecules. In addition, kaempferide reduced hypoxic stress, and enhanced the accumulation and sensitivity of doxorubicin in the spheroids. In contrast, dihydrokaempferide did not improve the sensitivity to doxorubicin. Further study is needed using an animal model, but we suggest that natural foods abundantly containing kaempferide are candidates for the prevention of the chemoresistance of lung adenocarcinoma.

Highlights

Lung cancer is one of the most lethal malignant tumors, and non-small cell lung cancer (NSCLC)accounts for approximately 85% of all lung cancer patients [1]
We have reported that the transcriptional activity of CLDN2 is upregulated by the phosphatidylinositol 3-kinase (PI3K)/Akt/nuclear factor-κB [19], mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) [10], and signal transducer and activator of transcription 3 (Stat3) pathways [20]
We examined the effects of extract of Brazilian green propolis (EBGP) and its components on CLDN2 expression by Western blotting and real-time polymerase chain reaction (PCR) experiments in A549 cells

Summary

Introduction

Lung cancer is one of the most lethal malignant tumors, and non-small cell lung cancer (NSCLC)accounts for approximately 85% of all lung cancer patients [1]. NSCLC is divided into three types: Adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. A decline in smoking habits leads to a suppression of the incidence of squamous cell carcinoma, but the frequency of adenocarcinoma has increased. Adenocarcinoma is the most common pathological type of NSCLC [2]. Nutrients 2020, 12, 1190 and immune checkpoint inhibitors (ICIs) are effective to the most common treatment for NSCLC [3,4]. Most patients treated with EGFR-TKI and ICIs show a resistance to chemotherapy around one year after the treatments. The formation of a tumor microenvironment consisting of fibroblasts, extracellular matrix, immune cells, and other cellular interactions in the body plays a key role in the development of chemoresistance [5], but the molecular mechanisms have not been understood well

Results

Discussion

Conclusion