Downregulation of the Phosphatase PHLPP1 Contributes to NNK-induced Malignant Transformation of Human Bronchial Epithelial Cells (HBECs)

Xuelei Liu; Shirui Huang; Xiaozhen Gu; Ziyi Yang; Jiajun Xiu; Xiaodan Xu; Yaxin Cao; Jingjing Wang; Yunping Zhao; Minggang Peng; Zhongxian Tian; Xiaohui Hua; Hui-Li Wang; Chuanshu Huang

doi:10.1016/j.jbc.2025.108221

Downregulation of the Phosphatase PHLPP1 Contributes to NNK-induced Malignant Transformation of Human Bronchial Epithelial Cells (HBECs)

J Biol Chem. 2025 Jan 23:108221. doi: 10.1016/j.jbc.2025.108221. Online ahead of print.

Authors

Affiliations

¹ Key Laboratory of Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University; Wenzhou, Zhejiang 325035, China.
² Key Laboratory of Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University; Wenzhou, Zhejiang 325035, China; Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou, Zhejiang 325053, China; Engineering Research Center of Bio-process, Ministry of Education, Hefei University of Technology, 193 Tunxi Road, Hefei, Anhui 230009, PR China; School of Food and Biological Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China.
³ Key Laboratory of Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University; Wenzhou, Zhejiang 325035, China; Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou, Zhejiang 325053, China.
⁴ Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei, China.
⁵ Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou, Zhejiang 325053, China; Engineering Research Center of Bio-process, Ministry of Education, Hefei University of Technology, 193 Tunxi Road, Hefei, Anhui 230009, PR China; School of Food and Biological Engineering, Hefei University of Technology, Hefei, Anhui 230009, PR China.
⁶ Key Laboratory of Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University; Wenzhou, Zhejiang 325035, China; Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou, Zhejiang 325053, China. Electronic address: [email protected].

PMID: 39863100
DOI: 10.1016/j.jbc.2025.108221

Abstract

Cigarette smoking (CS) is one of the greatest health concerns, which can cause lung cancer. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific nitrosamine, and has been well-documented for its carcinogenic activity in both epidemiological and laboratory studies. PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) and phosphatase and tensin homolog (PTEN) are two well-known phosphatase tumor suppressors that have been reported to be downregulated in human lung cancer tissues. However, the effect of NNK exposure on the expression of PHLPP1 and PTEN is unknown, and such effects may be early events leading to lung carcinogenesis. We explored this question in current studies and found that exposure of human bronchial epithelial BEP2D cells to NNK resulted in cell malignant transformation accompanied by a remarkable downregulation of PHLPP1 and PTEN. Such downregulation of PHLPP1 and PTEN was also consistently observed in vivo in Cigarette Smoking-exposed mouse lung tissues. Our studies further showed that overexpression of PHLPP1 or PTEN alleviated NNK-induced BEP2D cell transformation. Ectopic expression of PHLPP1 promoted PTEN protein expression, while PTEN overexpression did not affect PHLPP1 expression. Mechanistic studies showed that NNK was able to inhibit PP2A-C activity, which directly attenuated c-Jun phosphorylation at Ser63/73, and subsequently inhibited the PHLPP1 transcription and expression. Further, the downregulation of PHLPP1 led to a reduction of pten mRNA stability and expression through the HUR/Jun D/miR-613/NCL axis. Taken together, our studies advance the field of tobacco-induced lung cancer research by uncovering new mechanistic insights and identifying a novel molecular axis that could inform future therapeutic strategies. It also adds a new dimension by exploring the interaction between PHLPP1 and PTEN in the context of tobacco carcinogen exposure.

Keywords: NNK; PHLPP1; PP2AC; PTEN; lung carcinogenesis; miR-613.