Over-Time Risk of Lung Cancer Is Largely Owing to Continuing Smoking Exposition: A Good Reason to Quit

Upregulated DNMT3a coupling with inhibiting p62-dependent autophagy contributes to NNK tumorigenicity in human bronchial epithelial cells

NNK, formally known as 4-(methyl nitrosamine)-1-(3-pyridyl)-1-butanoe, is a potent chemical carcinogen prevalent in cigarette smoke and is a key contributor to the development of human lung adenocarcinomas. On the other hand, autophagy plays a complex role in cancer development, acting as a "double-edged sword" whose impact varies depending on the cancer type and stage. Despite this, the relationship between autophagy and NNK-induced lung carcinogenesis remains largely unexplored. Our current study uncovers a marked reduction in p62 protein expression in both lung adenocarcinomas and lung tissues of mice exposed to cigarette smoke. Interestingly, this reduction appears to be contingent upon the activity of extrahepatic cytochrome P450 (CYP450), revealing that NNK metabolic activation by CYP450 enzyme escalates its potential to induce p62 downregulation. Further mechanistic investigations reveal that NNK suppresses autophagy by accelerating the degradation of p62 mRNA, thereby promoting the malignant transformation of human bronchial epithelial cells. This degradation process is facilitated by the hypermethylation of the Human antigen R (HuR) promoter, resulting in the transcriptional repression of HuR - a key regulator responsible for stabilizing p62 mRNA through direct binding. This hypermethylation is triggered by the activation of ribosomal protein S6, which is influenced by NNK exposure and subsequently amplifies the translation of DNA methyltransferase 3 alpha (DNMT3a). These findings provide crucial insights into the nature of p62 in both the development and potential treatment of tobacco-related lung cancer.

Non-small cell lung cancer in China

In China, lung cancer is a primary cancer type with high incidence and mortality. Risk factors for lung cancer include tobacco use, family history, radiation exposure, and the presence of chronic lung diseases. Most early-stage non-small cell lung cancer (NSCLC) patients miss the optimal timing for treatment due to the lack of clinical presentations. Population-based nationwide screening programs are of significant help in increasing the early detection and survival rates of NSCLC in China. The understanding of molecular carcinogenesis and the identification of oncogenic drivers dramatically facilitate the development of targeted therapy for NSCLC, thus prolonging survival in patients with positive drivers. In the exploration of immune escape mechanisms, programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitor monotherapy and PD-1/PD-L1 inhibitor plus chemotherapy have become a standard of care for advanced NSCLC in China. In the Chinese Society of Clinical Oncology's guidelines for NSCLC, maintenance immunotherapy is recommended for locally advanced NSCLC after chemoradiotherapy. Adjuvant immunotherapy and neoadjuvant chemoimmunotherapy will be approved for resectable NSCLC. In this review, we summarized recent advances in NSCLC in China in terms of epidemiology, biology, molecular pathology, pathogenesis, screening, diagnosis, targeted therapy, and immunotherapy.