Purpose: D-limonene is a plant extract with widespread application, and it has been recently reported to have antiproliferative and proapoptotic effects on cancer cells. However, the mechanisms by which D-limonene achieves these effects, especially in lung cancer, are not entirely clear. Therefore, the goal of this study was to examine the effects of D-limonene on lung cancer and explore its mechanisms of action. Methods: We examined the therapeutic effects of D-limonene on lung cancer cells and in a xenograft animal model by characterizing its effects on the pathways of apoptosis and autophagy. Cell proliferation was measured using the Cell Counting Kit-8, and apoptosis was determined by flow cytometric analysis. Levels of LC3 puncta, an autophagy marker, were analyzed by laser scanning confocal microscopy. Autophagy and apoptosis-related gene expression were assessed by real-time quantitative polymerase chain reaction and Western blot. Results: D-limonene inhibited the growth of lung cancer cells and suppressed the growth of transplanted tumors in nude mice. Expression of apoptosis and autophagy-related genes were increased in tumors after treatment with D-limonene. Furthermore, the use of chloroquine, an autophagy inhibitor, and knockdown of the atg5 gene, suppressed the apoptosis induced by D-limonene. Conclusion: D-limonene may have a therapeutic effect on lung cancer as it can induce apoptosis of lung cancer cells by promoting autophagy.

Background/Aims: Ecological studies have shown that air pollution and prevalence of cigarette smoking are positively correlated. Evidence also suggests a synergistic effect of cigarette smoking and PM2.5 exposure (Environmental Particulate Matter ≤ 2.5 µm in diameter) on lung cancer risk. We aimed to evaluate the interaction between smoking prevalence and PM2.5 pollution in relation to lung cancer mortality and determine its underlying mechanisms in vitro. Methods: “MOVER” method was used to analyze the interaction between smoking prevalence and PM2.5 pollution in relation to lung cancer mortality. Cell autophagy and malignant behaviors induced by cigarette smoke extract (CSE) and PM2.5 exposure were examined in vitro. Gene expression was examined by qRT-PCR and western blot. RNA and protein interaction was determined using a RNA binding protein immunoprecipitation assay. Results: An increased risk for lung cancer death (RERI (the relative excess risk) =0.28) was observed with a synergistic interaction between cigarette smoking and PM2.5 pollution. Cell migration, invasion, EMT (epithelial-mesenchymal transition) and autophagy were elevated when lung cancer cells were treated with CSE and PM2.5 in combination. A lncRNA, named lung cancer progression-association transcript 1 (LCPAT1), was up-regulated after the treatment of CSE and PM2.5, and knocking down the lncRNA impaired the effect of CSE and PM2.5 on lung cancer cells. In addition, LCPAT1 was shown to bind to RCC2, and RCC2 mediated the effect of LCPAT1 on cell autophagy, migration, invasion and EMT in lung cancer. Conclusions: Our results suggest that combined exposure to CSE and PM2.5 induces LCPAT1 expression, which up-regulates autophagy, and promotes lung cancer progression via RCC2.

Genome-wide association studies (GWAS) have identified numerous genetic variants that are associated with lung cancer risk, but the biological mechanisms underlying these associations remain largely unknown. Here we investigated the functional relevance of a genetic region in 6q22.2 which was identified to be associated with lung cancer risk in our previous GWAS. We performed linkage disequilibrium (LD) analysis and bioinformatic prediction to screen functional SNPs linked to a tagSNP in 6q22.2 loci, followed by two case-control studies and a meta-analysis with 4403 cases and 5336 controls to identify if these functional SNPs were associated with lung cancer risk. A novel SNP rs17079281 in the DCBLD1 promoter was identified to be associated with lung cancer risk in Chinese populations. Compared with those with C allele, patients with T allele had lower risk of adenocarcinoma (adjusted OR = 0.86; 95% CI: 0.80–0.92), but not squamous cell carcinoma (adjusted OR = 0.99; 95% CI: 0.91–1.10), and patients with the C/T or T/T genotype had lower levels of DCBLD1 expression than those with C/C genotype in lung adenocarcinoma tissues. We performed functional assays to characterize its biological relevance. The results showed that the T allele of rs17079281 had higher binding affinity to transcription factor YY1 than the C allele, which suppressed DCBLD1 expression. DCBLD1 behaved like an oncogene, promoting tumor growth by influencing cell cycle progression. These findings suggest that the functional variant rs17079281C>T decreased lung adenocarcinoma risk by creating an YY1-binding site to suppress DCBLD1 expression, which may serve as a biomarker for assessing lung cancer susceptibility.

Silica nanoparticles (SiO2 NPs) are widely used in daily life and can enter organisms through several pathways, often causing unpredictable toxicity. Although SiO2 NPs are known to cause damage to the respiratory system, little is known about their oral toxicity, and their potential harm to the reproductive system is unclear. In this study, we used a Caenorhabditis elegans model to clarify SiO2 NPs oral toxicity in vivo and explore their effect on the reproductive system. We exposed C. elegans to 0.25, 0.5 and 1 mg /mL SiO2 NPs for 24 hr. Our results showed that SiO2 NPs exposure for 24 hr did not affect nematode survival rates, but did affect, to varying degrees, the reproduction, development, and movement of nematodes, with nematode fecundity being the most sensitive to SiO2 NPs toxicity. The NPs exposed group showed enhanced germ cell apoptosis and increased oxidative stress as seen through an increase in ROS and malondialdehyde (MDA), and decrease in reduced glutathione (GSH). N-acetyl-L-cysteine (NAC), an antioxidant, negated SiO2 NPs effect on germ cells and restored nematodes reproductive ability. We also found that SiO2 NPs could affect the expression of genes related to metal detoxification, oxidative stress, and apoptosis. The expression of metallothionein coding genes mtl-1 and mtl-2 changed most significantly among the tested genes. We demonstrated that SiO2 NPs could enhance germ cell apoptosis by inducing oxidative stress, providing a new area for studies of the mechanism of SiO2 NP toxicity.

Long non-coding RNAs (lncRNAs) are involved in numerous biological processes in lung cancer cells. In our previous studies, we identified a lncRNA, ENST00000439577, which is highly expressed in lung carcinomas, and termed it lung cancer progression-associated transcript 1 (LCPAT1). To characterize the role of LCPAT1 in lung cancer, we conducted the current study. Expression of LCPAT1 and autophagy-associated markers in tumor tissues and lung cancer cell lines was determined by real-time quantitative polymerase chain reaction (qPCR). Hematoxylin and eosin (HE) staining, qPCR, Western blot, and immunohistochemistry were performed to evaluate xenografted tumor tissues. Autophagy induced by rapamycin was detected by Western blot and immunofluorescence in lung cancer cell lines. Expression of LCPAT1 and microtubule-associated protein 1 light chain 3 beta (LC3B) was positively correlated in lung cancer. Knockdown of LCPAT1 inhibited tumor growth and suppressed cell autophagy in vivo. Moreover, LCPAT1 knockdown in lung cancer cell lines resulted in decreased autophagy-associated gene expression and alleviated the cell autophagy induced by rapamycin. We speculate that LCPAT1 plays a crucial role in regulating autophagy in lung cancer.