[Evaluation of serum cytokines in small cell lung cancer and its clinical significance]

[Leptin-mediated ERK Signaling Pathway Promotes the Transformation of Rat Alveolar Type II Epithelial Cells Induced by Yunnan Tin Mine Dust]

BACKGROUND

Currently, a significant number of miners are involved in mining operations at the Gejiu tin mine in Yunnan. This occupational setting is associated with exposure to dust particles, heavy metals, polycyclic aromatic hydrocarbons, and radioactive radon, thereby significantly elevating the risk of lung cancer. This study aims to investigate the involvement of leptin-mediated extracellular regulated protein kinase (ERK) signaling pathway in the malignant transformation of rat alveolar type II epithelial cells induced by Yunnan tin mine dust.

METHODS

Immortalized rat alveolar cells type II (RLE-6TN) cells were infected with Yunnan tin mine dust at a concentration of 200 μg/mL for nine consecutive generations to establish the infected cell model, which was named R₂₀₀ cells. The cells were cultured normally, named as R cells. The expression of leptin receptor in both cell groups was detected using the Western blot method. The optimal concentration of leptin and mitogen-activated protein kinase kinase (MEK) inhibitor (U0126) on R₂₀₀ cells was determined using the MTT method. Starting from the 20th generation, the cells in the R group were co-cultured with leptin, while the cells in the R₂₀₀ group were co-cultured with the MEK inhibitor U0126. The morphological alterations of the cells in each group were visualized utilizing hematoxylin-eosin staining. Additionally, concanavalin A (ConA) was utilized to detect any morphological differences, and an anchorage-independent growth assay was conducted to assess the malignant transformation of the cells. The changes in the ERK signaling pathway in epithelial cells after the action of leptin were detected using the Western blot method.

RESULTS

Both the cells in the R group and R₂₀₀ group express leptin receptor OB-R. Compared to the R₂₀₀ group, the concentration of leptin at 100 ng/mL shows the most significant pro-proliferation effect. The proliferation of R₂₀₀ cells infected with the virus is inhibited by 30 μmol/L U0126, and a statistically significant divergence was seen when compared to the control group (P<0.05). Starting from the 25th generation, the cell morphology of the leptin-induced R₂₀₀ group (R₂₀₀L group) underwent changes, leading to malignant transformation observed at the 30th generation. The characteristics of malignant transformation became evident by the 40th generation in the R₂₀₀L group. In contrast, the other groups showed agglutination of P40 cells, and the speed of cell aggregation increased with an increase in ConA concentration. Notably, the R₂₀₀L group exhibited faster cell aggregation compared to the U0126-induced R₂₀₀ (R₂₀₀LU) group. Additionally, the cells in the R₂₀₀L group were capable of forming clones starting from P30, with a colony formation rate of 2.25‰±0.5‰. However, no clonal colonies were observed in the R₂₀₀LU group and R₂₀₀ group. The expression of phosphorylated extracellular signal-regulated kinase (pERK) was enhanced in cells of the R₂₀₀L group. However, when the cells in the R₂₀₀L group were treated with U0126, a blocking agent, the phosphorylation level of pERK decreased.

CONCLUSIONS

Leptin can promote the malignant transformation of lung epithelial cells infected by mine dust, and the ERK signaling pathway may be necessary for the transformation of alveolar type II epithelial cells induced by Yunnan tin mine dust.

Serum and tissue leptin in lung cancer: A meta-analysis

Many studies have found that leptin is involved in tumorigenesis and the progression of lung cancer. However, these studies were inconsistent. Therefore, we performed a meta-analysis to investigate the role of leptin in the patients with lung cancer. A systematic literature search in the several databases and on commercial Internet search engines was carried out to identify studies published up to July 8, 2016. The standardized mean difference (SMD) and odds ratio (OR) with 95% confidence interval (CI) were used to investigate the effect sizes. Finally, 21 eligible articles were included in the current meta-analysis. Overall, there is no relationship between levels of serum leptin and lung cancer. However, a subgroup analysis in high-study quality group found a weak association between serum leptin concentrations and lung cancer in Chinese (SMD=0.77, P=0.035). Additionally, the meta-analysis indicates that the serum leptin levels were lower in the weight-losing group than in the sustained weight group (SMD=-0.80, P=0.001). Further, there was evidence of a significant association between expression levels of leptin protein in tissue and lung cancer (OR=7.35, P<0.001). The present meta-analysis suggests that the serum and tissue leptin may be involved in the pathogenesis of lung cancer and tumor metastasis, especially among Chinese. However, the leptin may not appear to play an important role in cancer cachexia development.