Characteristics of surfactant proteins in tumorigenic and inflammatory lung lesions in rodents

Relationship between Lung Carcinogenesis and Chronic Inflammation in Rodents

Simple Summary

Lung cancer is the most common cause of cancer-related deaths worldwide. There are various risk factors for lung cancer, including tobacco smoking, inhalation of dust particles, chronic inflammation, and genetic factors. Chronic inflammation has been considered a key factor that promotes tumor progression via production of cytokines, chemokines, cytotoxic mediators, and reactive oxygen species by inflammatory cells. Here, we review rodent models of lung tumor induced by tobacco, tobacco-related products, and pro-inflammatory materials as well as genetic modifications, and discuss the relationship between chronic inflammation and lung tumor. Through this review, we hope to clarify the effects of chronic inflammation on lung carcinogenesis and help develop new treatments for lung cancer.

Abstract

Lung cancer remains the leading cause of cancer-related deaths, with an estimated 1.76 million deaths reported in 2018. Numerous studies have focused on the prevention and treatment of lung cancer using rodent models. Various chemicals, including tobacco-derived agents induce lung cancer and pre-cancerous lesions in rodents. In recent years, transgenic engineered rodents, in particular, those generated with a focus on the well-known gene mutations in human lung cancer (KRAS, EGFR, and p53 mutations) have been widely studied. Animal studies have revealed that chronic inflammation significantly enhances lung carcinogenesis, and inhibition of inflammation suppresses cancer progression. Moreover, the reduction in tumor size by suppression of inflammation in animal experiments suggests that chronic inflammation influences the promotion of tumorigenesis. Here, we review rodent lung tumor models induced by various chemical carcinogens, including tobacco-related carcinogens, and transgenics, and discuss the roles of chronic inflammation in lung carcinogenesis.

Single Intratracheal Quartz Instillation Induced Chronic Inflammation and Tumourigenesis in Rat Lungs

Crystalline silica (quartz) is known to induce silicosis and cancer in the lungs. In the present study, we investigated the relationship between quartz-induced chronic inflammation and lung carcinogenesis in rat lungs after a single exposure to quartz. F344 rats were treated with a single intratracheal instillation (i.t.) of quartz (4 mg/rat), and control rats were treated with a single i.t. of saline. After 52 or 96 weeks, the animals were sacrificed, and the lungs and other organs were used for analyses. Quartz particles were observed in the lungs of all quartz-treated rats. According to our scoring system, the lungs of rats treated with quartz had higher scores for infiltration of lymphocytes, macrophages and neutrophils, oedema, fibrosis, and granuloma than the lungs of control rats. After 96 weeks, the quartz-treated rats had higher incidences of adenoma (85.7%) and adenocarcinoma (81.0%) than control rats (20% and 20%, respectively). Quartz-treated and control rats did not show lung neoplastic lesions at 52 weeks after treatment. The number of lung neoplastic lesions per rat positively correlated with the degree of macrophage and lymphocyte infiltration, oedema, fibrosis, and lymph follicle formation around the bronchioles. In conclusion, single i.t. of quartz may induce lung cancer in rat along with chronic inflammation.