Constitutive over expression of IL-1β, IL-6, NF-κB, and Stat3 is a potential cause of lung tumorgenesis in urethane (ethyl carbamate) induced Balb/c mice

BACKGROUND: Lung cancer is a leading cause of cancer death. There has been found a substantial gap in the understanding of lung cancer genesis at the molecular level. We developed urethane (ethyl carbamate) induced lung tumor mice model to understand the mechanism and molecules involved in the cancer genesis. There might be many molecules involved, but we subsequently emphasized here the study of alternation in the expression of NF-κB, Stat3, and inflammatory cytokines interleukin-1β and interleukin-6 to hypothesize that the microenvironment created by these molecules is promoting tumor formation. MATERIALS AND METHODS: 7–8 week old Balb/c mice of either sex were given intraperitoneal (i.p.) injection of urethane (1g/kgbw) for eight consecutive weeks. Histopathological analysis was done to detect abnormality or invasions occurred in the lung tissues. Automated cell counter was used to count the number of inflammatory cells. The expression of NF-κB, Stat3, and IL-1β was observed at translational level by western blot, while the expression of IL-1β and IL-6 was observed at transcriptional level by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) method. Secretion of IL-1β and IL-6 in the blood was measured by enzyme-linked immunosorbent assay (ELISA) method at different time intervals. RESULTS: Histopathological analysis showed various lung cancer stages hyperplasia, atypical adenomatous hyperplasia, and adenocarcinoma. Increased population of inflammatory cells, persistant expression of NF-κB, Stat3, pStat3, and IL-1β at translational level, while at transcriptional level constitutive enhanced expression of IL-1β and IL-6 followed by increased secretion of IL-1β and IL-6 in the blood were observed in urethane-injected mice in comparison to phosphate buffer saline (PBS) injected mice at 12, 24, and 36 weeks CONCLUSIONS: Overexpression of key molecules such as NF-κB, Stat3, pStat3, IL-1β, and IL-6 might have caused chronic inflammation, leading to the progression of lung cancer.