Benzo(a)pyrene-driven lung carcinogenesis reveals time-dependent macrophage reprogramming and alteration of key signaling & inflammatory cascades in Swiss albino mice.

BACKGROUND: Lung cancer remains the leading cause of cancer-related mortality worldwide, and Benzo[a]pyrene [B(a)P] is a major environmental carcinogen that promotes tumor development through oxidative stress, chronic inflammation, and immune dysregulation. Although several studies have investigated individual molecular events during B(a)P-induced lung carcinogenesis, the time-dependent macrophage polarization, inflammatory signaling, angiogenic factors, and tumor biomarkers remain poorly understood.

OBJECTIVE: In this study, we have explored the time-dependent alterations in macrophage plasticity (M1/M2 macrophage polarization), lung cancer biomarkers, oxidative stress, inflammatory mediators and angiogenic factors during B(a)P-induced lung carcinogenesis.

METHODS: A time-point study was performed in Swiss albino mice after treating with B(a)P orally, at a dose of 50 mg/kg of body weight. Using qRT-PCR, western blot, microscopy, and ELISA, we have studied the expression of different markers (CD86, CD206, iNOS, Arginase, IL- 10, IL-6, TNF-α, etc.) from lung tissue.

RESULTS: We found the elevated expression of the potent lung cancer biomarker, i.e. EGFR, from week post treatment 8 (WPT-8). Notably, we have found that B(a)P enhances ROS and lipid peroxidation (MDA) levels from WPT-6, which reduces the production of various antioxidant enzymes. Induction of oxidative stress in terms of ROS production in the cell activates STAT3/NF-κB signaling, leading to increased expression of various angiogenic factors from WPT-6, such as VEGF, TGF-β, MMP-2/9, CXCL5 and various pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), resulting tumor progression. By WPT-14, only 6.25% of macrophages were the M1 population, whereas a steep rise (about 59.5%) was observed in the M2 population. We further found reduced expression of different inflammatory markers, including iNOS, TNF-α, IL-6 and also ROS and NO in macrophages of B(a)P-treated mice by WPT-8.

CONCLUSION: This study identified the critical time points at which major alterations occur in the expression of key biomarkers, transcription factors, angiogenic factors, and macrophage phenotypes (M1 and M2) during lung carcinogenesis. These findings improve our understanding of lung cancer progression and suggest that stage-specific targeting of key molecular pathways and macrophage polarization may provide novel opportunities for therapeutic intervention.