Epigenetic Biomarkers for Risk Assessment of Particulate Matter Associated Lung Cancer.

BACKGROUND: Particulate matter directly emitted into the air by sources such as combustion processes and windblown dust, or formed in the atmosphere by transformation of emitted gases are the major contributors to air pollution that triggers a diverse array of human pathologies including lung cancer. The mortality in lung cancer is usually high as the disease is not symptomatic at its early treatable stage. Moreover, available methods for screening are costly and mainly rely on imaging techniques which lack sufficient sensitivity and specificity. Despite progress in the identification of biomarkers, gene mutation based approaches still face formidable challenges as the disease evolves from a complex interplay between environment and host. Therefore, identification of an epigenomic signature might be useful for early diagnosis with the potential to reduce the environmental-associated disease burden. OBJECTIVE: The review discusses the utility of epigenomic signature in identification and management of the environmental-associated lung cancers. CONCLUSION: Non-invasive 'liquid biopsy' based epigenomic screening has recently emerged as a methodology which has potential to characterize tumor heterogeneity at initial stages. Epigenetic signatures (methylated DNA, miRNA, and post transcriptionally modified histones) known to reflect the vital cellular changes, circulate at higher levels in the individuals with lung cancer. These circulating biological entities are reported to be closely associated with the clinical outcome of lung cancer patients and thus strongly stand as the probable candidate to identify disease at an early stage and monitor treatment response, thereby, benefiting patients and improving their lives. However, for effective implementation of the strategy as "point-of-care" test for screening population-at-risk will require exhaustive clinical validation.

Ultrafine particulate matter impairs mitochondrial redox homeostasis and activates phosphatidylinositol 3-kinase mediated DNA damage responses in lymphocytes.

Particulate matter (PM), broadly defined as coarse (2.5-10 µm), fine (0.1-2.5 µm) and ultrafine particles (≤0.1 µm), is a major constituent of ambient air pollution. Recent studies have linked PM exposure (coarse and fine particles) with several human diseases including cancer. However, the molecular mechanisms underlying ultrafine PM exposure induced cellular and sub-cellular repercussions are ill-defined. Since mitochondria are one of the major targets of different environmental pollutants, we herein aimed to understand the molecular repercussion of ultrafine PM exposure on mitochondrial machinery in peripheral blood lymphocytes. Upon comparative analysis, a significantly higher DCF fluorescence was observed in ultrafine PM exposed cells that confirmed the strong pro-oxidant nature of these particles. In addition, the depleted activity of antioxidant enzymes, glutathione reductase and superoxide dismutase suggested the strong association of ultrafine PM with oxidative stress. These results further coincided with mitochondrial membrane depolarization, altered mitochondrial respiratory chain enzyme activity and decline in mtDNA copy number. Moreover, the higher accumulation of DNA damage response proteins (γH2AX, pATM, p-p53), suggested that exposure to ultrafine PM induces DNA damage and triggers phosphatidylinositol 3 kinase mediated response pathway. Further, the alterations in mitochondrial machinery and redox balance among ultrafine PM exposed cells were accompanied by a considerably elevated pro-inflammatory cytokine response. Interestingly, the lower apoptosis levels observed in ultrafine particle treated cells suggest the possibility that the marked alterations may lead to the impairment of mitochondrial-nuclear cross talk. Together, our results showed that ultrafine PM, because of their smaller size possesses significant ability to disturb mitochondrial redox homeostasis and activates phosphatidylinositol 3 kinase mediated DNA damage response pathway, an unknown molecular paradigm of ultrafine PM exposure. Our findings also indicate that maneuvering through the mitochondrial function might be a viable, indirect method to modulate lymphocyte homeostasis in air pollution associated immune disorders.