Infection and
inflammation account for approximately 25% of
cancer-causing factors.
Inflammation-related
cancers are characterized by mutagenic DNA lesions, such as
8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and
8-nitroguanine. Our previous studies demonstrated the formation of
8-oxodG and
8-nitroguanine in the tissues of
cancer and precancerous lesions due to
infection (e.g., Opisthorchis viverrini-related
cholangiocarcinoma, Schistosoma haematobium-associated
bladder cancer, Helicobacter pylori-infected
gastric cancer, human papillomavirus-related
cervical cancer, Epstein-Barr virus-infected
nasopharyngeal carcinoma) and pro-inflammatory factors (e.g.,
asbestos, nanomaterials, and inflammatory diseases such as
Barrett's esophagus and
oral leukoplakia). Interestingly, several of our studies suggested that
inflammation-associated DNA damage in
cancer stem-like cells leads to
cancer development with aggressive clinical features. Reactive
oxygen/
nitrogen species from
inflammation damage not only
DNA but also other biomacromolecules, such as
proteins and
lipids, resulting in their dysfunction. We identified oxidatively damaged
proteins in
cancer tissues by 2D Oxyblot followed by MALDI-TOF/TOF. As an example, oxidatively damaged
transferrin released
iron ion, which may mediate Fenton reactions and generate additional
reactive oxygen species. Dysfunction of anti-oxidative
proteins due to this damage might increase oxidative stress. Such damage in biomacromolecules may form a vicious cycle of oxidative stress, leading to
cancer development. Epigenetic alterations such as DNA methylation and
microRNA dysregulation play vital roles in
carcinogenesis, especially in
inflammation-related
cancers. We examined epigenetic alterations, DNA methylation and
microRNA dysregulation, in Epstein-Barr virus-related
nasopharyngeal carcinoma in the endemic area of Southern China and found several differentially methylated tumor suppressor gene candidates by using a next-generation sequencer. Among these candidates, we revealed higher methylation rates of RAS-like
estrogen-regulated
growth inhibitor (RERG) in biopsy specimens of
nasopharyngeal carcinoma more conveniently by using restriction
enzyme-based real-time PCR. This result may help to improve
cancer screening strategies. We profiled
microRNAs of
nasopharyngeal carcinoma tissues using microarrays. Quantitative RT-PCR analysis confirmed the concordant downregulation of miR-497 in
cancer tissues and plasma, suggesting that plasma miR-497 could be used as a diagnostic
biomarker for
nasopharyngeal carcinoma. Chronic
inflammation promotes genetic and epigenetic aberrations, with various pathogeneses. These changes may be useful
biomarkers in liquid biopsy for early detection and prevention of
cancer.