DNA damage caused by inorganic particulate matter on Raji and HepG2 cell lines exposed to ultraviolet radiation.

Epidemiological studies have correlated exposure to ultraviolet-irradiated particulate matter with cardiovascular, respiratory, and lung diseases. This study investigated the DNA damage induced by two major inorganic particulate matter compounds found in diesel exhaust, ammonium nitrate and ammonium sulfate, on Burkitt's lymphoma (Raji) and hepatocellular carcinoma (HepG2) cell lines. We found a dose-dependent positive correlation of accumulated DNA damage at concentrations of ammonium nitrate (25 µg/ml, 50 µg/ml, 100 µg/ml, 200 µg/ml, 400 µg/ml) with ultraviolet exposure (250 J/m(2), 400 J/m(2), 600 J/m(2), 850 J/m(2)), as measured by the comet assay in both cell lines. There was a significant difference between the treated ammonium nitrate samples and negative control samples in Raji and HepG2 cells (p<0.001). Apoptosis was shown in Raji and HepG2 cells when exposed to high concentrations of ammonium nitrate (200 µg/ml and 400 µg/ml) for 1h in samples without ultraviolet exposure, as assessed by the comet assay. However, the level of apoptosis greatly diminished after ultraviolet exposure at these concentrations. Over a 24h period, at intervals of 1, 4, 8, 12, 18, and 24h, we also observed that ammonium nitrate decreased viability in Raji and HepG2 cell lines and inhibited cell growth. Ammonium sulfate-induced DNA damage was minimal in both cell lines, but there remained a significant difference (p<0.05) between the ultraviolet radiation treated and negative control samples. These results indicate that the inorganic particulate compound, ammonium nitrate, induced DNA strand breaks at all concentrations, and indications of apoptosis at high concentrations in Raji and HepG2 cells, with ultraviolet radiation preventing apoptosis at high concentrations. We hypothesize that ultraviolet radiation may inhibit an essential cellular mechanism, possibly involving p53, thereby explaining this phenomenon. Further studies are necessary to characterize the roles of apoptosis inhibition induced by DNA damage caused by inorganic particulate matter.

Serum detection of thymidine kinase 1 as a means of early detection of lung cancer.

BACKGROUND: Thymidine kinase 1 (TK1) is a biomarker elevated in several malignancies, including lung cancer. Up-regulation of TK1 is an early event in carcinogenesis and therefore a target for early cancer detection. We have developed a novel Enzyme Linked Immunosorbent Assay (ELISA) to detect TK1 in serum. MATERIALS AND METHODS: Forty patients with pulmonary nodules and 18 healthy individuals had their serum collected prior to surgery. All samples were analyzed using a radioassay and ELISA. RESULTS: TK1 was significantly elevated in all lung cancer samples. Patients with stage I (n=16) and stage II (n=17) disease had significantly higher TK1 levels than controls. The area under the curve was 0.792, using 4.9 nM TK1 as cut-off, for early-stage lung cancer. The sensitivity and specificity were 75.0 and 83.3, respectively. TK1 concentration was a more sensitive and accurate indicator of lung cancer than TK1 activity. CONCLUSION: TK1 is significantly elevated in serum from patients with stage I and stage II lung cancer as measured using the established ELISA. This novel TK1 ELISA is both sensitive and specific for the detection of early-stage and advanced lung cancer, and therefore may be an important tool in the management of this disease.

Thymidine kinase 1 upregulation is an early event in breast tumor formation.

Prognostic markers play an important role in our understanding of tumors and how to treat them. Thymidine kinase 1 (TK1), a proliferation marker involved in DNA repair, has been shown to have independent prognostic potential. This prognostic potential includes the novel concept that upregulation of serum TK1 levels is an early event in cancer development. This same effect may also be seen in tumor tissue. In order to demonstrate that TK1 upregulation is an early event in tumor tissue formation, tissue arrays were obtained and stained for TK1 by immunohistochemistry. Using a progressive breast tissue array, precancerous tissue including breast adenosis, simple hyperplasia, and atypical hyperplasia stained positive for TK1 expression. Different stages of breast carcinoma tissue also stained positive for TK1 including nonspecific infiltrating duct, infiltrating lobular, and infiltrating duct with lymph node metastasis carcinomas. This indicates that TK1 upregulation is an early event in breast carcinoma development, and may be useful in identifying precancerous tissue. Further work is needed to better understand the differences seen between TK1 positive and negative tissues.