A case-control study of asphalt and tar exposure and lung cancer in minorities

A metabolomics study on effects of polyaromatic compounds in oil sand extracts on the respiratory, hepatic and nervous systems using three human cell lines

Polyaromatic compounds (PACs) are by-products of combustion and are the major pollutants from the oil and gas industry. However, the mechanism of PACs induced toxicity still remains elusive. The aim of this study was to elucidate the effects of a typical mixture of PACs found in oil sand extract (OSE) on the respiratory, hepatic and nervous systems in humans using in vitro cell culture models followed by non-targeted metabolomics analysis. OSE collected from Alberta, Canada was fractionated into PAC and alkane fractions, and their effects after 24 h exposure on the cell viability measured by MTT assay in three human cell lines (A549, HepG2, and SK-N-SH) were studied. The PAC fractions showed significant dose-dependent cytotoxicity. A549 cells showed the highest sensitivity to OSE extracts, followed by SK-N-SH and HepG2. In contrast, the alkane fractions showed no effects on cell viability. The three human cell lines were further exposed with the PACs at 10% and 20% lethal concentration for 24 h. Metabolomics analysis of the cell extracts indicated that PACs treatments showed different disruptions on possible metabolic pathways on the three cell lines. PACs altered the sex steroid hormone metabolism and regulated the levels of leukotrienes metabolites in all three cell types. The amino acids L-cysteine, L-glutamine, L-tyrosine that are known to cause respiratory effects were significantly up-regulated in A549 cells. The PACs treated HepG2 cells showed down-regulation in metabolites responsible for the inflammatory mediation. Treatment of the differentiated SK-N-SH cells showed up-regulated metabolites involved with butanoate, fatty acid, and pyrimidine metabolism. Leukotriene metabolites were found to be significantly increased in all PACs treated cells. In conclusion, our results showed that PACs in OSE can alter the metabolism of the human lung, liver and neuronal cells and may induce toxicity in multiple target organs.

Cancer Risk Associated With Exposure to Bitumen and Bitumen Fumes: An Updated Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate whether cancer risks are increased among bitumen (asphalt) workers.

METHODS

Systematic review and meta-analysis of cancer risks (lung, upper aerodigestive tract (UADT), esophagus, bladder, kidney, stomach, and skin) and bitumen exposure. Certainty in the epidemiological evidence that bitumen-exposed workers experience increased cancer risks was rated using Grading of Recommendations Assessment, Development and Evaluation criteria.

RESULTS

After excluding lower-quality studies, lung cancer risks were not increased among bitumen-exposed workers (meta-relative risk [RR] 0.94, 95% CI 0.74 to 1.20, eight studies). Increased risks of UADT and stomach cancers were observed (meta-RR 1.31, 95% CI 1.03 to 1.67, 10 studies and meta-RR 1.29, 95% CI 1.03 to 1.62, seven studies, respectively).

CONCLUSIONS

Except for lung cancer, evidence for increased cancer risks among bitumen-exposed workers was judged to be of low certainty, due to inadequate exposure characterization and unmeasured confounders (coal tar exposure, smoking, and alcohol consumption).

Lung cancer mutations and use of targeted agents in Hispanics

Hispanic/Latinos (H/L) are expected to grow to over 24% of the USA population by 2050 and lung cancer is the number one cause of cancer death among H/L men. Due to the information that is becoming available via genetic testing, lung cancer molecular profiling is allowing for increasing application of personalized lung cancer therapies. However, to benefit the most people, development of these therapies and genetic tests must include research on as many racial and ethnic groups as possible. The purpose of this review is to bring attention to the fact that the mutations driving lung cancer in H/Ls differ in frequency and nature relative to the non-Hispanic White (WNH) majority that dominate current databases and participate in clinical trials that test new therapies. Clinical trials using new agents targeting genetic alterations (driver mutations) in lung cancer have demonstrated significant improvements in patient outcomes (for example, gefitinib, erlotinib or crizotinib for lung adenocarcinomas harboring EGFR mutations or EML4-ALK fusions, respectively). The nature and frequencies of some lung cancer driver mutations have been shown to be considerably different among racial and ethnic groups. This is particularly true for H/Ls. For example, several reports suggest a dramatic shift in the mutation pattern from predominantly KRAS in a WNH population to predominantly EGFR in multiple H/L populations. However, these studies are limited, and the effects of racial and ethnic differences on the incidence of mutations in lung cancer remain incompletely understood. This review serves as a call to address this problem.

Cellular alterations and modulation of protein expression in bitumen-challenged human osteoblast cells

PURPOSE

There are many arguments on the carcinogenic potential of bitumen extract. The mechanism of bitumen-induced damage is not well understood at the molecular level. Therefore, in the present study, cell-transforming and tumor-inducing potential of bitumen extract was studied using in vitro [human osteosarcoma (HOS) cells] and in vivo [nude and severe combined immunodeficiency (SCID) mice] models.

METHODS

Gas chromatography/mass spectrometry (GC/MS) analysis was carried out to find out the existence of carcinogenic compounds in the bitumen extract. Cell transformation test, anchorage independence assay, karyotyping assay, tumorigenicity assay, and 2-DE analysis were used to find out the effect of bitumen using the in vitro and in vivo models.

RESULTS

GC/MS analysis showed the existence of carcinogenic compounds in the bitumen extract. HOS cells were treated with different concentrations (25, 50, and 100 μl/ml) of bitumen extract. Compared to the parental HOS cells, bitumen transformants (HOS T1 and HOS T2) showed the characteristics of anchorage independency, chromosomal anomaly, and cellular transformation. Interestingly, bitumen transformants were not able to form tumor in nude/SCID mice. Proteomic analysis revealed the existence of 19 differentially expressed proteins involved in progression of cancer, angiogenesis, cell adhesion, etc.

CONCLUSIONS

Exposure of bitumen extract to HOS cells results in the cellular transformation similar to cancer cells and can modulate proteins involved in the progression of cancer. We state that the non-tumorogenic potential of bitumen transformant in nude/SCID mice can be attributed to the downregulation of galectin-1, chromodomain helicase DNA-binding protein 1-like gene, and membrane-associated guanylate kinase 2 protein.