Chronic inorganic arsenic exposure in vitro induces a cancer cell phenotype in human peripheral lung epithelial cells.

Inorganic arsenic is a human lung carcinogen. We studied the ability of chronic inorganic arsenic (2 µM; as sodium arsenite) exposure to induce a cancer phenotype in the immortalized, non-tumorigenic human lung peripheral epithelial cell line, HPL-1D. After 38 weeks of continuous arsenic exposure, secreted matrix metalloproteinase-2 (MMP2) activity increased to over 200% of control, levels linked to arsenic-induced cancer phenotypes in other cell lines. The invasive capacity of these chronic arsenic-treated lung epithelial (CATLE) cells increased to 320% of control and colony formation increased to 280% of control. CATLE cells showed enhanced proliferation in serum-free media indicative of autonomous growth. Compared to control cells, CATLE cells showed reduced protein expression of the tumor suppressor gene PTEN (decreased to 26% of control) and the putative tumor suppressor gene SLC38A3 (14% of control). Morphological evidence of epithelial-to-mesenchymal transition (EMT) occurred in CATLE cells together with appropriate changes in expression of the EMT markers vimentin (VIM; increased to 300% of control) and e-cadherin (CDH1; decreased to 16% of control). EMT is common in carcinogenic transformation of epithelial cells. CATLE cells showed increased KRAS (291%), ERK1/2 (274%), phosphorylated ERK (p-ERK; 152%), and phosphorylated AKT1 (p-AKT1; 170%) protein expression. Increased transcript expression of metallothioneins, MT1A and MT2A and the stress response genes HMOX1 (690%) and HIF1A (247%) occurred in CATLE cells possibly in adaptation to chronic arsenic exposure. Thus, arsenic induced multiple cancer cell characteristics in human peripheral lung epithelial cells. This model may be useful to assess mechanisms of arsenic-induced lung cancer.

Chronic cadmium exposure in vitro causes acquisition of multiple tumor cell characteristics in human pancreatic epithelial cells.

BACKGROUND: Cancer may be a stem cell (SC)-based disease involving formation of cancer SCs (CSCs) potentially arising from transformation of normal SCs. Cadmium has been linked to human pancreatic cancer. OBJECTIVE: We studied cadmium exposure of human pancreatic ductal epithelial (HPDE) cells and whether SCs may be targeted in this process. METHODS: We chronically exposed HPDE cells to low level cadmium (1 µM) for ≤ 29 weeks. Nonadherent spheroid formation was used to indicate CSC-like cell production, and we assessed tumor cell characteristics in such spheres. Assessed tumor cell characteristics including secretion of matrix metalloproteinase-9 (MMP-9), invasion, and colony formation were fortified by evaluating expression of relevant genes by real-time reverse transcription polymerase chain reaction and by Western blot. RESULTS: Increased MMP-9 secretion and overexpression of the pancreatic cancer marker S100P occurred in chronic (29 weeks of exposure) cadmium-exposed (CCE) cells. CCE cells also showed markedly higher colony formation and invasion, typical of cancer cells. Floating "spheres" of viable cells, known to contain an abundance of normal SCs or CSCs, form in vitro with many cell types. CCE cells produced 3-fold more spheres than control cells and were more invasive, secreted more MMP-9, and overexpressed markers for pancreatic SCs/CSCs (i.e., CXCR4, OCT4, CD44) and S100P, a marker for pancreatic cancer. CCE-derived spheres rapidly produced aggressive, highly branched, and poorly differentiated glandular-like structures in Matrigel. CONCLUSIONS: Chronic cadmium exposure produced multiple tumor cell characteristics in HPDE cells and CCE cell-derived spheres. These data support the plausibility of cadmium as a human pancreatic carcinogen.

Changes in hepatic gene expression in response to hepatoprotective levels of zinc.

BACKGROUND: Zinc (Zn) administration at non-toxic doses protects against the hepatotoxicity produced by many agents, but the underlying mechanisms remain elusive. AIM: To examine the basis of Zn-induced generalised hepatoprotective effects. METHODS: Rats and mice were given Zn at known hepatoprotective levels (100 mumol ZnCl2/kg/day, s.c., for 4 days) and molecular responses were assessed. RESULTS: Zn treatment produced changes in 5% of the genes on custom-designed mouse liver array and Rat Toxicology-II array. Changes in gene expression were further confirmed and extended by real-time reverse transcriptase-polymerase chain reaction. Zn treatment dramatically increased the expression of the metallothionein (Mt), and modestly increased the expression of acute-phase protein genes (ceruloplasmin, Stat3, egr1, Cxc chemokines and heat-shock proteins). For genes encoding for antioxidant enzymes, some were increased (Nrf2 and Nqo1), while others remained unaltered (Cu, Zn SOD and glutathione S-transferases). Expressions of cytokine and pro-inflammatory genes were not affected, while genes related to cell proliferation (cyclin D1) were modestly upregulated. Some metabolic enzyme genes, including cytochrome P450s and UDP-glucuronosyltransferase, were modestly suppressed, perhaps to switch cellular metabolic energy to acute-phase responses. Liver Zn content was increased between 1.6- and 2.1-fold, while hepatic MT protein was increased between 50 and 200-fold. Mice typically showed greater responses than rats. CONCLUSION: Such gene expression changes, particularly the dramatic induction of MT and Nrf2 antioxidant pathway, occur in the absence of overt liver injury, and are probably important in the hepatoprotective effects of Zn against toxic insults.