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

Abstract

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.

Silencing KRAS Overexpression in Cadmium-Transformed Prostate Epithelial Cells Mitigates Malignant Phenotype

“…Thus, KRAS activation in the transformed RWPE-1 cells is dependent on the carcinogen. Our current findings are consistent with other studies which report KRAS activation in Cd- and arsenic-transformed human lung cells, 17,26 suggesting KRAS activation appears to be an important event for both of these inorganic carcinogens. Interestingly, the lung is a human target tissue for both Cd and arsenic.…”

Selective cysteine modification of metal‐free human metallothionein 1a and its isolated domain fragments: Solution structural properties revealed via ESI‐MS

“…These special properties include binding of up to 7 Zn 2+ and Cd 2+ , forming two metal‐thiolate clustered domains (the α and β‐domains) that are joined by a short linker sequence . While the biological function(s) of this family of proteins are still debated, it is generally agreed that their functions are connected with zinc and copper homeostasis, redox signalling, and toxic metal sequestration . Despite these many proposed functions, and their capacity to bind so many metals, MTs are surprisingly small, flexible proteins that lack optically active structural features.…”

“…2,3 While the biological function(s) of this family of proteins are still debated, it is generally agreed that their functions are connected with zinc and copper homeostasis, [4][5][6][7] redox signalling, [8][9][10] and toxic metal sequestration. [11][12][13][14][15] Despite these many proposed functions, and their capacity to bind so many metals, 16,17 MTs are surprisingly small, flexible proteins that lack optically active structural features. This lack of formal secondary and tertiary structure in the absence of bound metal ions precludes traditional structural analysis via spectroscopic methods.…”

Long-term exposure of immortalized keratinocytes to arsenic induces EMT, impairs differentiation in organotypic skin models and mimics aspects of human skin derangements

“…Since several studies have shown that arsenic-induced malignant transformation is frequently accompanied by cellular morphology changes resembling EMT (Eckstein et al 2017;Person et al 2015;Wang et al 2013), we investigated EMT markers after longterm arsenic exposure. Indeed, we observed loss of keratin 14 and ZO-1 together with an increase in spheroid formation capability in all chronically treated cells.…”