Grants and Contracts Details
Description
Although the molecular mechanism of arsenic-induced carcinogenesis remains to be investigated, reactive
oxygen species (ROS) generated by arsenic are considered to be important. Arsenic-generated ROS could
cause DNA damage, lipid peroxidation and protein modification, leading to various carcinogernic responses. Our
preliminary studies have shown that the capacity of ROS generation induced by arsenic is substantially reduced
in arsenic-transformed human lung bronchial epithelial (BEAS-2B) cells relative to the non-transformed cells.
Such a reduction in ROS generation endows cells with premalignant features, including rapid growth. Arsenictransformed
cells exhibit a decreased apoptosis (apoptosis resistance) upon arsenic exposure. This proposal
hypothesizes that due to a low potency of ROS generation, arsenic-transformed cells develop apoptosis
resistance and increased cell survival, contributing to the overall mechanism of arsenic-induced carcinogenesis.
Three aims are proposed to test this hypothesis. Aim 1 will investigate the mechanism of decreased ROS
generation in the arsenic-transferred cells. We will investigate whether impairment of the ROS generating
pathway is responsible for a low level of arsenic-induced ROS generation in arsenic transformed BEAS-2B cells.
We will also investigate whether the increased level of antioxidant enzymes in transformed cells contributes to the
decreased level of ROS generation. The completion of this aim will establish the mechanism of decreased ROS
generation in arsenic-transformed cells. Aim 2 will investigate the role of reduced ROS generation in apoptosis
resistance of arsenic-transformed cells. We investigate (a) whether reduced ROS generation of arsenictransformed
cells is responsible for apoptosis resistance in arsenic-transformed cells; (b) whether arsenictransformed
cells have higher antioxidant activities of SOD and catalase than their passage-matched control
cells; (c) whether knock-down of antioxidant enzymes or overexpressing NADPH oxidase in the transformed cells
increases ROS generation and enhances apoptosis in response to arsenic stimulation; (d) whether knocking
down of Bcl-2 increases apoptosis of arsenic-transformed cells; and (e) whether arsenic- transformed cell will
show fast growth and enhanced invasion and migration due to the decreased ROS generation and apoptosis
resistance. Overall, this aim will demonstrate the role of ROS in apoptosis resistance of arsenic-transformed cells.
Aim 3 will investigate the arsenic-transformed cells-induced tumorigenesis and the role of apoptosis. We will
investigate the role of apoptosis resistance in tumorigenesis of arsenic-transformed cells. We will also investigate
the roles of ROS and apoptosis regulatory proteins, Bcl-2, in arsenic-transformed cells-induced tumorigenesis
using both skin tumorigenesis model and orthotopic lung cancer model. It is expected that the increase of
apoptosis of arsenic-transformed cells by Bcl-2 knockdown will decrease tumor growth. Similarly, alterations in
the ROS generating capacity of the cells, i.e., by ectopic overexpression and knockdown of the ROS-scavenging
and producing enzymes, will have an effect on tumorigenesis of arsenic-transformed cells.
Status | Finished |
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Effective start/end date | 1/15/12 → 10/31/17 |
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