p53 Regulates Cellular Responses to Environmental Carcinogen Benzo[a]pyrene-7,8-diol-9,10-epoxide in Human Lung Cancer Cells

Abstract

The p53 tumor suppressor is a mutational target of environmental carcinogen anti-benzo . We now demonstrate that p53 plays an important role in regulation of cellular responses to BPDE. Exposure of p53-null H1299 human lung cancer cells to BPDE resulted in S and G 2 phase cell cycle arrest, but not mitotic block, which correlated with induction of cyclin B1 protein expression, down-modulation of cell division cycle 25C (Cdc25C) and Cdc25B protein levels, and hyperphosphorylation of Cdc25C (S216), cyclin-dependent kinase 1 (Cdk1; Y15), checkpoint kinase 1 (Chk1; S317 and S345) and Chk2 (T68). The BPDE-induced S phase block, but not the G 2 /M phase arrest, was significantly attenuated by knockdown of Chk1 protein level. The BPDE-mediated accumulation of sub-diploid fraction (apoptotic cells) was significantly decreased in H1299 cells transiently transfected with both Chk1 and Chk2 specific siRNAs. The H460 human lung cancer cell line (wild-type p53) was relatively more sensitive to BPDE-mediated growth inhibition and enrichment of subdiploid apoptotic fraction compared with H1299 cells. The BPDE exposure failed to activate either S or G 2 phase checkpoint in H460 cells. Instead, the BPDE-treated H460 cells exhibited a nearly 8-fold increase in sub-diploid apoptotic cells that was accompanied by phosphorylation of p53 at multiple sites. Knockdown of p53 protein level in H460 cells attenuated BPDE-induced apoptosis but enforced activation of S and G 2 phase checkpoints. In conclusion, the present study points towards an important role of p53 in regulation of cellular responses to BPDE in human lung cancer cells.

Environmental carcinogenesis and pH homeostasis: Not only a matter of dysregulated metabolism

“…If the cells survive with more DNA damage due to pro-survival/anti-apoptotic signals, the probability of having a mutation may increase. Following B[a]P-triggered DNA damage, diverse signaling pathways activate p53 [83], thereby leading to cell cycle arrest and cell death when DNA damage is not repaired [84][85][86][87][88]. However, B[a]P has also been suggested to activate p53-independent cell death processes [89], notably involving modulation of the Bcl-2 family members, with an upregulation or downregulation of the expression of anti-apoptotic (eg.…”

“…Different types of cell death have been described upon B[a]P exposure, with the occurrence of apoptosis [85][86][87][88] as well as necrosis/necroptosis [90,91,94,95]. Regarding the B[a]P-induced apoptosis, the intrinsic mitochondrial pathway has been the most often reported, with an activation of effector caspases 3/7, associated or not with a release of cytochrome c [86,[96][97][98].…”

Low concentration of anti‐7,8‐dihydroxy‐9,10‐epoxy‐7,8,9,10‐tetrahydrobenzo[a]pyrene induces alterations of extracellular protein profile of exposed epithelial cells

“…In the present study, alterations of extracellular protein patterns were compared using differential proteomic analysis in cultured FL cells. This cell line (ATCC CCL‐62) was chosen as the model cell for this study, based on following considerations: though a large number of different cell lines, such as rodent or human fibroblasts 12, lymphocytes 13 and even cancer cell lines 4, 14, have been employed to study general biological effects of BPDE (not anchoring to its specific effects) in the literature, no agreement has been obtained concerning which cell line is the most ideal one for in vitro studies. We believe that epithelial cell lines of human origin and established from normal tissues are more suitable than other cell lines.…”

Linking Coregulated Gene Modules with Polycyclic Aromatic Hydrocarbon-Related Cancer Risk in the 3D Human Bronchial Epithelium

“…58−61 Our findings support several reports that exposure to BAP can cause S phase arrest through DNA damage signaling. 52,62,63 Bottleneck genes identified in the network (CDK1, MCM2, and PCNA) have roles central to controlling cell cycle progression, including M-phase transition, and responding to DNA damage (Figure 3A). However, their involvement with environmental carcinogens have not been clearly established.…”

“…67−71 While BAP exposure has previously been linked to alterations in CDK1 and MDM2 activity, the findings of this network analysis support S phase gene regulation as a major cellular network perturbed by carcinogenic PAH exposure. 62,63,72 Carcinogenic PAH Exposure Dysregulates Actin Cytoskeleton Gene Networks. In our analysis of prioritized MEred module genes significantly correlated to RPF, we identified the cytoskeleton actin filament network as a top negatively correlated gene network to PAH cancer risk.…”