Limits...
Cadmium induced cell apoptosis, DNA damage, decreased DNA repair capacity, and genomic instability during malignant transformation of human bronchial epithelial cells.

Zhou Z, Wang C, Liu H, Huang Q, Wang M, Lei Y - Int J Med Sci (2013)

Bottom Line: Cadmium and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not entirely understood.Decreased expression of the anti-apoptotic gene Bcl-2 and the DNA repair genes hMSH2, hMLH1, ERCC1, ERCC2, and hOGG1 was observed.This process could be a viable mechanism for cadmium-induced cancers.

View Article: PubMed Central - PubMed

Affiliation: 1. School of public health, Guangzhou Medical University, Guangzhou 510182, People's Republic of China.

ABSTRACT
Cadmium and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not entirely understood. Our study was designed to elucidate the mechanisms of DNA damage in cadmium-induced malignant transformation of human bronchial epithelial cells. We analyzed cell cycle, apoptosis, DNA damage, gene expression, genomic instability, and the sequence of exons in DNA repair genes in several kinds of cells. These cells consisted of untreated control cells, cells in the fifth, 15th, and 35th passage of cadmium-treated cells, and tumorigenic cells from nude mice using flow cytometry, Hoechst 33258 staining, comet assay, quantitative real-time polymerase chain reaction (PCR), Western blot analysis, random amplified polymorphic DNA (RAPD)-PCR, and sequence analysis. We observed a progressive increase in cell population of the G0/G1 phase of the cell cycle and the rate of apoptosis, DNA damage, and cadmium-induced apoptotic morphological changes in cerebral cortical neurons during malignant transformation. Gene expression analysis revealed increased expression of cell proliferation (PCNA), cell cycle (CyclinD1), pro-apoptotic activity (Bax), and DNA damage of the checkpoint genes ATM, ATR, Chk1, Chk2, Cdc25A. Decreased expression of the anti-apoptotic gene Bcl-2 and the DNA repair genes hMSH2, hMLH1, ERCC1, ERCC2, and hOGG1 was observed. RAPD-PCR revealed genomic instability in cadmium-exposed cells, and sequence analysis showed mutation of exons in hMSH2, ERCC1, XRCC1, and hOGG1 in tumorigenic cells. This study suggests that Cadmium can increase cell apoptosis and DNA damage, decrease DNA repair capacity, and cause mutations, and genomic instability leading to malignant transformation. This process could be a viable mechanism for cadmium-induced cancers.

Show MeSH

Related in: MedlinePlus

Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1 were detected by sequencing amplified PCR and primers in untransformed control and tumorigenic cells induced by cadmium chloride. (A) Sequence of exon8 in hMSH2; (B) Sequence of exon9 in hMSH2; (C) Sequence of exon12 in hMSH2; (D) Sequence of exon14 in ERCC1; (E) Sequence of exon17 in hOGG1. The mutation “↓” are marked.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3775105&req=5

Figure 8: Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1 were detected by sequencing amplified PCR and primers in untransformed control and tumorigenic cells induced by cadmium chloride. (A) Sequence of exon8 in hMSH2; (B) Sequence of exon9 in hMSH2; (C) Sequence of exon12 in hMSH2; (D) Sequence of exon14 in ERCC1; (E) Sequence of exon17 in hOGG1. The mutation “↓” are marked.

Mentions: To investigate cadmium-induced genomic instability, the DNA polymorphic characteristics of hMSH2, ERCC1, XRCC1, and hOGG1 were detected by sequencing amplified PCR and primers in 16HBE cells and tumorigenic cells induced by CdCl2. The objective fragments of the exons in these four DNA repair genes were obtained with PCR amplification. After the application was identified by gel electrophoresis, the amplified DNA strips were purified. Then the exons were detected by DNA sequence. We observed no mutations at exon6 in hMSH2, exon7 in hMSH2, exon3 in ERCC1, exon6 in XRCC1, or exon9 in XRCC1 identified in 16HBE cells and tumorigenic cells of nude mice induced by CdCl2. In the CdCl2-induced tumorigenic cells, there were thymine deletions at the first, second, and seventh sites of exon8 in hMSH2; adenine deletions at the 20th and 182th sites of exon9 in hMSH2; adenine insertions at the 241th site of exon12 in hMSH2; adenine deletions at the first site of exon4 in ERCC1; and adenine in the 162th site of exon7 in hOGG1 (Figure 8). All mutations of exons in these DNA repair genes were frame shift mutations.


Cadmium induced cell apoptosis, DNA damage, decreased DNA repair capacity, and genomic instability during malignant transformation of human bronchial epithelial cells.

Zhou Z, Wang C, Liu H, Huang Q, Wang M, Lei Y - Int J Med Sci (2013)

Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1 were detected by sequencing amplified PCR and primers in untransformed control and tumorigenic cells induced by cadmium chloride. (A) Sequence of exon8 in hMSH2; (B) Sequence of exon9 in hMSH2; (C) Sequence of exon12 in hMSH2; (D) Sequence of exon14 in ERCC1; (E) Sequence of exon17 in hOGG1. The mutation “↓” are marked.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3775105&req=5

Figure 8: Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence analysis of exons in hMSH2, ERCC1, XRCC1, and hOGG1. Sequence of exons in hMSH2, ERCC1, XRCC1, and hOGG1 were detected by sequencing amplified PCR and primers in untransformed control and tumorigenic cells induced by cadmium chloride. (A) Sequence of exon8 in hMSH2; (B) Sequence of exon9 in hMSH2; (C) Sequence of exon12 in hMSH2; (D) Sequence of exon14 in ERCC1; (E) Sequence of exon17 in hOGG1. The mutation “↓” are marked.
Mentions: To investigate cadmium-induced genomic instability, the DNA polymorphic characteristics of hMSH2, ERCC1, XRCC1, and hOGG1 were detected by sequencing amplified PCR and primers in 16HBE cells and tumorigenic cells induced by CdCl2. The objective fragments of the exons in these four DNA repair genes were obtained with PCR amplification. After the application was identified by gel electrophoresis, the amplified DNA strips were purified. Then the exons were detected by DNA sequence. We observed no mutations at exon6 in hMSH2, exon7 in hMSH2, exon3 in ERCC1, exon6 in XRCC1, or exon9 in XRCC1 identified in 16HBE cells and tumorigenic cells of nude mice induced by CdCl2. In the CdCl2-induced tumorigenic cells, there were thymine deletions at the first, second, and seventh sites of exon8 in hMSH2; adenine deletions at the 20th and 182th sites of exon9 in hMSH2; adenine insertions at the 241th site of exon12 in hMSH2; adenine deletions at the first site of exon4 in ERCC1; and adenine in the 162th site of exon7 in hOGG1 (Figure 8). All mutations of exons in these DNA repair genes were frame shift mutations.

Bottom Line: Cadmium and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not entirely understood.Decreased expression of the anti-apoptotic gene Bcl-2 and the DNA repair genes hMSH2, hMLH1, ERCC1, ERCC2, and hOGG1 was observed.This process could be a viable mechanism for cadmium-induced cancers.

View Article: PubMed Central - PubMed

Affiliation: 1. School of public health, Guangzhou Medical University, Guangzhou 510182, People's Republic of China.

ABSTRACT
Cadmium and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not entirely understood. Our study was designed to elucidate the mechanisms of DNA damage in cadmium-induced malignant transformation of human bronchial epithelial cells. We analyzed cell cycle, apoptosis, DNA damage, gene expression, genomic instability, and the sequence of exons in DNA repair genes in several kinds of cells. These cells consisted of untreated control cells, cells in the fifth, 15th, and 35th passage of cadmium-treated cells, and tumorigenic cells from nude mice using flow cytometry, Hoechst 33258 staining, comet assay, quantitative real-time polymerase chain reaction (PCR), Western blot analysis, random amplified polymorphic DNA (RAPD)-PCR, and sequence analysis. We observed a progressive increase in cell population of the G0/G1 phase of the cell cycle and the rate of apoptosis, DNA damage, and cadmium-induced apoptotic morphological changes in cerebral cortical neurons during malignant transformation. Gene expression analysis revealed increased expression of cell proliferation (PCNA), cell cycle (CyclinD1), pro-apoptotic activity (Bax), and DNA damage of the checkpoint genes ATM, ATR, Chk1, Chk2, Cdc25A. Decreased expression of the anti-apoptotic gene Bcl-2 and the DNA repair genes hMSH2, hMLH1, ERCC1, ERCC2, and hOGG1 was observed. RAPD-PCR revealed genomic instability in cadmium-exposed cells, and sequence analysis showed mutation of exons in hMSH2, ERCC1, XRCC1, and hOGG1 in tumorigenic cells. This study suggests that Cadmium can increase cell apoptosis and DNA damage, decrease DNA repair capacity, and cause mutations, and genomic instability leading to malignant transformation. This process could be a viable mechanism for cadmium-induced cancers.

Show MeSH
Related in: MedlinePlus