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Epigenetic Modifications and Accumulation of DNA Double-Strand Breaks in Oral Lichen Planus Lesions Presenting Poor Response to Therapy.

Dillenburg CS, Martins MA, Almeida LO, Meurer L, Squarize CH, Martins MD, Castilho RM - Medicine (Baltimore) (2015)

Bottom Line: Although an exciting prospect, the identification of early epigenetic markers associated with clinical outcome in premalignant and malignant disorders remains elusive.We analyzed 42 OLP patients, who had different responses to therapy, for acetyl-histone H3 at lys9 (H3K9ac), which is associated with enhanced transcription and nuclear decondensation, and the presence of DSBs, as determined by accumulation of phosphorylated γH2AX foci.Patients with high levels of H3K9ac acetylation failed to respond to therapy or experienced disease recurrence shortly after therapy.

View Article: PubMed Central - PubMed

Affiliation: From the Department of Oral Pathology (CSD, MDM), School of Dentistry; Department of Oral Medicine (MATM), Hospital de Clínicas de Porto Alegre (HCPA/UFRGS); Department of Pathology (LM), School of Medicine, Hospital de Clínicas de Porto Alegre (HCPA/UFRGS), Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; and Laboratory of Epithelial Biology (CSD, MATM, LOA, CHS, MDM, RMC), Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA.

ABSTRACT
Epigenetics refers to changes in cell characteristics that occur independently of modifications to the deoxyribonucleic acid (DNA) sequence. Alterations mediated by epigenetic mechanisms are important factors in cancer progression. Although an exciting prospect, the identification of early epigenetic markers associated with clinical outcome in premalignant and malignant disorders remains elusive. We examined alterations in chromatin acetylation in oral lichen planus (OLP) with distinct clinical behavior and compared the alterations to the levels of DNA double-strand breaks (DSBs). We analyzed 42 OLP patients, who had different responses to therapy, for acetyl-histone H3 at lys9 (H3K9ac), which is associated with enhanced transcription and nuclear decondensation, and the presence of DSBs, as determined by accumulation of phosphorylated γH2AX foci. Patients with high levels of H3K9ac acetylation failed to respond to therapy or experienced disease recurrence shortly after therapy. Similar to H3K9ac, patients who responded poorly to therapy had increased accumulation of DNA DSB, indicating genomic instability. These findings suggest that histone modifications occur in OLP, and H3K9ac and γH2AX histones may serve as epigenetic markers for OLP recurrence.

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Related in: MedlinePlus

Increased DNA damage correlates to poor response to therapy. (A) Representative examples of positive and negative OLP lesions for the γH2AX DNA double-strand break marker. Note the presence of γH2AX-positive cells next to the basal layer (arrow) of the oral mucosa (dashed line defines limit between connective and epithelial tissue). Quantification of γH2AX positive cells in (B) Type I OLP patients (mean value of 8.71% of positive cells), (C) Type II OLP patients (mean value of 41.90% positive cells), and (D) Type III OLP patients (mean value of 45.30% positive cells). OLP = oral lichen planus.
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Figure 3: Increased DNA damage correlates to poor response to therapy. (A) Representative examples of positive and negative OLP lesions for the γH2AX DNA double-strand break marker. Note the presence of γH2AX-positive cells next to the basal layer (arrow) of the oral mucosa (dashed line defines limit between connective and epithelial tissue). Quantification of γH2AX positive cells in (B) Type I OLP patients (mean value of 8.71% of positive cells), (C) Type II OLP patients (mean value of 41.90% positive cells), and (D) Type III OLP patients (mean value of 45.30% positive cells). OLP = oral lichen planus.

Mentions: The transformation potential of OLP is largely unknown. However, genetic aberrations have been reported in OLP40–43 and provide the rational for the presence of a subset of genetically instable OLP lesions. Our previous results suggest that the regulation of OLP response to therapy is directly associated with histone modifications, which enhance gene transcription. However, is unknown whether histone acetylation correlates with increased genomic instability. We next examined for chronic genomic injuries to OLP chromatin by identifying DSBs. Histone γH2AX detect DSBs in chromatin and initiates the DNA damage response complex. In response to phosphorylation at serine 139 by ATM, γH2AX recruits repair proteins, including p53, BRCA1 and 2, FANCD2, and others, to DSBs.44,45 However, sustained phosphorylation of γH2AX denotes chronic injury to the genome. Early-stage cancer development is associated with DNA replication stress, which enhances DNA DSBs and genomic instability, following increased pressure for p53 mutations.46 We found that the majority of OLP lesions were positive for γH2AX in the basal and parabasal layer of epithelial cells from the oral mucosa (Figure 3A). Interestingly, Type I patients had the lowest rate of γH2AX-postive cells (8.71%) (Figure 3B) compared to 49.10% and 45.30% in Types II (Figure 3C) and III patients (Figure 3D), respectively. Compared to Type I patients, the amount of DNA damage in Type II and Type III patients was 4.8 and 5.2-fold higher, respectively.


Epigenetic Modifications and Accumulation of DNA Double-Strand Breaks in Oral Lichen Planus Lesions Presenting Poor Response to Therapy.

Dillenburg CS, Martins MA, Almeida LO, Meurer L, Squarize CH, Martins MD, Castilho RM - Medicine (Baltimore) (2015)

Increased DNA damage correlates to poor response to therapy. (A) Representative examples of positive and negative OLP lesions for the γH2AX DNA double-strand break marker. Note the presence of γH2AX-positive cells next to the basal layer (arrow) of the oral mucosa (dashed line defines limit between connective and epithelial tissue). Quantification of γH2AX positive cells in (B) Type I OLP patients (mean value of 8.71% of positive cells), (C) Type II OLP patients (mean value of 41.90% positive cells), and (D) Type III OLP patients (mean value of 45.30% positive cells). OLP = oral lichen planus.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4554108&req=5

Figure 3: Increased DNA damage correlates to poor response to therapy. (A) Representative examples of positive and negative OLP lesions for the γH2AX DNA double-strand break marker. Note the presence of γH2AX-positive cells next to the basal layer (arrow) of the oral mucosa (dashed line defines limit between connective and epithelial tissue). Quantification of γH2AX positive cells in (B) Type I OLP patients (mean value of 8.71% of positive cells), (C) Type II OLP patients (mean value of 41.90% positive cells), and (D) Type III OLP patients (mean value of 45.30% positive cells). OLP = oral lichen planus.
Mentions: The transformation potential of OLP is largely unknown. However, genetic aberrations have been reported in OLP40–43 and provide the rational for the presence of a subset of genetically instable OLP lesions. Our previous results suggest that the regulation of OLP response to therapy is directly associated with histone modifications, which enhance gene transcription. However, is unknown whether histone acetylation correlates with increased genomic instability. We next examined for chronic genomic injuries to OLP chromatin by identifying DSBs. Histone γH2AX detect DSBs in chromatin and initiates the DNA damage response complex. In response to phosphorylation at serine 139 by ATM, γH2AX recruits repair proteins, including p53, BRCA1 and 2, FANCD2, and others, to DSBs.44,45 However, sustained phosphorylation of γH2AX denotes chronic injury to the genome. Early-stage cancer development is associated with DNA replication stress, which enhances DNA DSBs and genomic instability, following increased pressure for p53 mutations.46 We found that the majority of OLP lesions were positive for γH2AX in the basal and parabasal layer of epithelial cells from the oral mucosa (Figure 3A). Interestingly, Type I patients had the lowest rate of γH2AX-postive cells (8.71%) (Figure 3B) compared to 49.10% and 45.30% in Types II (Figure 3C) and III patients (Figure 3D), respectively. Compared to Type I patients, the amount of DNA damage in Type II and Type III patients was 4.8 and 5.2-fold higher, respectively.

Bottom Line: Although an exciting prospect, the identification of early epigenetic markers associated with clinical outcome in premalignant and malignant disorders remains elusive.We analyzed 42 OLP patients, who had different responses to therapy, for acetyl-histone H3 at lys9 (H3K9ac), which is associated with enhanced transcription and nuclear decondensation, and the presence of DSBs, as determined by accumulation of phosphorylated γH2AX foci.Patients with high levels of H3K9ac acetylation failed to respond to therapy or experienced disease recurrence shortly after therapy.

View Article: PubMed Central - PubMed

Affiliation: From the Department of Oral Pathology (CSD, MDM), School of Dentistry; Department of Oral Medicine (MATM), Hospital de Clínicas de Porto Alegre (HCPA/UFRGS); Department of Pathology (LM), School of Medicine, Hospital de Clínicas de Porto Alegre (HCPA/UFRGS), Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; and Laboratory of Epithelial Biology (CSD, MATM, LOA, CHS, MDM, RMC), Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA.

ABSTRACT
Epigenetics refers to changes in cell characteristics that occur independently of modifications to the deoxyribonucleic acid (DNA) sequence. Alterations mediated by epigenetic mechanisms are important factors in cancer progression. Although an exciting prospect, the identification of early epigenetic markers associated with clinical outcome in premalignant and malignant disorders remains elusive. We examined alterations in chromatin acetylation in oral lichen planus (OLP) with distinct clinical behavior and compared the alterations to the levels of DNA double-strand breaks (DSBs). We analyzed 42 OLP patients, who had different responses to therapy, for acetyl-histone H3 at lys9 (H3K9ac), which is associated with enhanced transcription and nuclear decondensation, and the presence of DSBs, as determined by accumulation of phosphorylated γH2AX foci. Patients with high levels of H3K9ac acetylation failed to respond to therapy or experienced disease recurrence shortly after therapy. Similar to H3K9ac, patients who responded poorly to therapy had increased accumulation of DNA DSB, indicating genomic instability. These findings suggest that histone modifications occur in OLP, and H3K9ac and γH2AX histones may serve as epigenetic markers for OLP recurrence.

Show MeSH
Related in: MedlinePlus