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SAN FRANCISCO—Preclinical research has revealed mutations that may affect the performance of histone deacetylase inhibitors (HDACis) in patients with peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS).
The researchers identified histone-modifying gene mutations in patients with PTCL-NOS and found evidence to suggest these mutations confer shorter survival.
The team also conducted experiments in Jurkat cells showing that certain HDACis could counteract loss-of-function mutations, while others could not.
Meng-Meng Ji, MD, PhD, of the Shanghai Institute of Hematology in China, presented this research at the 8th Annual T-cell Lymphoma Forum.
Dr Ji and her colleagues first performed targeted sequencing in tumor samples from 105 patients newly diagnosed with PTCL-NOS.
The team discovered 62 mutations of “important” lymphoma-associated histone-modifying genes in 31 patients. They found mutations in MLL2 (n=21), TET2 (n=17), EP300 (n=8), CREBBP (n=8), and SETD2 (n=6).
Clinical data revealed a significant difference in overall survival between patients who had these mutations and those who did not (P=0.0038).
Because most of the mutations they identified are loss-of-function mutations, Dr Ji and her colleagues wanted to determine whether HDACis could restore the expression of the mutated genes. So they tested 4 HDACis—valproic acid, vorinostat, romidepsin, and chidamide—in Jurkat cells.
All 4 HDACis upregulated expression of EP300 and CREBBP. However, only romidepsin and chidamide upregulated MLL2, and only valproic acid and vorinostat upregulated SETD2. Dr Ji said there was no obvious change in TET2 expression with any of the HDACis.
The researchers then took a closer look at the EP300, MLL2, and SETD2 mutations. They found that most EP300 mutations were located on the HAT domain. MLL2 mutations could be found in a variety of locations, but some were located on the SET domain. And most SETD2 mutations were located on the SET domain.
Based on the crystal structure of each gene, the team found that EP300 mutations on the HAT domain and both MLL2 mutations and SETD2 mutations located on the SET domain induce loss of function.
So the researchers constructed a mutant for EP300 (p.H1377R), MLL2 (p.V5389M), and SETD2 (p.R1598_) and transfected Jurkat cells with each mutant.
The mutants reduced gene expression significantly when compared to wild-type cells.
Like in the previous experiments, all 4 HDACis could restore the expression of EP300. But only romidepsin and chidamide could restore MLL2 expression, and only valproic acid and vorinostat could restore SETD2 expression.
In addition, all 4 HDACis restored H3K18 hypoacetylation, which was inhibited in Jurkat cells transfected with the EP300 mutant.
Romidepsin and chidamide restored H3K4me3 expression, which was inhibited by the MLL2 mutant. And valproic acid and vorinostat restored H3K36me3 expression, which was inhibited by the SETD2 mutant.
“HDACis targeted differently histone H3 acetylation or methylation modulated by the mutations, suggesting their distinct therapeutic efficiency in PTCL-NOS,” Dr Ji noted.
She said she and her colleagues are continuing this research in samples from patients with PTCL-NOS. 
Photo by Larry Young
SAN FRANCISCO—Preclinical research has revealed mutations that may affect the performance of histone deacetylase inhibitors (HDACis) in patients with peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS).
The researchers identified histone-modifying gene mutations in patients with PTCL-NOS and found evidence to suggest these mutations confer shorter survival.
The team also conducted experiments in Jurkat cells showing that certain HDACis could counteract loss-of-function mutations, while others could not.
Meng-Meng Ji, MD, PhD, of the Shanghai Institute of Hematology in China, presented this research at the 8th Annual T-cell Lymphoma Forum.
Dr Ji and her colleagues first performed targeted sequencing in tumor samples from 105 patients newly diagnosed with PTCL-NOS.
The team discovered 62 mutations of “important” lymphoma-associated histone-modifying genes in 31 patients. They found mutations in MLL2 (n=21), TET2 (n=17), EP300 (n=8), CREBBP (n=8), and SETD2 (n=6).
Clinical data revealed a significant difference in overall survival between patients who had these mutations and those who did not (P=0.0038).
Because most of the mutations they identified are loss-of-function mutations, Dr Ji and her colleagues wanted to determine whether HDACis could restore the expression of the mutated genes. So they tested 4 HDACis—valproic acid, vorinostat, romidepsin, and chidamide—in Jurkat cells.
All 4 HDACis upregulated expression of EP300 and CREBBP. However, only romidepsin and chidamide upregulated MLL2, and only valproic acid and vorinostat upregulated SETD2. Dr Ji said there was no obvious change in TET2 expression with any of the HDACis.
The researchers then took a closer look at the EP300, MLL2, and SETD2 mutations. They found that most EP300 mutations were located on the HAT domain. MLL2 mutations could be found in a variety of locations, but some were located on the SET domain. And most SETD2 mutations were located on the SET domain.
Based on the crystal structure of each gene, the team found that EP300 mutations on the HAT domain and both MLL2 mutations and SETD2 mutations located on the SET domain induce loss of function.
So the researchers constructed a mutant for EP300 (p.H1377R), MLL2 (p.V5389M), and SETD2 (p.R1598_) and transfected Jurkat cells with each mutant.
The mutants reduced gene expression significantly when compared to wild-type cells.
Like in the previous experiments, all 4 HDACis could restore the expression of EP300. But only romidepsin and chidamide could restore MLL2 expression, and only valproic acid and vorinostat could restore SETD2 expression.
In addition, all 4 HDACis restored H3K18 hypoacetylation, which was inhibited in Jurkat cells transfected with the EP300 mutant.
Romidepsin and chidamide restored H3K4me3 expression, which was inhibited by the MLL2 mutant. And valproic acid and vorinostat restored H3K36me3 expression, which was inhibited by the SETD2 mutant.
“HDACis targeted differently histone H3 acetylation or methylation modulated by the mutations, suggesting their distinct therapeutic efficiency in PTCL-NOS,” Dr Ji noted.
She said she and her colleagues are continuing this research in samples from patients with PTCL-NOS.
Photo by Larry Young
SAN FRANCISCO—Preclinical research has revealed mutations that may affect the performance of histone deacetylase inhibitors (HDACis) in patients with peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS).
The researchers identified histone-modifying gene mutations in patients with PTCL-NOS and found evidence to suggest these mutations confer shorter survival.
The team also conducted experiments in Jurkat cells showing that certain HDACis could counteract loss-of-function mutations, while others could not.
Meng-Meng Ji, MD, PhD, of the Shanghai Institute of Hematology in China, presented this research at the 8th Annual T-cell Lymphoma Forum.
Dr Ji and her colleagues first performed targeted sequencing in tumor samples from 105 patients newly diagnosed with PTCL-NOS.
The team discovered 62 mutations of “important” lymphoma-associated histone-modifying genes in 31 patients. They found mutations in MLL2 (n=21), TET2 (n=17), EP300 (n=8), CREBBP (n=8), and SETD2 (n=6).
Clinical data revealed a significant difference in overall survival between patients who had these mutations and those who did not (P=0.0038).
Because most of the mutations they identified are loss-of-function mutations, Dr Ji and her colleagues wanted to determine whether HDACis could restore the expression of the mutated genes. So they tested 4 HDACis—valproic acid, vorinostat, romidepsin, and chidamide—in Jurkat cells.
All 4 HDACis upregulated expression of EP300 and CREBBP. However, only romidepsin and chidamide upregulated MLL2, and only valproic acid and vorinostat upregulated SETD2. Dr Ji said there was no obvious change in TET2 expression with any of the HDACis.
The researchers then took a closer look at the EP300, MLL2, and SETD2 mutations. They found that most EP300 mutations were located on the HAT domain. MLL2 mutations could be found in a variety of locations, but some were located on the SET domain. And most SETD2 mutations were located on the SET domain.
Based on the crystal structure of each gene, the team found that EP300 mutations on the HAT domain and both MLL2 mutations and SETD2 mutations located on the SET domain induce loss of function.
So the researchers constructed a mutant for EP300 (p.H1377R), MLL2 (p.V5389M), and SETD2 (p.R1598_) and transfected Jurkat cells with each mutant.
The mutants reduced gene expression significantly when compared to wild-type cells.
Like in the previous experiments, all 4 HDACis could restore the expression of EP300. But only romidepsin and chidamide could restore MLL2 expression, and only valproic acid and vorinostat could restore SETD2 expression.
In addition, all 4 HDACis restored H3K18 hypoacetylation, which was inhibited in Jurkat cells transfected with the EP300 mutant.
Romidepsin and chidamide restored H3K4me3 expression, which was inhibited by the MLL2 mutant. And valproic acid and vorinostat restored H3K36me3 expression, which was inhibited by the SETD2 mutant.
“HDACis targeted differently histone H3 acetylation or methylation modulated by the mutations, suggesting their distinct therapeutic efficiency in PTCL-NOS,” Dr Ji noted.
She said she and her colleagues are continuing this research in samples from patients with PTCL-NOS.