Hypermethylation of the DLC1 CpG island does not alter gene expression in canine lymphoma.
BACKGROUND
This study is a comparative epigenetic evaluation of the methylation status of the DLC1 tumor suppressor gene in naturally-occurring canine lymphoma. Canine non-Hodgkin's lymphoma (NHL) has been proposed to be a relevant preclinical model that occurs spontaneously and may share causative factors with human NHL due to a shared home environment. The canine DLC1 mRNA sequence was derived from normal tissue. Using lymphoid samples from 21 dogs with NHL and 7 normal dogs, the methylation status of the promoter CpG island of the gene was defined for each sample using combined bisulfite restriction analysis (COBRA), methylation-specific PCR (MSP), and bisulfite sequencing methods. Relative gene expression was determined using real-time PCR.


RESULTS
The mRNA sequence of canine DLC1 is highly similar to the human orthologue and contains all protein functional groups, with 97% or greater similarity in functional regions. Hypermethylation of the 5' and 3' flanking regions of the promoter was statistically significantly associated with the NHL phenotype, but was not associated with silencing of expression or differences in survival.


CONCLUSIONS
The canine DLC1 is constructed highly similarly to the human gene, which has been shown to be an important tumor suppressor in many forms of cancer. As in human NHL, the promoter CpG island of DLC1 in canine NHL samples is abnormally hypermethylated, relative to normal lymphoid tissue. This study confirms that hypermethylation occurs in canine cancers, further supporting the use of companion dogs as comparative models of disease for evaluation of carcinogenesis, biomarker diagnosis, and therapy.
Bryan
Jeffrey N
JN
Dept of Veterinary Medicine and Surgery, University of Missouri-Columbia, 65211, USA. bryanjn@vetmed.wsu.edu
Jabbes
Mohamed
M
Berent
Linda M
LM
Arthur
Gerald L
GL
Taylor
Kristen H
KH
Rissetto
Kerry C
KC
Henry
Carolyn J
CJ
Rahmatpanah
Farah
F
Rankin
Wendi V
WV
Villamil
Jose A
JA
Lewis
Michael R
MR
Caldwell
Charles W
CW
D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D018899:CpG Islands; D019175:DNA Methylation; D004283:Dog Diseases / Q000175:diagnosis / Q000235:genetics*; D004285:Dogs; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000175:diagnosis / Q000235:genetics / Q000662:veterinary*; D008297:Male; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics*
D025521:Tumor Suppressor Proteins