Development of a multiple-marker polymerase chain reaction assay for detection of metastatic melanoma in lymph node aspirates of dogs.
OBJECTIVE
To develop a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect canine melanoma-associated antigens (MAAs) and to use this technique to screen aspirates of lymph nodes (LNs) for evidence of metastatic spread of oral malignant melanoma.


METHODS
7 dogs with oral malignant melanoma and 4 dogs with multicentric lymphosarcoma.


METHODS
We prepared cDNA from melanoma tumor biopsies and fine-needle aspirates obtained from submandibular LNs of dogs with oral malignant melanoma or multicentric lymphosarcoma. The RT-PCR assay was performed by use of tyrosinase, Melan-A, gp100, tyrosinase-related protein 2 (TRP-2), or melanoma antigen-encoding gene B (MAGE-B)-specific primers.


RESULTS
We detected MAGE-B mRNA in canine testicular tissue but not in melanoma biopsy specimens. Tyrosinase, Melan-A, gp100, and TRP-2 mRNAs were detected in tumor biopsy specimens and in 2 of 5 LN aspirates from dogs with melanoma, suggesting metastatic spread in those 2 dogs. We did not detect MAAs in LN aspirates obtained from dogs with multicentric lymphosarcoma. Sequencing of canine Melan-A and gp100 PCR products confirmed the specificity of the assay for these genes.


CONCLUSIONS
Clinical staging of dogs with oral malignant melanoma is useful to assist in designing appropriate treatments. However, results of histologic examination of LN biopsy specimens can be inconclusive and, in humans, can underestimate the number of patients with metastatic disease. Molecular staging of melanomas in dogs can be achieved by screening LN aspirates for MAA mRNA, and this can be performed in combination with cytologic examination to aid in detection of metastatic disease.
Catchpole
Brian
B
Department of Pathology and Infectious Diseases, Royal Veterinary College, University of London, London, UK.
Gould
Sara M
SM
Kellett-Gregory
Lindsay M
LM
Dobson
Jane M
JM
D000818:Animals; D000951:Antigens, Neoplasm; D001483:Base Sequence; D015415:Biomarkers; D018076:DNA, Complementary / Q000235:genetics; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000175:diagnosis*; D058965:MART-1 Antigen; D008297:Male; D008545:Melanoma / Q000175:diagnosis* / Q000235:genetics; D008969:Molecular Sequence Data; D009062:Mouth Neoplasms / Q000175:diagnosis / Q000235:genetics; D009363:Neoplasm Proteins / Q000032:analysis* / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods*; D012334:RNA, Neoplasm / Q000032:analysis / Q000235:genetics; D013737:Testis / Q000473:pathology
D000951:Antigens, Neoplasm; D015415:Biomarkers; D018076:DNA, Complementary; D058965:MART-1 Antigen; C548667:MLANA protein, human; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm