Advances in Animal and Veterinary Sciences. 2 (3S): 23 – 27 Special Issue–3 (Approaches in Diagnosis and Management of Diseases of Livestock and Poultry) http://dx.doi.org/10.14737/journal.aavs/2014/2.3s.23.27 Tiwari et al (2014). Detection of p53 Tumor Suppressor Protein 23 ISSN: 2307–8316 (Online); ISSN: 2309–3331 (Print) Research Article Keshaw Prasad Tiwari 1 , Muhammad Iqbal Bhaiyat 1 , Alfred Chikweto 1 , Allison Inga 1 , Ravindra Nath Sharma 1* , RVS Pawaiya 2 1 Pathobiology Academic Program, School of Veterinary Medicine, St. George’s University, Grenada, West Indies; 2 Central Institute for Research on Goats, Makhdoom, P.O. Farah–281122, Mathura, Uttar Pradesh, India *Corresponding author: rsharma@sgu.edu ARTICLE HISTORY ABSTRACT Received: Revised: Accepted: 2014–01–21 2014–02–23 2014–02–24 A study was undertaken on 40 round cell tumors in dogs namely, transmissible venereal tumor (TVT), 19 cases; mast cell tumor (MCT), 7 cases; canine cutaneous histiocytoma (CCH), 14 cases. These tumor cases were selected from biopsy and necropsy submissions for the period 2001 to 2011 on dogs residing in Grenada. The objective of this study was to evaluate the expression pattern of the tumor suppressor protein p53 in these tumors. Nuclear expression of p53 was detected as moderate to strong immuno–reactivity in most of the 3 tumors under study. The percentage of immuno–marked cells was 36.8, 50.0, and 57.1 for TVT, CCH and MCT, respectively. Intensity of p53 immunostaining was proportional to biological behavior of the tumors. Canine TVT in metastatic sites showed significantly (P=0.009) higher immune–reactivity compared to TVT in primary site. Strongly positive p53 expression was seen consistently in TVT at extragenital sites indicating a higher degree of malignant behavior of this tumor. This suggests that p53 expression could be a useful indicator of the malignant potential and prognosis of canine TVT. All copyrights reserved to Nexus® academic publishers Key Words: Cutaneous histiocytoma, Mast cell tumor, p53, Transmissible venereal tumor, tumor suppressor protein, Dog, Grenada ARTICLE CITATION: Tiwari KP, Bhaiyat MI, Chikweto A, Inga A, Sharma RN and Pawaiya RVS (2014) Immunohistochemical detection of p53 tumor suppressor protein in round cell tumors of dogs in grenada, West Indies. Adv. Anim. Vet. Sci. 2 (3S): 23 – 27. INTRODUCTION The p53 (also known as protein 53 or tumor protein 53) is a tumor suppressor protein that plays a central role in the maintenance of genomic integrity. p53 has been described as "the guardian of the genome", referring to its role in conserving stability of the cell genome by preventing mutation (Lane, 1992; Strachan and Read, 2003). The name is due to its molecular mass which is 53 kilo Dalton (kDa). It regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer. The p53 is one of the most important of the tumor suppressor genes involved in the development of neoplasia and the most frequently mutated gene in human cancers (Setoguchi et al., 2001; Soussi and Beround, 2001; Pawaiya and Ramkumar, 2007; Vousden and Lane, 2007). Known biological functions of p53 are transcriptional activation of genes involved in cell cycle control, DNA repair and metabolism, genomic plasticity, senescence, angiogenesis, programmed cell death, cellular differentiation, and immune response, including transcriptional, posttranscriptional and posttranslational roles (Levine, 1997; Hollstein and Hainaut, 2010). p53 protein is quickly eliminated due to its short half–life (about 20 minutes). In contrast, the mutant p53 protein has a half–life of several hours and may be detected by immunohistochemistry (Prokocimer and Rotter, 1994). Correlation between immunohistochemical detection of p53 protein and mutations in p53 gene has been described (Davidoff et al., 1991). These mutations often lead to production of an altered p53 protein that binds to and inactivates the normal p53 protein, thereby promoting tumorigenesis. Thus, immunohistochemical detection of p53 protein is equated to the detection of the mutant p53 protein or otherwise stabilized abnormal p53 protein, rather than due to overexpression of normal p53 (Ginn et al., 2000). Genetic instability is the one of the most common features of malignant neoplasms. P53 can arrest cell division, freezing the cell at the G1 checkpoint of the cellular cycle, thus the cell is unable to reproduce and its damaged genome is safely isolated. p53 can also initiate a more permanent solution namely programmed cell death or apoptosis if it fails to repair the damaged DNA (Hanahan and Weinberg, 2011; Ozer et al., 2012). Canine round cell tumors (RCTs) are composed of cells with a round morphology. They include transmissible venereal tumor (TVT), histiocytoma, lymphoma, melanoma, plasmacytoma, and mast cell tumor and neuroendocrine cell tumor (Sandusky et al., 1987). It is difficult to distinguish TVT from other round cell tumors especially when it occurs in extra genital locations. The aim of present study was to immunohistochemically detect and determine the Immunohistochemical Detection of p53 Tumor Suppressor Protein in Round Cell Tumors of Dogs in Grenada, West Indies