Morpho/Proteomic Comparative between High Grade Pleomorphic Sarcoma and Metastasis Diagnosed in an Old Captive Common Hippo

Abstract

Old age is a risk factor for cancer development in humans and animals, and studies have shown that tumors in animals are acceptable models for studying human cancers, considering the similarities between their factors. This work was conducted in a 53-year-old captive female common hippo (Hippopotamus amphibious) with a left leg tumor and metastatic mass. Histopathological and immunohistochemical analyses were carried out with a final diagnosis of a high grade pleomorphic sarcoma. A proteomic study using mass spectrometry was added in order to identify further aspects of the primary tumor and metastasis which could improve our understanding, and each tissue showed a proteomic profile indicative of its pathologic state with significant differences between healthy tissue, primary and metastatic tumors. Low levels of β-actin in primary tumors were identified, and this may be associated with a possible consequence of cytoskeleton dynamic modification. In metastatic tissue, these dynamics may be affected by the presence of HSP chaperone 60. Keywords:Hippopotamus amphibious, high grade pleomorphic sarcoma, cytoskeleton, β-actin, mass spectrometry IntroductionOncogenic phenomena in animals include a wide variety of benign and malignant tumors that develop during the life of the animal and have several health consequences. 1 Species with large bodies tend to have a lower cancer rate, which seems to indicate the presence of complex tumor detection systems (Peto's paradox).2 To illustrate this paradox, in contrast with humans, who have only two copies of the TP53 tumor suppressor gene, elephants, the largest of the land mammmals, have 20 copies of the TP53 gene. This allows for extra efficiency in their systems, enabling the correction of DNA damage or inducing apoptosis in mutated cells. As a result, only 3% of elephants develop cancer. 3,4 Despite some comparative cancer and lifespan analyses between wild and zoo animals showing that captive animals were susceptible to cancer and decreased longevity. 5,6 Tidière et al. 7 revealed that mammals from zoo populations generally lived longer than their wild counterparts (84% of species). Of particular interest, the common hippopotamus (Hippopotamus amphibius), a robust mammal with an estimated 40-year lifespan in nature and with slow pace of life, has increased longevity in captivity. [7][8][9] The relationship between life expectancy and environment may be associated with the low caloric diet and reduced metabolism present in captive animals, which slows ageing and the appearance of cancer cases. This is also true for humans. 10,11 Paradoxically, the exceptional longevity these captive animals exhibit can be associated with cancer due to several factors such as telomere shortening, increased cellular senescence, accumulation mutation of DNA in stem and progenitor cells required for active replenishment during the lifespan of the organism, mutations in tumor suppressor genes and metabolic changes. 12-14Based on available database information and proteomics approach, it is poss...