The role of the multi-drug resistance 1, p53, b cell lymphoma 2, and bcl 2-associated X genes in the biologic behavior and chemotherapeutic resistance of canine transmissible venereal tumors.

BACKGROUND: Canine transmissible venereal tumors (CTVTs) generally have different cytomorphologic subtypes and phases of progression. Some tumors have variable biologic behavior including a progressive increase in tumor aggressiveness and variable responses to chemotherapy. This behavior is partially due to high p-glycoprotein expression by tumor cells, which leads to the expulsion of chemotherapeutic drugs. Other possible causes include changes in pro- and anti-apoptotic genes from the BCL-2 family and DNA repair systems, which are associated with the p53 gene family. OBJECTIVES: We aimed to determine the relative expression of the multi-drug resistance 1 (MDR1), p53, b-cell lymphoma 2 (BCL2), and bcl 2-associated X (BAX) genes in CTVT before and after therapy and establish a relationship with treatment responses, cytomorphologic patterns, and tumor progression identified with histopathology. METHODS: RT-qPCR was performed on 21 CTVT tumor samples before and after initiating chemotherapy to determine specific gene expression. Normal canine testicular tissue was used as a negative control for all experiments. RESULTS: MDR1 expression was decreased before and after initiating vincristine therapy in CTVT tumor tissues compared with normal canine testicular tissue; p53 and BAX were overexpressed at both time points compared with normal tissue, and no statistical differences were seen between the different morphologic types. However, BAX expression was decreased in the group with quick therapeutic responses but was still overexpressed compared with normal testicular tissue. In the group with the slowest chemotherapeutic responses, BCL2 was overexpressed. CONCLUSION: The findings of this study showed a relative increase in MDR1 gene expression in response to chemotherapy and higher expression in plasmacytoid CTVTs compared with the other cytomorphologic patterns. BCL2 overexpression was related to a favorable prognosis, and p53, BAX, and BCL2 were expressed independent of the cytomorphologic CTVT type. All of the genes were expressed independent of tumor progression, as noted on histopathology.

In vitro and in silico studies reveal capsid-mutant Porcine circovirus 2b with novel cytopathogenic and structural characteristics.

Porcine circovirus 2 (PCV2) is an icosahedral, non-enveloped, and single-stranded circular DNA virus that belongs to the family Circoviridae, genus Circovirus, and is responsible for a complex of different diseases defined as porcine circovirus diseases (PCVDs). These diseases - including postweaning multisystemic wasting syndrome (PMWS), enteric disease, respiratory disease, porcine dermatitis and nephropathy syndrome (PDNS), and reproductive failure - are responsible for large economic losses in the pig industry. After serial passages in swine testicle (ST) cells of a wild-type virus isolated from an animal with PMWS, we identified three PCV2b viruses with capsid protein (known as Cap protein) cumulative mutations, including two novel mutants. The mutant viruses were introduced into new ST cell cultures for reisolation and showed, in comparison to the wild-type PCV2b, remarkable viral replication efficiency (> 1011 DNA copies/ml) and cell death via necrosis, which were clearly related to the accretion of capsid protein mutations. The analysis of a Cap protein/capsid model showed that the mutated residues were located in solvent-accessible positions on the external PCV2b surface. Additionally, the mutated residues were found in linear epitopes and participated in pockets on the capsid surface, indicating that these residues could also be involved in antibody recognition. Taking into account the likely natural emergence of PCV2b variants, it is possible to consider that the results of this work increase knowledge of Circovirus biology and could help to prevent future serious cases of vaccine failure that could lead to heavy losses to the swine industry.