Cancerogenic parasites in veterinary medicine: a narrative literature review

Parasite infection is one of the many environmental factors that can significantly contribute to carcinogenesis and is already known to be associated with a variety of malignancies in both human and veterinary medicine. However, the actual number of cancerogenic parasites and their relationship to tumor development is far from being fully understood, especially in veterinary medicine. Thus, the aim of this review is to investigate parasite-related cancers in domestic and wild animals and their burden in veterinary oncology. Spontaneous neoplasia with ascertained or putative parasite etiology in domestic and wild animals will be reviewed, and the multifarious mechanisms of protozoan and metazoan cancer induction will be discussed.

Exploring the link between viruses and cancer in companion animals: a comprehensive and comparative analysis

Currently, it is estimated that 15% of human neoplasms globally are caused by infectious agents, with new evidence emerging continuously. Multiple agents have been implicated in various forms of neoplasia, with viruses as the most frequent. In recent years, investigation on viral mechanisms underlying tumoral transformation in cancer development and progression are in the spotlight, both in human and veterinary oncology. Oncogenic viruses in veterinary medicine are of primary importance not only as original pathogens of pets, but also in the view of pets as models of human malignancies. Hence, this work will provide an overview of the main oncogenic viruses of companion animals, with brief notes of comparative medicine.

A pilot study of chemotherapy combinations in rats: Focus on mammary cancer treatment in female dogs

The use of combined chemotherapy is an essential alternative in treating breast cancer. However, knowledge of the pharmacokinetics of drugs is necessary to obtain maximum efficiency of the protocol and reduce adverse reactions. This study suggests for the first time the effect of the association of carboplatin with ivermectin and carboplatin with cyclophosphamide. This investigation was performed with 36 healthy Wistar rats, divided into four groups: group control, carboplatin (C), carboplatin preceded by ivermectin (C + IV), and carboplatin associated with cyclophosphamide (C + CI). Plasma concentrations quantification was performed using the High-Performance Liquid Chromatographic (HPLC) equipment with an Ultraviolet (UV) detector at eight different time points. Then, the animal was euthanized and necropsied. The bioanalytical method was validated for the two matrices (dogs and rats' plasma), with full validation in female dogs and partial validation in rats, as recommended by the EMA. In both matrices, the method was linear and reproducible. Here, we show the results in female rats' plasma. When comparing the experimental rats' groups (C; C + IV, and C + CI), there is a tendency to increase the bioavailability of carboplatin when used in association, a slight increase for C + IV and more evident to the C + CI group with an AUC rise higher than 2-fold (AUC0-∞ = 2983.61 for C; 4459.06 for C + CI; 7064.68 for C + CI min·mg·mL-1). The blood count, biochemistry profile, and histopathology of the organs revealed only alterations inherent to the metabolic effects of the drugs used. The carboplatin association with ivermectin appeared safe for this pilot group. We believe the carboplatin dose can be maintained without risk to the patient. However, in the carboplatin association with cyclophosphamide, a slight reduction in carboplatin's amount is suggested, seeking to avoid increased effects due to cyclophosphamide. Thus, studies with a more significant number per group must confirm the relevance of this pilot study.

Identification of new candidate biomarkers to support doxorubicin treatments in canine cancer patients

Background

Both human and veterinary cancer chemotherapy are undergoing a paradigm shift from a “one size fits all” approach to more personalized, patient-oriented treatment strategies. Personalized chemotherapy is dependent on the identification and validation of biomarkers that can predict treatment outcome and/or risk of toxicity. Many cytotoxic chemotherapy agents, including doxorubicin, base their mechanism of action by interaction with DNA and disruption of normal cellular processes. We developed a high-resolution/accurate-mass liquid chromatography-mass spectrometry DNA screening approach for monitoring doxorubicin-induced DNA modifications (adducts) in vitro and in vivo. We used, for the first time, a new strategy involving the use of isotope-labeled DNA, which greatly facilitates adduct discovery. The overall goal of this work was to identify doxorubicin-DNA adducts to be used as biomarkers to predict drug efficacy for use in veterinary oncology.

Results

We used our novel mass spectrometry approach to screen for adducts in purified DNA exposed to doxorubicin. This initial in vitro screening identified nine potential doxorubicin-DNA adduct masses, as well as an intense signal corresponding to DNA-intercalated doxorubicin. Two of the adduct masses, together with doxorubicin and its metabolite doxorubicinol, were subsequently detected in vivo in liver DNA extracted from mice exposed to doxorubicin. Finally, the presence of these adducts and analytes was explored in the DNA isolated from dogs undergoing treatment with doxorubicin. The previously identified nine DOX-DNA adducts were not detected in these preliminary three samples collected seven days post-treatment, however intercalated doxorubicin and doxorubicinol were detected.

Conclusions

This work sets the stage for future evaluation of doxorubicin-DNA adducts and doxorubicin-related molecules as candidate biomarkers to personalize chemotherapy protocols for canine cancer patients. It demonstrates our ability to combine in one method the analysis of DNA adducts and DNA-intercalated doxorubicin and doxorubicinol. The last two analytes interestingly, were persistent in samples from canine patients undergoing doxorubicin chemotherapy seven days after treatment. The presence of doxorubicin in all samples suggests a role for it as a promising biomarker for use in veterinary chemotherapy. Future studies will involve the analysis of more samples from canine cancer patients to elucidate optimal timepoints for monitoring intercalated doxorubicin and doxorubicin-DNA adducts and the correlation of these markers with therapy outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03062-x.

What can we learn from cancer of unknown primary in canine oncology?

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic tumors that lack an identifiable primary site despite an extensive diagnostic work-up. It is a well-recognized entity that is characterized by early dissemination, aggressive clinical course, unpredictable metastatic pattern, intrinsic treatment resistance, and a dismal prognosis. Despite the molecular diagnostic workup and personalized therapy, the expected improvements in the diagnosis and treatment of CUP have not been achieved. Comparative oncology has a promising role in the exchange of knowledge and practices between humans and canines. Therefore, we intended to review the literature reporting on CUP in dogs in order to identify some interesting parallels and unique results that could be transposed to in-human research.

Photodynamic therapy for cutaneous hemangiosarcoma in dogs

Cutaneous hemangiosarcoma is a malignant neoplasia that frequently occurs in dogs. The most effective treatment requires wide surgical excision of the tumor. To avoid mutilating surgeries, photodynamic therapy (PDT) could serve as an alternative treatment. This study aimed to treat cutaneous hemangiosarcomas in dogs using PDT with aluminium-chloride-phthalocyanine nanoemulsion (AlClPc-nano) as photosensitizer. Eight dogs with histopathological diagnosis of naturally occurring cutaneous hemangiosarcoma were treated. Animals were given intra and peritumoral injections of AlClPc-nano (13.3 μM). After 15 min, the masses were LED irradiated at a wavelength of 658-662 nm (80 mW potency) for 25 min (120 J/cm² fluency). The number of sessions was based on lesion observations, with PDT sessions repeated every 7 days until the mass was no longer macroscopically visible. On that occasion, an excisional biopsy of the area was taken for histopathology analysis. Blood was collected from each animal before each PDT session and excisional biopsy for hematological analysis (blood counts; liver and kidney function). The number of PDT sessions varied from 2 to 4, depending on the size of the initial mass. Seven of the eight cases demonstrated complete remission of neoplasia. Microscopic analysis of the excisional biopsies showed necrosis and hemorrhage only, with no cancer cells, except in one case. During the treatment, inflammation and necrosis were macroscopically observed in the treated areas. The dogs did not show any alteration in blood parameters that could be related to the PDT. In conclusion, PDT with AlClPc-nano is a safe and effective treatment for cutaneous hemangiosarcoma in dogs.

Current biomarkers of canine mammary tumors

Mammary tumors are the second most common neoplasia in dogs. Due to the high similarity of canine mammary tumors (CMT) to human breast cancers (HBC), human biomarkers of HBC are also detectable in cases of CMT. The evaluation of biomarkers enables clinical diagnoses, treatment options and prognosis for bitches suffering from this disease. The aim of this article is to give a short summary of the biomarkers of CMT based on current literature. Very promising biomarkers are miRNAs, cancer stem cells, and circulating tumor cells, as well as mutations of the breast cancer 1 gene (BRCA1) and breast cancer 2 gene (BRCA2). Until now, the most studied and reliable biomarkers of CMT have remained antigen Ki-67 (Ki-67), endothelial growth factor receptor, human epidermal growth factor receptor 2 (HER-2), estrogen receptor, progesterone receptor and cyclooxygenase 1 (COX-2), which can be detected in both serum and tissue samples using different molecular methods. However, carcinoembryonic antigen and cancer antigen 15-3 (CA 15-3), while poorly studied, seem to be good biomarkers, especially for the early detection and prognosis of CMT. We will also mention the following: proliferative cell nuclear antigen, tumor protein p53 (p53), E-cadherin, vascular endothelial growth factor, microRNAs, cancer stem cells and circulating tumor cells, which can also be useful biomarkers. Although many studies have been conducted so far, the estimation of biomarkers in cases of CMT is still not a common practice, and more detailed research should be done.

Challenges and opportunities for monoclonal antibody therapy in veterinary oncology

Monoclonal antibodies (mAbs) have come to dominate the biologics market in human cancer therapy. Nevertheless, in veterinary medicine, very few clinical trials have been initiated using this form of therapy. Some of the advantages of mAb therapeutics over conventional drugs are high specificity, precise mode of action and long half-life, which favour infrequent dosing of the antibody. Further advancement in the field of biomedical sciences has led to the production of different forms of antibodies, such as single chain antibody fragment, Fab, bi-specific antibodies and drug conjugates for use in diagnostic and therapeutic purposes. This review describes the potential for mAbs in veterinary oncology in supporting both diagnosis and therapy of cancer. The technical and financial hurdles to facilitate clinical acceptance of mAbs are explored and insights into novel technologies and targets that could support more rapid clinical development are offered.

Electroporation in veterinary oncology

Cancer treatments in veterinary medicine continue to evolve beyond the established standard therapies of surgery, chemotherapy and radiation therapy. New technologies in cancer therapy include a targeted mechanism to open the cell membrane based on electroporation, driving therapeutic agents, such as chemotherapy (electro-chemotherapy), for local control of cancer, or delivery of gene-based products (electro-gene therapy), directly into the cancer cell to achieve systemic control. This review examines electrochemotherapy and electro-gene therapy in veterinary medicine and considers future directions and applications.

Inflammation and cancer: till death tears them apart

Advances in biotechnology have enabled the collection of an immeasurable amount of information from genomic, transcriptomic, metabolomic and proteomic studies of tumours within their microenvironments. The dissection of cytokine and chemokine networks has provided new clues to the interactions between cancer cells and their surrounding inflammatory landscape. To bridge the gap between chronic inflammation and cancer, dynamic participants in the tumour microenvironment have been identified, including tumour-associated macrophages (TAMs) and regulatory T cells (Tregs). Both of these cell types are notable for their ability to cause immunosuppressive conditions and support the evasion of tumour immune surveillance. It is clear now that the tumour-promoting inflammatory environment has to be included as one of the major cancer hallmarks. This review explores the recent advances in the understanding of cancer-related inflammation and how this is being applied to comparative oncology studies in humans and domestic species, such as the dog.

Chemotherapy safety in clinical veterinary oncology

Exposure to chemotherapy is a health hazard for all personnel in facilities that store, prepare, or administer antineoplastic agents. Contamination levels have been measured as much as 15 times higher in the veterinary medicine sector than in human facilities. Recent publications in human and veterinary medicine indicate that exposure extends beyond the clinic walls to affect the patient's home and family. This article provides an update on the advances in chemotherapy safety, the current issues, and the impact on cancer management in veterinary medicine.

Immunotherapy in veterinary oncology

Tumor immunology and immunotherapy is one of the most exciting and rapidly expanding fields. The immune system is divided into 2 primary components: the innate immune response and the highly specific, but more slowly developing, adaptive or acquired immune response. Immune responses are separated by whether they are induced by exposure to a foreign antigen (active response) or transferred through serum or lymphocytes from an immunized individual (passive response). The ideal cancer immunotherapy agent should discriminate between cancer and normal cells (specificity), be potent enough to kill small or large numbers of tumor cells (sensitivity), and prevent recurrence of a tumor (durability).