Dysregulation of PI3K/Akt/PTEN Pathway in Canine Mammary Tumor

Immunohistochemical Expression of PTEN in Canine Gliomas

Phosphatase and tensin homolog (PTEN) is a critical tumor suppressor gene with a vital role in regulating cell proliferation, migration, and survival. The loss of PTEN function, either by genetic alterations or decreased protein expression, is frequent in human gliomas and has been correlated with tumor progression, grade, therapeutic resistance, and decreased overall survival in patients with glioma. While different genetic mutations in PTEN gene have been occasionally reported in canine gliomas, no alterations in protein expression have been reported. This study investigates the immunohistochemical expression of PTEN in canine gliomas to evaluate possible alterations, as those reported in human gliomas. Immunohistochemical PTEN expression and pattern distribution were analyzed in 37 spontaneous canine gliomas. Among gliomas, 52.6% cases showed high PTEN expression and 48.6% displayed reduced (13.5%) or highly reduced (35.1%) immunopositivity. Most oligodendrogliomas showed high expression (73.7%), while the majority of astrocytomas (69.2%) showed a reduced or highly reduced expression. A reduced PTEN expression was mostly associated with a heterogeneous loss of PTEN immunopositivity. These observations are in line with those reported in human gliomas and provide a rationale for future studies regarding abnormalities in PTEN expression and PI3K/Akt/mTor pathway in canine gliomas, to evaluate its prognostic and therapeutic implications.

Review: The PI3K-AKT-mTOR signal transduction pathway in canine cancer

Tumors in dogs and humans share many similar molecular and genetic features, incentivizing a better understanding of canine neoplasms not only for the purpose of treating companion animals, but also to facilitate research of spontaneously developing tumors with similar biologic behavior and treatment approaches in an immunologically competent animal model. Multiple tumor types of both species have similar dysregulation of signal transduction through phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB; AKT), and mechanistic target of rapamycin (mTOR), collectively known as the PI3K-AKT-mTOR pathway. This review aims to delineate the pertinent aspects of the PI3K-AKT-mTOR signaling pathway in health and in tumor development. It will then present a synopsis of current understanding of PI3K-AKT-mTOR signaling in important canine cancers and advancements in targeted inhibitors of this pathway.

Homoharringtonine induces apoptosis of mammary carcinoma cells by inhibiting the AKT/mTOR signaling pathway

Mammary tumour is the most common type of tumour in dogs, especially in unneutered female dogs. Homoharringtonine (HHT) is a natural alkaloid that can be used to treat various types of human tumour. However, the inhibitory effect and mechanism of HHT on canine mammary carcinomas (CMC) remain unclear. This study aimed to evaluate the inhibitory effect of HHT on CMC in vitro and determine its underlying molecular mechanism. The effects of HHT on the cytotoxicity of CMC U27 cells were evaluated by the cell counting kit-8, wound healing, and Transwell assays. HHT-induced apoptosis of U27 cells was detected by JC-1 and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay. Moreover, the gene expression of B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) were analysed using quantitative reverse transcription-polymerase chain reaction (RT-qPCR), and the protein expression of protein kinase B/mammalian target of rapamycin (AKT/mTOR) and mitochondrial apoptosis proteins were determined by western blotting. Furthermore, mammary tumour-bearing mouse models were established using 4T1 cells to evaluate the therapeutic effect of HHT. It was found that HHT could significantly down-regulated the protein expression of p-AKT, p-mTOR, and Bcl-2, and up-regulated the protein expression of P53, Bax, cleaved caspase-3, and cleaved caspase-9. In addition, HHT significantly suppressed both tumour volume and mass in mammary tumour mice. In conclusion, HHT damages CMC cells by inhibiting the AKT/mTOR signalling pathway and inducing mitochondrial apoptosis. Such findings lay a theoretical foundation for the clinical treatment of CMC and provide more options for clinical medication.

The role of lymph nodes and their drainage in canine mammary gland tumours: Systematic review

Mammary gland tumours are the most common neoplasms in intact bitches. Over the last decades, veterinary oncology has evolved in detecting and determining the lymph nodes to be removed in these patients for an accurate staging and prognosis, as well as to achieve better disease control and higher overall survival time. Our objective was to describe recent advances related to lymphatic drainage in bitches with mammary gland tumours, focusing on surgery, diagnosis, and prognosis. Through a systematic review using PubMed as the database, a thorough multi-step search reduced 316 studies to 30 for analysis. Vital dyes appear to be crucial in reducing the overall surgery time through transoperative staining of the lymph nodes. Imaging contrasts provide information regarding specific tumour drainage; however, there is still little evidence for their use. The axillary and superficial inguinal lymph nodes are well-established as regional lymph nodes of the cranial and caudal mammary glands. In sequence, accessory axillary, medial iliac, popliteal, and sternal lymph nodes should receive attention if they demonstrate contrast drainage, even considering that the literature has not shown a relationship between drainage and metastasis in these cases. In conclusion, recent studies have provided us with more support in regional lymph node excision regarding the TNM staging system. Studies are highly heterogeneous and method comparisons do not fit due to the non-uniformity of samples, materials, and procedures. We suggest further studies with a larger sample size, complete follow-up of patients, contrast use, and lymph node morphological and immunohistochemical analysis.

Molecular Profile of Canine Hemangiosarcoma and Potential Novel Therapeutic Targets

Canine hemangiosarcoma (HSA) is a relatively common neoplasia, occurring mainly in the skin, spleen, liver and right atrium. Despite the numerous studies investigating the treatment of canine HSA, no significant improvement in survival has been achieved in the last 20 years. Advancements in genetic and molecular profiling presented molecular similarities between canine HSA and human angiosarcoma. It could therefore serve as a valuable model for investigating new and more effective treatments in people and dogs. The most common genetic abnormalities in canine HSA have been found in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and neuroblastoma RAS viral oncogene homolog (NRAS) pathways. Mutations are also found in tumor protein p53 (TP53), phosphatase and tensin homolog (PTEN) and cyclin dependent kinase inhibitor 2A (CDKN2A). Known abnormal protein expression could be exploited to trial new target treatments that could be beneficial for both canine and human patients. Despite the high expression of vascular endothelial growth factor (VEGF) and its receptor (VEGFR), no correlation with overall survival time has ever been found. In this review, we explore the most recent developments in molecular profiling in canine HSA and discuss their possible applications in the prognosis and treatment of this fatal disease.

Protein Expression of PI3K/AKT/mTOR Pathway Targets Validated by Gene Expression and its Correlation with Prognosis in Canine Mammary Cancer

Mammary cancer is the main type of neoplasia in female dogs and is considered an adequate model for the biological and therapeutic study of cancer in women. The PIK3CA/AKT/mTOR pathway plays a central role in cellular homeostasis and is often dysregulated in cancer. The increased expression of PI3K protein in the literature is associated with a poor prognosis, and alterations in the PIK3CA gene can lead to changes in downstream pathways. Thus, the objective of this study was to validate the protein expression to confirm the gene expression of proteins belonging to the main pathway PI3K and PTEN, and their downstream pathways through ZEB1, ZEB2, HIF1A, VHL, CASP3 and PARP1 relating to prognosis in canine mammary cancer. For protein studies, the samples came from 58 female dogs with mammary neoplasia, immunohistochemistry was performed and its analysis by the histoscore method. For the genetic evaluation, the samples came from 13 patients, the DNA was extracted and the analysis for quantitative expression. Through immunohistochemistry, PI3K positivity was significantly associated with affected regional lymph node, distant metastasis, patients with HER2+, Triple Negative and Luminal B phenotypes, and the lowest survival rates. Through gene expression, we observed higher gene expression of ZEB2 and PARP1 both among patients who were alive and who died, which was not true for the expressions of PIK3CA and HIF1A. In conclusion, the data observed in this work are promising in the study of new molecular prognostic markers such as PI3K, ZEB2 and PARP1 for canine mammary cancer.

Molecular Characterization of CF33 Canine Cell Line and Evaluation of Its Ability to Respond against Infective Stressors in Sight of Anticancer Approaches

Simple Summary

Canine mammary cancer is very common and has many similarities with human breast cancer. Risk factors, physiological and pathological behaviors, and the clinical course in dogs are very similar to humans. Several molecular similarities have also been reported, such as overexpression of EGF, proliferation markers, metalloproteinase and cyclooxygenase, TP53 mutations, and CXCR4/SDF1 axis activation. These common characteristics make these breast tumors resistant to conventional therapies. It is therefore necessary to study therapeutic alternatives. Cell lines could be helpful to test in vitro immunomodulant anti-cancer therapies, allowing a reduction of laboratory animals’ involvement in the preliminary tests and achieving results in a shorter time. Although the canine mammary carcinoma cell line CF33 has been widely used in many studies on dog mammary cancer, characterization of its gene expression profile and of the influence of infective stressors of this cell line is poor. Our study shows the interaction of CF33 and Salmonella Typhimurium (ST) as an infective stressor, indicating that these cells may represent an in vitro model for assessing novel therapeutic approaches using bacteria.

Abstract

Spontaneous mammary tumors are the most frequent neoplasms in bitches and show similarities with human breast cancer in risk factors, clinical course, and histopathology. The poor prognosis of some cancer subtypes, both in human and dog, demands more effective therapeutic approaches. A possible strategy is the new anticancer therapy based on immune response modulation through bacteria or their derivatives on canine mammary carcinoma cell lines. The aim of the present study was to analyze the CF33 cell line in terms of basal expression of immune innate genes, CXCR4 expression, and interaction with infectious stressors. Our results highlight that CF33 maintains gene expression parameters typical of mammary cancer, and provides the basal gene expression of CF33, which is characterized by overexpression of CXCR4, CD44, RAD51, LY96, and a non-continuous expression of TP53 and PTEN. No mutations appeared in the CXCR4 gene until the 58th passage; this may represent important information for studying the CXCR4 pathway as a therapeutic target. Moreover, the CF33 cell line was shown to be able to interact with Salmonella Typhimurium (ST) (an infective stressor), indicating that these cells could be used as an in vitro model for developing innovative therapeutic approaches involving bacteria.