Carbon dioxide laser photoablation adjunctive therapy following superficial lamellar keratectomy and bulbar conjunctivectomy for the treatment of corneolimbal squamous cell carcinoma in horses: a review of 24 cases

DNA methylation aging and transcriptomic studies in horses

Cytosine methylation patterns have not yet been thoroughly studied in horses. Here, we profile n = 333 samples from 42 horse tissue types at loci that are highly conserved between mammalian species using a custom array (HorvathMammalMethylChip40). Using the blood and liver tissues from horses, we develop five epigenetic aging clocks: a multi-tissue clock, a blood clock, a liver clock and two dual-species clocks that apply to both horses and humans. In addition, using blood methylation data from three additional equid species (plains zebra, Grevy's zebras and Somali asses), we develop another clock that applies across all equid species. Castration does not significantly impact the epigenetic aging rate of blood or liver samples from horses. Methylation and RNA data from the same tissues define the relationship between methylation and RNA expression across horse tissues. We expect that the multi-tissue atlas will become a valuable resource.

Gigantic Ocular Squamous Cell Carcinoma Mixed With Fibrosarcoma in a Mare: Clinical, Laboratory, Ultrasonography and Histopathology Findings

Ocular neoplasms represent 10% of all equine neoplasms and ocular squamous cell carcinoma (OSCC) is the most common one. This report describes the clinical presentation, laboratory, ultrasonography, postmortem, histopathology and immunohistochemistry findings of a mixed ocular neoplasm in a 10-year-old draft mare. The mare had a one-year history of left ocular mass. Complete destruction of the left eye with loss of vision was observed. A large ulcerated mass oozing blood replaced the left eye. Left parotid lymph node was swollen and had a sinus tract discharging pus. Ultrasonography revealed absence of all intraocular structures, several lobular echogenic tissues and several hyperechoic areas of ossification with acoustic shadowing. Color Doppler scanning revealed numerous neovascularization all over the tumor, particularly along the periphery. The neovascularization demonstrated mainly arterial with few mixed blood flow signals. The amplitude of systolic and diastolic blood flow was markedly increased. Enucleation was decided but the mare died just after examination. The ocular mass was excised and its weight was 390 g. Postmortem examination revealed no distant metastasis in all internal organs. Histopathology confirmed OSCC mixed with fibrosarcoma and associated with cartilaginous and osseous metaplasia. The neoplastic cells gave positive nuclear p53 immunoreactivity. The left parotid lymph node revealed metastasis. Despite the unsuccessful outcome in this particular case, this report documents a mixed eye neoplasm, highlights the ultrasonography and histopathology features of OSCC, and reinforces the need for early diagnosis and surgical treatment in such cases to improve the outcome and to decrease the drastic complications and mortality.

DDB2 Genetic Risk Factor for Ocular Squamous Cell Carcinoma Identified in Three Additional Horse Breeds

Squamous cell carcinoma (SCC) is the most common cancer affecting the equine eye. A missense variant within the gene damage-specific DNA binding protein 2 (DDB2 c.1013C>T, p.Thr338Met) was previously identified as a causal recessive genetic risk factor for the development of ocular SCC within Haflingers, Belgian Draft horses, and Rocky Mountain Horses, but not in the Appaloosa or Arabian breeds. This study aimed to evaluate three cases of ocular SCC in additional breeds and determine if DNA testing for the DDB2 variant in warmblood horses and Connemara ponies is warranted. Histopathology confirmed ocular SCC in all three cases and DNA testing confirmed each horse was homozygous for the DDB2 risk factor. The DDB2 risk allele frequency was estimated to be 0.0043 for Holsteiners (N = 115), 0.014 for Belgian Warmbloods (N = 71), and 0.22 for Connemara Ponies (N = 86). Taken together these data support using DNA testing for DDB2 in Connemara Ponies to assist in mate selection and clinical management. Given the low observed allele frequencies in both the Holsteiner and Belgian Warmblood breeds and that the case under investigation was a warmblood cross-bred, evaluating additional SCC affected warmbloods is warranted to fully determine the importance of DDB2 genotyping as a risk factor in warmblood breeds.

Genetics of Equine Ocular Disease

Horses perform in a variety of disciplines that are visually demanding, and any disease impacting the eye has the potential to threaten vision and thus the utility of the horse. Advances in equine genetics have enabled the understanding of some inherited ocular disorders and ocular manifestations and are enabling cross-species comparisons. Genetic testing for multiple congenital ocular anomalies, congenital stationary night blindness, equine recurrent uveitis, and squamous cell carcinoma can identify horses with or at risk for disease and thus can assist in clinical management and breeding decisions. This article describes the current knowledge of inherited ocular disorders.

Eco-Friendly and Systematic Study for Synthesis of La3+/α-Al2O3 Nanoparticles: Antibacterial Activity Against Pathogenic Microbial Strains

Purpose

In this study, for the first time, new nanoparticles of La³⁺/α-Al₂O₃ were synthesized with the ultrasonic-assisted hydrothermal method in the presence of honey as an eco-friendly and natural reagent.

Methods

The as-synthesized La³⁺/α-Al₂O₃ nanoparticles were characterized using scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray (EDX), UV-visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR) techniques. In this work, we report optimum conditions to synthesize La³⁺/α-Al₂O₃ nanoparticles as novel material and as a candidate for antibacterial activity in antibacterial drugs.

Results and Conclusion

The XRD and SEM micrograph results demonstrate the formation of pure La³⁺/α-Al₂O₃ nanoparticles with a particle size in the range of 30-80 nm. The synthesis parameters were systematically examined using analysis of variance (ANOVA) through 2k^-1 factorial design, and the factors were an assay for product optimization. Various factors such as hydrothermal time, temperature, ultrasound irradiation and interaction between these factors were investigated on the product size of the products. To investigate antibacterial activity of the La³⁺/α-Al₂O₃ nanoparticles with the minimum inhibitory concentration (MIC) method, different dilutions of nanoparticles as 64, 32, 16, 8, 4, 2, 1 and 0.5 μg/mL were dissolved in dimethyl sulfoxide and diluted using distilled water and added to the Mueller-Hinton agar medium containing Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa and Serratia marcescens as gram-negative bacteria and Bacillus subtilis, Staphylococcus aureus, S. epidermidis and Micrococcus luteus as gram-positive bacteria.

Additional Evidence for DDB2 T338M as a Genetic Risk Factor for Ocular Squamous Cell Carcinoma in Horses

Squamous cell carcinoma (SCC) is the most common periocular cancer in horses and the second most common tumor of the horse overall. A missense mutation in damage-specific DNA-binding protein 2 (DDB2, c.1012 C>T, p.Thr338Met) was previously found to be strongly associated with ocular SCC in Haflinger and Belgian horses, explaining 76% of cases across both breeds. To determine if this same variant in DDB2 contributes to risk for ocular SCC in the Arabian, Appaloosa, and Percheron breeds and to determine if the variant contributes to risk for oral or urogenital SCC, histologically confirmed SCC cases were genotyped for the DDB2 variant and associations were investigated. Horses with urogenital SCC that were heterozygous for the DDB2 risk allele were identified in the Appaloosa breed, but a significant association between the DDB2 variant and SCC occurring at any location in this breed was not detected. The risk allele was not identified in Arabians, and no Percherons were homozygous for the risk allele. High-throughput sequencing data from six Haflingers were analyzed to ascertain if any other variant from the previously associated 483 kb locus on ECA12 was more concordant with the SCC phenotype than the DDB2 variant. Sixty polymorphisms were prioritized for evaluation, and no other variant from this locus explained the genetic risk better than the DDB2 allele (P = 3.39 × 10⁻¹⁷, n = 118). These data provide further support of the DDB2 variant contributing to risk for ocular SCC, specifically in the Haflinger and Belgian breeds.

A missense mutation in damage-specific DNA binding protein 2 is a genetic risk factor for ocular squamous cell carcinoma in Belgian horses

BACKGROUND

Belgian horses are commonly affected with ocular squamous cell carcinoma (SCC), the most common cancer of the equine eye. A missense mutation in damage-specific DNA binding protein 2 (DDB2 c.1013C>T, p.Thr338Met) has been established as a recessive genetic risk factor for ocular SCC in the Haflinger breed. A sample of Belgian horses with unknown SCC phenotype was shown to possess this variant at a similar frequency to the Haflinger breed. Retrospective studies indicate that chestnut coat colour may predispose to the development of SCC.

OBJECTIVES

To determine if DDB2 c.1013C>T is a risk factor for ocular SCC in a strictly phenotyped sample of Belgian horses. To investigate associations between coat colour loci genotypes and ocular SCC.

STUDY DESIGN

Retrospective and prospective case identification, genetic investigation.

METHODS

Genomic DNA was isolated from blood, hair or formalin-fixed paraffin-embedded tissue from 25 Belgian horses with histologically confirmed ocular SCC and 18 unaffected Belgian horses. Association testing of 34 single nucleotide variants from 11 genomic loci and genotyping for DDB2 c.1013C>T and coat colour alleles were performed. Exons of DDB2 were sequenced in four cases and two controls. Associations were analysed by Chi-square or Fisher's exact tests and relative risk was calculated.

RESULTS

Homozygosity for DDB2 c.1013C>T was significantly associated with ocular SCC (P = 7.4 × 10^-7 ). Seventy-six per cent of affected horses were homozygous for the variant. Relative risk for homozygous horses developing SCC was 4.0 (P = 1.0 × 10^-4 ). Sequencing DDB2 did not identify a variant more concordant with disease phenotype. An association between disease and coat colour loci was not identified.

MAIN LIMITATIONS

Phenotyping was determined at a single timepoint. Each included horse genotyped as chestnut, so association with this MC1R variant could not be investigated.

CONCLUSIONS

A missense variant, DDB2 c.1013C>T, p.Thr338Met, is a risk factor for ocular SCC in Belgian horses. A genetic risk test is commercially available.

Limbal squamous cell carcinoma in a Rocky Mountain Horse: Case report and investigation of genetic contribution

OBJECTIVE

To document a case of limbal squamous cell carcinoma (SCC) in a Rocky Mountain Horse stallion determined to be homozygous for the genetic risk factor (DDB2 c.1013C>T) strongly associated with the disease in Haflinger and Belgian horses, and to determine the frequency of this allele in a larger population of Rocky Mountain Horses.

ANIMALS STUDIED

One privately owned Rocky Mountain Horse and 84 Rocky Mountain Horses screened for allelic frequency.

PROCEDURES

A complete ophthalmic examination was performed on a Rocky Mountain Horse stallion for assessment of a mass affecting the right eye. A clinical diagnosis of suspected limbal SCC was made, and routine keratoconjunctivectomy and adjunctive strontium irradiation were performed. Genotyping for the DDB2 c.1013C > T (rs1139682898) risk variant was performed utilizing an allele-specific PCR assay on DNA isolated from whole blood and hair follicles.

RESULTS

Histopathology confirmed the limbal mass to be consistent with SCC. The horse was genotyped as homozygous for the DDB2 c.1013C >T risk variant. The frequency of the variant allele among a population of 84 Rocky Mountain Horses was found to be 0.20.

CONCLUSION

The Rocky Mountain Horse breed possesses the DDB2 variant allele determined to be a significant risk factor for ocular SCC in the Haflinger and Belgian breeds. Genotyping additional Rocky Mountain Horses diagnosed with ocular SCC as well as confirmed healthy controls for this variant should be undertaken to determine whether a significant association exists between ocular SCC and the variant in the Rocky Mountain Horse breed.

Periocular Neoplasia in the Horse

Periocular neoplasia is common in horses. Treatment of the periocular skin and ocular adnexal structures can be technically challenging. Common neoplastic conditions, a treatment algorithm, surgical principles, and therapeutic modalities are reviewed. Regardless of the type of neoplasia found or the treatment that is applied, success is most likely when the neoplastic tumor is small.

A missense mutation in damage-specific DNA binding protein 2 is a genetic risk factor for limbal squamous cell carcinoma in horses

Squamous cell carcinoma (SCC) is the most common cancer of the equine eye, frequently originating at the limbus, with the potential to invade the cornea, cause visual impairment, and result in loss of the eye. Several breeds of horses have a high occurrence of limbal SCC implicating a genetic basis for limbal SCC predisposition. Pedigree analysis in the Haflinger breed supports a simple recessive mode of inheritance and a genome-wide association study (N = 23) identified a 1.5 Mb locus on ECA12 significantly associated with limbal SCC (P_corrected = 0.04). Sequencing the most physiologically relevant gene from this locus, damage specific DNA binding protein 2 (DDB2), identified a missense mutation (c.1013 C > T p.Thr338Met) that was strongly associated with limbal SCC (P = 3.41 × 10^-10 ). Genotyping 42 polymorphisms narrowed the ECA12 candidate interval to 483 kb but did not identify another variant that was more strongly associated. DDB2 binds to ultraviolet light damaged DNA and recruits other proteins to perform global genome nucleotide excision repair. Computational modeling predicts this mutation to be deleterious by altering conformation of the β loop involved in photolesion recognition. This DDB2 variant was also detected in two other closely related breeds with reported cases of ocular SCC, the Belgian and the Percheron, suggesting it may also be a SCC risk factor in these breeds. Furthermore, in humans xeroderma pigmentosum complementation group E, a disease characterized by sun sensitivity and increased risk of cutaneous SCC and melanomas, is explained by mutations in DDB2. Cross-species comparison remains to be further evaluated.

Enucleation in equids with and without the use of an orbital suture meshwork implant: a retrospective study of 37 cases

This retrospective study on 37 horses was conducted to assess long-term complications, scarring, cosmetic appearance and owner satisfaction of horses that underwent transpalpebral enucleation with (n=26) or without (n=11) non-absorbable sutured meshwork prosthesis between 2006 and 2013. Postoperative complications related to the surgery were wound infection, discharge and dehiscence, and no significant difference between groups was found. In one horse, the meshwork had to be removed in order to treat a chronic fistula. Horses with infection or inflammation before surgery were more likely to encounter postoperative complications, whether or not a meshwork was used. Most owners were satisfied by the surgical technique for scarring, but contrary to the present hypothesis, most horses with a meshwork implant had a poor sunken-in appearance, and 26 per cent of owners would like to attempt other techniques to improve the cosmetic result. Also, a further 44 per cent of owners would prefer a better cosmetic result if the technique does not increase complication risk or cost. Meshwork implant prosthesis after transpalpebral enucleation was safe. However, in order to achieve a better cosmetic result, further improvements of the technique will be required.

A pulse-dose topical 1% 5-fluorouracil treatment regimen in a young dog with corneal squamous cell carcinoma

PURPOSE

To describe the use of a pulse-dose topical 5-fluorouracil (5-FU) treatment regimen in a Pug dog with corneal squamous cell carcinoma (SCC).

METHODS

A 1-year-old, spayed female Pug was evaluated for a corneal perforation of the right eye, which was surgically stabilized with a conjunctival pedicle graft. At the time of medial canthoplasty 7 weeks later, two areas of gray-white discoloration had developed medial and lateral to the graft. Biopsy samples were obtained via superficial keratectomy while under general anesthesia.

RESULTS

Definitive diagnosis of corneal SCC was made through histopathological examination of the surgical biopsies. Thoracic radiography and submandibular lymph node cytology revealed no evidence of metastatic neoplasia. Following healing of the corneal biopsy sites, topical 1% 5-FU ointment was applied four times daily for four consecutive days once a month, for six treatment cycles. Twenty-three months after diagnosis, the patient remains visual and comfortable with no evidence of SCC recurrence. Long-term therapy with once daily topical 1% cyclosporine solution was used to manage corneal pigmentation bilaterally.

CONCLUSIONS

The pulse-therapy 1% 5-FU protocol was a successful, convenient, and cost-effective adjunctive treatment with few adverse effects.

Management of canine corneal squamous cell carcinoma with lamellar keratectomy and strontium 90 plesiotherapy: 3 cases

PURPOSE

To report three cases of canine corneal squamous cell carcinoma (SCC) treated with strontium 90 beta radiation as an adjunct to surgical excision.

METHODS

Corneal SCC was excised with lamellar keratectomy. This was followed by local application of strontium 90 beta radiation.

RESULTS

Available case follow-up times range from 3 to 50 months. One case suffered a recurrence 5 months following initial excision and strontium 90 treatment.

CONCLUSION AND DISCUSSION

Strontium 90 beta radiation has been used extensively as an adjunctive treatment for equine corneal SCC and in other canine ocular tumors; however, there is a paucity of information regarding use in canine corneal SCC. The cases presented here suggest its use following keratectomy may be helpful in preventing disease recurrence. At the dosage used, severe adverse effects were not observed.

Corneolimbal squamous cell carcinoma with intraocular invasion in two cats

Unilateral corneolimbal squamous cell carcinoma associated with intraocular invasion is described in two unrelated cats. The diagnosis was made on histopathological examination of the enucleated globes in both cases. Findings revealed squamous cell carcinoma infiltrating the limbus, adjacent cornea, and sclera with associated intraocular invasion at the level of the limbus.