Neurodegenerative Disease Treatment Drug PBT2 Breaks Intrinsic Polymyxin Resistance in Gram-Positive Bacteria.

Gram-positive bacteria do not produce lipopolysaccharide as a cell wall component. As such, the polymyxin class of antibiotics, which exert bactericidal activity against Gram-negative pathogens, are ineffective against Gram-positive bacteria. The safe-for-human-use hydroxyquinoline analog ionophore PBT2 has been previously shown to break polymyxin resistance in Gram-negative bacteria, independent of the lipopolysaccharide modification pathways that confer polymyxin resistance. Here, in combination with zinc, PBT2 was shown to break intrinsic polymyxin resistance in Streptococcus pyogenes (Group A Streptococcus; GAS), Staphylococcus aureus (including methicillin-resistant S. aureus), and vancomycin-resistant Enterococcus faecium. Using the globally disseminated M1T1 GAS strain 5448 as a proof of principle model, colistin in the presence of PBT2 + zinc was shown to be bactericidal in activity. Any resistance that did arise imposed a substantial fitness cost. PBT2 + zinc dysregulated GAS metal ion homeostasis, notably decreasing the cellular manganese content. Using a murine model of wound infection, PBT2 in combination with zinc and colistin proved an efficacious treatment against streptococcal skin infection. These findings provide a foundation from which to investigate the utility of PBT2 and next-generation polymyxin antibiotics for the treatment of Gram-positive bacterial infections.

Increased thyroid malignancy in patients with primary hyperparathyroidism.

BACKGROUND: Multiple studies have reported the increased incidence of thyroid cancer in patients with primary hyperparathyroidism (PHPT). However, the underlying risk factors of concomitant thyroid cancer in patients with PHPT remain unknown. The primary aim of this study was to examine the records of patients with PHPT to identify characteristics that correlated with the presence of coexisting thyroid nodules, and which may have an implication for the prediction of thyroid cancer. METHODS: Medical records of consecutive patients with PHPT (n = 318) were reviewed from January 2010 to September 2020 in two tertiary medical centers in China. Patient clinicopathological and biological data were collected and analyzed. RESULTS: Of a total of 318 patients with PHPT, 105 (33.0%) patients had thyroid nodules and 26 (8.2%) patients were concomitant with thyroid cancer. A total of 38 thyroid nodules taken from 26 patients were pathologically assessed to be well-differentiated papillary thyroid carcinoma (PTC), with 81% being papillary thyroid microcarcinoma (PTMC). In 79% (30/38) of these cancers, thyroid nodules were considered suspicious following preoperative ultrasound. Multinomial logistic regression analysis revealed that female gender was associated with increased risk of thyroid nodules (OR = 2.13, 95% CI: 1.13-3.99, P = 0.019), while lower log-transformed parathyroid hormone levels were an independent predictor of thyroid cancer in patients with PHPT (OR = 0.50, 95% CI: 0.26-0.93, P = 0.028). CONCLUSION: In conclusion, we observed a relatively high prevalence of thyroid cancer in our cohort of Chinese patients with PHPT. Evaluation of thyroid nodules by preoperative ultrasound may be advisable in patients with PHPT, particularly for females and patients with modestly elevated serum parathyroid hormone levels.

Positive Thyroid Peroxidase Antibody and Thyroglobulin Antibody are Associated With Better Clinicopathologic Features of Papillary Thyroid Cancer.

OBJECTIVE: To compare the thyroid autoantibody status of patients with papillary thyroid cancer (PTC) and benign nodular goiter as well as possible associations between thyroid autoantibodies and clinicopathologic features of PTC. METHODS: A total of 3934 participants who underwent thyroidectomy were enrolled in this retrospective study. Patients were divided into PTC and benign nodule groups according to pathological diagnosis. Based on the preoperative serum antibody results, PTC patients were divided into thyroid peroxidase antibody (TPOAb)-positive, thyroglobulin antibody (TgAb)-positive, dual TPOAb- and TgAb-positive, or antibody-negative groups. RESULTS: Of the 3934 enrolled patients, 2926 (74.4%) were diagnosed with PTC. Multivariate regression analyses suggested that high thyroid-stimulating hormone levels (adjusted odds ratio [OR] = 1.732, 95% CI [1.485-2.021], P < .001), positive TgAb (adjusted OR = 1.768, 95% CI [1.436-2.178], P < .001), and positive TPOAb (adjusted OR = 1.452, 95% CI [1.148-1.836], P = .002) were independent risk factors for predicting malignancy of thyroid nodules. Multinomial multiple logistic regression analyses indicated that positive TPOAb alone was an independent predictor of less central lymph node metastasis in PTC patients (adjusted OR = 0.643, 95% CI [0.448-0.923], P = .017), whereas positive TgAb alone was significantly associated with less extrathyroidal extension (adjusted OR = 0.778, 95% CI [0.622-0.974], P = .028). PTC patients with dual-positive TPOAb and TgAb displayed a decreased incidence of extrathyroidal extension (adjusted OR = 0.767, 95% CI [0.623-0.944], P = .012) and central lymph node metastasis (adjusted OR = 0.784, 95% CI [0.624-0.986], P = .037). CONCLUSION: Although preoperative positive TPOAb and TgAb are independent predictive markers for PTC, they are also associated with better clinicopathologic features of PTC.

Vegetation forcing modulates global land monsoon and water resources in a CO2-enriched climate.

The global monsoon is characterised by transitions between pronounced dry and wet seasons, affecting food security for two-thirds of the world's population. Rising atmospheric CO2 influences the terrestrial hydrological cycle through climate-radiative and vegetation-physiological forcings. How these two forcings affect the seasonal intensity and characteristics of monsoonal precipitation and runoff is poorly understood. Here we use four Earth System Models to show that in a CO2-enriched climate, radiative forcing changes drive annual precipitation increases for most monsoon regions. Further, vegetation feedbacks substantially affect annual precipitation in North and South America and Australia monsoon regions. In the dry season, runoff increases over most monsoon regions, due to stomatal closure-driven evapotranspiration reductions and associated atmospheric circulation change. Our results imply that flood risks may amplify in the wet season. However, the lengthening of the monsoon rainfall season and reduced evapotranspiration will shorten the water resources scarcity period for most monsoon regions.

Predicting factors for central or lateral lymph node metastasis in conventional papillary thyroid microcarcinoma.

BACKGROUND: Optimal management for papillary thyroid microcarcinoma (PTMC) remains controversial. The purpose of this study was to explore risk factors predictive of cervical lymph node metastasis in conventional PTMCs. METHODS: Conventional PTMC patients (n = 2,404) undergoing surgery between 2010 and 2017 were grouped and analyzed according to the positivity of cervical lymph node. RESULTS: Central lymph node (CLN) metastases and lateral lymph node (LLN) metastases were observed in 915 (38.1%) and 184 (7.7%) cases, respectively. Multivariate analysis found that male (odds ratio [OR] = 1.974, p < 0.001), younger age (OR = 1.601, p < 0.001), tumor size (OR = 1.935, p < 0.001), extrathyroidal extension (ETE) (OR = 1.647, p < 0.001), multifocality (OR = 1.416, p < 0.001), and intrathyroidal spreading (OR = 3.355, p < 0.001) predicted increased CLN metastasis. In particular, younger age, multifocality, and intrathyroidal spreading were significantly associated with a high number of CLN metastases (n ≥ 5). The presence of CLN metastasis was strongly associated with LLN metastasis (OR = 5.426, p < 0.001). CONCLUSION: Male, younger age, tumor size, ETE, multifocality, and intrathyroidal spreading predict increased CLN metastasis in PTMCs. In patients with suspicious lateral lymphadenopathy, the presence of CLN metastasis is independently associated with LLN metastasis.

Discovery of glycerol phosphate modification on streptococcal rhamnose polysaccharides.

Cell wall glycopolymers on the surface of Gram-positive bacteria are fundamental to bacterial physiology and infection biology. Here we identify gacH, a gene in the Streptococcus pyogenes group A carbohydrate (GAC) biosynthetic cluster, in two independent transposon library screens for its ability to confer resistance to zinc and susceptibility to the bactericidal enzyme human group IIA-secreted phospholipase A2. Subsequent structural and phylogenetic analysis of the GacH extracellular domain revealed that GacH represents an alternative class of glycerol phosphate transferase. We detected the presence of glycerol phosphate in the GAC, as well as the serotype c carbohydrate from Streptococcus mutans, which depended on the presence of the respective gacH homologs. Finally, nuclear magnetic resonance analysis of GAC confirmed that glycerol phosphate is attached to approximately 25% of the GAC N-acetylglucosamine side-chains at the C6 hydroxyl group. This previously unrecognized structural modification impacts host-pathogen interaction and has implications for vaccine design.

Group A Streptococcus co-ordinates manganese import and iron efflux in response to hydrogen peroxide stress.

Bacterial pathogens encounter a variety of adverse physiological conditions during infection, including metal starvation, metal overload and oxidative stress. Here, we demonstrate that group A Streptococcus (GAS) utilises Mn(II) import via MtsABC during conditions of hydrogen peroxide stress to optimally metallate the superoxide dismutase, SodA, with Mn. MtsABC expression is controlled by the DtxR family metalloregulator MtsR, which also regulates the expression of Fe uptake systems in GAS. Our results indicate that the SodA in GAS requires Mn for full activity and has lower activity when it contains Fe. As a consequence, under conditions of hydrogen peroxide stress where Fe is elevated, we observed that the PerR-regulated Fe(II) efflux system PmtA was required to reduce intracellular Fe, thus protecting SodA from becoming mismetallated. Our findings demonstrate the co-ordinate action of MtsR-regulated Mn(II) import by MtsABC and PerR-regulated Fe(II) efflux by PmtA to ensure appropriate Mn(II) metallation of SodA for optimal superoxide dismutase function.

Mammary-specific ablation of Cyp24a1 inhibits development, reduces proliferation and increases sensitivity to vitamin D.

Active vitamin D (1,25(OH)2D) has been shown to regulate numerous cell processes in mammary cells. Degradation of 1,25(OH)2D is initiated by the mitochondrial enzyme, 25-hydroxyvitamin D 24-hydroxylase (CYP24 A1), and provides local control of 1,25(OH)2D bioactivity. Several reports of the association between elevated CYP24 A1 activity and breast cancer incidence, suggest that CYP24 A1 may be a target for therapeutic intervention. Whether CYP24 A1 activity within the mammary epithelium regulates 1,25(OH)2D levels and mammary gland development is yet to shown. We have used a conditional knockout of the Cyp24a1 gene specifically in the mammary epithelium to demonstrate reduced terminal end bud number, ductal outgrowth and branching during puberty and alveologenesis at early pregnancy, by inhibiting proliferation but not apoptosis in both basal and luminal MECs. In vitro study showed increased sensitivity of luminal MECs to lower levels of 1,25(OH)2D with the ablation of Cyp24a1 activity. In summary, Cyp24a1 within MECs plays an important role in modulating postnatal and pregnancy-associated mammary gland development which provides support for inhibiting CYP24 A1 as a potential approach to activating the vitamin D pathway in breast cancer prevention and therapy.

Vitamin D3 signaling and breast cancer: Insights from transgenic mouse models.

The biologically active form of vitamin D3 (1,25(OH)2D) regulates epithelial cell differentiation, proliferation, and apoptosis, lending weight to clinical evidence linking vitamin D3 insufficiency to breast cancer incidence and mortality. Local dysregulation of vitamin D3 metabolism has been identified in patients with breast cancer, implying that disruption of 1,25(OH)2D signaling may contribute to breast cancer development in an autocrine or paracrine manner. Mouse mammary glands express the critical enzymes responsible for 1,25(OH)2D synthesis (Cyp2r1 and Cyp27b1), degradation (Cyp24a1), as well as the vitamin D3 receptor (Vdr), and genetically modified mouse models have revealed a great deal about the role of vitamin D3 in cancer initiation and progression. Ablation of Vdr or Cyp27b1 in murine models of mammary cancer reduces the anti-tumor effects of vitamin D3, while elevation of Cyp24a1 levels increases degradation of 1,25(OH)2D, leading to diminished anti-tumor effects. This review discusses the recent transgenic mouse models of vitamin D3 metabolism and the Vdr signaling network, and how these contribute to mammary gland development, and cancer tumorigenesis and progression. Collectively, these mouse models have helped clarify mechanisms of action of vitamin D3 signaling and suggest that activation or restoration of the vitamin D3 regulated pathway is a potential approach for human breast cancer prevention.

Transition Metal Homeostasis in Streptococcus pyogenes and Streptococcus pneumoniae.

Trace metals such as Fe, Mn, Zn and Cu are essential for various biological functions including proper innate immune function. The host immune system has complicated and coordinated mechanisms in place to either starve and/or overload invading pathogens with various metals to combat the infection. Here, we discuss the roles of Fe, Mn and Zn in terms of nutritional immunity, and also the roles of Cu and Zn in metal overload in relation to the physiology and pathogenesis of two human streptococcal species, Streptococcus pneumoniae and Streptococcus pyogenes. S. pneumoniae is a major human pathogen that is carried asymptomatically in the nasopharynx by up to 70% of the population; however, transition to internal sites can cause a range of diseases such as pneumonia, otitis media, meningitis and bacteraemia. S. pyogenes is a human pathogen responsible for diseases ranging from pharyngitis and impetigo, to severe invasive infections. Both species have overlapping capacity with respect to metal acquisition, export and regulation and how metal homeostasis relates to their virulence and ability to invade and survive within the host. It is becoming more apparent that metals have an important role to play in the control of infection, and with further investigations, it could lead to the potential use of metals in novel antimicrobial therapies.

The PerR-Regulated P1B-4-Type ATPase (PmtA) Acts as a Ferrous Iron Efflux Pump in Streptococcus pyogenes.

Streptococcus pyogenes (group A Streptococcus [GAS]) is an obligate human pathogen responsible for a broad spectrum of human disease. GAS has a requirement for metal homeostasis within the human host and, as such, tightly modulates metal uptake and efflux during infection. Metal acquisition systems are required to combat metal sequestration by the host, while metal efflux systems are essential to protect against metal overload poisoning. Here, we investigated the function of PmtA (PerR-regulated metal transporter A), a P1B-4-type ATPase efflux pump, in invasive GAS M1T1 strain 5448. We reveal that PmtA functions as a ferrous iron [Fe(II)] efflux system. In the presence of high Fe(II) concentrations, the 5448ΔpmtA deletion mutant exhibited diminished growth and accumulated 5-fold-higher levels of intracellular Fe(II) than did the wild type and the complemented mutant. The 5448ΔpmtA deletion mutant also showed enhanced susceptibility to killing by the Fe-dependent antibiotic streptonigrin as well as increased sensitivity to hydrogen peroxide and superoxide. We suggest that the PerR-mediated control of Fe(II) efflux by PmtA is important for bacterial defense against oxidative stress. PmtA represents an exemplar for an Fe(II) efflux system in a host-adapted Gram-positive bacterial pathogen.

New Peptidomimetic Boronates for Selective Inhibition of the Chymotrypsin-like Activity of the 26S Proteasome.

Proteasome is a large proteinase complex that degrades proteins via its three catalytic activities. Among these activities, the "chymotrypsin-like" activity has emerged as the focus of drug discovery in cancer therapy. Here, we report new peptidomimetic boronates that are highly specific for the chymotrypsin-like catalytic activity of the proteasome. These new specific proteasome inhibitors were demonstrated to have higher in vitro potency and selective cytotoxicity for cancer cells compared to benchmark proteasome inhibitors: bortezomib and carfilzomib. In breast cancer cell lines, treatment with 1a or 2a induced accumulation of the high molecular weight polyubiqutinated proteins at similar levels observed for bortezomib and carfilzomib, indicating that cancer cell death caused by 1a/2a is chiefly due to proteasome inhibition.

Comparison of the biological effects of exogenous and endogenous 1,25-dihydroxyvitamin D3 on the mature osteoblast cell line MLO-A5.

Clinical and animal data indicate that serum 25-hydroxyvitamin D3 (25D) exerts an anabolic effect on bone while serum 1α,25-dihydroxyvitamin D3 (1,25D) stimulates bone mineral loss, although the mechanism responsible for these divergent actions is unknown. Biological effects of 25D on bone cells are dependent on the local conversion to 1,25D by the 25-hydroxyvitamin D-1α-hydroxylase enzyme, CYP27B1. Therefore, identification of possible differential activities of locally produced and exogenously supplied 1,25D in bone is likely to be informative for guiding optimal administration of vitamin D supplements for bone health. The mature osteoblastic cell line MLO-A5 expresses both the vitamin D receptor (Vdr) and Cyp27b1, and therefore is a suitable model for comparing the activities of 1,25D arising from these sources. Biologically, exogenous and endogenous sources of 1,25D have similar effects on proliferation, mineralisation and induction of a range of genes by MLO-A5 osteoblasts under osteogenic conditions although endogenous 1,25D levels are markedly lower than exogenous levels. Significant differences of pharmacokinetics and pharmacodynamics of 1,25D are evident between these two sources particularly in terms of modulating gene expression for Cyp24a1 and other genes largely expressed by embedded osteoblasts/osteocytes suggesting that endogenously synthesised 1,25D is more efficiently utilised by the differentiating osteoblast.

Identification of vitamin D3 target genes in human breast cancer tissue.

Multiple epidemiological studies have shown that high vitamin D3 status is strongly associated with improved breast cancer survival. To determine the molecular pathways influenced by 1 alpha, 25-dihydroxyvitamin D3 (1,25D) in breast epithelial cells we isolated RNA from normal human breast and cancer tissues treated with 1,25D in an ex vivo explant system. RNA-Seq revealed 523 genes that were differentially expressed in breast cancer tissues in response to 1,25D treatment, and 127 genes with altered expression in normal breast tissues. GoSeq KEGG pathway analysis revealed 1,25D down-regulated cellular metabolic pathways and enriched pathways involved with intercellular adhesion. The highly 1,25D up-regulated target genes CLMN, SERPINB1, EFTUD1, and KLK6were selected for further analysis and up-regulation by 1,25D was confirmed by qRT-PCR analysis in breast cancer cell lines and in a subset of human clinical samples from normal and cancer breast tissues. Ketoconazole potentiated 1,25D-mediated induction of CLMN, SERPINB1, and KLK6 mRNA through inhibition of 24-hydroxylase (CYP24A1) activity. Elevated expression levels of CLMN, SERPINB1, and KLK6 are associated with prolonged relapse-free survival for breast cancer patients. The major finding of the present study is that exposure of both normal and malignant breast tissue to 1,25D results in changes in cellular adhesion, metabolic pathways and tumor suppressor-like pathways, which support epidemiological data suggesting that adequate vitamin D3 levels may improve breast cancer outcome.

Keratomycosis in five dogs.

Five cases of canine keratomycosis were diagnosed and treated at a private Veterinary Ophthalmology Practice in Melbourne, Australia. Clinical presentations varied between dogs. Predisposing factors were identified in 4 of 5 cases. Diagnostic modalities utilized were corneal cytology and fungal culture. Corneal cytology confirmed the presence of fungal organisms in all five cases. Aspergillus, Scedosporium, and Candida were cultured from three cases, respectively. Specific antifungal treatment included 1% voriconazole solution or 1% itraconazole ointment. Keratectomy and conjunctival grafting surgery was performed in two patients. Resolution of infection and preservation of vision were achieved in 4 of 5 patients.

Diamond burr debridement of 34 canine corneas with presumed corneal calcareous degeneration.

OBJECTIVES: To describe the signalment, presence of systemic and/or ocular comorbidities, times to detected healing and probabilities of recurrence after diamond burr debridement (DBD) of eyes with presumed corneal calcareous degeneration and secondary ulceration and/or ocular pain. ANIMALS STUDIED: Twenty-six dogs with 42 eyes affected, 34 eyes treated with DBD. METHODS: A case series was conducted using medical records from a private veterinary ophthalmology referral practice. Dogs were included if they had white or gray corneal opacity consistent with corneal calcareous degeneration with either erosive or superficial ulceration and/or ocular pain in at least one eye and had at least one such eye treated with DBD. DBD was performed with a battery-operated handheld motorized burr (The Alger Company, Inc. Lago Vista, TX, USA), and a bandage contact lens was placed in the majority of eyes (30/34). Eyes were considered healed when the cornea was fluorescein negative, and there were no signs of ocular pain. Patient data (signalment, recurrence) were extracted from medical records. RESULTS: Dogs were first re-examined 7-62 days after treatment (median: 13 days). All DBD-treated eyes healed within 62 days (% healed: 100%; one-sided 97.5% CI: 90-100%, median: 14 days), 82% of eyes (28/34) were healed at first re-examination (median: 13 days after treatment), and all were healed by their second examination (median: 24 days). Of the 34 treated eyes, 11 were lost to follow up; 11 of the remaining 23 eyes recurred. Estimated 1-year recurrence probability was 58% (95% CI: 35-83%). Seven dogs had systemic disease; 7 had a history of prior ocular disease or intraocular surgery. CONCLUSIONS: Diamond burr debridement is a safe and effective treatment for rapid resolution of superficial corneal ulceration and ocular pain secondary to presumed corneal calcareous degeneration in dogs.

1,25-Dihydroxyvitamin D3 and extracellular calcium promote mineral deposition via NPP1 activity in a mature osteoblast cell line MLO-A5.

While vitamin D supplementation is common, the anabolic mechanisms that improve bone status are poorly understood. Under standard mineralising conditions including media ionised calcium of 1.1 mM, 1,25-dihydroxyvitamin D3 (1,25D) enhanced differentiation and mineral deposition by the mature osteoblast/pre-osteocyte cell line, MLO-A5. This effect was markedly increased with a higher ionised calcium level (1.5 mM). Gene expression analyses revealed that 1,25D-induced mineral deposition was associated with induction of Enpp1 mRNA, coding for nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) and NPP1 protein levels. Since MLO-A5 cells express abundant alkaline phosphatase that was not further modified by 1,25D treatment or exposure to increased calcium, this finding suggested that the NPP1 production of pyrophosphate (PPi) may provide alkaline phosphatase with substrate for the generation of inorganic phosphate (Pi). Consistent with this, co-treatment with Enpp1 siRNA or a NPP1 inhibitor, PPADS, abrogated 1,25D-induced mineral deposition. These data demonstrate that 1,25D stimulates osteoblast differentiation and mineral deposition, and interacts with the extracellular calcium concentration. 1,25D regulates Enpp1 expression, which presumably, in the context of adequate tissue non-specific alkaline phosphatase activity, provides Pi to stimulate mineralisation. Our findings suggest a mechanism by which vitamin D with adequate dietary calcium can improve bone mineral status.

Manganese homeostasis in group A Streptococcus is critical for resistance to oxidative stress and virulence.

UNLABELLED: Streptococcus pyogenes (group A Streptococcus [GAS]) is an obligate human pathogen responsible for a spectrum of human disease states. Metallobiology of human pathogens is revealing the fundamental role of metals in both nutritional immunity leading to pathogen starvation and metal poisoning of pathogens by innate immune cells. Spy0980 (MntE) is a paralog of the GAS zinc efflux pump CzcD. Through use of an isogenic mntE deletion mutant in the GAS serotype M1T1 strain 5448, we have elucidated that MntE is a manganese-specific efflux pump required for GAS virulence. The 5448ΔmntE mutant had significantly lower survival following infection of human neutrophils than did the 5448 wild type and the complemented mutant (5448ΔmntE::mntE). Manganese homeostasis may provide protection against oxidative stress, explaining the observed ex vivo reduction in virulence. In the presence of manganese and hydrogen peroxide, 5448ΔmntE mutant exhibits significantly lower survival than wild-type 5448 and the complemented mutant. We hypothesize that MntE, by maintaining homeostatic control of cytoplasmic manganese, ensures that the peroxide response repressor PerR is optimally poised to respond to hydrogen peroxide stress. Creation of a 5448ΔmntE-ΔperR double mutant rescued the oxidative stress resistance of the double mutant to wild-type levels in the presence of manganese and hydrogen peroxide. This work elucidates the mechanism for manganese toxicity within GAS and the crucial role of manganese homeostasis in maintaining GAS virulence. IMPORTANCE: Manganese is traditionally viewed as a beneficial metal ion to bacteria, and it is also established that most bacteria can tolerate high concentrations of this transition metal. In this work, we show that in group A Streptococcus, mutation of the mntE locus, which encodes a transport protein of the cation diffusion facilitator (CDF) family, results in accumulation of manganese and sensitivity to this transition metal ion. The toxicity of manganese is indirect and is the result of a failure of the PerR regulator to respond to oxidative stress in the presence of high intracellular manganese concentrations. These results highlight the importance of MntE in manganese homeostasis and maintenance of an optimal manganese/iron ratio in GAS and the impact of manganese on resistance to oxidative stress and virulence.

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.