Veterinary oncologists and pet owners differ in their perceptions of chemotherapy-related adverse events in cancer-bearing dogs

OBJECTIVE

Chemotherapy is widely used in veterinary oncology but carries real and perceived risks of adverse events (AEs). Human cancer patients perceive AEs from chemotherapy as more severe than do their attending physicians. It is currently unknown whether this discrepancy exists in veterinary oncology. This survey study's aim was to assess differences in the ways that pet owners and veterinary oncologists perceive chemotherapy-related AEs. We hypothesized that veterinary oncologists would accept higher grade AEs and tolerate a greater risk of AEs of any grade than pet owners.

SAMPLE

152 pet owners and 111 veterinary oncologists.

METHODS

Separate surveys were derived for pet owners and veterinary oncologists. Respondents were asked to define maximally acceptable AE scores and risks of AEs given 3 hypothetical outcomes of treatment: (1) cure, (2) extension of life, and (3) improved quality of life. Statistical tests were used to compare responses between groups.

RESULTS

Veterinary oncologists accepted higher grade AEs if the hypothetical goal of chemotherapy was cancer cure (P = .003) or extension of life (P = .026), but owners accepted higher grade AEs if the goal of chemotherapy was to improve quality of life (P = .002). Owners accepted greater risk of moderate (P < .0001) or serious (P < .0001) AEs across the 3 treatment outcomes.

CLINICAL RELEVANCE

This was the first study to assess how pet owners and veterinary oncologists differ in their perception of chemotherapy-related AEs. These initial results may help to frame discussions with pet owners on the expectations of chemotherapy.

Marked paraneoplastic basophilia in a cat with alimentary T-cell lymphoma

An 8-year-old, spayed female domestic shorthair cat was presented for acute weight loss, hyporexia, intermittent vomiting, and loose stools. A caudal abdominal mass and thickened intestinal loops were palpated on initial examination. An abdominal ultrasound identified a circumferential intramural jejunal mass with complete loss of wall layering, diffuse thickening of the jejunal muscularis, and jejunal and ileocecal lymphadenomegaly. Initial routine bloodwork revealed mild monocytosis and minimal lymphopenia with reactive lymphocytes. Cytologic evaluation of the jejunal mass and enlarged lymph nodes was consistent with lymphoma (intermediate cell size), and PCR for antigen receptor rearrangement revealed a clonal T-cell receptor rearrangement consistent with T-cell lymphoma. Chemotherapy (CHOP protocol) was initiated, but despite initial improvement of clinical signs, a repeat ultrasound examination 5 weeks after initiation of treatment revealed no improvement in the lymphadenomegaly or reduction in the size of the jejunal mass. At this visit, the cat also developed a marked basophilia (basophils 12.28 × 103 /μL, RI 0.00-0.10) with low numbers of circulating atypical lymphocytes; no concurrent eosinophilia was noted. Heartworm disease, ectoparasites, and allergic diseases were evaluated for and considered unlikely. The chemotherapy protocol was changed to L-asparaginase, followed by lomustine. The basophilia was significantly reduced 2 days after the initial dose of L-asparaginase and remained within the reference interval for 40 days before an eventual decline in the cat's health. To the authors' knowledge, this is the first report of paraneoplastic basophilia without concurrent eosinophilia in a cat with T-cell lymphoma.

Self-paced acceptance and commitment training reduces burden transfer, stress, and burnout in veterinary healthcare teams

OBJECTIVE

An acceptance and commitment training (ACT) educational program targeting reaction to difficult client interactions recently demonstrated efficacy in reducing burden transfer, stress, and burnout in veterinary healthcare teams. The current noninferiority trial compared effectiveness of the original program with a self-paced version.

SAMPLE

Employees of 2 corporate veterinary groups were randomized to live (n = 128) or self-paced (124) conditions. The workshop and assessments were completed by 137 (55 live and 82 self-paced).

PROCEDURES

Asynchronous modules containing the same content as the original program were placed on in-house veterinary clinic learning systems. Participants of this parallel arms trial completed pretest measures of burden transfer, stress, and burnout. Following assessment, the 3-week ACT program was delivered via videoconferencing (live) or asynchronous modules (self-paced). At post-test and 1-month follow-up, measures were repeated, with added assessment of knowledge, helpfulness ratings, and usage of techniques. A subset (n = 33) of participants repeated measures 9 to 12 months as an extended follow-up.

RESULTS

Program helpfulness was rated more highly by live versus self-paced participants. Self-paced showed better program retention. No differences in knowledge or use of program techniques (> 5 times daily) emerged. Relative to pretest, both conditions showed reduced burden transfer, stress, and burnout at post-test and follow-up; no differences by condition emerged. Participants completing extended follow-up maintained improvement from baseline.

CLINICAL RELEVANCE

Findings suggest a learning system-based version of this program can improve occupational distress in veterinary healthcare teams, with gains maintained over time. The flexibility of this format promotes program completion and allows broader dissemination.

Validation of the Burden Transfer Inventory‐abbreviated and examination across veterinary medicine positions and settings in the United States

Background

Burden transfer, when veterinary client caregiver burden underlies stressful encounters with providers, elevates risk for occupational distress in veterinary medicine. To date, burden transfer has been primarily examined in veterinarians working in general practice, using methods that are time consuming. The current work validates an abbreviated Burden Transfer Inventory (BTI‐A) and explores burden transfer across positions of employment and veterinary settings.

Methods

Participants completed online measures of burden transfer, stress and burnout. A BTI‐A with items representing each BTI domain was created with an initial validation sample (n = 1151 veterinarians). Confirmatory psychometric analyses were conducted in a cross‐validation sample (n = 440 veterinarians and support staff), followed by exploration of the BTI and BTI‐A across veterinary settings and position of employment.

Results

The BTI‐A correlated with the full‐length BTI (r = 0.89–0.96) shows good internal consistency (α = 0.72–0.88) and 1‐month test–retest reliability (r = 0.69–0.74). The BTI‐A correlated significantly (p < 0.001) with stress and burnout. Exploratory comparisons suggested group differences including greater reactivity in general compared to specialty referral/emergency practice (p = 0.02).

Conclusion

The BTI‐A can be used in place of the original measure when brevity is important. Use of the BTI‐A may help guide allied mental health professionals in providing support for wellbeing in veterinary healthcare team members.

Identification of a naturally-occurring canine model for early detection and intervention research in high grade urothelial carcinoma

BACKGROUND

Early detection and intervention research is expected to improve the outcomes for patients with high grade muscle invasive urothelial carcinoma (InvUC). With limited patients in suitable high-risk study cohorts, relevant animal model research is critical. Experimental animal models often fail to adequately represent human cancer. The purpose of this study was to determine the suitability of dogs with high breed-associated risk for naturally-occurring InvUC to serve as relevant models for early detection and intervention research. The feasibility of screening and early intervention, and similarities and differences between canine and human tumors, and early and later canine tumors were determined.

METHODS

STs (n=120) ≥ 6 years old with no outward evidence of urinary disease were screened at 6-month intervals for 3 years with physical exam, ultrasonography, and urinalysis with sediment exam. Cystoscopic biopsy was performed in dogs with positive screening tests. The pathological, clinical, and molecular characteristics of the "early" cancer detected by screening were determined. Transcriptomic signatures were compared between the early tumors and published findings in human InvUC, and to more advanced "later" canine tumors from STs who had the typical presentation of hematuria and urinary dysfunction. An early intervention trial of an oral cyclooxygenase inhibitor, deracoxib, was conducted in dogs with cancer detected through screening.

RESULTS

Biopsy-confirmed bladder cancer was detected in 32 (27%) of 120 STs including InvUC (n=29, three starting as dysplasia), grade 1 noninvasive cancer (n=2), and carcinoma in situ (n=1). Transcriptomic signatures including druggable targets such as EGFR and the PI3K-AKT-mTOR pathway, were very similar between canine and human InvUC, especially within luminal and basal molecular subtypes. Marked transcriptomic differences were noted between early and later canine tumors, particularly within luminal subtype tumors. The deracoxib remission rate (42% CR+PR) compared very favorably to that with single-agent cyclooxygenase inhibitors in more advanced canine InvUC (17-25%), supporting the value of early intervention.

CONCLUSIONS

The study defined a novel naturally-occurring animal model to complement experimental models for early detection and intervention research in InvUC. Research incorporating the canine model is expected to lead to improved outcomes for humans, as well as pet dogs, facing bladder cancer.

Reducing occupational distress in veterinary medicine personnel with acceptance and commitment training: a pilot study

AIMS

To determine whether an educational programme targeting the reaction of veterinary personnel to difficult client interactions reduced burden transfer, stress and burnout in veterinary staff.

METHODS

Employees of three small-animal veterinary hospitals in the south-western United States of America were recruited and randomised to intervention (educational programme; n = 16) or control (no intervention; n = 18) groups. Participants of this randomised, parallel arms trial completed pre-programme assessment including the Burden Transfer Inventory (BTI), Perceived Stress Scale, and Copenhagen Burnout Inventory. Assessment was followed by two, group-format educational sessions, based on acceptance and commitment training, tailored to reducing reactivity to difficult veterinary client interactions (intervention group only). After training was completed, both groups were assessed using the same measures and the intervention participants provided use and acceptability ratings.

RESULTS

Intervention participants rated the programme as useful and appropriate, and reported that programme techniques were used a median of 43 (min 9, max 68) times during the 2 weeks prior to retesting. Relative to pre-programme scores, median post-programme scores for reaction (subscore of BTI) to difficult client interactions decreased in the intervention group (33 vs. 54; p = 0.047), but not in the control group (51 vs. 59; p = 0.210). Changes in median scores for stress and burnout from pre- to post-programme were non-significant for both groups.

CONCLUSIONS

This pilot and feasibility trial showed high rates of acceptability and use by participants, as well as promising reductions in burden transfer. A larger scale clinical trial with follow-up at extended time points is needed to more fully examine the efficacy of this novel programme.

CLINICAL RELEVANCE

Preliminary findings suggest this programme may be a useful approach to reducing occupational distress for individuals working in veterinary practice.

Atypical multiple myeloma in 3 young dogs

Three dogs under 12 months old were diagnosed with atypical multiple myeloma (MM), having an aggressive multifocal anaplastic round cell sarcoma in bone marrow, viscera, and/or peripheral blood, which were confirmed by cytology and immunohistochemistry to be of plasma cell origin. The intramedullary sarcomas caused myelophthisis, osteolysis, and hypercalcemia. Complete or free light chain monoclonal gammopathy in the serum and/or urine was demonstrated by protein electrophoresis and immunofixation. The polymerase chain reaction for antigen receptor rearrangement assay performed on 2 cases identified a clonally rearranged immunoglobulin gene. Neoplastic cells lacked expression of CD45, CD3, CD18, CD21, CD34, and MHCII by flow cytometry. Immunohistochemistry revealed MUM1 immunoreactivity of the neoplastic cells. Combining all data, the diagnosis was MM. An aggressive form of MM in young dogs should be a differential diagnosis for patients with an immunoglobulin-productive, B cell-clonal, CD45-negative, MUM1-positive discrete cell neoplasm arising from the bone marrow.

Ultrasonographic detection of apex nodules in the urinary bladder of Scottish Terriers

An apex nodule was recently identified in the urinary bladder of Scottish Terriers being screened for bladder cancer at our institution. This prospective, single-center, case series study was performed to better characterize the apex nodule and assess the clinical importance of the nodule. Scottish Terriers ≥6 years of age with no evidence of urinary tract disease underwent urinary tract ultrasonography and urinalysis at 6-month intervals. In dogs with evidence of the apex nodule, ultrasound features such as location, margins, number, echogenicity, size, and shape of the lesion were recorded by a veterinary oncologist and veterinary radiologist. The apex nodule was identified in eight (6%) of 134 dogs in the absence of other detectable bladder disease. Features of the nodules included the following: one nodule per dog, triangular to an oval shape, smooth mucosal covering, well-defined margins, isoechoic to the bladder wall, 2-4 mm at the base, and 4-6 mm protruding into the bladder lumen. In five dogs undergoing multiple ultrasonographic examinations, the nodule did not appear to change over time (up to 3.5 years). Cystoscopy performed in three dogs revealed a column of tissue covered by normal mucosa protruding into the bladder lumen. Histological features consistent with a neoplastic growth were absent. Five dogs remained free of any bladder disease. Three dogs developed urothelial carcinoma at sites distant to the nodule at 8-53 months after the nodule was first observed. Findings indicated that incidental apex nodules could mimic neoplasia and other bladder diseases in Scottish Terriers.

Basal and Luminal Molecular Subtypes in Naturally-Occurring Canine Urothelial Carcinoma are Associated with Tumor Immune Signatures and Dog Breed

BACKGROUND: Improved therapies are needed for patients with invasive urothelial carcinoma (InvUC). Tailoring treatment to molecular subtypes holds promise, but requires further study, including studies in pre-clinical animal models. Naturally-occurring canine InvUC harbors luminal and basal subtypes, mimicking those observed in humans, and could offer a relevant model for the disease in people. OBJECTIVE: To further validate the canine InvUC model, clinical and tumor characteristics associated with luminal and basal subtypes in dogs were determined, with comparison to findings from humans. METHODS: RNA sequencing (RNA-seq) analyses were performed on 56 canine InvUC tissues and bladder mucosa from four normal dogs. Data were aligned to CanFam 3.1, and differentially expressed genes identified. Data were interrogated with panels of genes defining luminal and basal subtypes, immune signatures, and other tumor features. Subject and tumor characteristics, and outcome data were obtained from medical records. RESULTS: Twenty-nine tumors were classified as luminal and 27 tumors as basal subtype. Basal tumors were strongly associated with immune infiltration (OR 52.22, 95%CI 4.68–582.38, P = 0.001) and cancer progression signatures in RNA-seq analyses, more advanced clinical stage, and earlier onset of distant metastases in exploratory analyses (P = 0.0113). Luminal tumors were strongly associated with breeds at high risk for InvUC (OR 0.06, 95%CI 0.01 –0.37, P = 0.002), non-immune infiltrative signatures, and less advanced clinical stage. CONCLUSIONS: Dogs with InvUC could provide a valuable model for testing new treatment strategies in the context of molecular subtype and immune status, and the search for germline variants impacting InvUC onset and subtype.

Phase I/II Trial of Vemurafenib in Dogs with Naturally Occurring, BRAF-mutated Urothelial Carcinoma

BRAF-targeted therapies including vemurafenib (Zelboraf) induce dramatic cancer remission; however, drug resistance commonly emerges. The purpose was to characterize a naturally occurring canine cancer model harboring complex features of human cancer, to complement experimental models to improve BRAF-targeted therapy. A phase I/II clinical trial of vemurafenib was performed in pet dogs with naturally occurring invasive urothelial carcinoma (InvUC) harboring the canine homologue of human BRAF ^V600E The safety, MTD, pharmacokinetics, and antitumor activity were determined. Changes in signaling and immune gene expression were assessed by RNA sequencing and phosphoproteomic analyses of cystoscopic biopsies obtained before and during treatment, and at progression. The vemurafenib MTD was 37.5 mg/kg twice daily. Anorexia was the most common adverse event. At the MTD, partial remission occurred in 9 of 24 dogs (38%), with a median progression-free interval of 181 days (range, 53-608 days). In 18% of the dogs, new cutaneous squamous cell carcinoma and papillomas occurred, a known pharmacodynamic effect of vemurafenib in humans. Upregulation of genes in the classical and alternative MAPK-related pathways occurred in subsets of dogs at cancer progression. The most consistent transcriptomic changes were the increase in patterns of T lymphocyte infiltration during the first month of vemurafenib, and of immune failure accompanying cancer progression. In conclusion, the safety, antitumor activity, and cutaneous pharmacodynamic effects of vemurafenib, and the development of drug resistance in dogs closely mimic those reported in humans. This suggests BRAF-mutated canine InvUC offers an important complementary animal model to improve BRAF-targeted therapies in humans.

A prospective, randomized, placebo-controlled, double-blinded clinical trial comparing the incidence and severity of gastrointestinal adverse events in dogs with cancer treated with piroxicam alone or in combination with omeprazole or famotidine

OBJECTIVE

To assess the impact of prophylactic omeprazole and famotidine on the incidence and severity of gastrointestinal (GI) adverse events (AEs) in dogs with cancer treated with single agent piroxicam.

ANIMALS

39 dogs with a cytologic or histologic diagnosis of cancer with no history of GI disease and received piroxicam.

PROCEDURES

A prospective, randomized, placebo-controlled, double-blinded clinical trial was performed. All dogs received piroxicam (0.3 mg/kg [0.14 mg/lb], PO, q 24 h) and either omeprazole (1 mg/kg [0.45 mg/lb], PO, q 12 h), famotidine (1 mg/kg, PO, q 12 h), or placebo (lactose; PO, q 12 h). Monthly assessments of GI AEs were performed and scored by using the Veterinary Comparative Oncology Group's Common Terminology Criteria for Adverse Events (version 1.1).

RESULTS

Compared with dogs in the placebo group, more dogs in the omeprazole group (84.6% vs 36.4%) and famotidine group (80.0% vs 36.4%) experienced GI AEs by day 56. The severity of GI AEs was higher in the omeprazole group, compared with the placebo group.

CONCLUSIONS AND CLINICAL RELEVANCE

Omeprazole was not helpful in reducing the frequency or severity of GI AEs and was associated with more frequent and severer GI AEs in dogs with cancer treated with single agent piroxicam. Proton-pump inhibitors and H2-receptor antagonists should not be prescribed as prophylaxis with NSAIDs for dogs with cancer.

Anal sacculiths may be an incidental finding in dogs

Mineral-attenuating material is occasionally seen in the anal sacs of dogs during abdominal CT studies. This retrospective, descriptive study was performed to estimate the prevalence and CT appearance of this mineral-attenuating material. A total of 357 abdominal CTs were reviewed retrospectively. The mineral-attenuating material was most easily identifiable using the brain window setting (window width: 120 HU; window level: 40 HU). In the current study, the prevalence of mineral-attenuating material in the anal sacs was 7.6% (95% confidence interval, 5.0-10.8%) with 48.1% bilateral involvement and equal distribution in the right and left in dogs with unilateral involvement. Successful collection and material analysis were performed in three dogs. The material was determined to be 100% dried blood, 100% waxy matter, and a "small amount of fat enmeshed in unidentified noncrystallined material." Given the CT appearance and the Hounsfield unit of these mineral-attenuating material within the anal sacs, the term "anal sacculiths" is proposed. All dogs with anal sacculiths within this study population did not have any reported disease of the anal sacs.

Early caregiver burden in owners of pets with suspected cancer: Owner psychosocial outcomes, communication behavior, and treatment factors

BACKGROUND

Owners of companion animals with serious illnesses are likely to experience "caregiver burden." This topic has not been fully evaluated in veterinary oncology.

OBJECTIVES

To examine owners of a dog or cat with suspected cancer for relationships between early caregiver burden and (a) psychosocial factors: depression, stress, and quality of life; (b) owner communication behavior; and (c) specific pet treatment plan factors.

ANIMALS

None.

METHODS

This cross-sectional, observational study recruited 164 owners of a cat or dog presenting for evaluation by a veterinary oncology service at a single referral institution. Measures of caregiver burden, psychosocial function, treatment plan elements, and demographics were collected online via owner self-report. Medical records were reviewed to identify factors including diagnosis, medications, treatment schedules, and owner communications.

RESULTS

Caregiver burden correlated with higher stress (r_s = 0.40, P < .001), greater symptoms of depression (r_s = 0.50, P < .001), and lower quality of life (r_s = 0.39, P < .001). Pet treatment plan factors related to caregiver burden included changes in care routines, perception that compliance with new routines was challenging, and difficulty adhering to medication routines. There was low correlation between caregiver burden and owner-driven communications (r_s = 0.15, P = .07).

CONCLUSIONS AND CLINICAL IMPORTANCE

Findings suggest caregiver burden is similar in owners of pets with cancer and owners of pets with other diseases. Caregiver burden is present in the earliest stages of disease. Major correlates of burden including life-disruptive treatments and schedules provide key areas for potential intervention by veterinary teams.

Naturally-Occurring Invasive Urothelial Carcinoma in Dogs, a Unique Model to Drive Advances in Managing Muscle Invasive Bladder Cancer in Humans

There is a great need to improve the outlook for people facing urinary bladder cancer, especially for patients with invasive urothelial carcinoma (InvUC) which is lethal in 50% of cases. Improved outcomes for patients with InvUC could come from advances on several fronts including emerging immunotherapies, targeted therapies, and new drug combinations; selection of patients most likely to respond to a given treatment based on molecular subtypes, immune signatures, and other characteristics; and prevention, early detection, and early intervention. Progress on all of these fronts will require clinically relevant animal models for translational research. The animal model(s) should possess key features that drive success or failure of cancer drugs in humans including tumor heterogeneity, genetic-epigenetic crosstalk, immune cell responsiveness, invasive and metastatic behavior, and molecular subtypes (e.g., luminal, basal). Experimental animal models, while essential in bladder cancer research, do not possess these collective features to accurately predict outcomes in humans. These key features, however, are present in naturally-occurring InvUC in pet dogs. Canine InvUC closely mimics muscle-invasive bladder cancer in humans in cellular and molecular features, molecular subtypes, immune response patterns, biological behavior (sites and frequency of metastasis), and response to therapy. Thus, dogs can offer a highly relevant animal model to complement other models in research for new therapies for bladder cancer. Clinical treatment trials in pet dogs with InvUC are considered a win-win-win scenario; the individual dog benefits from effective treatment, the results are expected to help other dogs, and the findings are expected to translate to better treatment outcomes in humans. In addition, the high breed-associated risk for InvUC in dogs (e.g., 20-fold increased risk in Scottish Terriers) offers an unparalleled opportunity to test new strategies in primary prevention, early detection, and early intervention. This review will provide an overview of canine InvUC, summarize the similarities (and differences) between canine and human InvUC, and provide evidence for the expanding value of this canine model in bladder cancer research.

Occult tonsillar squamous cell carcinoma in 2 dogs presenting for treatment of primary oral squamous cell carcinoma

Canine non-tonsillar oral squamous cell carcinoma (OSCC) is generally regarded as locally invasive with low rates of metastasis. Two cases of canine non-tonsillar OSCC with occult tonsillar squamous cell carcinoma (TSCC) detected with tonsillar biopsies are reported. Tonsillar biopsies and detection of occult TSCC changed the therapeutic plan and may have contributed to long-term tumor control.

Ultrasonographic features of colonic B-cell lymphoma with mesenteric lymphomatosis in a cat

A 10-year-old male neutered Domestic Shorthair cat was referred for chronic inappetence, weight loss, and hematochezia and an abdominal mass. Abdominal ultrasonography revealed a heterogeneously hypoechoic transmural colonic mass, which extended beyond the serosa and into the adjacent mesentery. Cytology and clonality assays of fine needle aspirates of the mass and mesenteric nodules yielded a diagnosis of B-cell lymphoma. Colonic lymphoma with mesenteric involvement can have a similar appearance to carcinomatosis, therefore a definitive diagnosis requires sampling and further testing of the mesenteric lesions.

A Nonselective Cyclooxygenase Inhibitor Enhances the Activity of Vinblastine in a Naturally-Occurring Canine Model of Invasive Urothelial Carcinoma

Background: Chemotherapy is expected to remain an important part of invasive urothelial carcinoma (UC) treatment. Strategies to enhance chemotherapy efficacy are needed.

Objective: To determine the chemotherapy-enhancing effects of a nonselective cyclooxygenase (COX) inhibitor on vinblastine in a naturally-occurring canine model of invasive UC.

Methods: With IACUC approval, privately-owned dogs with naturally-occurring histologically-diagnosed invasive UC, expected survival ≥6 weeks, and informed owner consent were randomly allocated to receive vinblastine (2.5 mg/m² intravenously every 2 weeks) plus piroxicam (0.3 mg/kg daily per os) or vinblastine alone (same dose) with the option to receive piroxicam alone when vinblastine failed. Scheduled evaluations included physical exam, standard laboratory analyses, thoracic radiography, abdominal ultrasonography, and standardized measurement of urinary tract tumors.

Results: Dogs receiving vinblastine alone (n = 27) and vinblastine-piroxicam (n = 24) were similar in age, sex, breed, tumor stage, and grade. Remission occurred more frequently (P <  0.02) with vinblastine-piroxicam (58.3%) than with vinblastine alone (22.2%). The median progression free interval was 143 days with vinblastine alone and 199 days with the combination. Interestingly, the overall median survival time was significantly longer (P <  0.03) in dogs receiving vinblastine alone followed by piroxicam alone (n = 20, 531 days) than in dogs receiving the combination (299 days). Treatment was well tolerated in both arms.

Conclusions: Piroxicam significantly enhanced the activity of vinblastine in dogs with UC where the cancer closely mimics the human condition, clearly justifying further study. The study suggest the potential importance of tracking COX inhibitor use in patients in clinical trials as COX inhibitors could affect treatment response.

Pharmacokinetics and toxicity of the novel oral demethylating agent zebularine in laboratory and tumor bearing dogs

The purpose of this study was to determine the plasma pharmacokinetics (PK) and toxicity of zebularine, an oral cytidine analog with demethylating activity, in dogs. Plasma zebularine concentrations were determined by HPLC-MS/MS following an oral zebularine dose of 8 or 4 mg kg^-1 . Plasma zebularine clearance was constant. Mean maximum concentration (C_max ) was 23 ± 4.8 and 8.6 ± 1.4 µM following 8 and 4 mg kg^-1 , respectively. Mean half-life was 5.7 ± 0.84 and 7.1 ± 2.1 following 8 and 4 mg kg^-1 , respectively. A single 8 mg kg^-1 dose was well tolerated. Daily 4 mg kg^-1 treatment in three laboratory dogs resulted in grade 4 neutropenia (n = 3), grade 1 anorexia (n = 2) and grade 1 or 2 dermatologic changes (n = 2). All adverse events resolved with supportive care. A 4 mg kg^-1 dose every 21 days was well tolerated. A follow-up dose escalation study is in progress with a lower starting dose.

Mutations in Lyar and p53 are synergistically lethal in female mice

BACKGROUND

Ly-1 antibody reactive clone (LYAR) is a nucleolar zinc finger protein that has been implicated in cell growth, self-renewal of embryonic stem cells, and medulloblastoma. To test whether LYAR is critical for cell growth and development, we generated Lyar mutant mice.

METHODS

Mice carrying the mutant Lyar(gt) allele were generated from embryonic stem cells that contained a gene-trap insertion in the Lyar gene. Phenotypic analyses were performed on Lyar mutant mice and mouse embryonic fibroblasts. Lyar(gt/gt) mice were crossed to mice lacking the p53 tumor suppressor protein and Lyar/p53 compound mutants scored for external abnormalities.

RESULTS

Lyar(gt/gt) homozygotes are viable, fertile, and indistinguishable from wild type littermates. However, the growth of Lyar(+/gt) and Lyar(gt/gt) mouse embryonic fibroblasts (MEFs) was impaired, coincident with an increase in the steady-state level of p53 and a key p53 effector of growth arrest, p21, suggesting that a cellular stress response is triggered in the absence of a wild type level of LYAR. Remarkably, the majority of Lyar(+/gt) and Lyar(gt/gt) female mice lacking p53 mice failed to survive. The neural tube defect (NTD) exencephaly was observed in ≈26% and ≈61% of female Lyar(+/gt;) p53(-/-) and Lyar(gt/gt;) p53(-/-) embryos, respectively.

CONCLUSIONS

Lyar/p53 mutant mice represent a new digenic model of NTDs. Furthermore, these studies identify Lyar as a novel candidate gene for a role in human NTDs. These results provide new data to support the idea that loss of a p53-mediated developmental checkpoint may increase the risk of NTDs owing to some germline mutations.