Carla Rohrer Bley

Canine mast cell tumours: a review of the pathogenesis, clinical features, pathology and treatment

Mast cells (MCs) are well known for their neoplastic transformation in solitary and multiple cutaneous mast cell tumours (MCTs), as well as visceral and systemic mastocytosis. Dogs have a unique risk of developing cutaneous MCTs, and they account for 7% to 21% of all canine skin tumours. The aetiology of canine MCTs is unknown but is probably multifactorial. This article reviews up-to-date knowledge on the pathogenesis, the clinical presentation, the clinical prognostic factors, the diagnostic workup including clinical staging, cytological findings, histological findings and the various grading systems which have been evaluated based on morphology, the assessment of proliferation markers and other factors such as vessel density. Furthermore, detailed information about current treatment protocols for canine cutaneous MCTs is provided.

Optimizing Photodynamic Therapy: In vivo Pharmacokinetics of Liposomal meta-(Tetrahydroxyphenyl)Chlorin in Feline Squamous Cell Carcinoma

Purpose: The aim of the present study was to optimize and simplify photodynamic therapy using a new liposomal formulation of the photosensitizer meta-(tetrahydroxyphenyl)chlorin [m-THPC (Foscan); liposomal m-THPC (Fospeg)] and to reduce systemic reactions to the photosensitizer. Experimental Design: To examine the pharmacokinetics of liposomal m-THPC, we determined tissue and plasma variables in feline patients with spontaneous squamous cell carcinoma. In vivo fluorescence intensity measurements of tumor and skin were done with a fiber spectrophotometer after i.v. injection of m-THPC or liposomal m-THPC in 10 cats. Blood samples, drawn at several time points after photosensitizer administration, were analyzed by high-performance liquid chromatography. Results: None of the liposomal m-THPC–treated cats showed side effects during or after drug injection. Fluorescence intensities, fluorescence ratios (tumor fluorescence divided by skin fluorescence), and bioavailability in the tumor were 2 to 4 times higher with liposomal m-THPC compared with m-THPC. Liposomal m-THPC concentration in the tumor increased constantly to reach a maximum at 4 hours after injection. Plasma concentration and bioavailability were ∼3 times higher with liposomal m-THPC compared with m-THPC measured at the time points of highest plasma concentration. The distribution half-life was shorter with liposomal m-THPC, resulting in maximal tumor accumulation up to 5.5 times earlier. Maximal tumor accumulation and maximal fluorescence ratio with liposomal m-THPC occurred at the same time point, indicating maximal selectivity. In both groups, all cats responded to therapy. Conclusions: Liposomal m-THPC was well tolerated by all cats and seems to have superior pharmacokinetic properties compared with m-THPC. The efficacy of the drug warrants further study.

Irradiation of Brain Tumors in Dogs with Neurologic Disease

Radiation therapy is the treatment of choice for many primary canine brain tumors. The radiation dose tolerated by surrounding healthy brain tissue can be a limiting factor for radiation treatment and total dose as well as fractionation schedules, and volume effects may play a role in the outcome of patients undergoing radiation therapy. The purpose of this retrospective study was to evaluate the efficacy of radiation therapy in dogs with brain tumors that showed signs of neurologic disease. Forty-six dogs with brain tumors were included in the analysis. In 34 dogs, computer-generated treatment plans were available, and dose-volume data could be obtained. The totally prescribed radiation therapy doses ranged from 35 to 52.5 Gy (mean = 40.9 [SD +/- 2.91) applied in 2.5- to 4-Gy fractions (mean = 3.2). The median overall survival time calculated for deaths attributable to worsening of neurologic signs was 1,174 days (95% confidence interval [CI], 693-1,655 days). Assuming that all deaths were due to disease or treatment consequences, the median survival time was 699 days (95% CI, 589-809 days). No prognostic clinical factors such as the location or size of the tumor or neurologic signs at presentation were identified. With computerized treatment planning and accurate positioning, high doses of radiation (> 80% of the total dose) could be limited to mean relative brain volumes of 35.3% (+/- 12.6). These small volumes may decrease the probability of severe late effects such as infarction or necrosis. In this study, very few immediate or early delayed adverse effects and no late effects were noted, and quality of life was good to excellent.

Oxygenation of spontaneous canine tumors during fractionated radiation therapy.

Background and Purpose:Tumor oxygenation predicts treatment outcome, and reoxygenation is considered important in the efficacy of fractionated radiation therapy. Therefore, the purpose of this study was to document the changes of the oxygenation status in spontaneous canine tumors during fractionated radiation therapy using polarographic needle electrodes.Material and Methods:Tumor oxygen partial pressure (pO2) measurements were performed with the Eppendorf-pO2-Histograph. The measurements were done under general anesthesia, and probe tracks were guided with ultrasound. pO2 was measured before radiation therapy in all dogs. In patients treated with curative intent, measurements were done sequentially up to eight times (total dose: 45–59.5 Gy). Oxygenation status of the palliative patient group was examined before each fraction of radiation therapy up to five times (total dose: 24–30 Gy).Results:15/26 tumors had a pretreatment median pO2 ≤ 10 mmHg. The pO2 values appeared to be quite variable in individual tumors during fractionated radiation therapy. The pO2 of initially hypoxic tumors (pretreatment median pO2 ≤ 10 mmHg) remained unchanged during fractionated radiotherapy, whereas in initially normoxic tumors the pO2 decreased.Conclusion:Hypoxia is common in spontaneous canine tumors, as 57.7% of the recorded values were ≤ 10 mmHg. The data of this study showed that initially hypoxic tumors remained hypoxic, whereas normoxic tumors became more hypoxic.Hintergrund und Ziel:Die Sauerstoffversorgung von Tumoren ist ein wichtiger prognostischer Faktor. Die Reoxygenierung von Tumoren nach Bestrahlung wird als wichtiger Mechanismus bei der fraktionierten Radiotherapie angesehen. Ziel der Studie war es, die Veränderungen in der Oxygenierung von spontan gewachsenen Tumoren des Hundes unter fraktionierter Radiotherapie zu beschreiben.Material und Methodik:Der Sauerstoffpartialdruck (pO2) wurde polarographisch mit dem Eppendorf-pO2-Histographen gemessen. Die Messungen erfolgten unter Vollnarkose und Ultraschallkontrolle. Die pO2-Werte wurden vor der Strahlentherapie gemessen. Bei Hunden mit kurativem Behandlungsschema wurden bis zu acht sequentielle Messungen während der Strahlentherapie durchgeführt (Gesamtdosis: 45–59.5 Gy). Der Oxygenierungsstatus der Tumoren mit palliativem Protokoll wurde vor jeder Fraktion bis zu fünfmal bestimmt (Gesamtdosis: 24–30 Gy).Ergebnisse:15/26 Tumoren hatten vor Beginn der Strahlentherapie einen medianen pO2 ≤ 10 mmHg. Der Verlauf der pO2-Werte während fraktionierter Radiotherapie erschien in individuellen Tumoren ziemlich variabel. Wurden die Tumoren in initial hypoxisch (prätherapeutischer medianer pO2 ≤ 10 mmHg) und normoxisch unterteilt, so zeigte sich, dass die pO2-Werte der hypoxischen Tumoren unverändert blieben, während normoxische Tumoren eine Abnahme des pO2 zeigten.Schlussfolgerung:Hypoxie ist normalerweise in spontanen Tumoren des Hundes messbar, lagen doch fast 60% der gemessenen Werte ≤ 10 mmHg. Die Daten dieser Studie zeigten, dass initial hypoxische Tumoren unter fraktionierter Radiotherapie hypoxisch blieben, während initial normoxische Tumoren vermehrt hypoxisch wurden.

POSSIBLE HUMAN-AVIAN TRANSMISSION OF MYCOBACTERIUM TUBERCULOSIS IN A GREEN-WINGED MACAW (ARA CHLOROPTERA)

Abstract This report describes a case of Mycobacterium tuberculosis infection in a green-winged macaw (Ara chloroptera), confirmed by microbiologic and pathologic diagnostics, and notes a possible human–avian transmission. Clinical signs included cutaneous swellings, profound leukocytosis, and signs of osteomyelitis in the long bones. Proliferation consisted of several nodules with small greenish-caseous foci in cross-section and revealed a severe granulomatous inflammation with intralesional acid-fast rods. Mycobacterium tuberculosis was isolated from subcutaneous nodules and biochemically confirmed. The disease in avian species is of zoonotic importance.

Role of the microenvironment for radiosensitization by patupilone

Purpose: The combined treatment modality of ionizing radiation (IR) and the clinically relevant microtubule-stabilizing compound patupilone (epothilone B, EPO906) is a promising approach for anticancer therapy. Here, we investigated the role of the tumor microenvironment for the supra-additive in vivo response in tumor xenografts derived from patupilone-sensitive and patupilone-resistant non-small cell lung cancer cells. Experimental Design: The treatment response to a combined regimen of patupilone and IR was investigated in vitro and in tumor xenografts derived from wild-type A549 and A549.EpoB40 cells, which are resistant to patupilone due to a β-tubulin mutation. Results: In both A549 and A549.EpoB40 cells, proliferative activity and clonogenicity were reduced in response to IR, whereas patupilone, as expected, inhibited proliferation of the mutant cell line with reduced potency. Combined treatment with patupilone and IR induced a cytotoxic effect in vitro in an additive way in A549 cells but not in the tubulin-mutated, patupilone-resistant A549.EpoB40 cells. A supra-additive tumor growth delay was induced by combined treatment in xenografts derived from A549 cells but not in xenografts derived from A549.EpoB40 cells. Histologic analysis revealed a significant decrease in tumor cell proliferation (Ki-67) and microvessel density and a treatment-dependent change of tumor hypoxia in A549 but not A549.EpoB40 xenografts. Conclusions: Using a genetically defined patupilone-sensitive and patupilone-resistant tumor model, we here showed that the major cytotoxic effect of the combined treatment modality of IR and patupilone is directed against the tumor cell compartment. The induced antiangiogenic effect derives indirectly from the tumor cell.

Influence of pretreatment polarographically measured oxygenation levels in spontaneous canine tumors treated with radiation therapy

Background and Purpose:The level of hypoxia in primary tumors has been described to influence response to treatment. The aim of the present study was to investigate the impact of pretreatment oxygen level measurements in spontaneous canine tumors on treatment outcome.Materials and Methods:Data of pretreatment tumor oxygenation status and local tumor response after primary radiation therapy in a group of spontaneously occurring tumors in dogs (n = 52) was collected. Radiation therapy was given with curative (14–17 × 3–3.5 Gy) or palliative intent (3 × 8 Gy or 4–5 × 6 Gy). Progression-free interval and overall survival were correlated to polarographically measured tumor oxygenation status.Results:In the curatively irradiated group, tumors with median pO2 values ≤ 10 mmHg tended to have shorter median progression- free interval compared to better oxygenated tumors (246 vs. 739 days). The same trend could be shown for overall survival (330 vs. 745 days), indicating a cutoff value in this region. In the group treated with lower doses of radiation, the level of oxygen was no longer found to be of prognostic value; however, in this group hemoglobin had a significant impact on outcome.Conclusion:In curatively irradiated spontaneous canine tumors, tumor hypoxia was found to be a prognostic indicator, independent of tumor histologies and volume.Hintergrund und Ziel:Das Ausmaß der Hypoxie in Primärtumoren beeinflusst das Ansprechen auf eine Therapie. Das Ziel der vorliegenden Studie war, den Zusammenhang zwischen dem prätherapeutischen Sauerstoffstatus und Ansprechen auf die Strahlentherapie bei Hunden zu untersuchen.Material und Methodik:Bei Hunden (n = 52) mit spontan auftretenden Tumoren, die entweder einer kurativen (14–17 × 3–3,5 Gy) oder einer palliativen Strahlentherapie (3 × 8 Gy oder 4–5 × 6 Gy) unterzogen wurden, wurde der prätherapeutische Sauerstoffpartialdruck gemessen. Die progressionsfreie Zeit sowie die Gesamtüberlebenszeit nach Therapie wurden mit den polarographisch gemessenen Sauerstoffdaten korreliert (Tabelle 1; Abbildung 1).Ergebnisse:In der kurativ bestrahlten Gruppe konnte gezeigt werden, dass Tumoren mit einem Median der pO2-Messwerte von ≤ 10 mmHg eine kürzere progressionsfreie Zeit (246 vs. 739 Tage) und Gesamtüberlebenszeit hatten als besser oxygenierte Tumoren (330 vs. 745 Tage; Abbildung 2). In der palliativ bestrahlten Tiergruppe konnte dieser Effekt nicht gezeigt werden, jedoch wurde ein Einfluss des Hämoglobins auf das Therapieergebnis offensichtlich (Tabellen 2 bis 4).Schlussfolgerung:Bei kurativ bestrahlten spontan auftretenden Tumoren des Hundes ist die Hypoxie ein von Histologie und Tumorvolumen unabhängiger prognostischer Faktor.

Regulation of VEGF-expression by patupilone and ionizing radiation in lung adenocarcinoma cells.

The use of microtubule stabilizing agents (MSAs) is a promising strategy for anti-cancer therapy alone and as part of combined treatment modalities with ionizing radiation. However MSA-provoked molecular and cellular processes including the regulation of intercellular, paracrine signaling pathways are far from clear. Here we investigated the interference of the novel, clinically relevant MSA patupilone (epothilone B) with the tumor-cell derived vascular endothelial growth factor (VEGF), which is most relevant for tumor angiogenesis. Low-dose, sub-nanomolar concentrations of patupilone specifically reduced hypoxia-driven stabilization of the transcription factor HIF-1α in the patupilone-sensitive lung adenocarcinoma cell line A549, but not in the mutant derivative cell line A549.EpoB40. Patupilone further reduced hypoxia-induced VEGF expression and secretion but only in the A549 wildtype cell line. In the wildtype cell line, ionizing radiation alone induced hypoxia-dependent VEGF-expression but a strong dominant counteracting effect of patupilone was always observed when ionizing radiation was combined with patupilone, on the level of HIF-1α protein stability, VEGF-expression and VEGF-secretion. These results demonstrate that patupilone and ionizing radiation dysregulate hypoxia-induced stress responses, which might contribute to the potency of this promising, combined treatment modality.

Microtubule stabilising agents and ionising radiation: Multiple exploitable mechanisms for combined treatment

Combined radiochemotherapy treatment modalities are in use for many indications and therefore of high interest. Even though a combined modality in clinical use is often driven by pragmatic aspects, mechanistic preclinical-based concepts of interaction are of importance in order to translate and implement an optimal combination and scheduling of two modalities into the clinics. The use of microtubule stabilising agents is a promising strategy for anti-cancer therapy as a part of combined treatment modality with ionising radiation. Traditionally, microtubule targeting agents are classified as cytotoxic chemotherapeutics and are mostly used in a maximally tolerated dose regimen. Apart from direct cytotoxicity and similar to mechanisms of molecular targeting agents, microtubule stabilising agents interfere with multiple cellular processes, which can be exploited as part of combined treatment modalities. Recent preclinical investigations on the combination of ionising radiation and microtubule stabilising agents reveal new mechanistic interactions on the cellular and tumour level and elucidate the supra-additive tumour response observed particularly in vivo. The major focus on the mechanism of interaction was primarily based on radiosensitisation due to cell cycle arrest in the most radiosensitive G2/M-phase of the cell cycle. However, other mechanisms of interaction such as reoxygenation and direct as well as indirect endothelial damage have also been identified. In this review we summarise and allocate additive and synergistic effects induced by the combined treatment of clinically relevant microtubule stabilising agents and ionising radiation along a described radiobiological framework encompassing distinct mechanisms relevant for exploiting the combination of drugs and ionising radiation.

Correlation of quantified contrast-enhanced power Doppler ultrasonography with immunofluorescent analysis of microvessel density in spontaneous canine tumours.

Conventionally, tumour vascularity is assessed invasively by immunofluorescent analysis. Quantified contrast-enhanced power Doppler ultrasound has been used to measure tumour angiogenesis non-invasively in humans and experimental animals. The purpose of this study was to correlate quantified contrast-enhanced power Doppler ultrasound with immunofluorescent results in 45 spontaneous canine tumours. With power Doppler, mean vascularity was high in squamous cell carcinomas, moderate in malignant oral melanomas and low in sarcomas. There was high mean vascularity in squamous cell carcinomas and low mean vascularity in sarcomas and malignant oral melanomas. Although Doppler parameters correlated moderately with microvascular density for all tumours (P=0.004, r=0.4), they did not correlate within histology groups. These analyses show that vascularity differs among canine tumour histology groups. However, dependent on the method used, measurement of tumour vascularity can provide different biological information.