Identification of new candidate biomarkers to support doxorubicin treatments in canine cancer patients.

BACKGROUND: Both human and veterinary cancer chemotherapy are undergoing a paradigm shift from a "one size fits all" approach to more personalized, patient-oriented treatment strategies. Personalized chemotherapy is dependent on the identification and validation of biomarkers that can predict treatment outcome and/or risk of toxicity. Many cytotoxic chemotherapy agents, including doxorubicin, base their mechanism of action by interaction with DNA and disruption of normal cellular processes. We developed a high-resolution/accurate-mass liquid chromatography-mass spectrometry DNA screening approach for monitoring doxorubicin-induced DNA modifications (adducts) in vitro and in vivo. We used, for the first time, a new strategy involving the use of isotope-labeled DNA, which greatly facilitates adduct discovery. The overall goal of this work was to identify doxorubicin-DNA adducts to be used as biomarkers to predict drug efficacy for use in veterinary oncology. RESULTS: We used our novel mass spectrometry approach to screen for adducts in purified DNA exposed to doxorubicin. This initial in vitro screening identified nine potential doxorubicin-DNA adduct masses, as well as an intense signal corresponding to DNA-intercalated doxorubicin. Two of the adduct masses, together with doxorubicin and its metabolite doxorubicinol, were subsequently detected in vivo in liver DNA extracted from mice exposed to doxorubicin. Finally, the presence of these adducts and analytes was explored in the DNA isolated from dogs undergoing treatment with doxorubicin. The previously identified nine DOX-DNA adducts were not detected in these preliminary three samples collected seven days post-treatment, however intercalated doxorubicin and doxorubicinol were detected. CONCLUSIONS: This work sets the stage for future evaluation of doxorubicin-DNA adducts and doxorubicin-related molecules as candidate biomarkers to personalize chemotherapy protocols for canine cancer patients. It demonstrates our ability to combine in one method the analysis of DNA adducts and DNA-intercalated doxorubicin and doxorubicinol. The last two analytes interestingly, were persistent in samples from canine patients undergoing doxorubicin chemotherapy seven days after treatment. The presence of doxorubicin in all samples suggests a role for it as a promising biomarker for use in veterinary chemotherapy. Future studies will involve the analysis of more samples from canine cancer patients to elucidate optimal timepoints for monitoring intercalated doxorubicin and doxorubicin-DNA adducts and the correlation of these markers with therapy outcome.

Novel presentation of a feline patient with visceral and cervical lymph node hemangiosarcoma.

OBJECTIVE: To report a novel presentation of feline hemangiosarcoma. ANIMALS: A 14-year-old spayed female feline patient diagnosed with hemangiosarcoma of the spleen and a cervical lymph node. CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES: The patient presented to the emergency service following a 1-week history of lethargy and hiding. Abdominal ultrasound revealed splenomegaly with multiple nodules and peritoneal fluid that was consistent with hemorrhagic effusion. TREATMENT AND OUTCOME: The patient underwent a routine splenectomy and was started on doxorubicin. Histopathologic evaluation of the spleen confirmed visceral hemangiosarcoma. When the disease showed signs of progression, combination chemotherapy with cyclophosphamide and vincristine was initiated. Four months following presentation, a submandibular lymph node was removed and found to have metastatic hemangiosarcoma. From presentation to euthanasia, the patient survived 205 days. CLINICAL RELEVANCE: Hemangiosarcoma is a rare cancer in feline patients, with a lack of veterinary literature on its presentation and chemotherapy protocols. The subject of this case report had a novel presentation of hemangiosarcoma and responded favorably to a chemotherapy protocol not previously described for this disease.