| dc.description.abstract | Fibrosarcomas arise at sites commonly used for injection in cats, such as interscapular region and thigh. Various studies demonstrated a relation between the tumors at sites of injections and vaccinations, and it is suggested a species specific local immune response, adjuvants and host factors contribute to the pathogenesis. Prevalence of injection site sarcoma (ISS) is relatively low. However, this type of cancer affects younger cats and their tumors are significantly larger than with other types of tumors. Injection induced sarcomas grow invasively and recur more rapidly and frequently than sarcomas at other locations. Most current available treatment options, including surgery and adjuvant radiation or chemotherapy, show high recurrence rates. Therefore, additional therapies are needed. Doxorubicin and Carboplatin are commonly used chemotherapeutic agents that have shown most promise in feline ISS.
The goal of this pilot study was to determine if expression of DNA damage checkpoint and repair proteins correlates with chemosensitivity of feline injection site sarcomas. It was hypothesized that alterations in DNA damage response mechanisms modulate chemosensitivity of feline injection site sarcomas, explaining the inconsistent benefit of adjuvant chemotherapy and the low response rates noted for macroscopic disease.
Biopsies from sarcomas on three different cats were used in this project, one being a fast growing recurrent sarcoma on the head with similar characteristics as ISS. Cells were grown in primary cell culture, showing variable growth patterns. We determined the optimal density for colony forming assays (CFAs) to be 1,000 cells/ml. This density was used in pilot CFA’s treated with 20 µg/ml and 40µg/l Carboplatin. Cells failed to grow colonies at 20µg/ml and 40µg/ml, however positive control did show colony formation. We determined the dosage of Carboplatin would need to be less than 20µg/ml in CFAs in order to detect a difference in chemosensitivity for sarcoma cells from different feline patients. On HE staining of both true ISSs the tumor cells showed similar morphology, conform what has been described on tumor morphology of feline ISS. Immunohistochemistry was performed with antibodies against gH2AX , checkpoint proteins Atm an p53, and DNA damage proteins ERCC1 and Rad51. IHC for gH2AX stained positive, indicating presence of DNA damage in these sarcoma cells. IHC for Atm showed pervasive staining. IHC for p53, ERCC1 and Rad51 did not stain positive, but no positive control was used.
From the results of this research project, it could be concluded that sarcoma cells derived from different feline patients show variable in vitro growth patterns. DNA damage was detected in FISS. It is unknown whether there is upregulation of Atm or if optimalization of the IHC protocol is needed. For IHC for p53, ERCC1 and Rad51 it is unknown if antibodies used could not detect feline protein, or if optimalization of the IHC protocol is needed. Many methods of the study need to be optimalized in order to obtain useful results, and evaluation of additional samples is needed and is going. Ultimately we hope expression of these proteins can be used to target patients to specific chemotherapy regimens. | |
