Feline injection site sarcomas (ISS) are aggressive cancers that can occur at the site of injections. They grow quickly and invasively. Radical surgery and/or radiation therapy are often required and still do not necessarily result in cures. The role of chemotherapy in treatment is not well defined and there is little data supporting a positive impact on outcome. This study looks at ways to increase the beneficial effect of chemotherapy by evaluating a variety of therapeutic combinations on cancer cells. The combinations are designed to inhibit the way cancer cells recognize and respond to DNA damage inflicted by the chemotherapeutic.