Inflammation, apoptosis, and necrosis induced by neoadjuvant fas ligand gene therapy improves survival of dogs with spontaneous bone cancer.

Fas ligand (FasL) gene therapy for cancer has shown promise in rodents; however, its efficacy in higher mammals remains unknown. Here, we used intratumoral FasL gene therapy delivered in an adenovirus vector (Ad-FasL) as neoadjuvant to standard of care in 56 dogs with osteosarcoma. Tumors from treated dogs had greater inflammation, necrosis, apoptosis, and fibrosis at day 10 (amputation) compared to pretreatment biopsies or to tumors from dogs that did not receive Ad-FasL. Survival improvement was apparent in dogs with inflammation or lymphocyte-infiltration scores >1 (in a 3-point scale), as well as in dogs that had apoptosis scores in the top 50th percentile (determined by cleaved caspase-3). Survival was no different than that expected from standard of care alone in dogs with inflammation scores ≤1 or apoptosis scores in the bottom 50th percentile. Reduced Fas expression by tumor cells was associated with prognostically advantageous inflammation, and this was seen only in dogs that received Ad-FasL. Together, the data suggest that Ad-FasL gene therapy improves survival in a subset of large animals with naturally occurring tumors, and that at least in some tumor types like osteosarcoma, it is most effective when tumor cells fail to express Fas.

Clinicopathologic significance of histologic grade, pgp, and p53 expression in canine lymphoma.

To characterize the expression of P-glycoprotein (Pgp) and p53 in different histologic grades of canine multicentric lymphosarcoma (LSA), 31 cases of LSA without prior treatment were studied. The expression levels of the Pgp and p53 proteins were evaluated for their clinicopathologic significance among standard histologic evaluation. Immunohistochemistry (IHC) was performed on formalin-fixed, paraffin-embedded archival samples of 31 previously untreated LSA cases to detect the expression of Pgp and p53. All dogs were subsequently treated with a combination chemotherapy protocol. Remission and survival durations were evaluated for correlation with histologic grade and presence of drug resistance markers. Of the 31 cases, 24 (80%) and 7 (22%) were positive for Pgp and p53, respectively. Overall, the median survival and duration of remission in the study was 246 days and 137 days, respectively. The National Cancer Institute working formulation histologic grade was not associated with either survival or duration of first remission (DOR). The Pgp protein expression and DOR and survival was not statistically significant. Expression of p53 was statistically correlated with survival.