Simple and effective bacterial-based intratumoral cancer immunotherapy.

BACKGROUND: We describe intratumoral injection of a slow-release emulsion of killed mycobacteria (complete Freund's adjuvant (CFA)) in three preclinical species and in human cancer patients. METHODS: Efficacy and safety were tested in mammary tumors in mice, in mastocytomas in mice and dogs, and in equine melanomas. In mice, survival, tumor growth, and tumor infiltration by six immune cell subsets (by flow cytometry) were investigated and analyzed using Cox proportional hazards, a random slopes model, and a full factorial model, respectively. Tumor growth and histology were investigated in dogs and horses, as well as survival and tumor immunohistochemistry in dogs. Tumor biopsies were taken from human cancer patients on day 5 (all patients) and day 28 (some patients) of treatment and analyzed by histology. CT scans are provided from one patient. RESULTS: Significantly extended survival was observed in mouse P815 and 4T1 tumor models. Complete tumor regressions were observed in all three non-human species (6/186 (3%) of mouse mastocytomas; 3/14 (21%) of canine mastocytomas and 2/11 (18%) of equine melanomas). Evidence of systemic immune responses (regression of non-injected metastases) was also observed. Analysis of immune cells infiltrating mastocytoma tumors in mice showed that early neutrophil infiltration was predictive of treatment benefit. Analysis of the site of mastocytoma regression in dogs weeks or months after treatment demonstrated increased B and T cell infiltrates. Thus, activation of the innate immune system alone may be sufficient for regression of some injected tumors, followed by activation of the acquired immune system which can mediate regression of non-injected metastases. Finally, we report on the use of CFA in 12 human cancer patients. Treatment was well tolerated. CT scans showing tumor regression in a patient with late-stage renal cancer are provided. CONCLUSION: Our data demonstrate that intratumoral injection of CFA has major antitumor effects in a proportion of treated animals and is safe for use in human cancer patients. Further trials in human cancer patients are therefore warranted. Our novel treatment provides a simple and inexpensive cancer immunotherapy, immediately applicable to a wide range of solid tumors, and is suitable to patients in developing countries and advanced care settings.

Ovine intestinal adenocarcinomas: histologic and phenotypic comparison with human colon cancer.

Approximately 7% of old, unthrifty sheep (Ovis aries) in New Zealand have intestinal adenocarcinomas. To investigate whether these sheep might be used as a model of human colonic neoplasia, the biologic behavior and histologic appearance of ovine intestinal adenocarcinomas were compared with those reported for human colonic adenocarcinomas. We collected 50 intestinal tracts with grossly visible intestinal neoplasia from slaughtered sheep. Neoplasms were assessed using World Health Organization guidelines for assessment of human colonic adenocarcinomas. All ovine adenocarcinomas developed in the small intestine. In contrast, only 4% of human intestinal tumors develop at this location, whereas the majority develop in the colon. A visible polyp is present within 89% of human colonic adenocarcinomas, whereas polyps were present in only 46% of the ovine neoplasms. Intestinal wall infiltration by the neoplastic cells and rates of lymph node (84% in sheep; 61% in humans) and distant (52% in sheep; 17% in humans) metastases were comparable between ovine and human adenocarcinomas. However, ovine adenocarcinomas developed more peritoneal and fewer hepatic metastases than human adenocarcinomas. Histologic grading of ovine tumors revealed cell differentiation similar to that reported within human colonic adenocarcinomas. In conclusion, ovine intestinal adenocarcinomas, like human colonic adenocarcinomas, typically arise spontaneously and consistently develop widespread metastases. In addition, tumors appear histologically similar between these species. Therefore, sheep may provide a model of advanced human colonic cancer, possibly allowing evaluation of novel therapeutics and surgical procedures.