Even after zinc administration was discontinued, tumor growth was slower than in control animals (figure 2). Importantly, at the dosage delivered to the animals, we did not observe any evidence of biotoxicity during the treatment protocol and no animal death was recorded. Further, a blinded pathologist performed a full post-mortum histological analysis of tissues and uncovered no evidence of tissue toxicity in the animals enrolled in the zinc treatment protocol (data not shown). Liver changes reported by others
at the LD50 level were not seen with our substantially lower dosage even with the chronic administration schedule. Survival of Animals following treatment of prostate cancer xenografts with zinc As a final measure of the potential Selleckchem PKC412 usefulness of zinc as a component Selleck Lapatinib of prostate cancer chemotherapeutics, we assayed the ability of the intra-tumoral zinc injection protocol to extend the life of animals in our prostate cancer xenograft model. Because they are growing subcutaneously rather than orthotopically xenograft tumors may grow to significant size without causing animal death. For humane reasons, a scoring system was established to assess animal welfare and animals
not able to meet two requirements were euthanized. The scoring system consisted of the following: 1. Maintenance of normal weight (Weight loss > 12%); 2. Normal ambulation; 3. Normal grooming; 4. Normal feeding. Importantly, the decision to remove an animal from the protocol due to extreme tumor burden was made by an animal care technician unaware of the treatment group of the particular animal at the time of the Docetaxel price decision. Thus, humane removal of an animal from the protocol was recorded as a death event, and with these data we evaluated survival. As seen in figure 5, intra-tumoral injection of zinc acetate significantly extended the lifespan
of animals in this xenograft model of prostate cancer. Dramatically, although the treatment protocol extended for only two weeks, the enhanced survival of animals in the zinc treatment group was persistent for several weeks beyond (figure 5). In the control group, all animals had succumbed to the debilitating effects of the growing tumor within eight weeks of the beginning of the treatment protocol. However, in the same time period, 80% of those treated with zinc acetate injections remained alive (figure 5). This dramatic result was significant (p = 0.002) by Kaplan-Meier Survival Analysis and revealed the intra-tumoral injection can halt the growth of prostate cancer in vivo with marked in gains in survival. Figure 5 Effect of Intra-Tumoral Zinc Injection on Survival. Prostate cancer cell xenografts were placed into SCID mice and allowed to grow to a size of 200 mm3. Every 48 hours for 14 days, mice were then anesthetized and injected with 200 μL of either saline or 3 mM zinc acetate.