CRYOSURGICAL ABLATION OF THE NORMAL VENTRAL PROSTATE PLUS ADJUVANT DOES NOT PROTECT COPENHAGEN RATS FROM DUNNING PROSTATIC ADENOCARCINOMA CHALLENGE

Purpose: We wished to determine if cryosurgical ablation of the normal ventral prostate of Copenhagen rats confers protective immunity again st a subsequent challenge with Dunning R3327 MatLyLu prostatic adenoca rcinoma. In human melanoma, tumor antigens have been characterized as normal cellular proteins. We reasoned that cryosurgical ablation of th e normal prostate along with immunostimulatory adjuvants might release prostatic antigens to the immune system engendering an immune respons e and rendering rats immune to prostatic cancer cells. Materials and M ethods: On day 0, Copenhagen rats underwent cryosurgical ablation of t he normal ventral prostate, cryosurgery and intraprostatic injection o f Complete Freund's Adjuvant (CFA), CFA injection alone, or laparotomy alone. On day 21, animals received a subcutaneous challenge of MatLyL u tumor cells. Tumor dimensions were recorded at regular intervals by a single blinded investigator. Results: Animals receiving cryosurgical ablation of the normal ventral prostate or intraprostatic CFA develop ed tumors more frequently than animals receiving laparotomy alone and the effect was statistically significant if animals received both cryo surgical ablation of the prostate and intraprostatic CFA (3 experiment s, 1 x 10(4) MatLyLu cells), total number with tumors/total number cha llenged: laparotomy alone 3/17, cryosurgical ablation 7/17, cryosurger y plus CFA 10/16 (p = 0.013 versus laparotomy, Fisher's exact test), C FA alone 9/17. Conclusions: Cryosurgical ablation of the normal rat ve ntral prostate and intraprostatic CFA does not protect against and can enhance the tumorigenicity of MatLyLu prostatic cancer cells at dista nt sites. This could be occurring through specific immunologic effects or non-specific mechanisms induced by cryosurgery and CFA.