Aromatase inhibitors increase the sensitivity of human tumor cells to monocyte-mediated, antibody-dependent cellular cytotoxicity.

OBJECTIVE: A randomized, placebo-controlled phase III trial of the breast cancer vaccine Theratope (Biomira Corporation, Edmonton, Alberta, Canada), which expresses the underglycosylated, mucin-associated peptide STn showed that patients treated concomitantly with hormone therapy plus vaccine survived significantly longer than patients treated with hormone therapy plus a control vaccine. The objective of this study was to elucidate a mechanism to explain this effect. METHODS: Tumor cells characterized for expression of estrogen receptor (ER), STn, and Mucin-1 (Muc1) were pretreated (24 hours) with the aromatase inhibitor (AI) formestane, followed by assessment of sensitivity to monocyte-mediated killing in the presence and absence of STn or Muc1 antibodies (Abs) using the (51)Cr-release assay. RESULTS: ER+/STn+/Muc1+ tumor cells cultured in medium were equally sensitive to killing by monocytes in the absence or presence of STn and Muc1 Abs (mean = 54% and 55% cytolysis, respectively, P = not significant). Formestane-pretreated cells showed decreased sensitivity to killing by monocytes in the absence of Abs (mean = 45% cytolysis, P = .07) but significantly increased sensitivity to monocyte-mediated, antibody-dependent cellular cytotoxicity (MM-ADCC) (mean = 65%, P = .003). These effects were not seen with either ER+/STn-/Muc1+ cells or ER-/STn+/Muc1+ cells, indicating the need for both ER and STn positivity of the target tumor cells. CONCLUSIONS: Tumor cells treated with an AI exhibit increased sensitivity to MM-ADCC. The capacity of an AI to "sensitize" tumor cells to this form of antitumor immunity represents a heretofore, undescribed mechanism whereby a hormone-based treatment may collaborate with antigen-specific tumor immunity to produce improved tumor control in vivo in metastatic breast cancer patients.

Characterization of rat ovarian adenocarcinomas developed in response to direct instillation of 7,12-dimethylbenz[a]anthracene (DMBA) coated suture.

Human ovarian cancer is predominantly of epithelial cell origin (>90% of malignant tumors) and most often presents at an advanced stage with poor prognosis. Most animal models of ovarian carcinoma yield thecal/granulosa cell tumors, rather than adenocarcinomas. Induction of adenocarcinoma in 10-45% of rats following an ovarian implantation of 7,12-dimethylbenz[a]anthracene (DMBA) coated silk suture has been reported. Here, DMBA of 99% purity was melted at 124 degrees C to impregnate a 1 cm length of sterile suture for direct ovarian implantation in Wistar Furth rats at 7 weeks of age. DMBA-treated ovaries showed a nearly complete loss of primary follicles and degeneration of granulosa cells at 16 weeks, consistent with the known toxic response of the ovary to direct DMBA application. No tumors were present. Untreated right ovaries and sham dimethyl sulfoxide-treated ovaries were normal. Ovarian tumors in DMBA-treated rats were first noted at 26 weeks post implantation reaching a cumulative tumor incidence of 77% (23/30) at 52 weeks. Controls showed no evidence of tumor at 52 weeks (0/31). Tumor histology was distributed as well differentiated adenocarcinoma (1/23), poorly differentiated adenocarcinoma (8/23), thecal/granulosa cell tumor (8/23), undifferentiated sarcoma (5/23) and one undifferentiated carcinoma with no adeno character. Tumors occasionally seeded to peritoneal mesentery, spleen and abdominal wall. Adenocarcinomas appeared to originate from the ovarian surface epithelium, with focal papillary extension into cystic space. Epithelial derived tumor cells positively react with antibodies to cytokeratin (8/8), epithelial cell adhesion molecule (Ep-CAM 5/5) and prostaglandin synthetase-1 (COX-1 4/4). Vimentin positive epithelial cells when present in adenocarcinomas (4/7), showed perinuclear staining, quite distinct from the uniformly stained stromal cells in thecal/granulosa cell tumors (8/8). The thecal/granulosa cell tumors were Ep-CAM negative (0/5) and weakly COX-1 positive (4/4). Thus, the DMBA suture model in rats yields epithelial derived tumors histologically similar to humans and should prove suitable for the testing of preventive or therapeutic agents.

Detection of genomic alterations in human endometrial cancer by two-dimensional gel electrophoresis.

OBJECTIVE: The purpose of this study was to detect genomic alterations in human endometrial cancer by two-dimensional gel electrophoresis. STUDY DESIGN: With use of a newly developed two-dimensional gel electrophoresis assay, we scanned 19 high-risk DNA fragments for alterations in human endometrial hyperplasias and adenocarcinomas. This method includes cleaving of high-molecular-weight DNA, radioactive labeling, and separating DNA fragments by two-dimensional gel electrophoresis. By comparing the two-dimensional gel electrophoresis profile (spots) of neoplastic with normal endometrium, genetic alterations such as amplification, allelic loss, and hypermethylation or hypomethylation can be detected. RESULTS: Seven of 8 human endometrial adenocarcinoma (88%) and 1 of 2 hyperplasias (50%) revealed changes in spot density. The number of spots changed per specimen was 4. The median percentage of specimens with changes in an individual spot was 30%. Eleven spots had a reduction or loss of spot density, and 8 spots had an increase in spot density. CONCLUSION: By use of a novel two-dimensional gel electrophoresis assay, we identified genetic alterations in 50% of hyperplasias and 88% of endometrial adenocarcinomas.