Prognostic factors in MNU and DMBA-induced mammary tumors in female rats.

Chemically-induced mammary tumors in rats by the carcinogens 1-methyl-1-nitrosourea- (MNU) and 7,12-dimethylbenz[a]anthracene (DMBA) are the most widely used models for studies related with human breast cancer. This study aimed to evaluate the immunoexpression of the prognostic factors estrogen receptor α (ERα), progesterone receptor (PR) and Ki-67, in MNU and DMBA-induced rat mammary tumors, in order to know the model that best suits to woman breast cancer. Twenty-eight MNU-induced and 16 DMBA-induced mammary tumors in virgin female Sprague-Dawley rats were analyzed. The expression of the prognostic markers ERα, PR and Ki-67 proliferation index (Ki-67 PI) was assessed by immunohistochemistry. Mitotic activity index (MAI) was also evaluated. More than one histological pattern was identified in each mammary tumor. Carcinomas constituted the lesions most frequently induced by both carcinogens: 33 MNU-induced carcinomas and 23 DMBA-induced carcinomas. All MNU and DMBA-induced mammary carcinomas were ER+/PR+, with a higher expression of ERα when compared with PR. Tumors' weight, the expression of ERα, PR, Ki-67 PI and MAI were higher in MNU-induced mammary carcinomas when compared with the DMBA-induced ones. Statistically significant differences between groups were observed for ERα, PR and MAI (p<0.05). The higher KI-67 PI and MAI in MNU-induced mammary carcinomas are suggestive of a higher aggressiveness of these carcinomas when compared with the DMBA-induced ones, and consequently a worse response to the therapy and a worse prognosis. In this way, the use of the rat model of MNU-induced mammary tumors is advised in experimental protocols aiming to study more aggressive mammary tumors within the group of double-positive mammary tumors (ER+/PR+).

Improving discrimination in the grading of rat mammary tumors using two-dimensional mapping of histopathological observations.

This work aims at characterizing rat mammary tumors induced by 7,12-dimethylbenz(a)anthracene (DMBA) and the respective malignancy potential, commonly graded with histopathology features grouped by intensity levels. Tumors were described over fourteen multiple ranged microscopic parameters and a comprehensive characterization of the histological patterns and their relation with tumor grade was carried out by principal component analysis (PCA). The number of histological patterns present on a tumor tends to correlate with malignant features. High grade tumors are characterized by the presence of several structural patterns, with cribriform prevalence and necrosis. The cribriform pattern correlates with grading, i.e., tumors having a higher predominance of the cribriform pattern are likely to be more malignant. The findings may represent a benchmark for similar characterization studies in other models.

Immobilisation of cardosin A in chitosan sponges as a novel implant for drug delivery.

Cardosin A is extracted from the pistils of the plant Cynara cardunculus L. and chitosan is a polysaccharide derived from chitin with valuable properties as a biomaterial. In this work we report our experiments on the synthesis of chitosan sponges and immobilisation of cardosin A, by entrapment. We observed that 10-15% of the incorporated cardosin A were released over 6 days of incubation. In addition, we could also note that this immobilisation procedure did not induce any specificity alterations on cardosin A. The specificity study of the enzyme, using beta-chain of oxidised insulin, showed that the immobilised and released enzymes have the same hydrolysis pattern as the free enzyme. The ability of this enzyme to hydrolyse type I collagen was maintained, after the immobilisation procedure. The biocompatibility in vivo of these sponges was evaluated by histological staining after implantation in rats submitted to abdominal surgery. Results of this study demonstrated that these chitosan sponges are very promising vehicles for the application of cardosin A, in abdominal cavity for prevention and reduction of the adhesions formation.