Cytogenetic Analysis of Genomic Destabilization in Solely Estrogen-Induced Female ACI Rat Mammary Neoplasms

A high frequency of aneuploid cells in carcinoma in-situ (CIS) and in small and large mammary tumors of female ACI rats are induced by estrogen (E) treatment alone. Employing G-banding karyotype analysis, consistent numerical chromosome alterations were detected as gains in chromosome 7, 11, 13, 19, and 20, and loss of chromosome 12, when the data were analyzed by binomial distribution for a frequency of occurrence ≥ 30.0%. Recurrent chromosome gains were also detected in chromosomes 3, 4, 6, 10, 14, and 15, whereas infrequent losses were observed in chromosome 5. Regional genomic alterations were detected by comparative genomic hybridization (CGH) in eleven individual E- induced primary mammary gland tumors (MGTs) obtained from an equal number of female ACI rats. CGH analysis revealed consistent regional gains at 1p11, 1q11-q22, 4q41-q44, 7q31-q33, 11p12-q11, 13p, and 20p12.