Induction of mammary gland tumor in female Sprague- Dawley rats with LA7 cells

Background and Objective: Due to the importance of carcinogenicity experimentin cancer research studies, many attempts have been devoted to the development ofnew methods for transduction and evolution of tumor in animals. The induction ofmammary gland tumors issue in animal has been a controversial and much disputedsubject in cancer research. Recently, there has been an increasing interest incarcinogenic chemicals to induce mammary carcinoma in rat models for the study ofhuman breast cancers. However, far too little attention has been paid to rat than mouseand only limited types of transgenic rats have been developed for carcinogenic study.In addition, the benefit of rat animal model is its simplicity and different inductionmethods, transplantation ability and resemblance to human breast cancer in theirhormone sensitivity and histology. Mammary gland LA7 cells were isolated in 1979from a DMBA-induced mammary adenocarcinoma in rats. The purpose of this paperis to design an easy, costeffective, rapid induction, and readily applied rat mammarygland tumor model for breast cancer study, using the LA7 cell line.Materials and Methods: Twenty virgin female Sprague-Dawley (SD) rats (6-8weeks old), with weigh of 180 - 200 g were divided into two groups; ten animals astumor-bearing and ten as normal control group. The rats were anesthetized byintraperitoneal injections of a mixture of ketamine-HCl and xylazine. The cellsuspension (Rat mammary gland tumor cell line, LA7) was inoculated subcutaneouslyinto the mammary fat pad (right flank) of the SD rats. The 300 μl cell suspension wasinjected slowly over five minutes.All animals were monitored for mammary tumordevelopment. Then, the tumor mass in rat breast area was confirmed by radiographsusing a soft X-ray instrument. Blood samples were collected from all rats andanalyzed for lactate dehydrogenase (LDH), alkaline phosphatase (ALP), alanineaminotransferase (ALT) and glutamate dehydrogenase (GGT). At the end of the study,the tumor masses, lungs and livers of rats were removed and examined for tissueabnormalities.Results: Mammary tumors were observed as early as 7 to 10 days after LA7 cell injectionswhich indicated that the cells have strong tumorigenicity properties. The rats with mammarygland tumors were reactive lymphatic follicular hyperplasia, typical appearance of neoplasticcell with invasive features, high mitotic activity and necrosis consistent withadenocarcinomas. Also all measured LDH, ALP, ALT and GGT concentrations wereincreased in the tumor-bearing rat when compared to the normal group.Conclusion: The result of this study suggested that the LA7 cell-induced ratmammary gland tumor model may be useful for studies in breast cancer drug ornutraceutical research and development.