Pathology of LA7 cell induced tumours in Sprague Dawley rats

Development and evaluation of various experimental animal models for study of various aspects of human and animal cancers is a continuous requirement in cancer research. In the present study, pathology of LA7 cell induced tumours were studied in 50 female Sprague Dawley rats of about 30 days of age which were divided into two groups. Group A (experimental) included 36 rats which were administered with LA7 cells at the dose rate of 6×10⁶ cells in 200pl subcutaneously. Group B (n = 14) served as control. After development of palpable tumours, 3 animals each were sacrificed at three days interval till 30 days and three animals were sacrificed on 45^th day. Two animals each were sacrificed at weekly interval from the control group. During 45 days of experimental period, total 33 (91.66%) mammary tumours were induced in Group A. The average number of tumours per animal (Tumour frequency) was found to be 1.0 tumour. The appearance of first tumour was observed at 3^rd to 7^th day post injection (DPI) of cells. The average latency period was found to be 4.82 ± 0.29 day. Out of 33 induced tumours, 12 tumours were growing and 11 regressing and 10 were of regressed type. Within the experiment period, 10 tumours completely regressed after attaining growth stage and were found to regress to original detectable size or smaller, as early as on 9^th DPI and as late as on 27^th DPI. Histologically, the tumours were mostly undifferentiated or poorly differentiated carcinomas. Only five tumours showed either distinct acinar pattern or cystic appearance. The tumour induction with LA7 cells was found to be very fast with very high rate of induction. However, due to autoregressive nature of tumour, use of this model for different experiments need to be done cautiously.