When MDA cells were inoculated orthotopically in the mammary gland, tumor appearance was slightly retarded in hypothyroid animals in both parental and TRβ-expressing cells (Figure 2C) and tumor volume was also smaller (Figure 2D), although differences were less marked than those observed with hepatocarcinoma cells and were only statistically significant at 9 weeks post-inoculation of MDA-TRβ cells. The gene discussed is THRB; the disease is neoplasm.