Like the primary tumor tissue from ovariectomized animals, the myc-MT1 cells had a much greater abundance of the 61-kD MC20RP (arrow, Fig. 5A) than the wt ERα that was at such a low abundance that it could only be visualized when the immunoblot film was overexposed (Fig. 5A, arrowhead in the top panel). The gene discussed is ESR1; the disease is neoplasm.