Notably, <i>Egr1</i> emerged as a strong tumor suppressor and its knockout resulted in approximately a fivefold increase in tumor size at 20 weeks (two-sample <i>t</i>-test, <i>p</i> < 0.05), exceeding the impact observed with <i>Rb1</i> loss. This evidence concerns the gene EGR1 and neoplasm.