The activation of doxycycline-inducible NOTCH1 and NOTCH3 in TT cells, through treatment with increased doses of doxycycline, has demonstrated a dose-dependent increase in NOTCH1, NOTCH3 and HES1 protein, a decrease in ASCL1 levels and ultimately a reduction in tumour growth in vitro and in vivo. The gene discussed is HES1; the disease is neoplasm.