Prolonged treatment with γ-secretase inhibitor caused changes in expression of not only genes which were immediately downregulated, but also those of IKZF1 family of transcription factors: in Jurkat and 697 cells IKZF3 was decreased, and in CLL IKZF1, regardless of the Notch pathway inhibition. The gene discussed is IKZF1; the disease is B-cell chronic lymphocytic leukemia.