(A) Tumour growth of parental Dbt-indP3F cells and associated primary tumour-derived cell lines in the presence of doxycycline. (B) Tumour growth of parental Dbt-MYCN/indP3F cells and associated primary tumour derived cell lines in the presence of doxycycline. (C) Tumour growth of parental Dbt-MYCN/indP3F cells and three subclones (C2, C11, C12) in the presence of doxycycline. (D) Tumour growth of a Dbt-MYCN/indP3F recurrent tumour-derived cell line in the presence or absence of doxycycline. (E) Regression and recurrent tumour formation of parental Dbt-MYCN/indP3F cells and subclones C2, C11, and C12 after doxycycline withdrawal. (F) Regression and recurrent tumour formation of Dbt-MYCN/indP3F primary tumour-derived cell lines after doxycycline withdrawal. In parts E and F, doxycycline was withdrawn after the tumours were palpable. Arrows indicate time points of doxycycline withdrawal. Symbols: +/+, continuous doxycycline treatment; −/−, no doxycycline treatment; +/−, doxycycline treatment followed by doxycycline withdrawal.