Quantitative MRI establishes the efficacy of PI3K inhibitor (GDC-0941) multi-treatments in PTEN-deficient mice lymphoma

Aim: To assess the efficacy of multiple treatment of phosphatidylinositol-3-kinase (PI3K) inhibitor on autochthonous tumours in Phosphatase and tensin homologue (PTEN)-deficient genetically engineered mouse Cancer models using a longitudinal magnetic resonance imaging (MRI) protocol.

Materials and methods: Using 3D MRI, B-cell follicular lymphoma growth was quantified in a PTEN(+/-)Lkb1(+/hypo) mouse line, before, during and after repeated treatments with a PI3K Inhibitor GDC-0941 (75 mg/kg).

Results: Mean pre-treatment linear tumour growth rate was 16.5±12.8 mm(3)/week. Repeated 28-day GDC-0941 administration, with 21 days 'off-treatment', induced average tumour regression of 41±7%. Upon cessation of the second treatment (which was not permanently cytocidal), tumours re-grew with an average linear growth rate of 40.1±15.5 mm(3)/week. There was no evidence of chemoresistance.

Conclusion: This protocol can accommodate complex dosing schedules, as well as combine different Cancer therapies. It reduces biological variability problems and resulted in a 10-fold reduction in mouse numbers compared with terminal assessment methods. It is ideal for preclinical efficacy studies and for phenotyping molecularly characterized mouse models when investigating gene function.