A) The mitotic checkpoint complex (Mad2, Cdc20, BubR1 and Bub3) is shown to inhibit the anaphase promoting complex/cyclosome (APC/C) until the last kinetochore is correctly attached to microtubules.
B) Evidence of lagging chromosomes and aneuploidy measured by FISH analysis on cells overexpressing Mad2.
C) MR images of Kras transgenic mice (TI-K) and Kras+Mad2 (TI-KM) mice on doxycycline at indicated times showing lung tumours (yellow circles) (left panel), after 2-6 weeks of doxycycline withdrawal showing complete regression (middle panel) and after 14-16 weeks off doxycycline (right panel) showing recurrent tumours in mice that overexpress Mad2. Moreover recurrent tumours from these mice are highly aneuploid.
Primary mammary cells from TetO-Mad2/TetO-Myc/MMTV-rtTA mice grown in 3D culture. Left panel shows never induced cells that are beginning to form a polarized acinus. Right panel: loss of epithelial cell polarity in an acinus grown from tritransgenic cells and exposed to doxycycline for 36h. White arrows show abundant mitotic cells and lagging chromosomes after Mad2 overexpression.
Sotillo’s research uses genetics and 3D cell culture systems to study the molecular mechanisms that lead to chromosomal instability and its consequences in tumour initiation and suppression.
Previous and current research
Chromosomal instability (CIN), the inability to correctly segregate sister chromatids during mitosis, is a hallmark of cancer cells. Overexpression of the mitotic checkpoint protein Mad2, commonly found in human tumours, leads to CIN and the development of aneuploid tumours in mouse models. Moreover, CIN can facilitate escape from oncogene addiction (the dependence of tumour cells on their initiating lesion for survival) and may be responsible for tumour relapse after targeted therapies. Very little is known about the mechanism of how and when CIN promotes tumour relapse. Our lab focuses on understanding the molecular mechanisms that lead to CIN and the consequences it may have in tumour initiation, suppression and relapse. We hope that the genes or proteins identified could be targeted therapeutically. We will use a combination of mouse genetics and highly innovative 3D in vitro culture systems.
Future projects and goals
- To study the dependence of tumour cells on the mitotic checkpoint in vivo and evaluate the potential for therapeutic interference with mitotic checkpoint genes.
- To study the effects of tumour regression and recurrence in chromosomally unstable tissues.
- To analyse the dual role of chromosome instability (tumour initiating and tumour suppressive) dependent on levels of aneuploidy, tissue type and molecular nature of the cooperating lesion(s).