Mechanisms of oncogene dependence and tumour relapse
(A) One cell in anaphase divides with the sets of chromosomes perpendicular to the apical surface, while keeping ZO1 localised to the luminal membrane.
(B) Confocal microscopy (5mm projection through the middle) shows epithelial cell polarity. E-Cadherin, (adherens junctions, lateral); ZO1, (tight junctions, apical); Integrin a6 (basolateral).
(C) Doxycycline exposure causes loss of epithelial polarity and filling of the lumen; Removal of doxycycline results in survival of a re-polarised cell layer, that acquires the ability to exclude Hoechst 33342. Left panels: Confocal microscopy (5mm projection through the middle) shows Dapi, GM130 (apical), ZO1 (tight junction), Integrina6 (basal) at indicated times. Middle panels: Bright-field pictures show: (top) small, hollow acini; (middle) filled, irregular shaped spheres (bottom) hollow, irregular shaped spheres that show debris of internal cells. Right panels: Exclusion of Hoechst 33342 (1 hour incubation) at indicated times
The Jechlinger group uses a 3D culture system of primary mouse mammary epithelial cells to study cancer-initiating oncogenes.
Previous and current research
Extensive evidence now supports the concept of oncogene addiction (the dependence of tumour cells on their initiating lesion for survival). In patients and mouse models interference with the activity of cancer-initiating oncogenes can result in tumour regression. However, novel therapies that target the products of mutant alleles in human cancers are only partly successful, since maintenance of remission requires long-term treatment and relapse often occurs in the presence of therapeutic agents. Hence, a better understanding of drug resistance and tumour recurrence is needed for the design of more successful anti-cancer strategies.
Transgenic mice carrying regulatable transgenes represent tractable systems for studying the mechanisms of oncogene dependence, the response and resistance to targeted drugs and tumour recurrence. In a complementary approach, we have developed a 3D culture system of primary mouse mammary epithelial cells to study detailed responses to the induction and de-induction of oncogenes (mimicking treatment with an ideally targeted drug). This 3D system produced phenotypic changes similar to those observed in the mammary glands of the transgenic mice from which the cultures were derived. In addition, this new approach identified and isolated cells that had survived oncogene withdrawal, exhibited characteristics of mammary gland progenitors and could efficiently re-populate the mammary fat pads of immundeficient mice. The successful isolation of a pure population of surviving cells after oncogene withdrawal will allow us to characterise these residual ‘dormant’ tumour cells in detail.
Future projects and goals
- Determine at which point during tumourigenesis cells acquire the ability to survive oncogene withdrawal.
- Identify the molecular properties that distinguish surviving-residual cells, from naïve cells.
- Interfere with the mechanisms important for survival of residual ‘dormant’ cells.