The making of mammary organoids to study mechanisms of squamous metaplasia

Abstract

Squamous Cell Carcinoma (SCC) is a frequent solid tumour and a major cause of mortality. In non-epidermoid epithelia SCC may arise from squamous metaplasia (SQM). Even though it is known to arise from environmental hazard, the mechanisms leading to SQM are still unknown. Previous work in the host lab has shown that DNA damage in the non-squamous cells of the human lung or the mammary gland, leads to squamous metaplasia. This might explain why SCC is frequent in the lung (30% of the tumours) but very rare in the mammary gland, less exposed to genotoxics. We aimed to study this precancerous process in a physiological mimicking 3D system. We wanted to study the relationship between the DNA damage epithelium and the SMQ, by using Mammary Gland Organoids (MGO). In this TFM, I have focused on the development of MGOs from mouse, first and human second, mammary gland. To this end, I have set up a method to analyze mammary branching following the induction of DNA damage or the block of mitosis. I have then studied the capacity of the MGOs to undergo SQM in response to severe DNA damage or to replication stress. These MGOs will constitute a good model to study the molecular and cellular mechanisms driving SQM.