Journal Article

PIK3CAH1047R induces multipotency and multi-lineage mammary tumours

Kohler, Hubertus, Reavie, Linsey, Eichlisberger, Tobias, Couto, Joana Pinto, De Silva, Duvini, Roloff, Tim, Koren, Shany, Bentires-Alj, Mohamed, Cardiff, Robert D., Aina, Olulanu, Stadler, Michael B., Britschgi, Adrian

2015

Overview

PIK3CA mutations are associated with distinct types of human breast cancers but the cellular origin and mechanisms responsible for this heterogeneity were unclear; here, using a genetic approach in mice, the PIK3CA H1047R mutation is shown to induce multipotent stem-like cells and mammary tumours with different levels of malignancy depending on the cell of origin. Effects of mutant PIK3CA on mammary cell fate PIK3CA mutations are associated with distinct types of human breast cancers, however, the cellular origin and the mechanisms responsible for this heterogeneity was unclear. Two groups reporting in this issue of Nature have used a genetic approach in mice to demonstrate that tumours originating from different breast cell types induced cancer with different morphologies, growth and invasiveness properties. PIK3CA mutations appear to activate a genetic program directing multiple cells fates in normally lineage-restricted cell types. The adult mouse mammary epithelium contains self-sustained cell lineages that form the inner luminal and outer basal cell layers, with stem and progenitor cells contributing to its proliferative and regenerative potential 1 , 2 , 3 , 4 . A key issue in breast cancer biology is the effect of genomic lesions in specific mammary cell lineages on tumour heterogeneity and progression. The impact of transforming events on fate conversion in cancer cells of origin and thus their contribution to tumour heterogeneity remains largely elusive. Using in situ genetic lineage tracing and limiting dilution transplantation, we have unravelled the potential of PIK3CA H1047R , one of the most frequent mutations occurring in human breast cancer 5 , to induce multipotency during tumorigenesis in the mammary gland. Here we show that expression of PIK3CA H1047R in lineage-committed basal Lgr5-positive and luminal keratin-8-positive cells of the adult mouse mammary gland evokes cell dedifferentiation into a multipotent stem-like state, suggesting this to be a mechanism involved in the formation of heterogeneous, multi-lineage mammary tumours. Moreover, we show that the tumour cell of origin influences the frequency of malignant mammary tumours. Our results define a key effect of PIK3CA H1047R on mammary cell fate in the pre-neoplastic mammary gland and show that the cell of origin of PIK3CA H1047R tumours dictates their malignancy, thus revealing a mechanism underlying tumour heterogeneity and aggressiveness.

• Publisher: Nature Publishing Group UK
• Subject: 13/100 / 13/31 / 13/51 / 14/63 / 38/61 / 631/532/2436 / 64/60 / Humanities and Social Sciences / letter / multidisciplinary / Science