Cdh1 and Pik3ca mutations cooperate to induce Immune-Related Invasive Lobular Carcinoma of the Breast

CDH1 and PIK3CA are the two most frequently mutated genes in Invasive Lobular Carcinoma (ILC) of the breast. Transcription profiling has identified molecular subtypes for ILC, one of which - Immune-Related (IR) - is associated with gene expression linked to lymphocyte and macrophage infiltration. Here we report that homozygous deletion of Cdh1 together with mutational activation of Pik3ca in mammary epithelium of genetically modified mice leads to rapid formation of IR-ILC-like tumors with immune cell infiltration, as well as gene expression signatures linked to TRegulatory (Treg) cell signaling and immune checkpoint inhibitor pathway activation. Interestingly, these tumors show enhanced Oct4-, Hif1á-, YAP-, Shh-, Rac- and Notch-dependent transcription/signaling, features in common with human IR-ILC and therefore potential targets for therapy. Gene expression profiling reveals immune infiltration and similarities to a subtype of human Invasive Lobular carcinoma. Agilent gene expression profiling of mouse mammary tumors.