p53 controls the plasticity of mammary luminal progenitor cells downstream of Met signaling

Abstract

BackgroundThe adult mammary epithelium is composed of basal and luminal cells. The luminal lineage comprises two major cell populations, positive and negative for estrogen and progesterone receptors (ER and PR, respectively), both containing clonogenic progenitor cells. Deregulated ER/PR− luminal progenitor cells are suspected to be at the origin of basal-type triple-negative (TNBC) breast cancers, a subtype frequently associated with loss of P53 function and MET signaling hyperactivation. Using mouse models, we recently reported that p53 restricts luminal progenitor cell amplification whereas paracrine Met activation stimulates their growth and favors a luminal-to-basal switch. Here, we analyzed how these two critical pathways interact to control luminal progenitor function.MethodsWe have (i) established and analyzed the gene expression profile of luminal progenitors isolated by ICAM-1, a robust surface marker we previously identified; (ii) purified luminal progenitors from p53-deficient and p53-proficient mouse mammary epithelium to compare their functional and molecular characteristics; and (iii) analyzed their response to HGF, the major Met ligand, in three-dimensional cultures.ResultsWe found that luminal progenitors, compared to non-clonogenic luminal cells, overexpress Trp53 and numerous p53 target genes. In vivo, loss of Trp53 induced the expansion of luminal progenitors, affecting expression of several important p53 target genes including those encoding negative regulators of cell cycle progression. Consistently, p53-deficient luminal progenitors displayed increased proliferative and self-renewal activities in culture. However, they did not exhibit perturbed expression of luminal-specific markers and major regulators, such as Hey1, Elf5, and Gata3. Moreover, although expressing Met at higher level than p53-proficient luminal progenitors, p53-deficient luminal progenitors failed to acquire basal-specific features when stimulated by HGF, showing that p53 promotes the plastic behavior of luminal progenitors downstream of Met activation.ConclusionsOur study reveals a crosstalk between Met- and p53-mediated signaling pathways in the regulation of luminal progenitor function. In particular, it shows that neither p53 loss alone nor p53 loss combined with Met signaling activation caused an early detectable cell fate alteration in luminal progenitors. Conceivably, additional events are required to confer basal-specific characteristics to luminal-derived TNBCs.Electronic supplementary materialThe online version of this article (10.1186/s13058-019-1101-8) contains supplementary material, which is available to authorized users.

Laminin-binding integrins are essential for the maintenance of functional mammary secretory epithelium in lactation

“…S1). The two luminal populationsprogenitors (mostly ER -) and mature (ER + ) cells -were separated on the basis of their ICAM1 expression, as previously described (Chiche et al, 2019;Di-Cicco et al, 2015); Fig. S1A).…”

RAB6 GTPase regulates mammary secretory function by controlling the activation of STAT5

“…As previously described (Di-Cicco et al, 2015), we used ICAM-1 expression combined with the epithelial-specific marker CD24 to discriminate CD24 low ICAM1 + basal cells, CD24 high ICAM1luminal cells (ER + /PR + , referred to as HR + ) and CD24 high ICAM1 + luminal cells (mostly ER -/PR -; referred to as HR -) ( Fig.1A). Using the transcriptomic profiles of the HR + (ICAM1 -) and HR -(ICAM1 + ) luminal cell subsets that we previously established (Chiche et al, 2019), we analyzed the expression levels of the 58 Rab GTPase genes present in the microarrays. Only 19 Rab genes were found robustly expressed in both HR + and HRluminal cell populations ( Fig.…”

“…Heat map based on microarray data (Chiche et al, 2019) showing the relative gene expression of 58 RAB GTPases in the HR + and HRluminal cell populations isolated from adult virgin mice as shown in A (left). Genes expressed at a significant level appear in pink to red.…”

“…/www.ncbi.nlm.nih.gov/geo/ query/acc.cgi?acc=GSE122928(Chiche et al, 2019). The expression values (normalized Log2 gene expression level) are shown as mean ± SEM.…”

RAB6 GTPase is a crucial regulator of the mammary secretory function controlling STAT5 activation

“…RNA was isolated from whole mammary glands using Trizol reagent (Life Technologies) and further purified on a cleanup column (Qiagen). RNeasy Microkit was used for RNA extraction from isolated mammary cells, as described Chiche et al, 2019). To avoid eventual DNA contamination, purified RNA was treated with DNAse (Qiagen).…”