Downregulation of estrogen receptor and modulation of growth of breast cancer cell lines mediated by paracrine stromal cell signals

Abstract

Purpose Breast cancers have a poorer prognosis if estrogen receptor expression was lost during recurrence. It is unclear whether this conversion is cell autonomous or whether it can be promoted by the microenvironment during cancer dormancy. We explored the ability of marrow-derived stromal cell lines to arrest co-cultured breast cancer cells and suppress estrogen receptor alpha (ER) expression during arrest, facilitating the emergence of estrogen-independent breast cancer clones. Methods Cancer cell growth, ER protein, microRNA and mRNA levels were measured in breast cancer cell lines exposed to conditioned medium from marrow stromal lines in the presence and absence of estrogen and of signaling pathway modulators. Results We demonstrate that paracrine signaling from the stromal cell line HS5 downregulated ER in T47D and MCF7 breast cancer cells. This occurred at the mRNA level and also through decreased ER protein stability. Additionally, conditioned medium (CM) from HS5 arrested the breast cancer cells in G0/G1 in part through interleukin-1 (IL1) and inhibited cancer cell growth despite activation of proliferative pathways (Erk and AKT) by the CM. Similar findings were observed for CM from the hFOB 1.19 osteoblastic cell line but not from two other fibroblastic marrow lines, HS27A and KM101. HS5-CM inhibition of MCF7 proliferation could not be restored by exogenous ER, but was restored by the IL1-antagonist IL1RA. In the presence of IL1RA, HS5-CM activation of AKT and Erk enabled the outgrowth of breast cancer cells with suppressed ER that were fulvestrant-resistant and estrogen-independent. Conclusions We conclude that marrow-derived stromal cells can destabilize estrogen receptor protein to convert the ER status of growth-arrested ER+ breast cancer cell lines. The balance between stromal pro- and anti-proliferative signals controlled the switch from a dormant phenotype to estrogen-independent cancer cell growth.

Syngeneic tobacco carcinogen–induced mouse lung adenocarcinoma model exhibits PD-L1 expression and high tumor mutational burden

“…We had shown that the selected marrow lines, HS-5 and HS-27A ( 41 ), express mesenchymal stem cell (MSC) markers (ref. 42 and data not shown), and CM from MSCs has been shown to augment growth of human lung cancer cell lines ( 43 ). We found that addition of CM from any of these sources to our DMEM culture medium augmented the growth of the FVBW-17 cells, with MG-63 CM increasing the growth most robustly.…”

The Tumor Microenvironment as a Regulator of Endocrine Resistance in Breast Cancer

“…This phenomenon was associated to reduced apoptosis in the co-culture model (63). Other publications have shown regulation of ER signaling in MCF-7 and T47D cells using either immortalized skin fibroblasts or marrow-derived stromal cells (64, 65). In first case the authors show that CAFs induce tamoxifen resistance by increasing mitochondrial activity in breast cancer cells.…”

Signaling pathways and steroid receptors modulating estrogen receptor α function in breast cancer

“…Paracrine signaling is likely to be the major mechanism through which stromal cells affect tumor cell function, as stromal cells secrete a variety of signaling molecules, including hormones and inflammatory cytokines, many of which have been shown to be associated with tumor progression in breast cancer patients, where they impinge on the function and phenotype of cancer epithelial cells. For example, coculture of fibroblasts with breast cancer cells has been shown to decrease expression of ER in the cancer cells (Brechbuhl et al 2017;Huang et al 2017;Morgan et al 2018) and activate potent growth factor pathways (e.g., AKT and MAPK), thereby modulating the response of the epithelial cancer cells to anti-estrogen treatment (Brechbuhl et al 2017;Huang et al 2017). Furthermore, the adipokines leptin and interleukin-6 (IL-6) have been shown to be associated with increased tumor size and metastasis in ER + breast cancer patients (Madeddu et al 2014).…”