A functional drug re-purposing screening identifies carfilzomib as a drug preventing 17β-estradiol: ERα signaling and cell proliferation in breast cancer cells

Abstract

Most cases of breast cancer (BC) are estrogen receptor α-positive (ERα+) at diagnosis. The presence of ERα drives the therapeutic approach for this disease, which often consists of endocrine therapy (ET). 4OH-Tamoxifen and faslodex (i.e., fulvestrant - ICI182,780) are two ETs that render tumor cells insensitive to 17β-estradiol (E2)-dependent proliferative stimuli and prevent BC progression. However, ET has limitations and serious failures in different tissues and organs. Thus, there is an urgent need to identify novel drugs to fight BC in the clinic. Re-positioning of old drugs for new clinical purposes is an attractive alternative for drug discovery. For this analysis, we focused on the modulation of intracellular ERα levels in BC cells as target for the screening of about 900 Food and Drug Administration (FDA) approved compounds that would hinder E2:ERα signaling and inhibit BC cell proliferation. We found that carfilzomib induces ERα degradation and prevents E2 signaling and cell proliferation in two ERα+ BC cell lines. Remarkably, the analysis of carfilzomib effects on a cell model system with an acquired resistance to 4OH-tamoxifen revealed that this drug has an antiproliferative effect superior to faslodex in BC cells. Therefore, our results identify carfilzomib as a drug preventing E2:ERα signaling and cell proliferation in BC cells and suggest its possible re-position for the treatment of ERα+ BC as well as for those diseases that have acquired resistance to 4OH-tamoxifen.

A high throughput method to study the physiology of E2:ERα signaling in breast cancer cells

“…Moreover, the fact that both everolimus and bortezomib (Velcade®), a 26S proteasome inhibitor, have been previously shown to induce ERα degradation and to prevent MCF-7 cell proliferation (Lui, New, Ogony, Thomas, & Lewis-Wambi, 2016;Thaler et al, 2015) strongly support the notion that our procedure can efficiently recognize compounds modulating ERα levels and cell proliferation. Remarkably, it is important to note here that present discoveries additionally support the concept that the selective modulation of ERα intracellular levels can be used as a pharmacological target to identify novel molecules targeting E2:ERα signaling in BC cells Busonero, Leone, Klemm, et al, 2017).…”

“…In this respect, multiple high throughput methods (e.g., in silico and in vitro ERα binding assays; screens either for drugs inhibiting receptor transcriptional activity or for anti‐proliferative drugs) have been employed either to discover ERα ligands, which could work as ERα degraders, to identify inhibitors of ERα transcriptional activity or to select specific molecules that directly inhibit E2‐induced cell proliferation (Campbell et al, ; Giamas et al, ; Overk et al, ; Singh et al, ). We have recently added to this repertoire of methods the evaluation of the effects of drugs on ERα levels by assuming that drug‐induced deregulation of ERα content in BC cells would block cell proliferation (Acconcia et al, ; Busonero, Leone, Acconcia, et al, ; Busonero, Leone, Klemm, et al, ; Totta et al, ).…”

“…Recently, we approached this task by administering about 900 molecules to BC cells with the aim of identifying novel drugs changing ERα intracellular levels. We found that emetine, an alkaloid extracted from the ipecac root with anti‐parasitic and anti‐contraceptive effects and carfilzomib, a third generation 26S proteasome inhibitor used for the treatment of multiple myeloma, induce ERα degradation and prevent BC cell proliferation by affecting cellular pathways unrelated to E2:ERα signaling (Busonero, Leone, & Acconcia, ; Busonero, Leone, Klemm, & Acconcia, ). In turn, we proposed that the measurement of ERα intracellular levels can be used to fish out molecules that interfere with E2:ERα signaling and/or to identify novel and potentially druggable pathways affecting it (Acconcia et al, ).…”

The Network of Angiotensin Receptors in Breast Cancer

“…In this respect, different strategies are being used to identify novel BC treatments [ 14 ]. Our research group has recently introduced the concept of targeting the selective modulation of ERα levels as a promising approach to discover new anti-BC compounds [ 14 , 59 , 60 , 61 ]. We have indeed demonstrated that drugs that do not necessarily bind to ERα but instead change the amount of ERα protein in BC cells can prevent BC cell proliferation and subsequent tumor growth [ 14 ].…”

“…We have indeed demonstrated that drugs that do not necessarily bind to ERα but instead change the amount of ERα protein in BC cells can prevent BC cell proliferation and subsequent tumor growth [ 14 ]. In turn, we demonstrated this by screening a library of 1018 Food and Drug Administration (FDA)-approved drugs in BC cells to search for molecules that modify ERα content and prevent BC cell growth [ 14 , 59 , 61 , 62 ]. This line of research led to the discovery that more than 50 FDA-approved compounds affected ERα content in MCF-7 cells and, among them, 11 also inhibited cell proliferation [ 59 ].…”