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Molecular and Cellular Endocrinology
journal homepage: www.elsevier.com/locate/mce
Molecular and Cellular Endocrinology
The GRP78/BiP inhibitor HA15 synergizes with mitotane action against adrenocortical carcinoma cells through convergent activation of ER stress pathways
Carmen Ruggiero a, b, c, d, 1, Mabrouka Doghman-Bouguerra a, b, c, d, 1, Cyril Ronco a, e, Rachid Benhida a, e, Stéphane Rocchi a, f, Enzo Lalli a, b, c, d, *
a Université Côte d’Azur, Valbonne, 06560, France
b CNRS UMR 7275, Sophia Antipolis, Valbonne, 06560, France
” NEOGENEX CNRS International Associated Laboratory, Valbonne, 06560, France
d Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, 06560, France
e Faculté des Sciences, Institut de Chimie de Nice (ICN) - CNRS UMR 7272, 28, Avenue de Valrose, Nice, 06108, France INSERM U1065 - Equipe 12, Centre Méditerranéen de Médecine Moléculaire (C3M), Nice, 06200, France
ARTICLE INFO
Article history: Received 27 November 2017 Received in revised form 10 February 2018
Accepted 18 February 2018 Available online xxx
Keywords: Adrenocortical carcinoma ER stress Steroidogenesis
ABSTRACT
Many types of cancer cells present constitutively activated ER stress pathways because of their significant burden of misfolded proteins coded by mutated and rearranged genes. Further increase of ER stress by pharmacological intervention may shift the balance towards cell death and can be exploited therapeu- tically. Recent studies have shown that an important component in the mechanism of action of mitotane, the only approved drug for the medical treatment of adrenocortical carcinoma (ACC), is represented by activation of ER stress through inhibition of the SOAT1 enzyme and accumulation of toxic lipids. Here we show that HA15, a novel inhibitor of the essential ER chaperone GRP78/BiP, inhibits ACC H295R cell proliferation and steroidogenesis and is able to synergize with mitotane action. These results suggest that convergent activation of ER stress pathways by drugs acting via different mechanisms represents a valuable therapeutic option for ACC.
2018 Elsevier B.V. All rights reserved.
1. Introduction
The best therapeutic results in adrenocortical carcinoma (ACC) are obtained when the disease is localized at diagnosis and can be completely resected by surgery. However, prognosis is unfavorable for patients with relapsed or metastatic disease (Else et al., 2014; Creemers et al., 2016). In those cases, the mainstay of therapy consists in treatment with the adrenolytic agent mitotane, which can be associated to polychemotherapy in patients with progressive disease (Fassnacht et al., 2012). Mitotane (o,p’-DDD), a derivative of the dichlorodiphenyl-trichloroethane (DDT) insecticide, is also
used as an adjuvant treatment in patients resected for localized ACC but at a high risk of relapse (Terzolo et al., 2007). The specific toxicity of mitotane on adrenocortical cells has long been known (Nelson and Woodard, 1949), even if its mechanism of action remained uncertain. It has been shown that mitotane inhibits mitochondrial respiratory chain activity (Hescot et al., 2013) and induces mitochondrial morphofunctional changes (Poli et al., 2013) in adrenocortical cancer cells. Mitotane also has relevant effects on transcriptome (Zsippai et al., 2012) and proteome (Stigliano et al., 2008) profiles. A recent breakthrough study documented that mitotane inhibits sterol-O-acyl-transferase (SOAT1) (Sbiera et al., 2015). SOAT1 (also known as acyl-coenzyme A cholesterol acyl- transferase; ACAT1) is an enzyme enriched in mitochondria- associated membranes (MAM) (Rusiñol et al., 1994) which has the function to produce stores of esterified cholesterol, thereby pro- tecting cells from the damaging effects of free cholesterol. Choles- terol esters can then be rapidly made available as substrates for steroidogenesis after ACTH stimulation by the action of hormone- sensitive lipase (Kraemer, 2007). Mitotane inhibition of SOAT1,
Abbreviations: ACC, adrenocortical carcinoma; ER, endoplasmic reticulum; SERCA, sarcoplasmic/endoplasmic reticulum Ca2+-ATPase; UPR, unfolded protein response.
* Corresponding author. Institut de Pharmacologie Moléculaire et Cellulaire 660 route des Lucioles - Sophia Antipolis, 06560, Valbonne, France.
E-mail address: ninino@ipmc.cnrs.fr (E. Lalli).
1 These authors contributed equally to this study.
Please cite this article in press as: Ruggiero, C., et al., The GRP78/BiP inhibitor HA15 synergizes with mitotane action against adrenocortical carcinoma cells through convergent activation of ER stress pathways, Molecular and Cellular Endocrinology (2018), https://doi.org/10.1016/ j.mce.2018.02.010
C. Ruggiero et al. / Molecular and Cellular Endocrinology xxx (2018) 1-8
which probably occurs through interaction of this very lipophilic drug with membrane lipids (Scheidt et al., 2016), has the effect to substantially increase the intracellular content of free cholesterol. This is correlated to activation of endoplasmic reticulum (ER) stress in ACC cells (Sbiera et al., 2015). Accumulation of toxic lipids and misfolded proteins in the ER is sensed by several signaling cascades and triggers a homeostatic response aimed at limiting the effects of ER stress itself. Collectively this phenomenon is termed the unfolded protein response (UPR) (Walter and Ron, 2011). However, activation of ER stress beyond a certain threshold leads to impaired steroidogenesis and apoptosis in ACC cells, which are typical effects of mitotane action.
Severe adrenal toxicity in various animal species has been recognized as an important side effect of other SOAT1 inhibitors, which has limited their development as hypolipidemic and anti- atherosclerotic agents (Floettmann et al., 2013). Those findings led to the development of a selective and potent inhibitor of SOAT1 (ATR-101) as a novel therapeutic agent for ACC, which entered a clinical trial (https://clinicaltrials.gov/ct2/show/NCT01898715). Similarly to mitotane, ATR-101 activates the UPR in ACC cells and leads to their subsequent apoptosis (LaPensee et al., 2015). ATR-101 may also have additional mechanisms of action beyond SOAT-1 inhibition to produce ACC cell death and impair steroidogenesis (Cheng et al., 2016; Burns and Kerppola, 2017). Altogether, these results show that activation of the UPR and induction of ER stress are of important therapeutic value for ACC (Lalli, 2015).
The thiazole benzensulfonamide compound HA15 is a novel inhibitor of GRP78/BiP (Cerezo et al., 2016), a highly conserved molecular chaperone belonging to the Hsp70 family encoded by the HSPA5 gene, which has a pivotal role to assist protein folding in the ER and to regulate UPR (Wang et al., 2017). Recent studies have shown that treatment with HA15 is able to kill melanoma cells and even to overcome BRAF inhibitor resistance (Cerezo et al., 2016). Since mitotane has limited activity and relevant toxicity when used in the clinic, the aim of our work was to study the effect of GRP78/ BiP inhibition by HA15, which represents an alternative mechanism to produce ER stress compared to SOAT1 inhibition, and to assess its synergism with the action of mitotane in ACC cells.
2. Materials and methods
2.1. Chemicals
HA15 was synthesized as described (Ronco et al., 2017) and dissolved in DMSO (Sigma-Aldrich). Forskolin, mitotane, choles- terol-methyl-B-cyclodextrin and thapsigargin were purchased from Sigma-Aldrich; 22-NBD-cholesterol was purchased from Thermo Fisher.
2.2. Cell culture
H295R cells were cultured in DMEM/F-12 medium (Invitrogen) supplemented with 2% NuSerum (Corning), 1% ITS Plus (Corning) and penicillin-streptomycin (Invitrogen). H295R/TR N-Flag FATE1 cells where FATE1 expression can be induced by doxycycline (1 µg/ ml) treatment were cultured in H295R complete medium con- taining blasticidin (5 µg/ml; Cayla-InvivoGen) and zeocin (100 µg/ ml; Cayla-InvivoGen), as described (Doghman-Bouguerra et al., 2016).
2.3. RT-PCR
RNA was extracted using the RNeasy Mini kit (Qiagen). After reverse transcription using Superscript III (Invitrogen), RT-qPCR was performed on a LightCycler 480 instrument (Roche) using
the following primer pairs, as described (Doghman et al., 2007):
DDIT3: fwd CATCACCACACCTGAAAGCA; rev TCAGCTGCCATCTC TGCA.
StAR: fwd GCCACAGACTTCGGGAACAT; rev AGTAGCCACGTAAGT TTGGTCTTAGAG.
CYP11A1: fwd AGTCCACCTTCACCATGTCC; rev GAGAAGGGCCAC ATCTTCAG.
HSD3B2: fwd CGGGCCCAACTCCTACAAG; rev GCCATGTGTTTTCC AGAGGC.
CTP21A2: fwd GTCATCATTCCGAACCTCCAA; rev GAACTCATGTGG CCTCTCCC.
CYP17A1: fwd GGCACCAAGACTACAGTGATTG; rev AGAGTCAGCG AAGGCGATAC.
TBP: fwd GAACATCATGGATCAGAACAACAG; rev ATTGGTGTTCTG AATAGGCTGTG.
TATA-binding protein (TBP) was used as a reference gene for RT- qPCR normalization. RT-PCR to detect both spliced and unspliced isoforms of the XBP1 transcript was performed as described (Cerezo et al., 2016) using primers: fwd TTACGAGAGAAAACTCATGGCC; rev GGGTCCAAGTTGTCCAGAATGC. PCR products corresponding to spliced and unspliced XBP1 mRNA (289 bp and 263 bp, respec- tively) were separated on 4% agarose gels and visualized by ethidium bromide staining. GAPDH mRNA was amplified as control using primers fwd ACCAGGGCTGCTTTTAACTCT and rev AGTCC TTCCACGATACCAAAG.
2.4. Western blotting
Immunoblotting was performed as described (Doghman et al., 2007) using the following primary antibodies: anti GRP78/BiP (ab21685 Abcam), anti CHOP (5554S Cell Signaling), anti phospho- (Ser51, 3398S Cell Signaling) and total eIF2% (5324S Cell Signaling), anti ß-tubulin (T8328 Sigma-Aldrich), anti StAR (a kind gift of Dr. D. Stocco), anti HSD3B2 (a kind gift of Dr. V. Luu-The) and anti CYP17 (a kind gift of Dr. A. Conley).
2.5. Viability and apoptosis assays
H295R cells were seeded in 96-well plates at a density of 5000 cells/well. 24 h after treatment, cell viability was measured by the CellTiter-Glo and apoptosis by the Caspase-Glo 3/7 lumines- cence assays (Promega).
2.6. Proliferation assays
H295R cells were seeded in 96-well plates at a density of 5000 cells/well. Cell proliferation after 6 days incubation in the presence of the drugs or vehicle as a control was measured with the CellTiter-Glo luminescence assay (Promega).
2.7. Steroid assays
H295R cells were seeded in triplicate at a density of 50,000 cells/ ml in 24-well plates. Cortisol and DHEA-S were measured in tissue culture supernatants by specific enzyme-linked immunoasssays (Diagnostics Biochem Canada) after 24 of incubation with HA-15 (10 µM), mitotane (10 µM) or thapsigargin (5 µM) in basal condi- tions or after stimulation with forskolin (10 µg/ml). Hormone concentrations were normalized by protein content measured by the Bradford assay (Bio-Rad).
2.8. Immunofluorescence and visualization of intracellular lipid droplets by NBD-cholesterol
Immunofluorescence was performed as described (Doghman-
Please cite this article in press as: Ruggiero, C., et al., The GRP78/BiP inhibitor HA15 synergizes with mitotane action against adrenocortical carcinoma cells through convergent activation of ER stress pathways, Molecular and Cellular Endocrinology (2018), https://doi.org/10.1016/ j.mce.2018.02.010
Bouguerra et al., 2016) using the anti-ATF6 antibody (ab122897 Abcam). Intracellular lipid droplets were stained by NBD- cholesterol, as described (Sbiera et al., 2015). The total corrected cellular fluorescence (TCCF) of NBD-cholesterol was quantified by Image] (v1.48, https://imagej.nih.gov/ij/). Briefly, a contour was drawn around each cell and area and mean fluorescence and in- tegrated density were measured, along with several adjacent background readings. The TCCF = integrated density - (area of selected cell x mean fluorescence of background readings), was then calculated for each cell (n = 34/condition).
2.9. Statistical analysis
At least three biological replicates were performed for each experiment. Statistical analysis was performed on GraphPad Prism 5.0 software using one-way ANOVA with Bonferroni’s correction for multiple testing. A p-value <0.05 was considered to be statistically significant. Drug synergism was measured as described (Kroiss et al., 2016) according to Chou-Talalay method (Chou, 2010) using the CompuSyn software (http://www.combosyn.com). Coopera- tivity indices (CI) below 1 indicate additivity, while values between 0.3 and 0.7 indicate synergism.
3. Results
3.1. HA15 treatment induces ER stress in H295R cells
The HA15 molecule has been shown to induce ER stress and subsequent apoptosis in melanoma and other human tumor cell lines by inhibiting the GRP78/BIP ER chaperone (Cerezo et al.,
2016). However, no data still exist for ACC cells, that recent studies have shown to be sensitive to drugs causing ER stress by indirect mechanisms (Sbiera et al., 2015; LaPensee et al., 2015). For this reason we set up to study the effects of HA15 on cell viability, proliferation and steroidogenesis in ACC H295R cells.
In H295R cells HA15 dose-dependently increased expression of the DDIT3 mRNA, encoding the bZip transcription factor CHOP, which is upregulated following ER stress and has a pivotal role in the UPR (Fig. 1A). Cells were then cotreated with HA15 and stim- ulations known to increase steroidogenesis (forskolin and angio- tensin II), cholesterol loading (water-soluble cholesterol) or cause cell damage through ER stress (mitotane). None of those treatments by itself significantly increased DDIT3 mRNA expression compared to vehicle-treated cells. At the concentration used (10 uM), mito- tane caused a modest increase of DDIT3 transcript levels, that were however not significantly different from control. As expected, cotreatment with HA15 strongly increased DDIT3 mRNA expression in all conditions tested. Remarkably, DDIT3 transcript levels were significantly increased by cotreatment with HA15 plus mitotane compared to either drug alone (Fig. 1B). HA15, alone or in combi- nation with those other treatments, also increased the abundance of the XBP1 spliced isoform (Fig. 1C), which is consequent to acti- vation of the IRE1 endoribonuclease triggered by the UPR and lies upstream to DDIT3 upregulation (Schröder and Kaufman, 2005). CHOP was upregulated by HA15 also at the protein level (Fig. 1D). Mitotane by itself, but not the other treatments, also elicited lower levels of CHOP upregulation, consistently with the mRNA data (Fig. 1B). No change in GRP78/BiP protein levels or in the phos- phorylation state of eIF2%, which is a substrate for the PERK kinase during ER stress, was detected following HA15 treatment (Fig. 1D).
A
B
**
30
30
DDIT3 mRNA (fold of control)
DDIT3 mRNA (fold of control)
20
**
20.
T
10
10
T
T
0
0
[HA15] uM
0
0.5
1
5
7.5
10
HA15
+
+
+
+
+
FSK
All
Chol.
Mito.
C
D
kDa
CHOP
25
XBP1
unspliced
spliced
GRP78
70
GAPDH
p-eIF2a
35
HA15
+
+
+
+
+
elF2a
35
FSK
All
Chol.
Mito. Tg.
ß-tubulin
55
HA15
+
+
+
+
+
FSK
All
Chol. Mito. Tg.
Conversely, HA15 treatment could increase nuclear translocation of ATF6, which is also a marker of ER stress, compared to vehicle- treated cells (Fig. S1). We have previously shown that FATE1 upregulation driven by SF-1 transcription factor overexpression protects H295R cells from calcium- and drug-induced apoptosis by uncoupling ER and mitochondria (Doghman-Bouguerra et al., 2016). We then tested whether FATE1 expression in H295R/TR N- Flag FATE1 cells is able to counteract the effect of HA15 on trig- gering ER stress. However, FATE1 expression could not protect those cells from HA15-induced ER stress, as monitored by DDIT3 mRNA induction (Fig. S2).
3.2. HA15 reduces cell viability in H295R cells
While short-term (24 h) treatment with HA15 alone had no significant effect on H295R cell viability, it significantly decreased viability of cells cotreated with FSK, AII, cholesterol and mitotane (10 µM). None of those treatments was able to significantly reduce cell viability by itself (Fig. 2A). Conversely, only the HA15-
A
B
1
T
T
-
T
-
*
**
0.75
T
T
% viability
T
0.50
0.25
0
HA15
+
+
+
+
+
FSK
All
Chol.
Mito.
5
caspase 3/7 activity (fold of control)
4
3
2
T
-
T
1
0
HA15
+
+
+
+
+
FSK
All
Chol.
Mito.
cholesterol combination induced a significant increase of caspase 3/7 activity (Fig. 2B). No change in the intracellular content of lipid droplets, visualized by fluorescent cholesterol staining, was deter- mined by HA15 treatment compared to vehicle-treated cells (Fig. S3).
3.3. HA15 inhibits H295R cell proliferation synergizing with mitotane action
HA15 inhibited H295R cell proliferation in a dose-dependent manner with an IC50 of 3.8 uM (Fig. 3A). Combined treatment of different concentrations of the drug with a fixed concentration of mitotane (10 µM), that had no effect by itself (Fig. 3B), decreased HA15 IC50 to 2.9 µM, while combined treatment with 30 µg/ml cholesterol, which also had no effect by itself (data not shown), decreased HA15 IC50 to 1 µM (Fig. 3A). While mitotane had an IC50
A
150
+- HA15
- HA15 + mitotane
% viability
100
HA15 + cholesterol
50
0
0
2
4
6
8
10
[HA15] uM
B
100
Mitotane
80
Mitotane + HA15 (2.5 µM)
% viability
Mitotane + HA15 (5 u.M)
60
Mitotane + HA15 (7.5 µM)
40
20
0
5
10
20
50
100
[mitotane] uM
C
mitotane
HA15
1
(LM)
(LM)
O
5
2.5
10
2.5
20
2.5
50
2.5
100
2.5
mitotane
5
5
0.5
10
5
20
5
50
5
100
5
7
5
7.5
X
10
7.5
20
7.5
7
+
50
7.5
0
0
0.5
1
100
7.5
HA15
Please cite this article in press as: Ruggiero, C., et al., The GRP78/BiP inhibitor HA15 synergizes with mitotane action against adrenocortical carcinoma cells through convergent activation of ER stress pathways, Molecular and Cellular Endocrinology (2018), https://doi.org/10.1016/ j.mce.2018.02.010
| Dose mitotane (µM) | Dose HA15 (LM) | Fa | CI | DRI mitotane | DRI HA15 |
|---|---|---|---|---|---|
| 5 | 2.5 | 0.39 | 0.311 | 10.41 | 4.63 |
| 10 | 2.5 | 0.33 | 0.335 | 6.23 | 5.72 |
| 20 | 2.5 | 0.21 | 0.315 | 4.76 | 9.43 |
| 50 | 2.5 | 0.08 | 0.285 | 4.11 | 23.36 |
| 100 | 2.5 | 0.006 | 0.082 | 12.95 | 203.21 |
| 5 | 5 | 0.22 | 0.276 | 18.30 | 4.49 |
| 10 | 5 | 0.21 | 0.316 | 9.53 | 4.71 |
| 20 | 5 | 0.16 | 0.328 | 5.99 | 6.18 |
| 50 | 5 | 0.02 | 0.115 | 11.18 | 37.83 |
| 100 | 5 | 0.007 | 0.097 | 11.63 | 89.59 |
| 5 | 7.5 | 0.22 | 0.388 | 18.30 | 2.99 |
| 10 | 7.5 | 0.19 | 0.383 | 10.39 | 3.48 |
| 20 | 7.5 | 0.17 | 0.432 | 5.70 | 3.88 |
| 50 | 7.5 | 0.05 | 0.257 | 5.82 | 11.69 |
| 100 | 7.5 | 0.01 | 0.132 | 9.08 | 44.61 |
Fa, fraction affected; CI, cooperativity index; DRI, dose-reduction index.
of 23 µM on H295R cell proliferation, combination treatment with three fixed concentrations of HA15 (2.5, 5 and 7.5 uM) decreased mitotane IC50 to 3.8, 2.4 and 1.8 uM, respectively (Fig. 3B). We determined drug synergy using the Chou-Talalay method (Chou, 2010). This analysis showed that the two drugs exhibited signifi- cant synergism in antagonizing H295R cell proliferation (Table 1 and Fig. 3C).
3.4. HA15 and other treatment inducing ER stress inhibit cortisol and DHEA-S production in H295R cells
Since ER stress was shown to inhibit steroidogenesis in mouse
Leydig cells (Park et al., 2013), we investigated the effect of HA15 and other stimulations producing ER stress on steroid production in H295R cells. HA15 significantly decreased forskolin-stimulated, but not basal, cortisol (Fig. 4A) and DHEA-S (Fig. 4B) production. In addition, other treatments able to induce ER stress (the SOAT1 in- hibitor mitotane and the SERCA inhibitor thapsigargin) inhibited forskolin-stimulated cortisol (Fig. 4C) and DHEA-S (Fig. 4D), simi- larly to HA15. The effect of HA15 on steroidogenesis could be explained by a reduction in the forskolin-stimulated expression of HSD3B2, CYP11A1, CYP21A2 and CYP17A1, but not StAR mRNAs (Fig. 5A-E). The effects of HA15 on transcript levels were confirmed by protein analysis for StAR, 3ß-HSD and CYP17 (Fig. 5F).
A
B
400
400
cortisol (% of control)
300
DHEA-S (% of control)
300
**
200
200
100
100
0
0
HA15
+
+
HA15
+
+
FSK
FSK
C
D
500
control
400
control
cortisol (% of control)
400
HA15
mitotane
DHEA-S (% of control)
HA15
T
200
mitotane
300
TG
T
T
TG
T
200
T
100
T
T
T
100
T
0
0
basal
FSK
basal
FSK
A
B
StAR relative expression (fold over control)
6
CYP11A1 relative expression (fold over control)
3
5
4
2
3
2
1
1
*
0
0
FSK
FSK
C
D
HSD3B2 relative expression (fold over control)
12
CYP21A2 relative expression (fold over control)
3
10
8
2.
6
**
4
1
2
0
0
FSK
FSK
E
F
CYP17A1 relative expression (fold over control)
kDa
10
StAR
34
8
36-HSD
55
6
4
CYP17
55
2
ß-tubulin
55
0
HA15
+
+
FSK
FSK
4. Discussion
ER stress pathways are often activated in cancer cells, due to the accumulation of misfolded proteins produced because of gene mutations and genomic rearrangements. This finding led to the
suggestion that further increase of ER stress by pharmacological intervention may shift the balance towards cell death and can be exploited therapeutically (Nagelkerke et al., 2014). The HA15 molecule is the lead compound of a novel series of N-(4-(3- aminophenyl)thiazol-2-yl)acetamide molecules which have anti-
C. Ruggiero et al. / Molecular and Cellular Endocrinology xxx (2018) 1-8
proliferative and cytotoxic activities against a panel of cancer cell lines, including melanoma cell lines resistant to standard treat- ments (Cerezo et al., 2016; Ronco et al., 2017). HA15 has been shown to bind to and to inhibit the essential ER chaperone GRP78/ BiP, leading to strong activation of ER stress pathways and subse- quent cell death by apoptosis and autophagy (Cerezo et al., 2016). Here we have shown that HA15 is also active against the ACC cell line H295R, inhibiting both its proliferation and steroid production. Importantly, HA15 displays a synergistic effect with mitotane, the only drug approved for treatment of ACC. The effects of mitotane and HA15 converge to activate ER stress pathways through different mechanisms: inhibition of SOAT-1 activity by mitotane, with consequent accumulation of toxic free cholesterol (Sbiera et al., 2015) and GRP78/BiP inhibition by HA15, which triggers the UPR (Cerezo et al., 2016). As expected, we could not detect depletion of intracellular lipid droplets after HA15 treatment of H295R cells (Fig. S3), as shown for mitotane (Sbiera et al., 2015). On the other side, cholesterol concentrations that were not toxic by themselves could significantly potentiate the action of HA15 on H295R caspase 3/7 activity and proliferation (Figs. 2B and 3A). These results sug- gest that HA15 and mitotane act through different mechanisms to boost ER stress responses in ACC cells.
The results of our study are relevant in a therapeutic perspective since mitotane has serious drawbacks as a therapy for ACC: mild to moderate toxicity, long time needed to reach therapeutic plasma concentrations and limited activity in the treatment of metastatic disease (Haak et al., 1994; Vezzosi et al., 2018). For this reason, it would be very important to have available pharmacological agents that may potentiate the action of mitotane. In this line, it has been shown that the proteasome inhibitors bortezomib and carfilzomib, which also activate ER stress, can synergize with mitotane to kill H295R cells (Kroiss et al., 2016). Another therapeutically relevant effect of HA15 in the perspective to decrease the hormonal burden in ACC consists in its capacity to suppress steroidogenesis in H295R cells by inhibiting the expression of steroidogenic enzymes downstream of StAR (Fig. 5). Remarkably, other treatments able to activate ER stress pathways (mitotane and thapsigargin) had the same effect (Fig. 4C and D). These data are consistent with previous observations that induction of ER stress by elevated doses of hCG significantly decreases steroidogenesis in mouse Leydig cells (Park et al., 2013). Altogether, the effects of HA15 on ACC cell proliferation and steroid production and its lack of apparent toxicity in mouse (Cerezo et al., 2016) suggest that this molecule and its derivatives are promising candidates to be further evaluated in animal models and in clinical studies.
Conflicts of interest
None declared.
Acknowledgements
This work was supported by the French National Research Agency (ANR) through the “Investments for the Future” Labex SIGNALIFE (ANR-11-LABX-0028-01) grant. C.R. was the recipient of a postdoctoral fellowship from the Fondation de France. We thank Drs. D. Stocco, V. Luu-The and A. Conley for the gift of antibodies and Dr. S. Sbiera for discussions.
Appendix A. Supplementary data
Supplementary data related to this article can be found at https://doi.org/10.1016/j.mce.2018.02.010.
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