INTRODUCTION & HYPOTHESIS
Androgens are key regulators of sebaceous function. We previously showed that DHT clearly induced the lipogenic differentiation of androgen sensitive sebocytes cultured in defined medium without the addition of any factor or specific metabolic complementation1. In a functional DHT-induced lipid accumulation assay, we identified the mTOR inhibitors rapamycin and torin as potential active compounds (SID poster#3). A link between mTOR and androgen signaling has previously been reported e.g. in androgen-sensitive prostate cancer cells, as well as a link between these processes and lipid synthesis2. Here we aimed at confirming that DHT-induced lipid synthesis/accumulation is at least in part dependent on mTOR activation in the SEBO662AR cell line and that the autophagic process is consequently modified by the androgenic treatment.
Androgen-induced lipogenic differentiation of androgen sensitive sebocytes is linked to mTOR pathway activation.
*Poster#3: Pharmacological effects of anti-androgens and other compounds in an androgen-sensitive sebocyte cell line.
MATERIALS & MEHODS
The mTOR antagonists rapamycin and torin were tested at 0.1 µM (SID poster#3*), alone or in association. Lipid accumulation was evidenced after 7 days by incubation with the fluorescent probe Bodipy®, and image analysis1. Lipid neosynthesis was measured after [14C]- acetate incorporation into lipids, chromatography and phosphorimaging1. Phospho-RPS6 and p62/SQSMT1 were evidenced by immunofluorescence after 6 h and 3/7 days, respectively. LC3II/I and p62/SQSMT1 relative expression were analysed by western blot after 3/7 days, as well as AKT phosphorylation (20 min activation by DHT or EGF).
1 – Effects of rapamycin, torin and their association (0.1 µM) on lipid synthesis/accumulation, after 7 days in control and DHT-treated sebocyte cells; immunofluorescence imaging & fluorescence quantification.
2 – DHT strongly increased phospho-RPS6 immunolabelling after 6 h of treatment.
In this model,
– The mTOR inhibitors Rapamycin and Torin inhibit DHT-induced lipid neosynthesis and accumulation in SEBO662AR cells.
– Conversely, DHT stimulates mTOR activation, through an AKT-independent pathway. Such effects have been previously reported in other androgen-sensitive models.
– As an expected consequence, DHT slows down the autophagic process.
– These results highlight a link between androgen stimulation, mTOR activation, autophagy limitation and lipogenic effects, in these sebocyte cells.
1 Barrault et al. (2015) J Steroid Biochem Mol Biol ;152:34-44
2 Audet-Walsh et al. (2018) Mol Cancer Res ; 16:1396-1405