Figure 3 from Synergistic Effects of PARP Inhibition and Cholesterol Biosynthesis Pathway Modulation

Niraparib-specific modulation of cholesterol biosynthesis pathway. A, A scheme of cholesterol biosynthesis pathway, on the right indicated is modulation observed upon partial LSS inhibition (resulting from activation of the 24,25-epoxycholesterol shunt pathway). B, Quantification of steroids levels from the cholesterol biosynthesis pathway in breast cancer cell line T47D treated for 48 hours with niraparib (4 μmol/L), olaparib (10 μmol/L) or LSS inhibitor Ro-48-8071 (1 nmol/L). Mean of technical replicates per steroid (n = 2–3) is shown (two-tailed unpaired T test with Welch’s correction vs. DMSO, *, P ≤ 0.05, **, P ≤ 0.01). Niraparib-specific modulation correlates with partial inhibition of LSS enzyme by Ro-48-8071: increase in 24,25-epoxycholesterol levels pointing out to activation of 24,25-epoxysterol shunt pathway and up-regulation of Bloch pathway metabolites (details in Supplementary Fig. S3C). C, Heat map (n = 1) displaying relative stabilization (compared with control treatment) of DHCR24 observed upon 48 hours treatment with niraparib (x-axis: 0.24, 1.2, 6, and 30 μmol/L) across 12 temperatures (y-axis: 42°C–63.9°C) in T47D in 2D-TPP experiment. Olaparib has no significant effect in this cell line on the thermal stability of enzymes in the cholesterol biosynthesis pathway (Supplementary Table S5). D, Transcriptomic analysis of T47D cell line treated with niraparib or olaparib (10 μmol/L; 48 hours). Mean fold changes (n = 3) and adjusted P values from one representative experiment are shown. Black are all detected transcripts belonging to the cholesterol biosynthesis pathway, the significantly [adj. P < 0.05, |log₂ fc| > log₂ (1.5)] modulated ones are indicated with name. Niraparib-induced modulation leads to the downregulation of several enzymes involved in all branches of the cholesterol biosynthesis pathway (mevalonate, prenylation, Bloch, and Kandutsch–Russell) and to upregulation of genes involved in cholesterol efflux (LXR signaling). The effect size after olaparib treatment is much smaller. E, Proteomic analysis of T47D cells treated with niraparib or olaparib (10 μmol/L; 48 hours). Mean fold changes (n = 3) and adjusted P values from one representative experiment are shown. Black are all detected proteins belonging to the steroid biosynthesis pathway, the significantly [adj. P < 0.05, |log₂ fc| > log₂ (1.5)] modulated ones are indicated with name. Niraparib decreases CYP51A1 (lanosterol 14α-demethylase) enzyme levels (Supplementary Fig. S4A).