Repurposing of Antifungal Drug Flucytosine/Flucytosine Cocrystals for Anticancer Activity against Prostate Cancer Targeting Apoptosis and Inflammatory Signaling Pathways

This study aimed to repurpose the
antifungal drug flucytosine (FCN)
for anticancer activity together with cocrystals of nutraceutical
coformers sinapic acid (SNP) and syringic acid (SYA). The cocrystal
screening experiments with SNP resulted in three cocrystal hydrate
forms in which two are polymorphs, namely, FCN-SNP F–I and
FCN-SNP F–II, and the third one with different stoichiometry
in the asymmetric unit (1:2:1 ratio of FCN:SNP:H2O, FCN-SNP
F–III). Cocrystallization with SYA resulted in two hydrated
cocrystal polymorphs, namely, FCN-SYA F–I and FCN-SYA F–II.
All the cocrystal polymorphs were obtained concomitantly during the
slow evaporation method, and one of the polymorphs of each system
was produced in bulk by the slurry method. The interaction energy
and lattice energies of all cocrystal polymorphs were established
using solid-state DFT calculations, and the outcomes correlated with
the experimental results. Further, the in vitro cytotoxic activity
of the cocrystals was determined against DU145 prostate cancer and
the results showed that the FCN-based cocrystals (FCN-SNP F–III
and FCN-SYA F–I) have excellent growth inhibitory activity
at lower concentrations compared with parent FCN molecules. The prepared
cocrystals induce apoptosis by generating oxidative stress and causing
nuclear damage in prostate cancer cells. The Western blot analysis
also depicted that the cocrystals downregulate the inflammatory markers
such as NLRP3 and caspase-1 and upregulate the intrinsic apoptosis
signaling pathway marker proteins, such as Bax, p53, and caspase-3.
These findings suggest that the antifungal drug FCN can be repurposed
for anticancer activity.