Synthesis and biological evaluation of 6,9-disubstituted purine analogues inducing autophagy-mediated apoptosis and potentiating carboplatin response in high-grade serous ovarian cancer

Abstract

High-grade serous ovarian carcinoma (HGSOC) is the most lethal ovarian cancer subtype, characterized by late diagnosis, high recurrence, and resistance to platinum-based chemotherapy and PARP inhibitors. TP53 inactivation and defects in homologous recombination repair, including BRCA1/2 loss, necessitate new therapeutic strategies that engage alternative cell death pathways. Among candidate scaffolds, purine analogues have attracted attention due to their antimetabolite and kinase-modulating properties. Herein, we report the synthesis and biological evaluation of novel purine analogues, highlighting two derivatives bearing (4′-methyl-[1,1′-biphenyl]-4-yl) sulfonyl piperazine (26) or (4′-methoxy-[1,1′-biphenyl]-4-yl)sulfonyl piperazine (27) at the C-6 position of purine. Both compounds exhibited potent and consistent cytotoxicity across OVCAR-3, OVSAHO, and KURAMOCHI cell lines, with IC50 values below 10 μM. Mechanistic investigations revealed apoptosis induction, evidenced by caspase-3/7 activation, PARP cleavage, SubG1 accumulation, and Annexin V positivity in OVCAR-3 and OVSAHO cells. In addition, autophagy-associated responses, including LC3-II accumulation, p62 modulation, and sensitivity to pharmacological autophagy inhibition, were observed following treatment. Compounds 26 and 27 suppressed colony formation, retained activity in ex vivo patient-derived cultures and therapy-resistant cellular models, and exhibited lower cytotoxicity toward non-tumorigenic HGRC1 cells. Combination treatment with carboplatin resulted in synergistic cytotoxic effects. Molecular docking analyses suggested potential interactions with several signaling proteins, including Src, MAPK14, GSK3β, PDGFRA, and VEGFR2. Collectively, these findings identify compounds 26 and 27 as biologically active purine analogues with promising anti-HGSOC activity and support further evaluation in advanced preclinical models.