Nitroalkenes exploit dependence on autophagy-lysosome pathway in PARPi-Resistant triple negative breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Poly-ADP ribose polymerase inhibitors (PARPi) are effective against cancers with deficient DNA double-strand break repair.
• Resistance to PARPi, often due to enhanced DNA repair or autophagy, presents a significant clinical challenge.
• Unsaturated fatty acid nitroalkene derivatives (NFA) demonstrate anticancer properties, sensitizing cancer cells to DNA-damaging agents.

Purpose of the Study:

• To investigate the potential of nitro-oleic acid (OA-NO2) in re-sensitizing PARPi-resistant triple-negative breast cancer (TNBC) cells to PARPi therapy.
• To elucidate the molecular mechanisms underlying OA-NO2's action in overcoming PARPi resistance.

Main Methods:

• RNA-sequencing (RNA-seq) analysis of PARPi-resistant TNBC cell lines to identify molecular pathways involved in resistance.
• Bio-orthogonal chemical analysis to identify novel targets of OA-NO2.
• Functional assays to assess the impact of OA-NO2 on autophagy, lysosome function, and SQSTM1/p62 protein behavior.

Main Results:

• RNA-seq revealed upregulation of autophagy and lysosomal pathways in PARPi-resistant TNBC cells.
• SQSTM1/p62 was identified as a novel OA-NO2 target, with OA-NO2 alkylating critical redox-sensitive cysteine residues (Cys105 and Cys113).
• Alkylation of p62 by OA-NO2 impaired its oligomerization, degradation, and subsequent inhibition of autophagy, mimicking Cys-to-Ala mutations.

Conclusions:

• Nitro-oleic acid (OA-NO2) re-sensitizes PARPi-resistant TNBC cells by targeting and inhibiting the autophagy regulator SQSTM1/p62.
• Combination therapy with PARPi and OA-NO2 demonstrates synergistic effects, inhibiting p62-associated autophagy and lysosome function.
• OA-NO2 holds significant clinical potential for treating patients with PARPi-resistant TNBC.