👤 Michal Mikula

Resistance to olaparib is the major obstacle in targeted therapy for ovarian cancer (OC) with poly(ADP-ribose) polymerase inhibitors (PARPis), prompting studies on novel combination therapies to enhance olaparib efficacy. Despite identifying various mechanisms, understanding how OC cells acquire PARPi resistance remains incomplete. This study investigated microRNA (miRNA) expression in olaparib-sensitive (PEO1, PEO4) and previously established olaparib-resistant OC cell lines (PEO1-OR) using high-throughput RT-qPCR and bioinformatic analyses. The role of miRNAs was explored regarding acquired resistance and resensitization with the ATR/CHK1 pathway inhibitors. Differentially expressed miRNAs were used to construct miRNA-mRNA regulatory networks and perform functional enrichment analyses for target genes with miRNet 2.0. TCGA-OV dataset was analyzed to explore the prognostic value of selected miRNAs and target genes in clinical samples. We identified potential processes associated with olaparib resistance, including cell proliferation, migration, cell cycle, and growth factor signaling. Resensitized PEO1-OR cells were enriched in growth factor signaling via PDGF, EGFR, FGFR1, VEGFR2, and TGFβR, regulation of the cell cycle via the G2/M checkpoint, and caspase-mediated apoptosis. Antibody microarray analysis confirmed dysregulated growth factor expression. The addition of the ATR/CHK1 pathway inhibitors to olaparib downregulated FGF4, FGF6, NT-4, PLGF, and TGFβ1 exclusively in PEO1-OR cells. Survival and differential expression analyses for serous OC patients revealed prognostic miRNAs likely associated with olaparib resistance (miR-99b-5p, miR-424-3p, and miR-505-5p) and resensitization to olaparib (miR-324-5p and miR-424-3p). Essential miRNA-mRNA interactions were reconstructed based on prognostic miRNAs and target genes. In conclusion, our data highlight distinct miRNA profiles in olaparib-sensitive and olaparib-resistant cells, offering molecular insights into overcoming resistance with the ATR/CHK1 inhibitors in OC. Moreover, some miRNAs might serve as potential predictive signature molecules of resistance and therapeutic response. Show less

Although the degradome, which comprises proteolytic fragments of blood proteins, presents a potential source of diagnostic biomarkers, studies on cancer peptide biomarkers have provided inconsistent conclusions. In the present study, we reevaluated the usefulness of serum degradome analyses for searching peptide cancer biomarker candidates. Particular attention was paid to pre-analytical factors influencing the variability of determined peptide levels, including clotting time and control group selection. Studies were conducted on 44 and 86 serum samples collected from cancer patients and healthy individuals, respectively, using liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS)-based analyses. We identified 1373 unique peptides, nearly 40% of which originated from five blood proteins: fibrinogen alpha chain, apolipoprotein A-IV (APOA4), complement C3, apolipoprotein A-I, and alpha-1-antitrypsin. A set of 118 and 88 peptides exhibited highly significant differences (adjusted p-value ≤ 0.01 and fold change ≥ 2) in pair-wise comparisons of control vs. prostate cancer and control vs. colorectal cancer, respectively, with 37 peptides displaying a consistent direction of change for these pair-wise comparisons. The levels of 67 peptides differed significantly in serum samples collected from healthy individuals immediately prior to colonoscopy and those who underwent colonoscopic examination at least four weeks earlier. Of them, 49 peptides originated from APOA4. Whereas earlier studies, including ours, have utilized fragments of fibrinopeptide A (FPA) to distinguish cancer from healthy cases, here we show that their absolute abundance is a sensitive indicator of clotting time. These observations may have implications for future serum peptidome studies since these issues have not previously been recognized. Show less