Anticancer activity of RAPTA-EA1 in triple-negative BRCA1 proficient breast cancer cells: single and combined treatment with the PARP inhibitor olaparib

Abstract

RAPTA-EA1 is a promising glutathione transferase (GSTP-1) inhibitor that has previously been shown to inhibit the growth of various breast cancer cells. We studied the anticancer activity of RAPTA-EA1 on triple-negative BRCA1 competent breast cancer MDA-MB-231 cells. MDA-MB-231 cells are significantly more sensitive to RAPTA-EA1 than MCF-7 cells. Treatment reveals a higher degree of cytotoxicity than cisplatin against both cell lines. Ruthenium accumulation in MDA-MB-231 cells is mainly in the nuclear fraction (43%), followed by the cytoplasm (30%), and the mitochondria (27%). RAPTA-EA1 blocks cell growth at the G2/M phase, leading to nuclear condensation and cell death. The compound slightly inhibits DNA replication of the 3,426-bp fragment of the BRCA1 exon 11 of the cells, with approximately 0.6 lesion per the BRCA1 fragment. The expression of BRCA1 mRNA and its protein in the Ru-treated cells is curtailed by 50-80% compared to the untreated controls. Growth inhibition of the triple-negative BRCA1 wild-type MDA-MB-231 and the sporadic BRCA1 wild-type MCF-7 cells by olaparib (a poly [ADP-ribose] polymerase (PARP) inhibitor) is dose-dependent, with MDA-MB-231 cells being two-fold less susceptible to the drug than MCF-7 cells. Combining olaparib with RAPTA-EA1 results in a combination index (CI) of 0.78 (almost additive) in MDA-MB-231 cells and 0.24 (potent synergy) in the MCF-7 cells. The PARP inhibitor alone differently regulates the expression of BRCA1 mRNA in both cell lines, whereas the olaparib-RAPTA-EA1 combination induces overexpression of BRCA1 mRNA in these cells. However, the expression level of the BRCA1 protein is dramatically reduced after treatment with the combined inhibitors, compared with the untreated controls. This observation highlights the cellular responses of triple-negative BRCA1 proficient breast cancer MDA-MB-231 cells to RAPTA-EA1 through BRCA1 inhibition and provides insights into alternative treatments for breast cancer.

Fine-tuning the cytotoxicity of ruthenium(ii) arene compounds to enhance selectivity against breast cancers

“…Furthermore, 11 CA are more cytotoxic than RAPTA-EA, a selective glutathione transferase (GSTP-1) inhibitor, which shows good cytotoxicity profiles against breast cancer cell lines (20.0 ± 2.2 μM and 10.5 ± 0.5 μM for MCF-7 and MDA-MB-231 cells, respectively). 47…”

“…Furthermore, 11CA are more cytotoxic than RAPTA-EA, a selective glutathione transferase (GSTP-1) inhibitor, which shows good cytotoxicity profiles against breast cancer cell lines (20.0 ± 2.2 µM and 10.5 ± 0.5 µM for MCF-7 and MDA-MB-231 cells, respectively). 47 The most active and selective compounds identified from the cytotoxicity studies are 10 and 11CA and were therefore tested for their ability to induce cell death via apoptosis, the preferred mechanism of cell death 48 and sometimes associated with multidrug-resistance. 49 The compounds were incubated with MCF-7 and MDA-MB-231 cells at their 24 h IC 50 dose and Annexin V caspase assay was used to determine the extent of apoptosis (Fig.…”

Half-Sandwich Ruthenium Arene Complexes Bearing Clinically Approved Drugs as Ligands: The Importance of Metal–Drug Synergism in Metallodrug Design

“…Complex 47a has also shown higher cytotoxicity in BRCA1-wild type breast cancer cells than cisplatin. Also, it displayed cellular responses in triple negative breast cancer cells through BRCA1 inhibition . EA has been further tethered to Ru­(arene) unit via N or P donor linkage to explore the anticancer activity against different cancer cells.…”

“…Also, it displayed cellular responses in triple negative breast cancer cells through BRCA1 inhibition. 130 EA has been further tethered to Ru(arene) unit via N or P donor linkage to explore the anticancer activity against different cancer cells. Against cisplatin sensitive and cisplatin resistant human ovarian cancer cells, Ru(p-cymene) complexes containing EA-modified pyridine and phosphine ligands 48−50 (Figure 17) were more active than EA and well-known Ru-based anticancer active complexes, viz., NAMI-A and RAPTA-C. 131 While complexes 48 and 49 were less stable in DMSO due to weak Ru−N bond strength, complex 50 with Ru−P bond was substantially more stable.…”