Unraveling BOLD-100 synergistic potential in pleural mesothelioma treatment: an in vitro study

Abstract

Pleural mesothelioma (PM) is a rare cancer affecting the pleural layer on the body's serosal surfaces. Exposure to asbestos fibers, a naturally occurring fibrous material with insulating characteristics, contributes to PM's prevalence. PM has a long latency period, making major surgery ineffective and necessitating systemic treatment. Despite the progress of mesothelioma treatment, the median survival is very poor; so, there is a strong need to explore new therapeutic approaches. This study explores the use of BOLD-100, a novel therapeutic drug that targets GRP78, a protein overexpressed in PM cells. BOLD-100, a ruthenium-based small molecule therapeutic drug, is being investigated for the treatment of advanced gastrointestinal malignancies in conjunction with chemotherapy. Our aim is to investigate cellular responses of several PM cell lines to a regimen that includes BOLD-100 in addition to other commonly used treatments. BOLD-100 is a ruthenium-based anticancer therapeutic.

Keywords: Chemotherapy; GRP78; Mesothelioma; Synergy.

Fig. 1

GRP78 protein expression in mesothelial Met5 A cells compared to pleural mesothelioma cells. Blots in the upper part of the figure are representative of three; each lane was loaded with 20 μg of proteins, probed with anti-GRP78 mouse mouse-clonal antibody and managed as described in the “Materials and methods” section. Bars in the lower part of the figure are means ± SD derived from three independent samples. Statistics indicate differences between Met5A and PM cell lines (* p < 0.05, **** p < 0.0001; one-way ANOVA followed by Dunnet post-test)

Fig. 2

Combination index plots (fa–CI plots) for BOLD-100/cisplatin combination. CI values are plotted against the fractional inhibition (fa) of MSTO-211H, MPP89, 570, 718, 729 and 748 cell viability, as obtained by the Calcein-AM endpoint. CI < 1 indicates synergy, CI = 1 indicates additive effect, and CI > 1 indicates antagonism. Six replicates in three independent experiments were used

Fig. 3

Combination index plots (fa–CI plots) for BOLD-100/gemcitabine combination. CI values are plotted against the fractional inhibition (fa) of MSTO-211H, MPP89, 570, 718, 729 and 748 cell viability, as obtained by the Calcein-AM endpoint. CI < 1 indicates synergy, CI = 1 indicates additive effect, and CI > 1 indicates antagonism. Six replicates in three independent experiments were used

Fig. 4

Combination index plots (fa–CI plots) for BOLD-100/vinorelbine combination. CI values are plotted against the fractional inhibition (fa) of MSTO-211H, MPP89, 570, 718, 729 and 748 cell viability, as obtained by the Calcein-AM endpoint. CI < 1 indicates synergy, CI = 1 indicates additive effect, and CI > 1 indicates antagonism. Six replicates in three independent experiments were used

Fig. 5

Heat maps for combination of BOLD-100/drug at different fa. Heat map showing cell lines and fractional inhibition (fa) at value 0.5, 0.9, 0.97. The entries are CI values. The CIs are mapped as 0–0.29 strong synergism, 0.3–0.69 synergism, 0.7–0.89 moderate synergism, 0.9–1.1 additive, 1.11–1.3 moderate antagonism, 1.31–3.3 antagonism, 3.31–10 strong antagonism, 10.1- ∞ very strong antagonism (Modified from Chou, 2006 [40]). Panel A is referred to BOLD-100+cisPlatin combination, Panel B to BOLD-100+Gemcitabine, Panel C to BOLD-100+Vinorelbine

Fig. 6

Mitochondrial membrane potential. Mitochondrial membrane potential (ΔΨm) variation after 1-h exposure to single agents (BOLD-100 and single drugs) or combinations BOLD-100 + drug. Data resulting from 5 independent treatments have been obtained as JC-1 red/green fluorescence ratio and converted as % of effect on mitochondrial membrane potential stability (so, the control condition, not indicated, is posed at zero). In the graphs, the % of effect is referred to the expected effect indicated as a dotted line

Fig. 7

Heat maps for combination of BOLD-100/drug at fa 0.5. Heat map showing cell lines and combinations BOLD-100/drug. The entries are CI values obtained from ΔΨm data. The CIs are mapped as 0–0.29 strong synergism, 0.3–0.69 synergism, 0.7–0.89 moderate synergism, 0.9–1.1 additive, 1.11–1.3 moderate antagonism, 1.31–3.3 antagonism, 3.31–10 strong antagonism, 10.1- ∞ very strong antagonism (Modified from Chou, 2006 [40])