Exploring the Anti-Cancer Mechanism of Novel 3,4′-Substituted Diaryl Guanidinium Derivatives

Abstract

We previously identified a guanidinium-based lead compound that inhibited BRAF through a hypothetic type-III allosteric mechanism. Considering the pharmacophore identified in this lead compound (i.e., “lipophilic group”, “di-substituted guanidine”, “phenylguanidine polar end”), several modifications were investigated to improve its cytotoxicity in different cancer cell lines. Thus, several lipophilic groups were explored, the di-substituted guanidine was replaced by a secondary amine and the phenyl ring in the polar end was substituted by a pyridine. In a structure-based design approach, four representative derivatives were docked into an in-house model of an active triphosphate-containing BRAF protein, and the interactions established were analysed. Based on these computational studies, a variety of derivatives was synthesized, and their predicted drug-like properties calculated. Next, the effect on cell viability of these compounds was assessed in cell line models of promyelocytic leukaemia and breast, cervical and colorectal carcinomas. The potential of a selection of these compounds as apoptotic agents was assessed by screening in the promyelocytic leukaemia cell line HL-60. The toxicity against non-tumorigenic epithelial MCF10A cells was also investigated. These studies allowed for several structure-activity relationships to be derived. Investigations on the mechanism of action of representative compounds suggest a divergent effect on inhibition of the MAPK/ERK signalling pathway.

A novel aryl-guanidinium derivative, VP79s, targets the signal transducer and activator of transcription 3 signaling pathway, downregulates myeloid cell leukaemia-1 and exhibits preclinical activity against multiple myeloma

“…Therefore, there is a need for novel agents targeting key oncogenic signaling pathways. VP79s derives from a class of 3,4 ′ -bis-guanidinium pyridinophenyl ether compounds which we have previously shown to exhibit anti-cancer activity against a number of leukaemia and solid tumour cell lines [12][13][14]. Some of these compounds inhibit BRAF activity through a hypothetical type-III allosteric mechanism, although VP79s appears to induce cytotoxicity independent of Ras/BRAF inhibition in promyelocytic leukaemia cells [14].…”

“…We have recently shown that VP79s does not inhibit downstream BRAF signaling in promyelocytic leukaemia cells, unlike related compounds which exhibit type III allosteric inhibition of BRAF [14]. Here, we investigated the effect of VP79s on the activation of ERK, a MAP kinase which lies downstream of BRAF, in MM cells.…”

“…We have previously shown that VP79s, a novel aryl-guanidinium compound with a molecular weight of 421.81 Da (Fig. 1.A), exhibits cytotoxicity in promyelocytic leukaemia, breast, cervical and colorectal carcinoma cell lines [14]. Here, we utilised the alamarBlue viability assay to evaluate the cytotoxic activity of VP79s in a panel of drugsensitive and drug-resistant myeloma cell lines at various time points up to 72 h. The U266B1 cell line exhibits relative drug-resistance compared to the NCI-H929 cell line, possibly, in part, due to the presence of a TP53 mutation [18,20].…”

“…Synthesis and characterization of VP79s have previously been described [14] and its purity was assessed to be >95% by HPLC. VP79s was dissolved in 100% ethanol at 10 mM and stored at 4 • C. Recombinant Human IL-6 (Biolegend, San Diego, California, United States), bortezomib (SelleckChem, Houston, Texas, United States), U0126 (Cell Signaling, Danvers, Massachusetts, United States), SP125600 (Fluorochem Ltd., Glossop, United Kingdom) and SB203580 (SelleckChem) were prepared and stored as per manufacturer's instructions.…”

“…We have previously described a 3,4 ′ -bis-guanidinium diphenyl compound capable of inhibiting B Rapidly Accelerated Fibrosarcoma (BRAF) through a hypothetical type-III allosteric mechanism [12,13]. A derivative of this compound, VP79s, exhibits cytotoxicity in promyelocytic leukaemia, breast, cervical and colorectal carcinoma cell lines with IC 50 values in the low micromolar range; however, it does not inhibit the Rat sarcoma (Ras)/BRAF/Extracellular Signal-Regulated Kinase (ERK) signaling pathway in promyelocytic leukaemia cells suggesting a novel mechanism of action [14].…”