Identification of a new member of Mortaparib class of inhibitors that target mortalin and PARP1

Abstract

Mortalin, a heat shock family protein enriched in cancer cells, is known to inactivate tumor suppressor protein p53. Abrogation of mortalin-p53 interaction and reactivation of p53 has been shown to trigger growth arrest/apoptosis in cancer cells and hence, suggested to be useful in cancer therapy. In this premise, we earlier screened a chemical library to identify potential disruptors of mortalin-p53 interaction, and reported two novel synthetic small molecules (5-[1-(4-methoxyphenyl) (1,2,3,4-tetraazol-5-yl)]-4-phenylpyrimidine-2-ylamine) and (4-[(1E)-2-(2-phenylindol-3-yl)-1-azavinyl]-1,2,4-triazole) called Mortaparib and MortaparibPlus, respectively. These compounds were shown to possess anticancer activity that was mediated through targeting mortalin and PARP1 proteins, essential for cancer cell survival and proliferation. Here, we report characterization of the third compound, {4-[(4-amino-5-thiophen-2-yl-1,2,4-triazol-3-yl)sulfanylmethyl]-N-(4-methoxyphenyl)-1,3-thiazol-2-amine}, isolated in the same screening. Extensive computational and molecular analyses suggested that the new compound has the capability to interact with mortalin, p53, and PARP1. We provide evidence that this new compound, although required in high concentration as compared to the earlier two compounds (Mortaparib and MortaparibPlus) and hence called MortaparibMild, also downregulates mortalin and PARP1 expression and functions in multiple ways impeding cancer cell proliferation and migration characteristics. MortaparibMild is a novel candidate anticancer compound that warrants further experimental and clinical attention.

Mixtures of Three Mortaparibs with Enhanced Anticancer, Anti-Migration, and Antistress Activities: Molecular Characterization in p53-Null Cancer Cells

“…The long-term (2 weeks) effect, as examined by colony forming assay, showed a decrease in clonogenicity in Mortaparib Mild -treated cells (~15, 30, and 40% in Saos2 and ~20, 40, and 55% in SKOV3 with 1, 2.5, and 5 μM Mortaparib Mild , respectively ( Figure 1 C)). These data suggested that Mortaparib Mild is effective for p53-null cancer cells in addition to its p53-dependent cytotoxicity in p53 wild-type cancer cells [ 28 ]. We investigated the mechanism of its cytotoxicity in p53-null cells as follows.…”

“…Mortaparib (5-[1-(4-methoxyphenyl)(1,2,3,4-tetraazol-5-yl)]-4-phenylpyrimidine-2-ylamine) [ 25 ], Mortaparib Plus (4-[(1E)-2-(2-phenylindol-3-yl)-1-azavinyl]-1,2,4-triazole) [ 26 , 27 ], and Mortaparib Mild (4-[(4-amino-5-thiophen-2-yl-1,2,4-triazol-3-yl)sulfanylmethyl]-N-(4-methoxyphenyl)-1,3-thiazol-2-amine) [ 28 ] were purchased from NAMIKI SHOJI Co., Ltd. (Shinjuku, Japan). Stock solutions (50 mM) were prepared in Dimethyl Sulfoxide (DMSO) (WAKO, Osaka, Japan) and were diluted in complete cell culture media to obtain concentrations from 5 to 30 µM.…”

“…We previously screened a small molecule library consisting of 12,000 compounds by a cell-based multiple assay platform including (i) a shift in mortalin distribution from perinuclear to pancytoplasmic and (ii) the nuclear translocation and reactivation of wild-type p53 function. Three top hits of this screening were the novel molecules that we named Mortaparib [ 25 ], Mortaparib Plus [ 26 , 27 ], and Mortaparib Mild [ 28 ] due to their functions including the inhibition of mortalin, mortalin-p53 interaction, and PARP1. Subsequent studies have supported the idea that the action of these molecules is not restricted to the wild-type p53-harboring cancer cells.…”

“…Mortaparib Plus was shown to be more potent and target PARP1, p73, and CARF proteins, critically involved in carcinogenesis and metastasis [ 26 , 27 ]. Mortaparib Mild inhibited mortalin and PARP1 functions, although it showed a low level of cytotoxicity [ 28 ]. In the present study, we examined the response of p53-null cancer cells to Mortaparib Mild .…”

Synthetic Small Molecule Modulators of Hsp70 and Hsp40 Chaperones as Promising Anticancer Agents

“…In contrast to colon cancer cells, in breast cancer cells, compound 24b upregulated only p21 in the p53-wildtype MCF-7 cells, while T47D cells (p53 L194F ) treated with compound 24b showed no p21 changes but activation of PARP1, albeit compound 24b inhibited the mortalin-p53 interaction in both cell lines [ 101 ]. More recently, compound 24c ( Figure 4 , mortaparib mild ) was identified as an inhibitor of PARP1 and mortalin-p53 interaction in HCT-116 cells, however, at higher concentrations than compounds 24a and 24c , thus leading to the attribute “mild” for compound 24c [ 102 ].…”