Discovery and Identification of Small Molecules as Methuosis Inducers with in Vivo Antitumor Activities

Abstract

Methuosis is a novel nonapoptotic mode of cell death characterized by vacuole accumulation in the cytoplasm. In this article, we describe a series of azaindole-based compounds that cause vacuolization in MDA-MB-231 cells. The most potent vacuole inducer, compound 13 (compound 13), displayed differential cytotoxicities against a broad panel of cancer cell lines, such as MDA-MB-231, A375, HCT116, and MCF-7, but it did not inhibit the growth of the nontumorigenic epithelial cell line MCF-10A. A mechanism study confirmed that the cell death was caused by inducing methuosis. Furthermore, compound 13 exhibited substantial pharmacological efficacy in the suppression of tumor growth in a xenograft mouse model of MDA-MB-231 cells without apparent side effects, which makes this compound the first example of a methuosis inducer with potent in vivo efficacy. These results demonstrate that methuosis inducers might serve as novel therapeutics for the treatment of cancer.

The JNK signaling pathway plays a key role in methuosis (non-apoptotic cell death) induced by MOMIPP in glioblastoma

“…Possibilities include: 1) disruption of interactions with pro-apoptotic proteins like Bax, facilitating outer mitochondrial membrane pore formation and release of cytochrome c [62]; 2) alteration of Bcl-2 function in the endoplasmic reticulum, causing discharge of Ca 2+ , with consequential mitochondrial calcium overload [63]; 3) release of Beclin-1 from inhibitory Beclin-1/Bcl-2 complexes, causing increased autophagy [41]; or 4) loss of mitochondrial membrane potential and release of proteins like AIF, which are capable of inducing caspase-independent cell death [64, 65]. The latter mechanism merits serious consideration, since methuosis is not blocked by caspase inhibitors [8, 15]. Finally, it should be noted that activation of JNK by MOMIPP could have pleiotropic effects beyond phosphorylation of Bcl-2/Bcl-xL.…”

“…However, two recent studies have highlighted the potential for exploiting this novel form of cell death for treating cancers in vivo. In one study Huang et al [15] identified a unique 4′6’-disubstituted aza-indole that selectively induced methuosis in a broad panel of cancer cell lines in vitro and suppressed the growth of subcutaneous MDA-MB-231 breast cancer xenografts in immunocompromised mice. In a separate study, Ahlstedt et al [69] found that a quinolone-based methuosis inducer, Vacquinol-1, reduced the size of brain tumors in syngeneic rat models, although no survival advantage was noted.…”

“…The product of PIKfyve, PI(3,5)P 2 , is known to play a critical role in late endosome trafficking [11, 12]. Since our initial description of methuosis, a number of other reports have noted similar cell death phenotypes promoted by a variety of chemical agents and natural products [13–15]. Features of methuosis have also been described in cells responding to overexpression of miR-199a-3p [16], co-expression of mutant EGFR and K-Ras [17], immunotargeting of CD99 [18], treatment with an oligonucleotide aptamer [19], or NGF-stimulation of TrkA [20].…”

Epimedokoreanin C, A Prenylated Flavonoid Isolated from Epimedium Koreanum, Induces Non-Apoptotic Cell Death with the Characteristics of Methuosis in Lung Cancer Cells

“…As a unique form of non-apoptotic cell death, methuosis was initially de ned in glioblastoma cells after overexpression of Ras [33]. In recent years, some methuosis inducers were identi ed and all of these compounds displayed meaningful effects in killing cancer cells [10][11][12][13][14][15]. This indicated that small molecules with the capacity to induce methuosis may be of considerable interest as potential therapeutics for cancers that are resistant to apoptosis.…”

“…As a novel nonapoptotic mode of cell death, methuosis has attracted particular attention as a target for cancer treatments. Several methuosis inducers have been reported, for example, indole-based chalcones MIPP and MOMIPP triggered cell death by methuosis in glioblastoma [10,11]; an ursolic acid derivative led cell death via methuosis [12]; a 4,6-disubstituted Aza-indole compound 13 induced methuosis and displayed cytotoxicities against a panel of cancer cells [13]; a quinoline derivative vacquinol also caused methuosis in glioblastoma [14] and CX-4945 induced methuosis in cholangiocarcinoma cells [15]. These reported results con rmed that the identi cation of methuosis inducers could provide both probes for studying the speci c molecular mechanism of the nonconventional cell death pathway, and promising therapeutic agents for the treatment of cancers.…”