Cancer Cell Mitochondria Targeting by Pancratistatin Analogs is Dependent on Functional Complex II and III

Abstract

Enhanced mitochondrial stability and decreased dependence on oxidative phosphorylation confer an acquired resistance to apoptosis in cancer cells, but may present opportunities for therapeutic intervention. The compound pancratistatin (PST) has been shown to selectively induce apoptosis in cancer cells. However, its low availability in nature has hindered its clinical advancement. We synthesized PST analogs and a medium-throughput screen was completed. Analogs SVTH-7, -6, and -5 demonstrated potent anti-cancer activity greater than PST and several standard chemotherapeutics. They disrupted mitochondrial function, activated the intrinsic apoptotic pathway, and reduced growth of tumor xenografts in vivo. Interestingly, the pro-apoptotic effects of SVTH-7 on cancer cells and mitochondria were abrogated with the inhibition of mitochondrial complex II and III, suggesting mitochondrial or metabolic vulnerabilities may be exploited by this analog. This work provides a scaffold for characterizing distinct mitochondrial and metabolic features of cancer cells and reveals several lead compounds with high therapeutic potential.

Exploiting mitochondrial and oxidative vulnerabilities with a synthetic analog of pancratistatin in combination with piperlongumine for cancer therapy

“…A new class of compounds, collectively known as mitocans, includes anticancer agents that directly or indirectly target cancer cell mitochondria to selectively induce apoptosis (8). On the basis of our previous work, we classify SVTH-6 as such (24). Likewise, this study has shown SVTH-6 to selectively dissipate MMP in cancer cells, decrease oxygen consumption, and cause release of apoptogenic factors cytochrome c and AIF from isolated cancer cell mitochondria alone and in combination with a molecule that induces increased oxidative stress, PL (Fig.…”

“…The natural compound PL has previously been demonstrated to preferentially cause cytotoxicity in cancer cells by selectively targeting their stress response mechanisms against ROS (25). We wanted to investigate if PL is capable of enhancing the effect of SVTH-6 in cancer cells because we have previously shown SVTH-6 to be targeting cancer cell mitochondria (24). Interestingly, an enhanced cytotoxic effect was selectively produced with this combination treatment in cancer cells, including BxPC-3 pancreatic cancer, OVCAR-3 ovarian cancer, NCI-H23 nonsmall-cell lung cancer, MV-4-11 leukemia, and G-361 melanoma cells ( Fig.…”

“…Although the precise mechanism of its affinity for cancerous mitochondria remains elusive to date, we have found that the natural compound pancratistatin (PST), isolated from the Hymenocallis littoralis plant, specifically induces apoptosis in numerous cancer cell types with minimal effect on noncancerous cells by mitochondrial targeting (16)(17)(18)(19)(20). We have previously synthesized JCTH-4, a C-1 acetoxymethyl analog of 7-deoxypancratistatin, and found it to possess comparable anticancer activity to ABBREVIATIONS: AIF, anti-apoptosis-inducing factor; AV, annexin V; BMX, basement membrane extract; DCF, 29,79-dicholorofluorescein; DIC, differential interference contrast; FBS, fetal bovine serum; H 2 DCFDA, 29,79-dicholorofluorescin diacetate; MMP, mitochondrial membrane potential; NAC, N-acetyl cysteine; PBMC, peripheral blood mononuclear cell; PBMCs V1/2, peripheral blood mononuclear cells from healthy volunteer 1/2; PI, propidium iodide; PL, piperlongumine; PST, pancratistatin; ROS, reactive oxygen species; RPMI, Roswell Park Memorial Institute; TBST, Tris-buffered saline-Tween 20; TMRM, tetramethylrhodamine methyl ester that of PST, inducing apoptosis in numerous cancer cell types by way of mitochondrial targeting (21)(22)(23)(24). Recently we created a C-7 hydroxylated version of JCTH-4, SVTH-6, a C-1 acetoxymethyl analog of PST, by de novo synthesis; to our knowledge, this is the first time that chemical synthesis of a PST analog with the full pharmacophore for anticancer activity has been achieved (24).…”

Synthesis of (+)-Pancratistatins via Catalytic Desymmetrization of Benzene

“…3 For example, pancratistatin ( 1 ) showed substantial in vivo activity against murine P-388 lymphocytic leukemia and murine M-5076 ovary sarcoma, and reduced growth of subcutaneous colon HT-29 tumors. 4 Moreover, experiments examining pancratistatin-induced apoptosis revealed noticeably reduced death in noncancerous cells relative to cancer cell lines, making these compounds appealing clinical lead candidates. 5 Finally, pancratistatins also showed significant antiviral activities, including in vivo models for Japanese encephalitis, 6 a disease for which no other known small-molecule anti-infective agent exists.…”

“…To this end, deprotection of urazole 12 to free amine 14 using conditions to affect hydrolysis and N–N bond cleavage proved challenging, as aggressively acidic or basic conditions led to complete decomposition of starting material. Therefore, we explored hydride-based reducing agents and found that treatment of 12 with LiAlH 4 could reduce the urazole; however, the resulting cyclic hydrazine hemiaminal 13 proved unstable, complicating its isolation and the overall reproducibility of this step. To overcome this hurdle, we decided to developed a one-pot protocol that directly reduced urazole 12 to amine 14 without handling the sensitive intermediate 13 .…”