Botryococcene biosynthesis is thought to resemble that of squalene, a metabolite essential for sterol metabolism in all eukaryotes. Squalene arises from an initial condensation of two molecules of farnesyl diphosphate (FPP) to form presqualene diphosphate (PSPP), which then undergoes a reductive rearrangement to form squalene. In principle, botryococcene could arise from an alternative rearrangement of the presqualene intermediate. Because of these proposed similarities, we predicted that a botryococcene synthase would resemble squalene synthase and hence isolated squalene synthase-like genes from Botryococcus braunii race B. While B. braunii does harbor at least one typical squalene synthase, none of the other three squalene synthase-like (SSL) genes encodes for botryococcene biosynthesis directly. SSL-1 catalyzes the biosynthesis of PSPP and SSL-2 the biosynthesis of bisfarnesyl ether, while SSL-3 does not appear able to directly utilize FPP as a substrate. However, when combinations of the synthase-like enzymes were mixed together, in vivo and in vitro, robust botryococcene (SSL-1+SSL-3) or squalene biosynthesis (SSL1+SSL-2) was observed. These findings were unexpected because squalene synthase, an ancient and likely progenitor to the other Botryococcus triterpene synthases, catalyzes a two-step reaction within a single enzyme unit without intermediate release, yet in B. braunii, these activities appear to have separated and evolved interdependently for specialized triterpene oil production greater than 500 MYA. Coexpression of the SSL-1 and SSL-3 genes in different configurations, as independent genes, as gene fusions, or targeted to intracellular membranes, also demonstrate the potential for engineering even greater efficiencies of botryococcene biosynthesis.algae | biofuels | terpene enzymology

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality in the United States. CRC is initiated by mutations of the tumor suppressor gene, adenomatous polyposis coli (APC) or β-catenin gene. These mutations stabilize β-catenin and constitutively activate Wnt/β-catenin target genes, such as c-Myc and Cyclin D1, ultimately leading to cancer. Naturally occurring stilbene derivatives, resveratrol and pterostilbene, inhibit Wnt signaling and repress CRC cell proliferation but are ineffective at concentrations lower than 10 µM. To understand the structure/activity relationship within these stilbene derivatives and to develop more efficacious Wnt inhibitors than these natural products, we synthesized and evaluated a panel of fluorinated N,N-dialkylaminostilbenes. Among this panel, (E)-4-(2,6-difluorostyryl)-N,N-dimethylaniline (4r) inhibits Wnt signaling at nanomolar levels and inhibits the growth of human CRC cell xenografts in athymic nude mice at a dosage of 20mg/kg. These fluorinated N,N-dialkylaminostilbenes appear to inhibit Wnt signaling downstream of β-catenin, probably at the transcriptional level.

The tumor suppressor protein Par-4, which is secreted by normal cells, selectively induces apoptosis in cancer cells. We identified a 3-arylquinoline derivative, designated Arylquin 1, as a potent Par-4 secretagogue in cell cultures and mice. Mechanistically, Arylquin 1 binds to vimentin, displaces Par-4 from vimentin for secretion and triggers the efficient paracrine apoptosis of diverse cancer cells. Thus, targeting vimentin with Par-4 secretagogues efficiently induces paracrine apoptosis of tumor cells.

Methionine S-adenosyltransferase 2A (MAT2A) is the catalytic subunit for synthesis of S-adenosylmethionine (SAM), the principal methyl donor in many biological processes. MAT2A is up-regulated in many cancers, including liver cancer and colorectal cancer (CRC) and is a potentially important drug target. We developed a family of fluorinated N,N-dialkylaminostilbene agents, called FIDAS agents, that inhibit the proliferation of CRC cells in vitro and in vivo. Using a biotinylated FIDAS analog, we identified the catalytic subunit of MAT2A as the direct and exclusive binding target of these FIDAS agents. MAT2B, an associated regulatory subunit of MAT2A, binds indirectly to FIDAS agents through its association with MAT2A. FIDAS agents inhibited MAT2A activity in SAM synthesis, and depletion of MAT2A by shRNAs inhibited CRC cell growth. A novel FIDAS agent delivered orally repressed CRC xenografts in athymic nude mice. These findings suggest that FIDAS analogs targeting MAT2A represent a family of novel and potentially useful agents for cancer treatment.

The importance of upregulated Wnt signaling in colorectal cancers led to efforts to develop inhibitors that target β-catenin in this pathway. We now report that several “Wnt inhibitors” that allegedly target β-catenin actually function as mitochondrial proton uncouplers that independently activate AMPK and concomitantly inhibit Wnt signaling. As expected for a process in which mitochondrial uncoupling diminishes ATP production, a mitochondrial proton uncoupler, FCCP, and a glucose metabolic inhibitor, 2-DG, activated AMPK and inhibited Wnt signaling. Also consistent with these findings, a well-known “Wnt inhibitor”, FH535, functioned as a proton uncoupler, and in support of this finding, the N-methylated analog, 2,5-dichloro-N-methyl-N-(2-methyl-4-nitrophenyl)­benzenesulfonamide (FH535-M), was inactive as an uncoupler and Wnt inhibitor. Apart from suggesting an opportunity to develop dual Wnt inhibitors and AMPK activators, these findings provide a cautionary tale that claims for Wnt inhibition alone require scrutiny as possible mitochondrial proton uncouplers or inhibitors of the electron transport chain.

Inhibition of the catalytic subunit of the heterodimeric methionine S-adenosyl transferase-2 (MAT2A) with fluorinated N,N-dialkylaminostilbenes (FIDAS agents) offers a potential avenue for the treatment of liver and colorectal cancers where upregulation of this enzyme occurs. A study of structure–activity relationships led to the identification of the most active compounds as those with (1) either a 2,6-difluorostyryl or 2-chloro-6-fluorostyryl subunit, (2) either an N-methylamino or N,N-dimethylamino group attached in a para orientation relative to the 2,6-dihalostyryl subunit, and (3) either an N-methylaniline or a 2-(N,N-dimethylamino)pyridine ring. These modifications led to FIDAS agents that were active in the low nanomolar range, that formed water-soluble hydrochloride salts, and that possessed the desired property of not inhibiting the human hERG potassium ion channel at concentrations at which the FIDAS agents inhibit MAT2A. The active FIDAS agents may inhibit cancer cells through alterations of methylation reactions essential for cancer cell survival and growth.

Adenosine monophosphate-activated kinase (AMPK) plays a central role in regulating energy homeostasis in eukaryotic cells. AMPK also regulates lipid synthesis by inhibiting acetyl-CoA carboxylase (ACC) and regulates mTOR signaling by activating TSC2. Due to its important roles in cell metabolism, AMPK is an attractive target for metabolic diseases, such as type II diabetes and obesity. AMPK activators, such as metformin, that are used for diabetes treatment are also effective anticancer agents. However, the efficacies of many known AMPK activators are relatively low. For example, metformin activates AMPK at millimolar levels. In this study, we identified a novel family of AMPK activators, namely fluorinated N,N’-diarylureas, that activate AMPK at 1–3µM concentrations. These novel agents strongly inhibit the proliferation of colon cancer cells. We studied the potential mechanisms of these agents, performed a structure-activity relationship (SAR) study and identified several fluorinated N,N’- diarylureas as potent AMPK activators.

PurposeTriple negative breast cancer (TNBC) is the most lethal and aggressive subtype of breast cancer. AMP-activated protein kinase (AMPK) is a major energy regulator that suppresses tumor growth, and 1-(3-chloro-4-((trifluoromethyl)thio)phenyl)-3-(4-(trifluoromethoxy)phenyl)urea (FND-4b) is a novel AMPK activator that inhibits growth and induces apoptosis in colon cancer. The purpose of this project was to test the effects of FND-4b on AMPK activation, proliferation, and apoptosis in breast cancer with a particular emphasis on TNBC.Materials and methods(i) Estrogen-receptor positive breast cancer (ER+BC; MCF-7, and T-47D), TNBC (MDA-MB-231 and HCC-1806), and breast cancer stem cells were treated with FND-4b for 24h. Immunoblot analysis assessed AMPK, acetyl-CoA carboxylase (ACC), ribosomal protein S6, cyclin D1, and cleaved PARP. (ii) Sulforhodamine B growth assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h. Proliferation was also assessed by counting cells after 72h of FND-4b treatment. (iii) Cell death ELISA assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h.Results(i) FND-4b increased AMPK activation with concomitant decreases in ACC activity, phosphorylated S6, and cyclin D1 in all subtypes. (ii) FND-4b decreased proliferation in all cells, while dose-dependent growth decreases were found in ER+BC and TNBC. (iii) Increases in apoptosis were observed in ER+BC and the MDA-MB-231 cell line with FND-4b treatment.ConclusionsOur findings indicate that FND-4b decreases proliferation for a variety of breast cancers by activating AMPK and has notable effects on TNBC. The growth reductions were mediated through decreases in fatty acid synthesis (ACC), mTOR signaling (S6), and cell cycle flux (cyclin D1). ER+BC cells were more susceptible to FND-4b-induced apoptosis, but MDA-MB-231 cells still underwent apoptosis with higher dose treatment. Further development of FND compounds could result in a novel therapeutic for TNBC.