Ribosomally synthesized and post-translationally modified peptides are a rapidly expanding class of natural products. They are typically biosynthesized by modification of a C-terminal segment of the precursor peptide (the core peptide). The precursor peptide also contains an N-terminal leader peptide that is required to guide the biosynthetic enzymes. For bioengineering purposes, the leader peptide is beneficial because it allows promiscuous activity of the biosynthetic enzymes with respect to modification of the core peptide sequence. However, the leader peptide also presents drawbacks as it needs to be present on the core peptide and then removed in a later step. We show that fusing the leader peptide for the lantibiotic lacticin 481 to its biosynthetic enzyme LctM allows the protein to act on core peptides without a leader peptide. We illustrate the use of this methodology for preparation of improved lacticin 481 analogues containing non-proteinogenic amino acids.

The transcription factor FOXM1 is upregulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 signaling is also a key driver in many other cancers. Here, we identify a new class of compounds effective in suppressing FOXM1 activity in breast cancers, and displaying good potency for antitumor efficacy. The compounds bind directly to FOXM1 and alter its proteolytic sensitivity, reduce the cellular level of FOXM1 protein by a proteasome- dependent process, and suppress breast cancer cell proliferation and cell cycle progression and increase apoptosis. RNA-seq and gene set enrichment analyses indicate that the compounds decrease expression of FOXM1-regulated genes and suppress gene ontologies under FOXM1 regulation. Several compounds have favorable pharmacokinetic properties and show good tumor suppression in preclinical breast tumor models. These compounds may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1.

The biosynthesis of ribosomally synthesized and posttranslationally modified peptide (RiPP) natural products typically involves a precursor peptide that contains a leader peptide that is important for the modification process, and that is removed in the final step by a protease. Genome mining efforts for new RiPPs are often hampered by the lack of a general method to remove the leader peptides. We describe here the incorporation of hydroxy acids into the precursor peptides in E. coli that results in connection of the leader peptide via an ester linkage that is readily cleaved by simple hydrolysis. We demonstrate the method for two lantibiotics, lacticin 481 and nukacin ISK-1.

Labeling of natural products with biophysical probes has greatly contributed to investigations of their modes of action and has provided tools for visualization of their targets. A general challenge is the availability of a suitable functional group for chemoselective modification. We demonstrate here that an N-terminal ketone is readily introduced into various lanthipeptides by the generation of a cryptic N-terminal dehydro amino acid by the cognate biosynthetic enzymes. Spontaneous hydrolysis of the N-terminal enamines results in α-ketoamides that site-specifically react with an aminooxy-derivatized alkyne or fluorophore. The methodology was successfully applied to prochlorosins 1.7 and 2.8, as well as the lantibiotics lacticin 481, haloduracin α, and haloduracin β. The fluorescently-modified lantibiotics were added to bacteria, and their cellular localization was visualized by confocal fluorescence microscopy. Lacticin 481 and haloduracin α localized predominantly at sites of new and old cell division as well as in punctate patterns along the long axis of rod shaped bacilli, similar to the localization of lipid II. On the other hand, haloduracin β was localized non-specifically in the absence of haloduracin α, but formed specific patterns when co-administered with haloduracin α. Using two-color labeling, colocalization of both components of the two-component lantibiotic haloduracin was demonstrated. These data with living cells supports a model in which the α component recognizes lipid II and then recruits the β-component.

We report a photolabile linker compatible with Fmoc solid phase peptide synthesis and Cu(I)-catalyzed alkyne–azide cycloaddition that allows photochemical cleavage to afford a C-terminal peptide fragment with a native amino terminus.

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The transcription factor FOXM1 is up-regulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 pathway signaling is also a key driver in other aggressive cancers including those in prostate, lung, ovary, and gastrointestinal tract, and in glioblastoma. Therefore, our goal has been to identify FOXM1 inhibitors effective in suppressing breast cancer proliferation both in vitro and in vivo and displaying potency, selectivity and good pharmacokinetic properties for in vivo efficacy. We screened large chemical libraries of over 130,000 compounds from which several were identified and characterized as potential FOXM1 inhibitors. These were then chemically modified and optimized for potency and good pharmacokinetic properties. The best were shown to effectively suppress the proliferation of FOXM1 expressing breast cancer cells, decrease the expression of FOXM1 and FOXM1- regulated genes, and inhibit the chromatin binding of FOXM1 to FOXM1 binding sites in these genes. Inhibitors that had long half-lives (t1/2 greater than 24H) were selected for studies in experimental preclinical mouse models. One inhibitor had good oral efficacy in suppressing the growth of FOXM1-containing breast tumors in NOD-SCID-gamma (NSG) mice, and several others had good efficacy in tumor suppression by subcutaneous but not oral administration. Our findings identify and characterize several compounds that effectively antagonize FOXM1 actions and tumor growth that may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1. Citation Format: Mary J. Laws, Sung Hoon Kim, Yvonne Ziegler, Noah Bindman, Ping Gong, Valeria Sanabria Guillen, Mayuri Yasuda, Divya Singh, Dorraya El-Ashry, John A. Katzenellenbogen, Benita S. Katzenellenbogen. Suppression of hormone receptor-positive and triple-negative breast cancers by new inhibitors of the transcription factor FOXM1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1955.

The transcription factor FOXM1 is up-regulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 signaling is also a key driver in many other cancers. Here, we identify a new class of compounds effective in suppressing FOXM1 activity in breast cancers, and displaying good potency for antitumor efficacy. The compounds bind directly to FOXM1 and alter its proteolytic sensitivity, reduce the cellular level of FOXM1 protein by a proteasome-dependent process, and suppress breast cancer cell proliferation and cell cycle progression and increase apoptosis. RNA-seq and gene set enrichment analyses indicate that the compounds decrease expression of FOXM1-regulated genes and suppress gene ontologies under FOXM1 regulation. Several compounds have favorable pharmacokinetic properties and show good tumor suppression in preclinical breast tumor models. These compounds may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1. (Supported by Breast Cancer Research Foundation grant (BCRF-083 to BSK), The Julius and Mary Landfield Cancer Research Fund (to BSK), NIH grant R01 DK015556 (to JAK), NIH T32 GM070421 Fellowship (to VSG), Bankhead-Coley Foundation grant 09BW04 (to DEA), USDA award ILLU-698-909 and National Center for Supercomputing Applications Faculty Fellowship (to ZME), and UIUC Environmental Toxicology Scholarship (to BPS)). Citation Format: Benita S. Katzenellenbogen, Yvonne Ziegler, Mary J Laws, Valeria S. Guillen, SungHoon Kim, Parama Dey, Brandi P. Smith, Ping Gong, Noah Bindman, Yuechao Zhao, Kathryn Carlson, Mayuri A. Yasuda, Divya Singh, Zhong Li, Dorraya El-Ashry, Zeynep Madak-Erdogan, John A. Katzenellenbogen. Suppression of FOXM1 activities and breast cancer growth in vitro and in vivo by a new class of compounds [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-05-05.