Fibrostatin D

The structures of six inhibitors of prolyl hydroxylase, fibrostatins A, B, C, D, E and F produced by a strain of Streptomyces, were deduced to be 1, 2, 3, 4, 5 and 6, respectively, from chemical and spectroscopic evidence, especially from extensive 13C NMR studies including selective decoupling and low power selective decoupling experiments monitored by 13C-1H long-range couplings. These compounds are the first naturally occurring 2,6,7- or 3,6,7-tri-substituted or 2,3,6,7-tetra-substituted 5-hydroxy-1,4-naphthoquinone inhibitors possessing N-acetyl-L-cystein-S-yl moieties in the molecule.

Goodpasture antigen-binding protein (GPBP) is an exportable1 Ser/Thr kinase that induces collagen IV expansion and has been associated with chemoresistance following epithelial-to-mesenchymal transition (EMT). Here we demonstrate that cancer EMT phenotypes secrete GPBP (mesenchymal GPBP) which displays a predominant multimeric oligomerization and directs the formation of previously unrecognized mesh collagen IV networks (mesenchymal collagen IV). Yeast two-hybrid (YTH) system was used to identify a 260SHCIE264 motif critical for multimeric GPBP assembly which then facilitated design of a series of potential peptidomimetics. The compound 3-[4''-methoxy-3,2'-dimethyl-(1,1';4',1'')terphenyl-2''-yl]propionic acid, or T12, specifically targets mesenchymal GPBP and disturbs its multimerization without affecting kinase catalytic site. Importantly, T12 reduces growth and metastases of tumors populated by EMT phenotypes. Moreover, low-dose doxorubicin sensitizes epithelial cancer precursor cells to T12, thereby further reducing tumor load. Given that T12 targets the pathogenic mesenchymal GPBP, it does not bind significantly to normal tissues and therapeutic dosing was not associated with toxicity. T12 is a first-in-class drug candidate to treat cancer by selectively targeting the collagen IV of the tumor cell microenvironment.

Fibrostatins, potent inhibitors of prolyl hydroxylase, were isolated as orange crystals from the culture broth of strain No. 23924, which was identified as Streptomyces catenulae subsp. griseospora. In vitro inhibitory activity (ID50 value) of fibrostatins A, B, C, D, E and F against prolyl hydroxylase of chick embryos was 23, 39, 29, 180, 10 and 14 microM, respectively.