Late-stage cascade of oxidation reactions during the biosynthesis of oxalicine B in Penicillium oxalicum

Oxalicine B(1)is an a-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum.The biosynthetic pathway of 15-deoxyoxalicine B(4)was preliminarily reported in Penicillium canescens,however,the genetic base and biochemical characterization of tailoring reactions for oxalicine B(1)has remained enigmatic.In this study,we characterized three oxygenases from the metabolic pathway of oxalicine B(1),including a cytochrome P450 hydroxylase OxaL,a hydroxylating Fe(II)/a-KG-dependent dioxygenase OxaK,and a multifunctional cytochrome P450 OxaB.Intriguingly,OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity.OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A(3)to 1 with a spiro-lactone core skeleton through oxidative rearrangement.We also solved the mystery of OxaL that controls C-15 hydroxylation.Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds,and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC50values in the range of 4.0-19.9μmol/L.Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B(1)and create downstream derivatizations of oxalicines by employing enzymatic strategies.

Combination of Human Fas （CD95/Apo-1） Ligand with Adriamycin Significantly Enhances the Efficacy of Antitumor Response

The prognosis of hepatocellular carcinoma （HCC） is poor, even with the combined treatment of curative resection and adjuvant chemoradiotherapy. To solve this problem, many biologic therapies have been investigated. Fas ligand （FasL, CD95L） is mainly expressed in activated T lymphocytes and natural killer （NK） cells, and plays a central role in both cell-mediated immunity and immune downregulation. Several studies have shown that FasL is expressed in HCC. In the present report, we prepared recombinant human pET-22b（＋）/FasL protein and investigated the effect of FasL on HCC cells in vitro and on tumor growth in a murine HCC tumor model. The well-known cytotoxic chemotherapeutic reagent adriamycin （ADM） served as a control. We found that FasL effectively suppressed the viability of H22 tumor cells and significantly induced the apoptosis of H22 cells. The apoptotic levels of cells treated with FasL-ADM were significantly higher than those treated with FasL or ADM alone, and the FasL-ADM combination resulted in a more than additive effect on tumor growth delay in this model. The results suggested that combined treatment of FasL and other chemotherapeutic agents may be a new approach to improve the efficacy of chemotherapy for HCC.