Maramycin, a Cytotoxic Isoquinolinequinone Terpenoid Produced through Heterologous Expression of a Bifunctional Indole Prenyltransferase/Tryptophan Indole-Lyase in S. albidoflavus.

Isoquinolinequinones represent an important family of natural alkaloids with profound biological activities. Heterologous expression of a rare bifunctional indole prenyltransferase/tryptophan indole-lyase enzyme from Streptomyces mirabilis P8-A2 in S. albidoflavus J1074 led to the activation of a putative isoquinolinequinone biosynthetic gene cluster and production of a novel isoquinolinequinone alkaloid, named maramycin (1). The structure of maramycin was determined by analysis of spectroscopic (1D/2D NMR) and MS spectrometric data. The prevalence of this bifunctional biosynthetic enzyme was explored and found to be a recent evolutionary event with only a few representatives in nature. Maramycin exhibited moderate cytotoxicity against human prostate cancer cell lines, LNCaP and C4-2B. The discovery of maramycin (1) enriched the chemical diversity of natural isoquinolinequinones and also provided new insights into crosstalk between the host biosynthetic genes and the heterologous biosynthetic genes in generating new chemical scaffolds.

Pepticinnamins N, O, and P, Nonribosomal Peptides from the Soil-Derived Streptomyces mirabilis P8-A2.

Cinnamoyl moiety containing nonribosomal peptides represented by pepticinnamin E are a growing family of natural products isolated from different Streptomyces species and possess diverse bioactivities. The soil bacterium Streptomyces mirabilis P8-A2 harbors a cryptic pepticinnamin biosynthetic gene cluster, producing azodyrecins as major products. Inactivation of the azodyrecin biosynthetic gene cluster by CRISPR-BEST base editing led to the activation and production of pepticinnamin E (1) and its analogues, pepticinnamins N, O, and P (2-4), the structures of which were determined by detailed NMR spectroscopy, HRMS data, and Marfey's reactions. These new compounds did not show a growth inhibitory effect against the LNCaP and C4-2B prostate cancer lines, respectively.

Molecular Profiling of Docetaxel-Resistant Prostate Cancer Cells Identifies Multiple Mechanisms of Therapeutic Resistance.

Docetaxel-a taxane-based chemotherapeutic agent-was the first treatment to demonstrate significant improvements in overall survival in men with metastatic castration-resistant prostate cancer (mCRPC). However, the response to docetaxel is generally short-lived, and relapse eventually occurs due to the development of resistance. To explore the mechanisms of acquired docetaxel resistance in prostate cancer (PCa) and set these in the context of androgen deprivation therapy, we established docetaxel-resistant PCa cell lines, derived from the androgen-dependent LNCaP cell line, and from the LNCaP lineage-derived androgen-independent C4-2B sub-line. We generated two docetaxel-resistant LNCaPR and C4-2BR sub-lines, with IC50 values 77- and 50-fold higher than those of the LNCaP and C4-2B parental cells, respectively. We performed gene expression analysis of the matched sub-lines and found several alterations that may confer docetaxel resistance. In addition to increased expression of ABCB1, an ATP-binding cassette (ABC) transporter, and a well-known gene associated with development of docetaxel resistance, we identified genes associated with androgen signaling, cell survival, and overexpression of ncRNAs. In conclusion, we identified multiple mechanisms that may be associated with the development of taxane drug resistance in PCa. Actioning these mechanisms could provide a potential approach to re-sensitization of docetaxel-resistant PCa cells to docetaxel treatment and thereby further add to the life-prolonging effects of this drug in men with mCRPC.