Photoinduced Conversion of Antimelanoma Agent Dabrafenib to a Novel Fluorescent BRAFV600E Inhibitor.

Dabrafenib (Tafinlar) was approved in 2013 by the FDA as a selective single agent treatment for patients with BRAFV600E mutation-positive advanced melanoma. One year later, a combination of dabrafenib and trametinib was used for treatment of BRAFV600E/K mutant metastatic melanoma. In the present study, we report on hitherto not described photosensitivity of dabrafenib both in organic and aqueous media. The half-lives for dabrafenib degradation were determined. Moreover, we revealed photoinduced chemical conversion of dabrafenib to its planar fluorescent derivative dabrafenib_photo 2. This novel compound could be isolated and biologically characterized in vitro. Both enzymatic and cellular assays proved that 2 is still a potent BRAFV600E inhibitor. The intracellular formation of 2 from dabrafenib upon ultraviolet irradiation is shown. The herein presented findings should be taken in account when handling dabrafenib both in preclinical research and in clinical applications.

Biosynthesis of antifungal and antibacterial polyketides by Burkholderia gladioli in coculture with Rhizopus microsporus.

Fungi-bacteria interactions can impact the course of fungal infection and biotechnological use. The mucoralean fungus Rhizopus microsporus, traditionally used in food fermentations (tempe and sufu), is frequently accompanied by Burkholderia gladioli pv. cocovenenans. When producing tempe bongkrek, the bacterial contamination can lead to lethal food-related intoxications caused by the respiratory toxin bongkrekic acid. To unveil the metabolic potential of the fungus-associated bacterium, we sequenced its genome, assigned secondary metabolite biosynthesis gene clusters and monitored the metabolic profile under various growth conditions. In addition to the bongkrekic acid biosynthesis gene cluster we found gene clusters coding for the biosynthesis of toxoflavin and a complex polyketide. The orphan polyketide synthase gene cluster was activated under conditions that emulate tempe production, which enabled isolation and structure elucidation of four members of the enacyloxin family of antibiotics, out of which one is new. Moreover, we found that the fungus positively influences the growth of the bacteria and dramatically increases bongkrekic acid production in stationary culture, which inhibits the growth of the fungus. These results showcase the context-dependent formation of antifungal and antibacterial agents at the fungal-bacterial interface, which may also serve as a model for scenarios observed in mixed infections.