Greensporone C, a Freshwater Fungal Secondary Metabolite Induces Mitochondrial-Mediated Apoptotic Cell Death in Leukemic Cell Lines

Abstract

Therapeutic agents used in the treatment of cancer are known to develop resistance against cancer cells. Hence, there is a continuing need to investigate novel agents for the treatment and management of cancer. Antitumor activity of greensporone C (GC), a new resorcylic acid lactone isolated from an organic extract of a culture of a Halenospora sp. freshwater fungus, was subjected for screening against a panel of leukemic cell lines (K562, U937, and AR320). In all the three cell lines, cell proliferation was inhibited in dose-dependent fashion. GC further arrested the cells in SubG0 phase in dose-dependent manner. Annexin V/PI dual staining data confirmed apoptotic death of treated K562 and U937 leukemic cells. Treatment with GC suppressed constitutively phosphorylated AKT and downregulated expression of inhibitor of apoptotic proteins XIAP, cIAP-1, and cIAP-2. In summation to this, GC-treated leukemic cells upregulated protein expression of pro-apoptotic proteins, Bax with concomitant decrease in expression of anti-apoptotic proteins including Bcl-2 and Bcl-xL. Upregulation of Bax was associated with cytochrome c release which was confirmed from the collapse of mitochondrial membrane. Released cytochrome c further activated caspase cascade which in turn initiated apoptosis process. Anticancer activity of this isolated fungal compound GC was potentiated via stimulating production of reactive oxygen species (ROS) along with depletion of reduced glutathione (GSH) levels in K562 and U937 leukemic cells. Pretreatment of these cells with N-acetyl cysteine prevented GC-induced depletion of reduced GSH level and mitochondrial-caspase-induced apoptosis. Altogether, our data show that GC modulates the apoptotic response of human leukemic cells and raises the possibility of its use as a novel therapeutic strategy for hematological malignancies.

Antiproliferative Role of Secondary Metabolites From Aspergillus unguis AG 1.1 (G) Isolated From Marine Macroalgae Enteromorpha sp. by Inducing Intracellular ROS Production and Mitochondrial Membrane Potential Loss Leading to Apoptosis

“…In comparison with paclitaxel, it was observed that AUME treatment increased the number of cells in Go phase, while decreased the number of cells in G 1 , S, and G 2 /M phases. A similar observation of apoptotic phase increase was reported in leukemic cells when treated with Greensporone C, a fungal derived secondary metabolite (Prabhu et al, 2018).…”

Sanguinarine Induces Apoptosis Pathway in Multiple Myeloma Cell Lines via Inhibition of the JaK2/STAT3 Signaling

“…After the incubation period (24 h), 10 μL of CCK-8 reagent was added to the wells, followed by 2 h incubation at 37°C. Finally, the optical density was measured at 450 nm and percent cell viability was calculated as described previously (42).…”

“…U266, MM1S, and IM9 cell lines were treated with various doses of SNG for 24 h. The cells were stained with annexin V-FITC and propidium iodide as described earlier (42), and then analyzed by flow cytometry.…”

“…The cells were fixed and permeabilized using Fixation/Permeabilization solution kit, according to the manufacturer's protocol. 0.5 × 10 6 cells in 1x Perm-Wash buffer were stained with BV605 tagged anti-active caspase-3 and AF700 tagged PARP cleaved form antibodies (5.0 μl each) for 30 min, washed twice and then analyzed by flow cytometry using BD LSRFortessa analyzer as described previously (42).…”

“…MM cells IM9 and U266 were exposed to increasing doses of SNG for a period of 24 h. After incubation, cells were harvested, washed and then stained with ThiolTracker Violet reagent (5 μM in HBSS) for 30 min at 37°C. The stained cells were analyzed by flow cytometry as described earlier (42) to quantify the levels of reduced glutathione.…”