The antiproliferative function of violacein‐like purple violet pigment (PVP) from an Antarctic Janthinobacterium sp. Ant5‐2 in UV‐induced 2237 fibrosarcoma

Abstract

Background In this study, we have investigated the chemotherapeutic potential of a purple violet pigment (PVP), which was isolated from a previously undescribed Antarctic Janthinobacterium sp. (Ant5-2), against murine UV-induced 2237 fibrosarcoma and B16F10 melanoma cells. Methods The 2237, B16F10, C50, and NIH3T3 cells were treated with PVP at different doses and for different times, and their proliferation and viability were detected by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Cell cycle arrest induced by PVP in 2237 fibrosarcoma cells was assessed by flow cytometry and expression analysis of cell cycle regulatory proteins were done by Western blot. Apoptosis induced by PVP in 2237 cells was observed by annexin-V/propidium iodide double staining flow cytometry assay and fluorescence microscopy. To further determine the molecular mechanism of apoptosis induced by PVP, the changes in expression of Bcl-2, Bax and cytochrome c were detected by Western blot. The loss of mitochondrial membrane potential in PVP treated 2237 cells was assessed by staining with JC-1 dye following flow cytometry. Caspase-3, Caspase-9 and PARP cleavage were analyzed by Western blot and Caspase-3 and -9 activities were measured by colorimetric assays. Results In vitro treatment of murine 2237 cells with the PVP resulted in decreased cell viability (13–79%) in a time (24–72 h) and dose (0.1–1 μM)-dependent manner. The PVP-induced growth inhibition in 2237 cells was associated with both G0/G1 and G2/M phase arrest accompanied with decrease in the expression of cyclin dependent kinases (Cdks) and simultaneous increase in the expression of cyclin dependent kinase inhibitors (Cdki) – Cip1/p21 and Kip1/p27. Further, we observed a significant increase in the apoptosis of the 2237 fibrosarcoma cells which was associated with an increased expression of pro-apoptotic protein Bax, decreased expression of anti-apoptotic proteins Bcl-2, disruption of mitochondrial membrane potential, cytochrome c release, activation of caspase-3, caspase-9 and poly-ADP-ribose-polymerase (PARP) cleavage. Conclusions We describe the anti-cancer mechanism of the PVP for the first time from an Antarctic bacterium and suggest that the PVP could be used as a potent chemotherapeutic agent against nonmelanoma skin cancers.

Violacein induces p44/42 mitogen-activated protein kinase-mediated solid tumor cell death and inhibits tumor cell migration

“…Additionally, p44/42, a known apoptosis-promoting regulator and caspase 3 activator, was increased in brain tumor cells treated with violacein. These results established that violacein-induced apoptosis observed in the present study likely occurs via the intrinsic pathway, particularly in brain tumor cells, which is consistent with studies on leukemia, fibrosarcoma and colon cancer cells that have demonstrated the apoptosis-promoting properties of violacein by intrinsic as well as extrinsic pathways ( 23 , 27 , 35 ). It should also be noted that violacein has been described to elicit other types of cell death, as shown in resistant leukemia cells that underwent cell death as a consequence of endoplasmic reticulum stress and breakdown of the golgi apparatus, underscoring the tumor cell killing capacity of violacein via different cell death mechanisms ( 25 ).…”

Violacein induces cell death by triggering mitochondrial membrane hyperpolarization in vitro

“…2 ) suggest the occurrence of cell-type-specific mechanisms. Previous study [ 23 ] carried out with 2,237 fibrosarcoma cells treated for 48 h with PVP, a violacein-like pigment from the Antarctic Janthinobacterium sp bacteria, showed that the treatment induced the disruption of the mitochondrial membrane potential and occurrence of apoptosis via the mitochondrial pathway. Furthermore, another cell death mechanism has been suggested by Queiroz et al .…”

Draft Genome Sequence of Janthinobacterium sp. Ant5-2-1, Isolated from Proglacial Lake Podprudnoye in the Schirmacher Oasis of East Antarctica

“…Ant5-2-1, isolated from the seasonally frozen Proglacial Lake Podprudnoye in the Schirmacher Oasis of East Antarctica, is a psychrotolerant Gram-negative bacillus that thrives in extreme cold, dry, and high solar ultraviolet (UV) radiation environments ( 1 ). Previously, it has been reported that a violacein-like purple-violet pigment (PVP) produced by Ant5-2 absorbs UVA, UVB, and UVC radiation and manifests strong antimicrobial and anticancer activity ( 1 – 5 ). We describe here a draft genome of Janthinobacterium sp.…”