Canavanine augments proapoptotic effects of arginine deprivation in cultured human cancer cells

Abstract

Arginine deprivation achieved by means of recombinant arginine-degrading enzymes is currently being developed as a novel anticancer enzymotherapy. In this study, we showed that arginine deprivation in vitro profoundly and selectively sensitized human cancer cells of different organ origin to low doses of canavanine, an arginine analogue of plant origin. In sensitive cancer cells arginine starvation led to the activation of caspase-9, caspase-3 and caspase-7, cleavage of reparation enzyme, polyADP ribosyl polymerase, and DNA fragmentation, which are the typical hallmarks of intrinsic apoptosis realized by the mitochondrial pathway. Co-administration of canavanine significantly accelerated and enhanced apoptotic manifestations induced by arginine deprivation. The augmentation of canavanine toxicity for cancer cells was observed when either a formulated arginine-free medium or complete medium supplemented with bovine arginase preparation was used. Cycloheximide efficiently rescued malignant cells from canavanine-induced cytotoxicity under arginine deprivation, suggesting that it results mainly from canavanine incorporation into newly synthesized proteins. Cancer cells sensitive or resistant to arginine deprivation alone were not capable of restoring their proliferation after 24 h of combined treatment, whereas pseudonormal cells retained such ability. Our data suggest that the incorporation of canavanine into anticancer treatment schemes based on artificially created arginine starvation could be a novel strategy in tumor enzymochemotherapy.

Effect of combined arginase and nitric oxide donor treatment on normal and leukemic cells in vitro

“…In the opposite case, exogenous NO would rescue leukemic cells viability upon arginase treatment. This and other our studies on different cell models also support the notion that not arginine metabolism but other cell response signaling mechanisms must be potentially involved in determining cell fate upon arginine restriction [2,28].…”

Co-application of canavanine and irradiation uncouples anticancer potential of arginine deprivation from citrulline availability

“…We previously reported that the natural arginine analog canavanine potently enhances arginine deprivation-induced apoptosis in human cancer cells [23]. The impact of citrulline in this scenario is not yet known.…”

“…In the absence of arginine, canavanine not only induces programmed cell death in cancer cell subpopulations, but also severely interferes with growth recovery of the remaining membrane-intact cells after the termination of treatment [18, 23]. We therefore evaluated the impact of citrulline supplementation on the regrowth potential of arginine-starved, canavanine-treated CRC cells.…”

“…Therefore, it is reasonable to speculate that arginine deprivation therapy could prime CRC and other ASS1-positive malignancies to both standard-of-care and novel combinational therapies. Here we propose to co-apply arginine deprivation with a natural arginine analog canavanine, as such combination supposedly preserves the cytotoxic potential of canavanine [20–22] with a selectively high anticancer efficacy in vitro as indicated in an earlier study [23]. …”

Free Amino Acids, Including Canavanine, in the Seeds from 24 Wild Mediterranean Legumes

“…Nevertheless, it has also been found more recently that canavanine could have important therapeutic properties. Thus, canavanine inhibits cell proliferation [20] and induces apoptosis [21,22] in cell cultures, and it also increases susceptibility to radiation in cancer cells [23]. In addition, it inhibits some of the deleterious effects of endotoxic shock in rat models [24,25] and has potential as an antidiabetic agent because it has been found to increase uptake of glucose [26] and release of insulin [27] in cell cultures.…”