Early Response to the Plant Toxin Stenodactylin in Acute Myeloid Leukemia Cells Involves Inflammatory and Apoptotic Signaling

Abstract

Stenodactylin, a highly toxic type 2 ribosome-inactivating protein purified from the caudex of Adenia stenodactyla Harms, is a potential anticancer drug candidate. Previous studies demonstrated that stenodactylin induces apoptosis and necroptosis in treated cells, involving the production of reactive oxygen species. We analyzed the effect of stenodactylin on Raji and Ramos (Human Burkitt's lymphoma cells) and MOLM-13 (acute myeloid leukemia cells). Moreover, we focused on the early events in MOLM-13 cells that characterize the cellular response to the toxin by whole-genome microarray analysis of gene expression. Treatment with stenodactylin induced the depurination of 28S rRNA within 4 h and increased the phosphorylation of p38 and JNK. A timedependent activation of caspase 1, 2, 8, 9, 3/7 was also observed. Genome-wide gene expression microarray analysis revealed early changes in the expression of genes involved in the regulation of cell death, inflammation and stress response. After 4 h, a significant increase of transcript level was detectable for ATF3, BTG2, DUSP1, EGR1, and JUN. Increased upstream JUN signaling was also confirmed at protein level. The early response to stenodactylin treatment involves inflammatory and apoptotic signaling compatible with the activation of multiple cell death pathways. Because of the above described properties toward acute myeloid leukemia cells, stenodactylin may be a promising candidate for the design of new immunoconjugates for experimental cancer treatment.

Primary Sequence and 3D Structure Prediction of the Plant Toxin Stenodactylin

“…It has been reported that in a neuroblastoma cell line, stenodactylin can induce multiple cell death pathways, involving mainly apoptosis, but also necroptosis and the production of free radicals [ 10 ]. Similar results have been recently obtained in acute myeloid leukemia cells, in which stenodactylin can elicit a rapid stress response with production of pro-inflammatory factors and oxidative stress leading mainly to apoptosis, but also triggering other cell death pathways [ 11 ].…”

“…Due to its high systemic toxicity, native stenodactylin could only be employed for loco-regional treatments in cancer therapy. However, stenodactylin A-chain linked to a specific carrier by chemical conjugation or by genetic engineering, could find application to specifically target tumor cells in systemic therapy [ 11 ]. Moreover, stenodactylin may have an application in neurobiology.…”

Kirkiin: A New Toxic Type 2 Ribosome-Inactivating Protein from the Caudex of Adenia kirkii

“…It has been reported that in a neuroblastoma cell line, stenodactylin induced multiple cell death pathways, involving apoptosis, necroptosis, and oxidative stress [ 25 ]. Moreover, stenodactylin elicited a quick stress response in leukemia cells, producing pro-inflammatory factors and oxidative stress, triggering apoptosis and other cell death pathways [ 26 ].…”

Heterophyllin: A New Adenia Toxic Lectin with Peculiar Biological Properties

“…Being able to act on several independent substrates, RIPs are capable of inducing different death pathways in intoxicated cells. RIPs are hence able to kill cells even if they have alterations in proliferative or apoptotic mechanisms, thus making it impossible to select RIP-resistant mutants [ 14 , 15 , 16 , 17 ].…”