Human Cancer Antigen Globo H Is a Cell-Surface Ligand for Human Ribonuclease 1

Abstract

Pancreatic-type ribonucleases are secretory enzymes that catalyze the cleavage of RNA. Recent efforts have endowed the homologues from cow (RNase A) and human (RNase 1) with toxicity for cancer cells, leading to a clinical trial. The basis for the selective toxicity of ribonuclease variants for cancerous versus noncancerous cells has, however, been unclear. A screen for RNase A ligands in an array of mammalian cell-surface glycans revealed strong affinity for a hexasaccharide, Globo H, that is a tumor-associated antigen and the basis for a vaccine in clinical trials. The affinity of RNase A and RNase 1 for immobilized Globo H is in the low micromolar–high nanomolar range. Moreover, reducing the display of Globo H on the surface of human breast adenocarcinoma cells with a small-molecule inhibitor of biosynthesis or a monoclonal antibody antagonist decreases the toxicity of an RNase 1 variant. Finally, heteronuclear single quantum coherence (HSQC) NMR spectroscopy showed that RNase 1 interacts with Globo H by using residues that are distal from the enzymic active site. The discovery that a systemic human ribonuclease binds to a moiety displayed on human cancer cells links two clinical paradigms and suggests a mechanism for innate resistance to cancer.

Comparative functional analysis of ribonuclease 1 homologs: molecular insights into evolving vertebrate physiology

“…The association of RNase 1 with cell-surface glycans could aids this process [44, 50]. We were curious to know if the enzymes in our study have a similar ability to enter cells, and if this ability correlates with affinity for cell-surface moieties.…”

“…[ 15 N]-RNase 1 was produced in Escherichia coli as described previously, using a double-growth procedure in minimal medium containing [ 15 N]-NH 4 Cl after induction with IPTG [50]. Growth conditions yielded an average of 15 mg of RNase 1 from 1 L of medium.…”

Ribonuclease as Anticancer Therapeutics

“…The above information helps to identify cellular targets of cytotoxic RNases, distinguishes between their direct and indirect effects of ribonucleolytic action. Caspase-dependent process, low molecular weight compounds, alteration in protein and NF-κB signal pathway are cell death mechanisms which involve in response to cytotoxic RNases [69]. In a previous study, Onconase decreased the NF-κB1 tanscription factor in pleural mesothelioma cells and restrained the canonical NF-κB dependent pathways.…”

“…These nano-complexes are also used for drug delivery to the cancer cells. In previous studies, HA-RNase A was efficiently delivered to the CD44-overexpressing A549 cells which extensively inhibited cancer cells proliferation, indicating an efficient method of targeted cancer therapy [69,75].…”

“…In a previous study it has been reported that genes of canonical NF-κB dependent signal pathway and proinflammatory caspase 1 and 4 gene were activated by binase. Binase shows the cytotoxic effect against cancer cell lines by activating the TNF through caspase 8 and NF-κB which leads to activate the caspase 3, 4 and 7 for eventual cell death [69,70]. Currently, we are still unclear which of these targets is more effective in triggering apoptotic process and thus more promising for cancer therapy.…”