The scorpion is a predatory arthropod represented by more than 1500 different species worldwide (1). A part of the diverse arachnid class, scorpions possess a venomous stinger at the end of their tails used to paralyze prey or for self-defense. Although the venom is generally considered poisonous, there are varying degrees of pathogenicity and only a small fraction of scorpion species are deadly to humans (2).
The belief that scorpions have medicinal properties has existed for centuries, and many instances of their use have been recorded in both indigenous and folk medicine. In Traditional Chinese Medicine, the entire scorpion of the Buthus martensii Karsch (BmK) species is used to treat convulsions, spasms, and pain (3), and some laboratory studies confirm that scorpion venoms do contain antinociceptive properties (4) (5).
Scorpion venom has also been evaluated for other applications. It appears useful in killing intraerythrocytic malarial pathogens without harming the erythrocyte (6), and some species contain antimicrobial peptides that appear effective against yeast, fungi, bacteria, and viruses (7) (8). Scorpion venom could also be a source for the isolation of anticancer molecules. Preliminary assessments indicate that Tityus discrepans, Androctonus crassicauda, and Odontobuthus doriae venoms are effective inducers of apoptosis in breast cancer cell lines (9) (10) (11) . A component in BmK venom inhibits proliferation of human leukemia cells suggesting therapeutic potential in hematopoietic malignancies (12). Because the general composition and expression level of scorpion venom depends on genetic variations and geographical environments, research to identify the active components that have therapeutic potential across the various species continues (12) (13) (14).
Rhopalurus junceus, or blue scorpion venom, originated from Cuba, and is often marketed as having anticancer, anti-inflammatory, and analgesic properties. Claims for these products, known as Escozine and Escozul, are largely based on anecdotal information, testimonials, and preclinical experiments on laboratory animals. However, the manufacturers’ research cannot be corroborated and has not been published in any peer-reviewed journal (15) (16). In 2009, the Cuban government formally rejected the use of Escozul due to insufficient clinical data (17). Only recently has there been a functional characterization of R. junceus in the literature, but without any clinical evidence presented for R. junceus-derived products (18). A homeopathic version, Vidatox, has since been developed and has also not been evaluated in peer-reviewed journals.
The more likely scenario for future benefits with scorpion venom in cancer therapy may come from clinical trials involving chlorotoxin (CTX), a scorpion venom-derived peptide. CTX may facilitate the entry of chemotherapeutic compounds into tumor cells to target drug delivery and improve efficacy (19) (20) (21). In addition, it holds the potential for reducing side effects and can be synthesized in the laboratory (22). A synthetic CTX that selectively binds to glioma and other tumors cells is being evaluated as a radiopharmaceutical to deliver therapeutic levels of radiation directly to disease sites (23) (24). A CTX/near-infrared fluorescent molecule combination is under investigation as a cancer imaging agent, a kind of “tumor paint” that may help surgeons more clearly identify tumor margins and micrometastases, and spare normal tissue (25) (26) (27).
Continued research on the complex characteristics of scorpion venom among the various species is needed to both isolate the properties of therapeutic importance and develop their application in cancer research.