Four cytotoxic peptides and two insulin-stimulating proteins were isolated from black-necked spitting cobra venom, with the most potent peptide killing lung cancer cells at 0.8 μM and the proteins boosting insulin release 6-fold.
LC50 0.8 μM against lung cancer + 6-fold insulin boostThe most potent cobra cytotoxin killed lung cancer cells at sub-micromolar concentrations, while separately, venom phospholipases increased insulin release 6-fold at non-toxic doses — dual therapeutic potential from a single venom.
What the researchers found
Four three-finger toxin peptides from N. nigricollis venom showed cytotoxic activity. Cytotoxin-1N was most potent: LC50 = 0.8 μM (A549 lung cancer), 7 μM (MDA-MB-231 breast cancer), 9 μM (HT-29 colorectal cancer). However, all peptides were also cytotoxic to normal HUVEC endothelial cells (LC50 2-22 μM), and cytotoxin-2N was moderately hemolytic (LC50 45 μM). Separately, two phospholipase A2 isoforms stimulated insulin release approximately 6-fold from BRIN-BD11 beta-cells at 1 μM — a non-cytotoxic concentration.
Why it matters
This study highlights both the promise and challenge of venom-derived therapeutics. The potent anti-cancer activity (0.8 μM against lung cancer) shows these peptides are powerful cell killers, but their lack of selectivity for cancer over normal cells is a common problem with venom cytotoxins. The insulin-releasing discovery is potentially more translatable, as it works at non-toxic concentrations — representing a genuinely novel mechanism for stimulating insulin that could complement existing diabetes therapies.
How the study worked
Venom from N. nigricollis was fractionated using reversed-phase HPLC. Peptides were identified as three-finger toxins by ESI-MS/MS sequencing of tryptic fragments. Cytotoxicity was tested against three human tumor cell lines (A549, MDA-MB-231, HT-29), normal HUVEC cells, and BRIN-BD11 rat beta-cells. Hemolytic activity was tested against mouse erythrocytes. Insulin-releasing proteins were identified as phospholipase A2 isoforms and tested for insulin stimulation at non-cytotoxic concentrations.
What this study cannot tell us
In vitro study only — no animal or human testing. The cytotoxic peptides lack cancer selectivity, killing normal endothelial cells at similar concentrations. BRIN-BD11 cells are a rat beta-cell line that may not perfectly replicate human pancreatic islet responses. The insulin-releasing proteins are phospholipases, not peptides per se, which complicates their development as therapeutics due to size and immunogenicity. The concentration producing 6-fold insulin release (1 μM) may be difficult to achieve systemically without toxicity.
How to read the evidence
This is an in vitro venom characterization study with careful peptide identification and functional testing across multiple cell lines. The methodology is rigorous for a natural products discovery study, but all findings are preliminary and cell-based.
When this study was published
Published in 2020, this study adds to the ongoing exploration of snake venoms as sources of bioactive peptides and proteins for drug development.
The bigger picture
Venom-derived peptides have yielded several approved drugs (captopril from snake venom, exenatide from Gila monster, ziconotide from cone snail). This study adds two potential directions: cytotoxic peptides that would need engineering for tumor selectivity, and insulin-releasing proteins that could represent a new class of insulin secretagogues. The finding that a phospholipase from snake venom potently stimulates insulin is particularly novel and connects venom research to the metabolic disease field.
Questions still open
- Could the cytotoxin peptides be modified or conjugated to tumor-targeting antibodies to achieve cancer selectivity?
- What is the mechanism by which phospholipase A2 stimulates insulin secretion — direct beta-cell membrane effects or signaling pathway activation?
- Would the insulin-releasing phospholipases be effective and safe in animal models of type 2 diabetes?
Common questions
Can snake venom be used to fight cancer?
Could snake venom help with diabetes?
Read the original research
Isolation and characterization of cytotoxic and insulin-releasing components from the venom of the black-necked spitting cobra Naja nigricollis (Elapidae).
Toxicon: X, 6, 100030
Citation
Conlon, J M; Attoub, Samir; Musale, Vishal; Leprince, Jérôme; Casewell, Nicholas R; Sanz, Libia; Calvete, Juan J. (2020). Isolation and characterization of cytotoxic and insulin-releasing components from the venom of the black-necked spitting cobra Naja nigricollis (Elapidae).. Toxicon: X, 6, 100030. https://doi.org/10.1016/j.toxcx.2020.100030