Apoptosis, or programmed cell death, is a tightly regulated process essential for maintaining cellular homeostasis and preventing uncontrolled proliferation. In cancer, evasion of apoptosis is a hallmark feature that enables tumor cells to survive despite genetic damage and stress signals. Melittin (MEL), a major component of bee venom, has emerged as a potent inducer of apoptosis in various cancer types, including cervical carcinoma. This study investigates the molecular mechanisms by which melittin triggers apoptosis and induces cell cycle arrest in human cervical cancer CaSki cells.
Treatment with melittin led to a significant reduction in cell viability in a dose- and time-dependent manner, as confirmed by MTT and WST-1 assays. At concentrations ranging from 0.5 to 2 μg/mL, melittin effectively inhibited proliferation without causing substantial toxicity at lower doses, suggesting a therapeutic window. Flow cytometry analysis revealed that melittin induced G2/M phase cell cycle arrest, accompanied by a marked increase in the sub-G1 population, indicative of DNA fragmentation and apoptotic cell death.
Mechanistically, melittin activated key components of the intrinsic apoptotic pathway. Western blot analysis showed a progressive increase in cleaved caspase-9 and caspase-3, along with a decrease in pro-caspase forms. Concurrently, the levels of anti-apoptotic proteins Bcl-2 and Bcl-xL were significantly downregulated, while the pro-apoptotic protein Bax was upregulated. This shift in the Bcl-2/Bax ratio promoted mitochondrial outer membrane permeabilization (MOMP), leading to cytochrome c release into the cytosol. The subsequent formation of the apoptosome complex triggered caspase-9 activation, initiating the execution phase of apoptosis.
Further evidence was provided by caspase activity assays, which demonstrated a strong dose-dependent activation of caspase-3 and caspase-9 following melittin treatment. Pretreatment with pan-caspase inhibitor Z-VAD-FMK significantly attenuated apoptosis, confirming the critical role of caspases in mediating melittin-induced cell death.Pimicotinib site Additionally, melittin induced PARP cleavage, a hallmark of apoptotic execution, further supporting the activation of the caspase cascade.Alogliptin Protocol
In parallel, melittin suppressed the expression of cyclin-dependent kinases (CDKs) and cyclins involved in G2/M transition.PMID:34904508 Specifically, the levels of CDK1, CDK2, cyclin B1, and cyclin A were markedly reduced after melittin exposure. This downregulation disrupted the assembly of functional CDK-cyclin complexes necessary for cell cycle progression, thereby contributing to the observed G2/M arrest. Phosphorylation of retinoblastoma protein (Rb) was also diminished, indicating inhibition of the G1/S transition, although the primary arrest occurred at G2/M.
Immunofluorescence staining revealed nuclear condensation and fragmentation in melittin-treated cells, consistent with apoptotic morphology. Moreover, transmission electron microscopy showed characteristic ultrastructural changes, including chromatin margination and membrane blebbing, further validating apoptosis induction.
These findings demonstrate that melittin exerts dual anticancer effects in CaSki cells: it activates caspase-dependent apoptosis via mitochondrial dysfunction and inhibits cell cycle progression by suppressing CDK/cyclin activity. The selective targeting of these pathways suggests that melittin may overcome resistance mechanisms commonly seen in chemotherapy-resistant cancers. Given its ability to induce apoptosis without affecting normal cells at therapeutic doses, melittin holds promise as a natural agent for cervical cancer therapy. Future studies should focus on optimizing delivery systems and evaluating efficacy in vivo to advance its potential clinical application.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com