Mechanism of Marsdenia tenacissima extract promoting apoptosis of lung cancer by regulating Ca2+/CaM/CaMK signaling

Abstract

Ethnopharmacological relevance: Marsdenia tenacissima is a traditional Chinese medicine that has been used since the Ming dynasty. It is famous for its apoptotic effects on lung cancer. However, limited information is available about the underlying mechanisms.

Aim of the study: We aimed to determine the mechanisms by which different organic M. tenacissima extracts induce apoptosis in lung cancer cells.

Materials and methods: PubMed and CNKI databases were screened for M. tenacissima components that may targets lung cancer; 223 components were selected for drug-like and pharmacokinetic analysis. Moreover, the inhibitory effect of different extracts of M. tenacissima on tumor cells was illustrated using CCK-8 and apoptosis assays, and intracellular [Ca²⁺] was measured. The in vivo effects were examined by body weight, tumor pathology, and TUNEL staining analysis in a Lewis lung carcinoma mouse model. In vivo levels of the Ca²⁺ signaling-related proteins Calmodulin, CaMKⅡ, p-CaMKⅡ, MEK1/2, p-MEK1/2, ERK, and p-ERK were measured by Western blot.

Results: Petroleum ether and ethyl acetate extracts of M. tenacissima have stronger inhibitory effects than other extracts on lung cancer cells, with IC₅₀ values of 0.35 ± 0.04 mg/ml and 0.29 ± 0.02 mg/ml for LLC cells and 0.56 ± 0.05 mg/ml and 0.85 ± 0.04 mg/ml for A549 cells, respectively. Compared with the normal control group, A549 and LLC cells of treatment groups exhibited morphological changes typical of apoptosis, and the apoptosis rate was significantly higher, as determined by flow cytometry. Furthermore, the i[Ca²⁺] changed accordingly, causing a decrease in vivo in Calmodulin, CaMKⅡ, p-CaMKⅡ, p-MEK1/2 and p-ERK levels.

Conclusions: M. tenacissima induces apoptosis, both in vitro and in vivo. Hydrophobic extracts are most effective; they increase i[Ca²⁺], decrease intracellular Calmodulin, CaMKⅡ, p-CaMKⅡ, p-MEK1/2 and p-ERK levels, and activate the apoptotic cascade.

Keywords: Apoptosis; Cancer; Phytochemistry; Signal transduction; Traditional Chinese medicine.