Calliandra portoricensis Benth exhibits anticancer effects via alteration of Bax/Bcl-2 ratio and growth arrest in prostate LNCaP cells

Abstract

Ethnopharmacological relevance: Apoptosis is downregulated in all forms of cancers. The mitochondrion has been implicated in the apoptotic process and, recently has been targeted in cancer therapy because of its role in cancer progression. Medicinal plants are used in the treatment of cancer, in particular, Calliandra portoricensis (CP) in the management of prostate cancer in Nigeria ethnomedicine.

Aim of the study: This study was designed to investigate the effects of CP on mitochondrial-mediated apoptosis and cell proliferation using prostate cancer cells.

Materials and methods: Prostatic LNCaP, DU-145, lung adenocarcinoma and healthy VERO cells were used to assess cell proliferation. Cell cycle analysis was evaluated by flow cytometry. Levels of pro-apoptotic Bax, anti-apoptotic Bcl-2, Cytochrome C Release (CCR) and activation of caspases 3(C3) and 9 (C9) were determined by ELISA, while mitochondrial integrity was evaluated by Fluorescent Intensity Ratio (FIR).

Results: Methanol Fraction of C. portoricensis (MFCP) inhibited proliferation of prostatic LNCaP, DU-145, lung adenocarcinoma and healthy VERO cells with IC₅₀ values of 2.4 ± 0.2, 3.3 ± 0.2, 3.6 ± 0.2 and 17.9 ± 1.6 µg/mL, respectively. The growth inhibition by MFCP correlated with a 3-fold decreased expression of Bcl-2 and a 4-fold increase in Bax levels at 10 µg/mL in LNCaP cells. Furthermore, MFCP caused a 3.5-fold reduction in FIR at 10 µg/mL and induced CCR by 4.2 folds at the same concentration relative to control. The MFCP-induced CCR is associated with activation of C3 and C9 at 10 µg/mL by 4.2 and 5.1 folds, respectively which prompted cancer cells to arrest at S phase. The LC-MS analysis revealed the presence of polyphenols including gallic acid and afzelechin in MFCP.

Conclusion: Taken together, MFCP- induced cell death is mediated by alteration of mitochondrial integrity and cell cycle arrest. Hence, methanol fraction of C. portoricensis may be effective for cancer pharmacotherapy.

Keywords: Apoptosis; Calliandra portoricensis; Cancer; Cell proliferation; Cytochrome C; Mitochondria.