Abstract

Introduction: Oesophageal squamous cell carcinoma (ESCC) is an aggressive subtype of oesophageal cancer. Cisplatin is a standard chemotherapeutic agent for ESCC with limited treatment efficacy and chemoresistance occurrence. Thus, a novel anticancer candidate with a chemosensitising effect could be a promising ESCC therapy. Green macroalgae have exhibited cytotoxicity against several cancers preclinically, but their anticancer and chemosensiting effects against ESCC are unknown. This preliminary study investigated anticancer and cisplatin-chemosensitising potentials of two unidentified Ulva sp. extracts. Methods: Ulva sp. powder was macerated in ethanol and methanol by shaking for 48 h. The metabolites in the concentrated extracts were identified using phytochemical tests. Half-maximal inhibitory concentration (IC₅₀) was determined using MTT assay after treating KYSE-150 and Vero normal cells with different extract concentrations for 24 h. Caspase 3/7 apoptotic assay and morphological alteration were further evaluated after 6h treatment. Intracellular reactive oxygen species (ROS) levels were also measured using DCF-DA assay. In the chemosensitising study, the IC₅₀ of 24 h-cisplatin treatment and 2 h-extract pre-treatment were identified using MTT assay. Results: The phytochemical tests showed positive for glycosides, tannins, terpenoids, carbohydrates, fats and oils, proteins and flavonoids. The cytotoxicity induced by ethanolic (IC₅₀ = 237.2 µg/ml) and methanolic (IC₅₀ = 165.6 µg/ml) extracts in KYSE-150 cells was higher than in Vero cells, with a selectivity index of 1.35 and 1.22 respectively. Both extracts induced an increasing apoptotic event in Caspase 3/7 measurement and cellular morphology observation. Higher ROS levels in KYSE-150 cells than in Vero cells were observed. Elevated ROS levels were observed from 0-200 µg/ml as compared to higher concentrations, indicating early and late stages of apoptosis. Only methanolic extract increased KYSE-150 sensitivity towards cisplatin treatment (from 62.3 µM to 50 µM). Conclusion: Both Ulva sp. extracts show anticancer activity against KYSE-150 cells by inducing apoptosis via ROS modulation.

Keywords: Anticancer, Chemosensitising, Ulva sp., Cisplatin, Oesophageal squamous cell carcinoma