Antitumor Potential of Bioactive Crude Extracts Derived from Actinomycetes

Abstract

Marine actinomycetes constitute a vigorous source of bioactive compounds with potential anti-tumor activity. This study investigates the antitumor activity and classification of actinomycetes isolated from 32 marine soil samples collected across four seasons from Tyr City Beach, Lebanon. A total of 80 morphologically diverse isolates were recovered and characterized, with dominant genera including Streptomyces, Kocuria, and Micrococcus. Among these, three promising strains—Kocuria rosea, Micrococcus luteus, and Streptomyces longisporoflavus—were selected for further analysis. Crude extracts were tested against human colorectal adenocarcinoma (Caco-2) and human hepatocellular carcinoma (HepG-2) cancer cell lines using MTT and Western blot assays. At the highest concentration (8 µg/µL), the extracts reduced cell viability to 24–37% in Caco-2 and 12–25% in HepG-2. The IC50 values ranged from 1.72 to 3.53 µg/µL, depending on the extract and cell line. Western blot analysis showed dose-dependent increases in the Bax/Bcl-2 ratio, with fold changes reaching 4.35 (Kocuria), 11.39 (Micrococcus), and 14.25 (Streptomyces) in HepG-2 cells. The p53 protein expression also increased significantly, with fold changes up to 7.79 in Caco-2 and 3.0 in HepG-2 cells. These results indicate that marine actinomycetes from the Lebanese coastline hold strong potential as a source of antitumor agents targeting apoptosis pathways.