2-Amino-3-Chlorobenzoic Acid from Streptomyces coelicolor: A Cancer Antagonist Targeting PI3K/AKT Markers via miRNA Modulation

<b>Background/Objectives:</b> Actinomycetes, particularly species within the <i>Streptomyces</i> genus, are renowned for their ability to produce a wide array of bioactive molecules with therapeutic potential. This study aimed to comprehensively investigate the antimicrobial and anticancer properties of <i>Streptomyces coelicolor</i> ERI-15, with a particular focus on a purified compound, 2-amino-3-chlorobenzoic acid (2A3CB), and its efficacy against microbial pathogens and breast cancer cell lines. <b>Methods:</b> Antimicrobial compounds were produced through fermentation techniques and isolated via column chromatography. Bioassay-guided fractionation was conducted against <i>Staphylococcus aureus</i> (ATCC 25923), methicillin-resistant <i>Staphylococcus aureus</i> (MRSA), <i>Escherichia coli</i> (ATCC 25922), and <i>Bacillus subtilis</i> (ATCC 441). Major fractions were further purified using preparative thin-layer chromatography (TLC). The structures of active compounds were elucidated using spectral analyses including IR, mass spectrometry, and ¹H/¹³C NMR. The compound 2A3CB (<i>m</i>/<i>z</i> 171) was tested against MDA-MB-231 and 3T3 cell lines. Cytotoxicity was assessed by the MTT assay, and apoptotic mechanisms were explored via cell proliferation assays, dual fluorescent staining, migration and invasion assays, and analysis of apoptotic markers at mRNA and protein levels. <b>Results:</b> 2A3CB exhibited strong cytotoxic effects on MDA-MB-231 cells, with IC₅₀ values of 26 µM, 5 µM, and 7.2 µM at 24, 48, and 72 h, respectively. It significantly inhibited cell proliferation and migration, and induced apoptosis via caspase-mediated pathways. Expression levels of PTEN, PCNA, BAX, and STAT3 were downregulated, suggesting inhibition of metastasis through the suppression of invasion and migration. <b>Conclusions:</b> The results demonstrate that 2A3CB, derived from <i>S. coelicolor</i> ERI-15, possesses potent antimicrobial and anticancer properties. Its ability to inhibit growth and induce apoptosis in MDA-MB-231 breast cancer cells highlights its potential as a natural therapeutic candidate for targeted cancer treatment, particularly in breast cancer progression.