Abstract: A pharmacological composition for use in inhibiting differentiation, functional activities, and population of granulo-cytic myeloid-derived suppressor cells (gMDSCs) and/or suppressing, tumor metastasis in a subject in need thereof is disclosed. The composition comprises a therapeutically effective amount of Bidens pilosa extract, or more than one polyacetylenic compounds purified or isolated from the B. pilosa extract, and a pharmaceutically acceptable carrier.