Anti-proliferative and anti-tumour effect of active components in donkey milk on A549 human lung cancer cells

The anti-proliferative and anti-tumour effects of donkey milk on A549 human lung cancer cells were investigated in vitro, and its effects on cell cycle progression, apoptosis and cytokine production were examined. Donkey milk active fractions reduced the viability of A549 cells in dose-dependent and time-dependent manners. Fraction-IV, a fraction of whey protein with a molecular mass >10 kDa, was the most effective fraction (P < 0.05) in inducing an accumulation of A549 cells in the G0/G1 and G2/M phases, indicating a potent cytotoxicity and causing cell death by apoptosis. The anti-proliferative activity of conditioned medium, prepared with fraction-IV-stimulated murine splenocytes, was significantly higher than that of fraction-IV alone (P < 0.05). Moreover, it could increase the secretion of Interleukin-2 (IL-2), Interferon-γ (IFN-γ), Interleukin-6 (IL-6), tumour necrosis factor α (TNF-α) and Interleukin 1β (IL-1β). The active components of donkey milk not only could directly suppress tumour proliferation in vitro, but may also indirectly kill tumours through activation of lymphocytes and macrophages. A high content of lysozyme in fraction-IV may contribute to its anti-tumour activity.