Trichinella spiralis muscle larvae excretory/secretory products trigger apoptosis and S-phase arrest of the non-small-cell lung cancer line A549

Abstract

Trichinella spiralis (T. spiralis) muscle larvae (ML) excretory/secretory products (ESPs) are antitumor substances extracted from the culture medium of T. spiralis ML. The ESPs inhibit tumor growth and induce tumor cell apoptosis. To explore the effects of these products on the non-small-cell lung cancer (NSCLC) line A549, logarithmically growing A549 cells were co-cultured with different concentrations of T. spiralis ML ESPs for 24, 36 and 48 h. Our results showed that T. spiralis ML ESPs significantly inhibited A549 cells proliferation, which was dose-and time-dependent. To evaluate the inhibition by T. spiralis ML ESPs of the growth of A549 cells, we assayed their apoptosis and cell-cycle distribution by flow cytometry (FCM). To determine whether ESPs induced apoptosis of A549 cells via the mitochondrial pathway, we evaluated the levels of mitochondrion-related factors by Western blotting. The FCM indicated a clear trend toward apoptosis of A549 cells co-cultured with ESPs for 24 h. The cells were blocked in S-phase. Western blotting revealed that the expression levels of the genes encoding Bax, caspase-3, and caspase-9 increased (compared to a control group), and the Bcl-2 gene expression level decreased. Our results suggest that T. spiralis ML ESPs induce apoptosis of the NSCLC line A549 via the mitochondrial pathway; the cells become arrested in S-phase. This may explain the antineoplastic activity of T. spiralis ML ESPs.

Keywords: Apoptosis; Excretory/secretory products; Muscle larva; Non-small-cell lung cancer; Trichinella spiralis.