Syringolin A, a new plant elicitor from the phytopathogenic bacterium Pseudomonas syringae pv. syringae, inhibits the proliferation of neuroblastoma and ovarian cancer cells and induces apoptosis

. Syringolin A is a new plant elicitor produced by the plant pathogen Pseudomonas syringae pv. syringae. The goal of this study was to investigate whether syringolin A exhibits anti‐proliferative properties in cancer cells. The treatment of human neuroblastoma (NB) cells (SK‐N‐SH and LAN‐1) and human ovarian cancer cells (SKOV3) with syringolin A (0–100 µm) inhibited cell proliferation in a dose‐dependent manner. The IC50 (50% inhibition) for each cell line ranged between 20 µm and 25 µm. In SK‐N‐SH cells, the treatment with 20 µm syringolin A led to a rapid (24 h) increase of the apoptosis‐associated tumour suppressor protein p53. In addition, we found that the treatment of SK‐N‐SH cells caused severe morphological changes after 48 h such as rounding of cells and loss of adherence, both conditions observed during apoptosis. The induction of apoptosis by syringolin A was confirmed by both poly (ADP‐ribose) polymerase (PARP) cleavage and annexin V assay. Taken together, we show for the first time that the natural product syringolin A exhibits anti‐proliferative activity and induces apoptosis. Syringolin A and structurally modified syringolin A derivatives may serve as new lead compounds for the development of novel anticancer drugs.