Strigolactone analogs induce apoptosis through activation of p38 and the stress response pathway in cancer cell lines and in conditionally reprogrammed primary prostate cancer cells

Strigolactones are a novel class of plant hormones produced in roots and regulate shoot and root development. We have previously shown that synthetic strigolactone analogues potently inhibit growth of breast cancer cells and breast cancer stem cells. Here we show that strigolactone analogues inhibit the growth and survival of an array of cancer-derived cell lines representing solid and non-solid cancer cells including: prostate, colon, lung, melanoma, osteosarcoma and leukemic cell lines, while normal cells were minimally affected. Furthermore, we tested the response of patient-matched conditionally reprogrammed normal and prostate cancer cells. The tumor cells exhibited significantly higher sensitivity to the two most potent SL analogues with increased apoptosis compared to their normal counterpart cells. Treatment of cancer cells with strigolactone analogues was hallmarked by increased expression and activity of genes involved in stress signaling, cell cycle arrest and apoptosis. All five strigolactone analogues induced G2/M cell cycle arrest, accompanied with a decrease in the expression level of cyclin B1. Apoptosis was marked by increased percentages of cells in the sub-G1 fraction and was confirmed by Annexin V staining. In conditionally reprogramed matched tumor and normal prostate cells, the cleavage of PARP1 confirmed the specific increase in apoptosis of tumor cells. In summary, Strigolactone analogues are promising candidates for anticancer therapy by their ability to specifically induce cell cycle arrest, cellular stress and apoptosis in tumor cells with minimal effects on growth and survival of normal cells.

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Pollock CB, McDonough S, Wang VS, Lee H, Ringer L, Li X, Prandi C, Lee RJ, Feldman AS, Koltai H, Kapulnik Y, Rodriguez OC, Schlegel R, Albanese C, Yarden RI