KLK3 and prostate cancer: Gracilosulfate G (121) exhibited weak cytotoxicity against hormone-independent prostate cancer cells, with an IC50 = 64.4 μM, while the other isolated compounds were found effective in the concentration-dependent inhibition of a prostate-specific antigen (PSA) in human prostate cancer (22Rv1) cells, indicating that these compounds may inhibit androgen receptor (AR) signaling [28].