We present evidence that GSPs inhibit melanoma cancer cell proliferation and in vivo tumor xenograft growth and that they do so through: (i) down-regulation of miRNA-106b expression, and (ii) blocking of melanoma cell division in the G1 phase of the cell cycle through reactivation of tumor suppressor protein p21/WAF1/Cip1. The gene discussed is CDKN1A; the disease is melanoma.