Previous in vitro studies showed that ATRA inhibited MMP-2 expression in human cancer cell lines from glioblastoma [23, 24], breast cancer [25], lung cancer [26], ovarian cancer [27], chondrosarcoma [28], and osteosarcoma [29], but it did not affect [30] or enhance [31] MMP-2 expression in neuroblastoma cell line. The gene discussed is MMP2; the disease is lung cancer.