LRPAP1 and neoplasm: In addition, Rap was shown to enhance both the in vitro and in vivo antitumor activity of vincristine against HT-29 human colorectal cancer cells that had been rendered multidrug-resistant by overexpressing the mdr1 gene [18], and induce caspase-independent cell death in both drug-sensitive and -resistant neuroblastoma cells and tumor xenografts [19].