Homologs of the recently described mouse pro genes, that transfer sensitivity to promotion of neoplastic transformation by tumor promoters, have been cloned from a genomic library of the human nasopharyngeal carcinoma (NPC) cell line CNE2. Both pro-1 and pro-2 homologs were identified by screening this library with mouse probes, but only the pro-1 homologs were able to confer sensitivity to TPA-induced transformation when transferred to promotion-insensitive mouse JB6 cells. This suggests a possible role for the putative pro-1 gene in the etiology of human NPC.