Pre-B cell leukaemia transcription factor (Pbx1) is a member of a ubiquitous class of homeodomain (HOX) proteins. Subsequent studies have shown that Pbx1 is widely expressed and acts as a co-factor for a variety of HOX proteins. This also means that Pbx1 is a one of the markedly and specifically suppressed gene in Promyelocytic leukaemia zinc finger (PLZF) which has been characterized as one of the regulated genes in cancer. In addition, PLZF is also a transcription repressor which suppresses the transcription of genes such as c-myc, cyclin A2 and HoxD11. In this study, the use of differential display reverse transcriptase polymerase chain reaction was reported to identify a novel hybrid tilapia mRNA sequence which is highly homologous to Pbx1 gene. For this purpose, hybrid tilapia Pbx1 was cloned. Then, a specific primer for the hybrid tilapia was designed for the Pbx1 mRNA measurements using the real-time PCR. The hybrid tilapia was exposed to 0.469, 0.938, 1.875 and 2.813 mg/l cadmium (Cd) to determine the relationship between Pbx1 mRNA expression levels. The cloned Pbx1, consisting of 343 bp encoding a protein of 53 amino acids, showed higher than 60% identity with the deduced amino acid sequence. Pbx1 mRNA expression and Cd accumulation appeared to be dose-responsive following cadmium treatment. Based on these results, the Pbx1 mRNA expression levels could be used as a bio-indicator to monitor the carcinogenic level of Cd in biological samples. The study is currently in progress to obtain the full gene sequence of Pbx1 using RACE-PCR.