| First Author | Bush JA | Year | 2002 |
| Journal | Carcinogenesis | Volume | 23 |
| Issue | 10 | Pages | 1603-7 |
| PubMed ID | 12376467 | Mgi Jnum | J:79584 |
| Mgi Id | MGI:2388522 | Doi | 10.1093/carcin/23.10.1603 |
| Citation | Bush JA, et al. (2002) Regulation of the Mdr1 isoforms in a p53-deficient mouse model. Carcinogenesis 23(10):1603-7 |
| abstractText | Both p53 and multidrug transporters play important roles in chemoresistance. A transcriptional dependence of the Mdr1 gene promoter by p53 was first established a decade ago, and despite intense study, the p53-Mdr1 relationship still remains vague in vivo. The general model proposes that wild-type p53 down regulates, while mutant p53 up regulates, the Mdr1 promoter. Given that many studies have utilized cancer cell lines, minimal promoters and non-specific cDNA expression for in vitro experiments, we first sought to confirm the model using dermal fibroblasts isolated from the p53-knockout mice. We show that the gene products of the mouse Mdr1 homologue (Mdr1a and Mdr1b), namely P-glycoprotein (P-gp), appear upregulated at both the protein and mRNA levels in p53(-/-) mFbs compared with p53(+/+) cells. We demonstrate that transient transfection of a mouse p53(WT) expression plasmid into short-term primary p53(-/-) fibroblasts can revert P-gp overexpression. The difference in P-gp levels has functional significance in that p53(-/-) fibroblasts are more resistant to doxorubicin and vincristine treatment and this resistance can be attenuated in the presence of the P-gp inhibitor, verapamil. Furthermore, we demonstrate that in kidney, spleen and testis, P-gp expression is elevated in the absence of p53. In contrast, other organs such as heart, liver, lung, brain, thymus and skeletal muscle, show no difference in expression between p53(+/+) and p53(-/-) mice. Thus, our data shows a tissue-specific regulation of P-gp isoforms by p53 in the context of a p53-null mouse model. |
