Effect of inducible FHIT and p53 expression in the Calu-1 lung cancer cell line.
Loss of FHIT expression and p53 mutations are critical events in the early stages of lung carcinogenesis. The restoration of Fhit function in FHIT-negative cancer cells has been reported to cause tumour suppression by inhibition of cell proliferation and/or activation of apoptotic pathways. However, the studies designed to elucidate the biological role of Fhit and its potential interaction with p53 have produced conflicting results. We investigated here the effects of the simultaneous restoration of FHIT and p53 in Calu-1 cells by using a hormone-inducible gene expression system. We demonstrate that the restoration of FHIT expression reinforces the anti-proliferative effect associated with the simultaneous replacement of p53. Indeed, a more pronounced inhibition of cell proliferation associated with an earlier and higher induction of p21(waf1) mRNA and protein expression was observed in Fhit/p53-expressing cells compared with cells expressing p53 alone. This effect was not due to Fhit-mediated up-regulation of p53 expression; in fact p53 protein was expressed at the same level in both FHIT-positive and FHIT-negative cell clones. Consistent with this result, Fhit did not affect the expression of MDM2, a protein known to interact directly with p53 and target p53 for proteolytic degradation, thus down-regulating its activity.
Cavazzoni
A
A
Department of Experimental Medicine, University of Parma, Via Volturno 39, Parma, Italy.
Galetti
M
M
Fumarola
C
C
Alfieri
R R
RR
Roz
L
L
Andriani
F
F
Carbognani
P
P
Rusca
M
M
Sozzi
G
G
Petronini
P G
PG
D017766:Acid Anhydride Hydrolases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000099170:Bis(5'-adenosyl)triphosphatase
D017766:Acid Anhydride Hydrolases; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009363:Neoplasm Proteins; D051736:Proto-Oncogene Proteins c-mdm2; D016159:Tumor Suppressor Protein p53; D000099170:Bis(5'-adenosyl)triphosphatase; C493956:CDKN1A protein, human; C495901:TP53 protein, human; C497206:MDM2 protein, human