Lack of correlation between DNA copy number and mRNA expression levels of c-myc in gamma-radiation-induced mouse thymic lymphomas by using quantitative real-time PCR.
BACKGROUND
It is well documented that over-expression of the c-myc proto-oncogene occurs in the vast majority of mouse thymic lymphomas induced by gamma-irradiation, evidencing the importance of this gene in T-cell lymphomagenesis. However, it remains unknown whether elevated levels of c-myc expression are driven by extra c-myc copy numbers.


METHODS
Here we use a quantitative test on the basis of real-time PCR to determine the cellular copy number of c-myc in a set of 14 g-radiation- induced thymic lymphomas obtained from (C57BL/6J x BALB/cJ) F1 hybrid mice with increased mRNA c-myc expression.


RESULTS
Since 5 out of 14 (35.7%) cases had no extra copy numbers of c-myc, gene amplification was obviously not the cause of c-myc over-expression in these tumours. In the remaining 9 tumours, c-myc over-expression was also accompanied with extra DNA copy numbers. Therefore, c-myc amplification might be a consequence of the genomic instability subsequent to the up-regulation of c-myc. However, linear regression analysis showed a lack of correlation between increasing DNA copy numbers and mRNA over expression of c-myc in these tumours (r = 0.029, p = 0.94).


CONCLUSIONS
De-regulation of c-myc does not necessarily imply amplification of this gene in these tumours. This report is, to our knowledge, the first one comparing c-myc amplification with expression in lymphomas of the T-cell lineage.
Santos
J
J
Laboratorio de Genética Molecular Humana, Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Spain. javier-santos@uam.es
Vaquero
C
C
Reyes
J
J
López-Nieva
P
P
Matabuena
M
M
Villa
M
M
Fernández
P
P
Fernández-Piqueras
J
J
D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000528:radiation effects; D003199:Computer Systems; D003433:Crosses, Genetic; D004273:DNA, Neoplasm / Q000235:genetics; D005720:Gamma Rays / Q000009:adverse effects*; D005784:Gene Amplification; D018628:Gene Dosage; D016259:Genes, myc; D008223:Lymphoma / Q000209:etiology / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009381:Neoplasms, Radiation-Induced / Q000209:etiology / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D013953:Thymus Neoplasms / Q000209:etiology / Q000235:genetics*
D004273:DNA, Neoplasm; D012333:RNA, Messenger; D012334:RNA, Neoplasm