BACKGROUND: Heterogeneous nuclear ribonucleoproteins (hnRNPs) of the A/B type 
(hnRNP A1, A2/B1, A3) are highly related multifunctional proteins participating 
in alternative splicing by antagonising other splicing factors, notably ASF/SF2. 
The altered expression pattern of hnRNP A2/B1 and/or splicing variant B1 alone 
in human lung cancer and their potential to serve as molecular markers for early 
diagnosis remain issues of intense investigation. The main objective of the 
present study was to use paired tumour/non-tumour biopsies from patients with 
non-small cell lung cancer (NSCLC) to investigate the expression profiles of 
hnRNP A1, A2/B1 and A3 in conjunction with ASF/SF2.
METHODS: We combined western blotting of tissue homogenates with 
immunohistochemical examination of fixed tissue sections and quantification of 
mRNA expression levels in tumour versus adjacent normal-looking areas of the 
lung in the same patient.
RESULTS: Our study, in addition to clear evidence of mostly uncoupled 
deregulation of hnRNPs A/B, has revealed hnRNP A1 to be the most deregulated 
protein with a high frequency of over-expression (76%), followed by A3 (52%) and 
A2/B1 (43%). Moreover, direct comparison of protein/mRNA levels showed a lack of 
correlation in the case of hnRNP A1 (as well as of ASF/SF2), but not of A2/B1, 
suggesting that different mechanisms underlie their deregulation.
CONCLUSION: Our results provide strong evidence for the up-regulation of hnRNP 
A/B in NSCLC, and they support the existence of distinct mechanisms responsible 
for their deregulated expression.