mRNA expression array data correlates to the MMP-9 protein expression in colorectal biopsies

Introduction: Results concerning the correlation between mRNA expression array data and immunohistochemical detection of the corresponding proteins in colorectal cancer (CRC) are not available.

Aims: Determination of mRNA and protein expression of matrix metalloproteinase-9 (MMP-9) and comparison with staging in CRC.

Patients, methods: Biopsies were taken from the involved and corresponding normal colonic part of 10 adenoma and 10 CRC patients. Total RNA was extracted. The mRNA fraction from the extracted total RNA was amplified by T7 RNA amplification method. RNA expression profile was evaluated by Atlas Glass microarrays and the Genepix 4000B scanner. Expression of MMP-9 was determined on paraffin embedded biopsy sections by immunohistochemical labeling in 23 CRC patients and in 15 patients with adenoma. MMP-9 immunostaining was determined semi-quantitatively.

Results: MMP-9 was overexpressed in adenoma and in CRC samples on the mRNA expression arrays as compared to the normal tissue (p<0.05). Moderate and strong immunohistochemical staining of MMP-9 was observed in tumor as well as in stromal cells. In dysplastic lesions moderate expression was also detected. Staining intensity increased from normal-adenoma-adenoma with dysplasia- to CRC. Staining intensity strongly correlated both with Dukes' stage and grade of CRC.

Conclusions: MMP-9 protein expression level correlates to the mRNA expression array data. As the staining intensity followed the adenoma-dysplasia-carcinoma sequence, MMP-9 may play a crucial role in tumor progression. Our preliminary data suggest the prognostic impact of MMP-9 in CRC.

Supported in part by OTKA Grant No.: T 340345.