MicroRNA profiling of colorectal cancer (CRC) and precancerous lesions (adenoma) of CRC

MicroRNAs (miRNAs) are a recently discovered class of small (~ 22 nucleotides)
non-protein coding (npc) RNA molecules that negatively regulate gene expression
by binding to target messenger RNAs (mRNAs). miRNAs are involved in the control
of many fundamental cellular and physiological processes such as cellular
proliferation and differentiation, development and regulated cell death. In
recent years a compelling amount of evidence has been gathered indicating that
miRNAs also play a significant role in cellular transformation and
carcinogenesis acting either as oncogenes or tumor suppressors. Rather limited
information is available for colorectal carcinoma and its precancerous lesions.
Up till now only a handful of miRNAs notably let-7, miR-10a, miR-17-92 cluster,
miR-20a, miR-24-1, miR-29b-2, miR-31, miR-96, miR-133b, miR-135b, miR-143,
miR-145 and miR-183 have been reported to be aberrantly expressed. However, the
precise role these and other miRNAs play in colorectal carcinoma is still
unclear.

The purpose of this project is to determine and analyze miRNA expression
profiles from freshly frozen human colon tissue as well colorectal adenomas and
carcinomas to identify specific miRNAs or miRNA clusters whose expression is
altered in colorectal lesions. The identification of essential miRNAs and their
subsequent functional characterization improves our insight in the process of
carcinogenesis of colorectal cancer and may lead to novel therapeutic
approaches.

Biopsies of tumour or polyp and corresponding normal tissue will be obtained
during colonoscopy for routine histology evaluation at the Department of
Pathology. For this study, four additional biopsies (2mm) will be taken of the
polyp or tumour and biopsies of macroscopically normal colonic mucosa of the
same bowel segment (ascending colon, transverse colon, descending colon,
sigmoid, rectum) as the lesion will be taken.
The miRNA profiling will be performed using an LNA*modified oligonucleotide
array platform that was developed in our laboratory and which is capable of
detecting the full complement of human miRNAs as registered in the miRNA
repository as well as 150 putative miRNAs. Briefly, total RNA will be isolated
from biopsies obtained from normal and tumor tissue and from premaligant
lesions. Subsequently the RNA is fluorescently labeled and hybridized with Tm
normalized LNA* modified capture probes spotted on glass slides. The
hybridization signals will be quantified, analyzed and used to generate miRNA
expression profiles. Next, various statistical procedures will be employed to
identify the miRNAs that are aberrantly expressed in colorectal carcinoma and
precancerous lesions in the colon.

There is a risk on minimal rectal blood loss until two days after the
colonoscopy. The biopsy itself is not painful. The colonoscopy will be
lengthened with approx. 4 minutes. The is no personal benefit for the
participating patient.