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Characterization of colorectal-cancer-related cDNA clones obtained by subtractive hybridization screening
1Cancer Institute, Zhejiang Medical University, Hangzhou 310009, People's Republic of China.
Abstract:
In an attempt to seek out new factors that are related to colorectal carcinogenesis at the molecular level, subtractive hybridization between cDNA of normal mucosal tissues and mRNA of colorectal carcinoma tissues was performed. Subsequent screenings of the cDNA libraries, constructed from normal mucosal tissues, using the "subtractive probes" generated a total of 46 clones that were expressed in normal mucosa but were either expressed at a significantly reduced level or not expressed at all in cancer tissues. Partial nucleotide sequences of all of these cDNA clones were determined, and sequence homology analyses were performed with the Genbank database. Of the 46 cDNA samples, 44 contained substantial sequence homologies with 32 immunoglobulin gene fragments, a helix-loop-helix basic phosphoprotein gene, an acidic ribosomal phosphoprotein P2 gene, a BLR1 gene for Burkitt's lymphoma receptor 1 gene, D5S419 DNA segment containing (C-A) repeats, a glucokinase (GCK) gene, a Na+, K+-ATPase alpha-subunit gene, a histocompatibility system HLA-DR heavy-chain gene, a dystrophic gene, a mucin (MUC2) gene, a mu-glutathione S-transferase gene, a Menkes disease protein gene, and a 40-kDa keratin intermediate filament precursor gene. The remaining two cDNA clones (now registered under GenBank accession numbers U17714 and U20428) showed few (less than 60%) sequence homologies with any known sequences in the GenBank database and, therefore, may represent novel genes whose expression was down-regulated in human colorectal carcinomas. The possible clinical significance of these findings and the involvement of these two genes in the carcinogenesis of colorectal as well as other cancers are being investigated.
Insights
Researchers identified 46 genes expressed in normal colon tissue but downregulated in colorectal cancer. Two novel genes may play a role in colorectal carcinogenesis and other cancers.
Area of Science:
- Molecular Biology
- Genetics
- Oncology
Background:
- Colorectal cancer (CRC) development involves complex molecular alterations.
- Identifying novel genes associated with CRC is crucial for understanding carcinogenesis.
Purpose of the Study:
- To identify genes downregulated in colorectal carcinoma compared to normal mucosal tissues.
- To investigate potential novel genes involved in colorectal cancer development.
Main Methods:
- Subtractive hybridization was used to compare cDNA from normal mucosa and mRNA from colorectal carcinoma.
- cDNA libraries were screened using subtractive probes to identify differentially expressed genes.
- Partial nucleotide sequences of identified clones were analyzed for homology with the Genbank database.
Main Results:
- 46 cDNA clones were identified as expressed in normal mucosa but downregulated or absent in cancer tissues.
- 44 clones showed homology to known genes including immunoglobulin fragments, BLR1, GCK, HLA-DR, MUC2, and keratin.
- Two cDNA clones (U17714, U20428) exhibited low homology to known sequences, suggesting they may be novel genes.
Conclusions:
- Two potentially novel genes show downregulated expression in colorectal carcinomas.
- These novel genes may be implicated in the carcinogenesis of colorectal and potentially other cancers.
- Further investigation into the clinical significance of these findings is warranted.