miR-106a overexpression and pRB downregulation in sporadic colorectal cancer
Highlights
► Rb1 LOH showed no correlation with mRNA and protein expression. ► No Rb1 promoter methylation was detected in colorectal tumor and normal tissue. ► Rb1 mRNA was higher in tumors in comparison to normal colonic tissue. ► miR-106a was significantly higher in tumor in comparison to normal colonic tissue. ► Loss of pRb was found in majority of tumors.
Introduction
Colorectal cancer is one of the most frequent malignant diseases in the world. The incidence is expected to become even higher due to increasing porportion of elderly people in the world population and to increasing exposure to cancerous substances. (Jemal et al., 2011). Colorectal cancer arises from the accumulation of mutations during progression from normal colon epithelium to adenoma and carcinoma (Fearon and Vogelstein, 1990). This process implies changes in different types of genes and their expression pattern. Hanahan and Weinberg (2000) postulated that the aquired biological capabilities are common to all cancer types, but the timeline of mutations that occur in cancer related genes varies. One of the gatekeeper genes that codes for a transcription factor involved in the regulation of the cell cycle is Rb1 (retinoblastoma gene) (DiCiommo et al., 2000). It is a gene located at chromosome 13q14.2 that spreads over 180 kb of genomic DNA and contains 27 exons (Lee et al., 1987). It encodes a 110 kDa protein product, pRb (Lee et al., 1987), which is involved in maintaining the chromatine structure, and acts as a negative regulator of the cell cycle progression (Indovina et al., 2013). It is a member of the Rb protein family, together with p107 and p130. All three proteins are involved in the same cellular pathway but have distinct functions (Dannenberg and te Riele, 2006, Indovina et al., 2013). It is considered that the high majority, if not all human tumors, have defective Rb pathway (DiCiommo et al., 2000, Manning and Dyson, 2012). Rb1 was first found to be altered in retinoblastoma and it was a prototype model for studying a potential tumor supressor gene (Friend et al., 1986). Later extensive research revealed its association with other malignancies like small cell lung cancer, melanoma, prostate, breast, bladder and other types of cancer (Burkhart and Sage, 2008). Changes in Rb1 were also implicated in all stages of tumor development (Burkhart and Sage, 2008). In the gastrointestinal tract, loss of Rb1 function was associated with the progression of tumorigenesis (Kucherlapati et al., 2008). Vast amount of data are available from the published literature but its precise role in this type of cancer has been inconclusive due to newly appreciated complexity of its function and interactions (Viatour and Sage, 2011).
The aim of this study was to define the potential role of Rb1 as a prognostic biomarker in tumorigenesis of sporadic colorectal cancer. Loss of heterozygosity, methylation status and expression of Rb1 mRNA and protein were examined. The expression of miR-106a was also interesting for our research because it was reported to be specific for Rb1 mRNA, and that it functionally binds to its 3′UTR (Volinia et al., 2006). Therefore, we analyzed miR-106a expression level, and evaluated its role by comparring it to pRb expression. The results obtained from all patients' samples were correlated with the clinicopathological parameters in order to evaluate its role in the progression of sporadic colorectal cancer.
Section snippets
Patients and tissue specimens
Our research was carried out on tumor samples and samples of corresponding normal tissue obtained from Croatian Human Tumor Bank (Spaventi et al., 1994). The tumor specimens were collected through a routine surgery. Fresh samples of resected colon carcinoma and normal colon mucosa adjacent to resected carcinoma (more than 15 cm from the tumor) were snap-frozen in liquid nitrogen and stored in Human Tumor Bank at − 80 °C until further use. Tissue samples, adjacent to the segments of tissue that
LOH at the Rb1 gene locus
To analyze allelic imbalance at the Rb1 gene, we investigated LOH at two polymophic loci, D13S153 and Rb1.20. Heterozygosity was detected in 261 of 300 patients (87.0%) and LOH was found in 56 informative tumors (21.5%).
We found no statistically significant correlation of LOH occurrence at investigated loci with clinicopathological parameters (Table 1).
Methylation analysis
We analyzed 39 pairs of tumor tissue and corresponding normal tissue obtained from patients and no methylation was detected in the Rb1 promoter
Discussion
In this study, we investigated the changes in the Rb1 gene and its mRNA and protein expression patterns in sporadic colorectal carcinogenesis. Rb1 is one of the key regulators of the cell cycle, it interacts with numerous binding partners in the cell, and influences the transcription of several downstream targets (DiCiommo et al., 2000, Viatour and Sage, 2011). On the basis of the Knudson two-hit theory, it is expected to be lost during the early stages of tumorigenesis (Friend et al., 1986).
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Role of the funding source
This research was funded by Croatian Ministry of Science, Education and Sports (098-0982464-2508).
The study sponsor had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.
Acknowledgments
We thank Gordana Jurinic for technical assistance.
References (57)
- et al.
Housekeeping gene variability in normal and carcinomatous colorectal and liver tissues: applications in pharmacogenomic gene expression studies
Analytical Biochemistry
(2002) - et al.
Retinoblastoma: the disease, gene and protein provide critical leads to understand cancer
Seminars in Cancer Biology
(2000) - et al.
Progressive methylation during the serrated neoplasia pathway of the colorectum
Modern Pathology
(2005) - et al.
A genetic model for colorectal tumorigenesis
Cell
(1990) - et al.
The hallmarks of cancer
Cell
(2000) - et al.
Genetic and epigenetic alteration profiles for multiple genes in salivary gland carcinomas
Oral Oncology
(2005) - et al.
pRB, a tumor suppressor with a stabilizing presence
Trends in Cell Biology
(2011) - et al.
DNA methyltransferase expression and DNA hypermethylation in human hepatocellular carcinoma
Cancer Letters
(2006) - et al.
Human Tumor Bank in Croatia: a possible model for a small bank as a part of future European tumor bank network
European Journal of Cancer
(1994) - et al.
Detection of miR-106a in gastric carcinoma and its clinical significance
Clinica Chimica Acta
(2009)
Protein kinase CK2α is overexpressed in colorectal cancer and modulates cell proliferation and invasion via regulating EMT-related genes
Journal of Translational Medicine
RB1 protein in normal and malignant human colorectal tissue and colon cancer cell lines
The FASEB Journal
The retinoblastoma protein interacts with Bag-1 in human colonic adenoma and carcinoma derived cell lines
International Journal of Cancer
Cellular mechanisms of tumor suppression by the retinoblastoma gene
Nature Reviews. Cancer
Altered expression of the retinoblastoma gene product in human sarcomas
The New England Journal of Medicine
DNA methylation patterns in blood of patients with colorectal cancer and adenomatous colorectal polyps
International Journal of Cancer
A reappraisal of the Rb1 gene abnormalities in the diagnosis of parathyroid cancer
Clinical Endocrinology
The role of the retinoblastoma protein (Rb) in the nuclear localization of BAG-1: implications for colorectal tumor cell survival
Biochemical Society Transactions
The retinoblastoma gene family in cell cycle regulation and suppression of tumorigenesis
Results and Problems in Cell Differentiation
Prognostic factors in colorectal cancer
The British Journal of Surgery
Epigenetic patterns in the progression of esophageal adenocarcinoma
Cancer Research
A human DNA segment with properties of the gene that predisposes to retinoblastoma and osteosarcoma
Nature
LIMD1 is more frequently altered than RB1 in head and neck squamous cell carcinoma: clinical and prognostic implications
Molecular Cancer
Abundance and state of phosphorylation of the retinoblastoma susceptibility gene product in human colon cancer
Molecular and Cellular Biochemistry
Increased expression of the retinoblastoma gene in human colorectal carcinomas relative to normal colonic mucosa
Journal of the National Cancer Institute
Frequency and parental origin of hypermethylated RB1 alleles in retinoblastoma
Human Genetics
Transcriptional down-regulation of the retinoblastoma protein is associated with differentiation and apoptosis in human colorectal epithelial cells
British Journal of Cancer
Emerging roles of RB family: new defense mechanisms against tumor progression
Journal of Cellular Physiology
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