title: Correlation of telomere length shortening with promoter methylation profile of p16/Rb and p53/p21 pathways in breast cancer.
abstract: Unregulated cell growth, a major hallmark of cancer, is coupled with telomere shortening. Measurement of telomere length could provide important information on cell replication and proliferation state in cancer tissues. Telomere shortening and its potential correlation with downregulation of cell-cycle regulatory elements were studied by the examination of relative telomere length and methylation status of the TP53, P21 and P16 promoters in tissues from breast cancer patients. Telomere length was measured in 104 samples (52 tumors and paired adjacent normal breast tissues) by quantitative PCR. Methylation profile of selected genes was analyzed in all samples using a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Our results demonstrated a significant shortening of tumor telomere regions compared with paired adjacent normal tissues (P<0.001). Similarly, telomere lengths were significantly shorter in advanced stage cases and in those with higher histological grades (P<0.05). Telomere shortening in cancer tissues was correlated with a different level of hypermethylation in the TP53, P21 and P16 promoters (r=-0.33, P=0.001; r=-0.70, P<0.0001 and r=-0.71, P<0.0001, respectively). The results suggested that inactivation of p16/Rb and/or p53/p21 pathways by hypermethylation may be linked to critical telomere shortening, leading to genome instability and ultimately to malignant transformation. Thus, telomere shortening and promoter hypermethylation of related genes both might serve as breast cancer biomarkers.
authors.affiliation: Laboratory for Prenatal Medicine and Gynecologic Oncology, Women's Hospital/Department of Biomedicine, University of Basel, Basel, Switzerland.
authors.forename: Ramin
authors.initials: R
authors.lastname: Radpour
authors.forename: Zeinab
authors.initials: Z
authors.lastname: Barekati
authors.forename: Mahdi Montazer
authors.initials: MM
authors.lastname: Haghighi
authors.forename: Corina
authors.initials: C
authors.lastname: Kohler
authors.forename: Reza
authors.initials: R
authors.lastname: Asadollahi
authors.forename: Peyman Mohammadi
authors.initials: PM
authors.lastname: Torbati
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Holzgreve
authors.forename: Xiao Yan
authors.initials: XY
authors.lastname: Zhong
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018275:Carcinoma, Lobular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle / Q000235:genetics; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D013058:Mass Spectrometry; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D019098:Telomerase / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000235:genetics* / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009363:Neoplasm Proteins; D016159:Tumor Suppressor Protein p53; D019098:Telomerase