BORIS, a Novel Potential Cancer Biomarker is Expressed in Senescent Human Fibroblasts
Introduction: CTCF encodes a transcription factor involved in different aspects of gene regulation. A CTCF paralog named BORIS is expressed only in male germinal cells which correlates with re-setting of methylation marks while CTCF remains silenced. Opposite occurs in somatic cells. Abnormal coexpression of these genes has been observed only in transformed cell lines and cancer.
Purpose: Because the existing link between cancer and aging, the aim of this work was to study BORIS and CTCF expression at transcriptional level in the human fibroblast model of replicative senescence.
Methods: Two forearm fibroblast primary cultures from healthy young human males were established and confluent monolayers passaged routinely in a 1:4 split ratio. To assess the senescent state of cell cultures senescent associated β-Galactosidase activity was evaluated. Fibroblast cultures representing Hayflick's early, middle, and late culture phases were used as RNA source. Total RNA was isolated with Tri-Reagent™ and BORIS and CTCF transcription determined by RT-PCR using the One Step SuperScript II™ RT-PCR kit. The primer sequences used for BORIS and CTCF generate fragments of 271bp and 176 bp respectively.
Results: Fibroblasts in Hayflick's phase III showed more than 90% of the cells positively stained for SA-β-Gal. In this phase BORIS transcription was detected. On the other hand, the CTCF amplification product was detected in primary, middle and late cultures co-expressing with BORIS only in the latter stage as described.
Conclusions: This is the first communication showing BORIS expression by senescent stromal fibroblasts derived from normal skin, which suggests that BORIS expression could be up-regulated in vivo during aging and this expression could not be restricted to tumor and masculine germinal cells as described to date. Further studies are necessary to shed light about the possible implications of the interplay of BORIS and CTCF in the biology of cancer and aging.