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Updated: Jul 5, 2026
Analysis of Cell Cycle Position in Mammalian Cells
Published on: January 21, 2012
Distinct roles for p107 and p130 in Rb-independent cellular senescence
Brian D Lehmann1, Adam M Brooks, Matthew S Paine
1Department of Anatomy and Cell Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina, USA.
Abstract:
Telomere attrition, DNA damage and constitutive mitogenic signaling can all trigger cellular senescence in normal cells and serve as a defense against tumor progression. Cancer cells may circumvent this cellular defense by acquiring genetic mutations in checkpoint proteins responsible for regulating permanent cell cycle arrest. A small family of tumor suppressor genes encoding the retinoblastoma susceptibility protein family (Rb, p107, p130) exerts a partially redundant control of entry into S phase of DNA replication and cellular proliferation. Here we report that activation of the p53-dependent DNA damage response has been found to accelerate senescence in human prostate cancer cells lacking a functional Rb protein. This novel form of irradiation-induced premature cellular senescence reinforces the notion that other Rb family members may compensate for loss of Rb protein in the DNA damage response pathway. Consistent with this hypothesis, depletion of p107 potently inhibits the irradiation-induced senescence observed in DU145 cells. In contrast, p130 depletion triggers a robust and unexpected form of premature senescence in unirradiated cells. The dominant effect of depleting both p107 and p130, in the absence of Rb, was a complete blockade of irradiation-induced cellular senescence. Onset of the p107-dependent senescence was temporally associated with p53-mediated stabilization of the cyclin-dependent kinase inhibitor p27 and decreases in c-myc and cks1 expression. These results indicate that p107 is required for initiation of accelerated cellular senescence in the absence of Rb and introduces the concept that p130 may be required to prevent the onset of terminal growth arrest in unstimulated prostate cancer cells lacking a functional Rb allele.
Insights
Cellular senescence, a defense against tumors, can be accelerated by DNA damage in prostate cancer cells lacking Rb protein. p107 and p130 proteins play critical roles in regulating this senescence process.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Cellular senescence is a crucial tumor suppressive mechanism triggered by DNA damage, telomere attrition, or mitogenic stress.
- Cancer cells often evade senescence by mutating cell cycle checkpoint proteins.
- The retinoblastoma (Rb) protein family (Rb, p107, p130) regulates cell cycle progression and proliferation.
Purpose of the Study:
- To investigate the role of Rb family proteins in regulating DNA damage-induced senescence in prostate cancer cells.
- To elucidate the specific functions of p107 and p130 in the absence of functional Rb protein.
Main Methods:
- Utilized human prostate cancer cell lines (DU145) lacking functional Rb protein.
- Induced cellular senescence via irradiation and DNA damage response activation.
- Employed gene depletion techniques (siRNA) to knockdown p107 and p130 expression.
- Analyzed cell cycle arrest, senescence markers, and protein expression (p53, p27, c-myc, cks1).
Main Results:
- Activation of the p53-dependent DNA damage response accelerated senescence in Rb-deficient prostate cancer cells.
- Depletion of p107 inhibited irradiation-induced senescence, indicating its requirement for this process.
- Depletion of p130 induced premature senescence in unirradiated cells.
- Simultaneous depletion of p107 and p130 completely blocked irradiation-induced senescence.
- p107-dependent senescence onset correlated with p53-mediated p27 stabilization and decreased c-myc/cks1.
Conclusions:
- p107 is essential for initiating accelerated cellular senescence in Rb-deficient prostate cancer cells following DNA damage.
- p130 may act to prevent premature terminal growth arrest in unstimulated Rb-deficient prostate cancer cells.
- These findings highlight the complex interplay of Rb family proteins in tumor suppression and DNA damage response pathways.
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