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Updated: Jan 27, 2026
Radiosensitivity of Cancer Stem Cells in Lung Cancer Cell Lines
Published on: August 21, 2019
P53 pathway is a major determinant in the radiosensitizing effect of Palbociclib: Implication in cancer therapy
D M Fernández-Aroca1, O Roche2, S Sabater3
1Laboratorio de Oncología, Unidad de Medicina Molecular, Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Unidad Asociada de Biomedicina UCLM, Unidad asociada al CSIC, Albacete, Spain.
Abstract:
Targeting cell cycle has become one of the major challenges in cancer therapy, being Palbociclib, a CDK4/6 inhibitor, an excellent example. Recently, it has been reported that Palbociclib could be a novel radiosensitizer agent. In an attempt to clarify the molecular basis of this effect we have used cell lines from colorectal (HT29, HCT116) lung (A549, H1299) and breast cancer (MCF-7). Our results indicate that the presence of a p53 wild type is strictly required for Palbociclib to exert its radiosensitizing effect, independently of the inhibitory effect exerted on CDK4/6. In fact, abrogation of p53 in cells with functional p53 blocks the radiosensitizing effect of Palbociclib. Moreover, no radiosensitizing effect is observed in cells with non-functional p53, but restoration of p53 function promotes radiosensitivity associated to Palbociclib. Furthermore, the presence of Palbociclib blocks the transcriptional activity of p53 in an ATM-dependent-fashion after ionizing radiation exposure, as the blockage of p21/WAF1 expression demonstrates. These observations are a proof of concept for a more selective therapy, based on the combination of CDK4/6 inhibition and radiotherapy, which would only benefit to those patients with a functional p53 pathway.
Insights
Palbociclib enhances radiotherapy effects only in cancer cells with functional p53. This CDK4/6 inhibitor requires wild-type p53 to sensitize tumors to radiation, blocking p53 activity post-treatment.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- Targeting the cell cycle is crucial in cancer therapy, with CDK4/6 inhibitors like Palbociclib showing promise.
- Palbociclib is emerging as a potential radiosensitizer, but its molecular mechanism requires elucidation.
Purpose of the Study:
- To investigate the molecular basis of Palbociclib's radiosensitizing effect.
- To determine the role of p53 status in mediating Palbociclib-induced radiosensitivity.
Main Methods:
- Utilized colorectal, lung, and breast cancer cell lines (HT29, HCT116, A549, H1299, MCF-7).
- Assessed Palbociclib's radiosensitizing effect in cells with varying p53 functional status (wild-type, abrogated, restored).
- Examined p53 transcriptional activity and p21/WAF1 expression post-irradiation in the presence of Palbociclib.
Main Results:
- Palbociclib's radiosensitizing effect is strictly dependent on the presence of wild-type p53.
- Abrogating p53 function in wild-type cells abolished radiosensitization; restoring p53 in non-functional cells re-established it.
- Palbociclib inhibited p53 transcriptional activity in an ATM-dependent manner after ionizing radiation, evidenced by blocked p21/WAF1 expression.
Conclusions:
- Functional p53 is essential for Palbociclib to act as a radiosensitizer, independent of its CDK4/6 inhibitory action.
- This suggests a targeted therapeutic approach combining CDK4/6 inhibition and radiotherapy for patients with functional p53 pathways.
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