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RB expression confers sensitivity to CDK4/6 inhibitor–mediated radiosensitization across breast cancer subtypes

Standard radiation therapy (RT) does not reliably provide locoregional control for women with multinode-positive breast cancer and triple-negative breast cancer (TNBC). We hypothesized that CDK4/6 inhibition (CDK4/6i) would increase the radiosensitivity not only of estrogen receptor–positive (ER(+))...

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Detalles Bibliográficos
Autores principales: Pesch, Andrea M., Hirsh, Nicole H., Michmerhuizen, Anna R., Jungles, Kassidy M., Wilder-Romans, Kari, Chandler, Benjamin C., Liu, Meilan, Lerner, Lynn M., Nino, Charles A., Ward, Connor, Cobain, Erin F., Lawrence, Theodore S., Pierce, Lori J., Rae, James M., Speers, Corey W.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Society for Clinical Investigation 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8855810/
https://www.ncbi.nlm.nih.gov/pubmed/34932500
http://dx.doi.org/10.1172/jci.insight.154402
Descripción
Sumario:Standard radiation therapy (RT) does not reliably provide locoregional control for women with multinode-positive breast cancer and triple-negative breast cancer (TNBC). We hypothesized that CDK4/6 inhibition (CDK4/6i) would increase the radiosensitivity not only of estrogen receptor–positive (ER(+)) cells, but also of TNBC that expresses retinoblastoma (RB) protein. We found that CDK4/6i radiosensitized RB WT TNBC (n = 4, radiation enhancement ratio [rER]: 1.49–2.22) but failed to radiosensitize RB-null TNBC (n = 3, rER: 0.84–1.00). RB expression predicted response to CDK4/6i + RT (R((2)) = 0.84), and radiosensitization was lost in ER((+))/TNBC cells (rER: 0.88–1.13) after RB1 knockdown in isogenic and nonisogenic models. CDK4/6i suppressed homologous recombination (HR) in RB WT cells but not in RB-null cells or isogenic models of RB1 loss; HR competency was rescued with RB reexpression. Radiosensitization was independent of nonhomologous end joining and the known effects of CDK4/6i on cell cycle arrest. Mechanistically, RB and RAD51 interact in vitro to promote HR repair. CDK4/6i produced RB-dependent radiosensitization in TNBC xenografts but not in isogenic RB1-null xenografts. Our data provide the preclinical rationale for a clinical trial expanding the use of CDK4/6i + RT to difficult-to-control RB-intact breast cancers (including TNBC) and nominate RB status as a predictive biomarker of therapeutic efficacy.