Primary and compensatory roles for RB family members at cell cycle gene promoters that are deacetylated and downregulated in doxorubicin-induced senescence of breast cancer cells.
When treated with DNA-damaging chemotherapy agents, many cancer cells, in vivo and in vitro, undergo a terminal growth arrest and acquire a senescence-like phenotype. We investigated the molecular basis for this in breast cancer cells following a 2-hour treatment with 1 muM doxorubicin. Treated cells arrested in G1 and G2 phases of the cell cycle, with concomitant reductions in S-phase and G2-M regulatory genes. p53 and p21 protein levels increased within hours after treatment and were maintained for 5 to 6 days but were reduced 8 days posttreatment, though the cells remained growth arrested. Levels of p130 rose after drug treatment, and it was the primary RB family member recruited to the S-phase promoters cyclin A and PCNA and G2-M promoters cyclin B and cdc2, remaining present for the entire 8-day time period. In contrast, p107 protein and promoter occupancy levels declined sharply after drug treatment. RB was recruited to only the PCNA promoter. In MCF-7 cells with p130 knockdown, p107 compensated for p130 loss at all cell cycle gene promoters examined, allowing cells to retain the growth arrest phenotype. Cells with p130 and p107 knockdown similarly arrested, while cells with knockdown of all three family members failed to downregulate cyclin A and cyclin B. These results demonstrate a mechanistic role for p130 and compensatory roles for p107 and RB in the long-term senescence-like growth arrest response of breast cancer cells to DNA damage.
University of Texas Health Science Center at San Antonio, Department of Cellular and Structural Biology, Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas 78245-3207, USA. jacksonjg@uthscsa.edu
James G
JG
Jackson
Olivia M
OM
Pereira-Smith
D000107:Acetylation; D001943:Breast Neoplasms / Q000473:pathology*; D016922:Cellular Senescence / Q000187:drug effects*; D015536:Down-Regulation / Q000235:genetics*; D004317:Doxorubicin / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D020869:Gene Expression Profiling; D018816:Genes, cdc; D006657:Histones / Q000378:metabolism; D006801:Humans; D005810:Multigene Family; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011506:Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107 / Q000378:metabolism; D050717:Retinoblastoma-Like Protein p130 / Q000172:deficiency / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D006657:Histones; D011506:Proteins; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin