Similar Datasets
Project description:The tumor suppressor protein RB acts as a transcription repressor via the interaction of its pocket domain with an L/IXCXE motif in HDAC proteins such as HDAC1. Here we demonstrated that while lacking an L/IXCXE motif, HDAC5 interacts with both RB-N (via an FXXXV motif) and RB-C segments and this interaction is diminished by RB serine-249/threonine-252 and threonine-821 phosphorylation. HDAC5 gene is frequently downregulated or deleted in human cancers such as prostate cancer. Loss of HDAC5 increases histone H3 lysine 27 acetylation (H3K27-ac) and circumvents RB-mediated repression of cell cycle-related oncogenic genes. Accordingly, HDAC5 loss confers resistance to the CDK4/6 inhibitors such as Palbociclib in prostate cancer cells in vitro and in mice, but this effect is overcome by the BET-CBP/p300 dual inhibitor NEO2734. Our findings reveal an unknown role of HDAC5 in RB-mediated histone deacetylation and gene repression and a mechanism modulating CDK4/6 inhibitor therapeutic sensitivity in cancer cells.
2021-07-24 | GSE155003 | GEO
Project description:The tumor suppressor protein RB acts as a transcription repressor via the interaction of its pocket domain with an L/IXCXE motif in HDAC proteins such as HDAC1. Here we demonstrated that while lacking an L/IXCXE motif, HDAC5 interacts with both RB-N (via an FXXXV motif) and RB-C segments and this interaction is diminished by RB serine-249/threonine-252 and threonine-821 phosphorylation. HDAC5 gene is frequently downregulated or deleted in human cancers such as prostate cancer. Loss of HDAC5 increases histone H3 lysine 27 acetylation (H3K27-ac) and circumvents RB-mediated repression of cell cycle-related oncogenic genes. Accordingly, HDAC5 loss confers resistance to the CDK4/6 inhibitors such as Palbociclib in prostate cancer cells in vitro and in mice, but this effect is overcome by the BET-CBP/p300 dual inhibitor NEO2734. Our findings reveal an unknown role of HDAC5 in RB-mediated histone deacetylation and gene repression and a mechanism modulating CDK4/6 inhibitor therapeutic sensitivity in cancer cells.
2021-07-24 | GSE155001 | GEO
Project description:HDAC5 loss impairs RB repression of oncogenic related genes and confers CDK4/6 inhibitor resistance in cancer
| PRJNA648118 | ENA
Project description:HDAC5 loss impairs RB repression of oncogenic related genes and confers CDK4/6 inhibitor resistance in cancer [ChIP-seq]
| PRJNA648127 | ENA
Project description:HDAC5 loss impairs RB repression of oncogenic related genes and confers CDK4/6 inhibitor resistance in cancer [RNA-seq]
| PRJNA648121 | ENA
Project description:The tumor suppressor p16INK4A (p16) inhibits cell cycle progression through the CDK4/Rb pathway. We have previously shown that p16 regulates cellular oxidative stress, independent of its role in cell cycle control. We investigated whether loss of p16 had a direct impact on the mitochondria. We found that p16-null primary mouse fibroblasts (PMFs) displayed increased mitochondrial mass and expression of mitochondrial respiratory subunit proteins compared to wild-type (WT) PMFs. These findings in p16-null PMFs were associated with increased expression of the mitochondrial biogenesis transcription factors PRC and TFAM. On the other hand, p16-deficient PMFs demonstrated reduced mitochondrial respiration capacity consistent with electron microscopy findings showing that mitochondria in p16-deficient PMFs have abnormal morphology. Consistent with increased mitochondrial mass and reduced respiratory capacity, p16-deficient PMFs generated increased mitochondrial superoxide. One biological consequence of elevated ROS in p16-deficient PMFs was enhanced migration, which was reduced by the ROS scavenger N-acetylcysteine. Finally, p16-deficient PMFs displayed increased mitochondrial membrane potential, which was also required for their enhanced migration. The mitochondrial and migration phenotype was restored in p16-deficient PMFs by forced expression of p16. Similarly, over-expression of p16 in human melanocytes and A375 melanoma cells led to decreased expression of some mitochondrial respiratory proteins, enhanced respiration, and decreased migration. Inhibition of Rb phosphorylation in melanocytes and melanoma cells, either by addition of chemical CDK4 inhibitors or RNAi-mediated knockdown of CDK4, did not mimic the effects of p16 loss. These results suggest that p16 regulates mitochondrial biogenesis and function, which is independent of the canonical CDK4/Rb pathway.
| S-EPMC5593528 | biostudies-literature
Project description:The retinoblastoma protein (RB) restricts cell cycle gene expression and entry into the cell cycle. The RB-related protein p130 forms the DREAM (DP, RB-like, E2F, and MuvB) complex and contributes to repression of cell cycle-dependent genes during quiescence. Although both RB and DREAM bind and repress an overlapping set of E2F-dependent gene promoters, it remains unclear whether they cooperate to restrict cell cycle entry. To test the specific contributions of RB and DREAM, we generated RB and p130 knockout cells in primary human fibroblasts. Knockout of both p130 and RB yielded higher levels of cell cycle gene expression in G0 and G1 cells compared to cells with knockout of RB alone, indicating a role for DREAM and RB in repression of cell cycle genes. We observed that RB had a dominant role in E2F-dependent gene repression during mid to late G1 while DREAM activity was more prominent during G0 and early G1. Cyclin D-Cyclin-Dependent Kinase 4 (CDK4)-dependent phosphorylation of p130 occurred during early G1, and led to the release of p130 and MuvB from E2F4 and decreased p130 and MuvB binding to cell cycle promoters. Specific inhibition of CDK4 activity by palbociclib blocked DREAM complex disassembly during cell cycle entry. In addition, sensitivity to CDK4 inhibition was dependent on RB and an intact DREAM complex in both normal cells as well as in palbociclib-sensitive cancer cell lines. Although RB knockout cells were partially resistant to CDK4 inhibition, RB and p130 double knockout cells were significantly more resistant to palbociclib treatment. These results indicate that DREAM cooperates with RB in repressing E2F-dependent gene expression and cell cycle entry and supports a role for DREAM as a therapeutic target in cancer.
| S-EPMC6586519 | biostudies-literature
Project description:The elucidation of molecular events that confer tamoxifen resistance to estrogen receptor α (ER) positive breast cancer is of major scientific and therapeutic importance. Here, we report that LEM4 overexpression renders ER+ breast cancer cells resistant to tamoxifen by activating the cyclin D-CDK4/6 axis and the ERα signaling. We show that LEM4 overexpression accelerates tumor growth. Interaction with LEM4 stabilizes CDK4 and Rb, promotes Rb phosphorylation and the G1/S phase transition. LEM4 depletion or combined tamoxifen and PD0332991 treatment significantly reverses tamoxifen resistance. Furthermore, LEM4 interacts with and stabilizes both Aurora-A and ERα, promotes Aurora-A mediated phosphorylation of ERα-Ser167, leading to increase in ERα DNA-binding and transactivation activity. Elevated levels of LEM4 correlates with poorer relapse-free survival in patients with ER+ breast cancer undergoing endocrine therapy. Thus, LEM4 represents a prognostic marker and an attractive target for breast cancer therapeutics. Functional antagonism of LEM4 could overcome tamoxifen resistance.
| S-EPMC6177406 | biostudies-literature
Project description:Rb1 encodes a cell-cycle regulator that is functionally disrupted in most human cancers. Pancreatic ductal adenocarcinomas (PDACs) have a high frequency of mutations in KRAS and INK4A/CDKN2A that might allow cells to bypass the regulatory actions of retinoblastoma (RB). To determine the role of loss of RB function in PDAC progression, we investigated the effects of Rb disruption during pancreatic malignant transformation initiated by oncogenic Kras.We generated mice with pancreas-specific disruption of Rb, in the absence or presence of oncogenic Kras, to examine the role of RB in pancreatic carcinogenesis.In the presence of oncogenic Kras, loss of Rb from the pancreatic epithelium accelerated formation of pancreatic intraepithelial neoplasia (PanIN), increased the frequency of cystic neoplasms, and promoted rapid progression toward PDAC. Early stage cancers were characterized by acute pancreatic inflammation, associated with up-regulation of proinflammatory cytokines within the pancreas. Despite the presence of markers associated with oncogene-induced senescence, low-grade PanIN were highly proliferative and expressed high levels of p53. Pancreatic cancer cell lines derived from these mice expressed high levels of cytokines, and transcriptional activity of p53 was impaired.Rb encodes a tumor suppressor that attenuates progression of oncogenic Kras-induced carcinogenesis in the pancreas by mediating the senescence response and promoting activity of the tumor suppressor p53.
| S-EPMC3163782 | biostudies-literature
Project description:Deregulation of the p16(INK4a)-Cdk4/6-Rb pathway is commonly detected in patients with glioblastoma multiforme (GBM) and is a rational therapeutic target. Here, we characterized the p16(INK4a)-Cdk4/6-Rb pathway in the Mayo panel of GBM xenografts, established from primary tissue samples from patients with GBM, and evaluated their response to PD0332991, a specific inhibitor of Cdk4/6. All GBM xenograft lines evaluated in this study had disruptions in the p16(INK4a)-Cdk4/6-Rb pathway. In vitro evaluation using short-term explant cultures from selected GBM xenograft lines showed that PD0332991 effectively arrested cell cycle in G1-phase and inhibited cell proliferation dose-dependently in lines deleted for CDKN2A/B-p16(INK4a) and either single-copy deletion of CDK4 (GBM22), high-level CDK6 amplification (GBM34), or deletion of CDKN2C/p18(INK4c) (GBM43). In contrast, 2 GBM lines with p16(INK4a) expression and either CDK4 amplification (GBM5) or RB mutation (GBM28) were completely resistant to PD0332991. Additional xenograft lines were screened, and GBM63 was identified to have p16(INK4a) expression and CDK4 amplification. Similar to the results with GBM5, GBM63 was resistant to PD0332991 treatment. In an orthotopic survival model, treatment of GBM6 xenografts (CDKN2A/B-deleted and CDK4 wild-type) with PD0332991 significantly suppressed tumor cell proliferation and prolonged survival. Collectively, these data support the concept that GBM tumors lacking p16(INK4a) expression and with nonamplified CDK4 and wild-type RB status may be more susceptible to Cdk4/6 inhibition using PD0332991.
| S-EPMC3379801 | biostudies-literature