Project description:CDK4/6 kinase inhibitors have shown great promise in clinical trials in various cancer types and have recently entered clinical trial for advanced prostate cancer. Although patients are expected to respond well to this class of drugs, development of resistance in some patients is anticipated. To pre-empt this and study how prostate cancer may evade CDK4/6 inhibition, new resistance models were generated from LNCaP and LAPC4 prostate cancer cells cells by prolonged culturing in presence of 0.5uM palbociclib. A shotgun phosphoproteomics approach was utilized and integrated with RNA sequencing data to unravel the molecular underpinnings of acquired resistance to palbociclib and resultant broad CDK4/6 inhibitor resistance.
Project description:CDK4/6 kinase inhibitors have shown great promise in clinical trials in various cancer types and have recently entered clinical trial for advanced prostate cancer. Although patients are expected to respond well to this class of drugs, development of resistance in some patients is anticipated. To pre-empt this and study how prostate cancer may evade CDK4/6 inhibition, new resistance models were generated from LNCaP and LAPC4 prostate cancer cells cells by prolonged culturing in presence of 0.5uM palbociclib. RNA sequencing data was integrated with phospho-proteomics to unravel the molecular underpinnings of acquired resistance to palbociclib and resultant broad CDK4/6 inhibitor resistance.
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.
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.