RESUMO
KAT6A, and its paralog KAT6B, are histone lysine acetyltransferases (HAT) that acetylate histone H3K23 and exert an oncogenic role in several tumor types including breast cancer where KAT6A is frequently amplified/overexpressed. However, pharmacologic targeting of KAT6A to achieve therapeutic benefit has been a challenge. Here we describe identification of a highly potent, selective, and orally bioavailable KAT6A/KAT6B inhibitor CTx-648 (PF-9363), derived from a benzisoxazole series, which demonstrates anti-tumor activity in correlation with H3K23Ac inhibition in KAT6A over-expressing breast cancer. Transcriptional and epigenetic profiling studies show reduced RNA Pol II binding and downregulation of genes involved in estrogen signaling, cell cycle, Myc and stem cell pathways associated with CTx-648 anti-tumor activity in ER-positive (ER+) breast cancer. CTx-648 treatment leads to potent tumor growth inhibition in ER+ breast cancer in vivo models, including models refractory to endocrine therapy, highlighting the potential for targeting KAT6A in ER+ breast cancer.
Assuntos
Neoplasias da Mama , Humanos , Feminino , Neoplasias da Mama/genética , Histonas/metabolismo , Histona Acetiltransferases/genética , Histona Acetiltransferases/metabolismo , Transdução de Sinais , Linhagem Celular TumoralRESUMO
Palbociclib, a selective CDK4/6 kinase inhibitor, is approved in combination with endocrine therapies for the treatment of advanced estrogen receptor positive (ER+) breast cancer. In pre-clinical cancer models, CDK4/6 inhibitors act primarily as cytostatic agents. In two commonly studied ER+ breast cancer cell lines (MCF7 and T47D), CDK4/6 inhibition drives G1-phase arrest and the acquisition of a senescent-like phenotype, both of which are reversible upon palbociclib withdrawal (incomplete senescence). Here we identify an ER+ breast cancer cell line, CAMA1, in which palbociclib treatment induces irreversible cell cycle arrest and senescence (complete senescence). In stark contrast to T47D and MCF7 cells, mTORC1 activity is not stably suppressed in CAMA1 cells during palbociclib treatment. Importantly, inhibition of mTORC1 signaling either by the mTORC1 inhibitor rapamycin or by knockdown of Raptor, a unique component of mTORC1, during palbociclib treatment of CAMA1 cells blocks the induction of complete senescence. These results indicate that sustained mTORC1 activity promotes complete senescence in ER+ breast cancer cells during CDK4/6 inhibitor-induced cell cycle arrest. Consistent with this mechanism, genetic depletion of TSC2, a negative regulator of mTORC1, in MCF7 cells resulted in sustained mTORC1 activity during palbociclib treatment and evoked a complete senescence response. These findings demonstrate that persistent mTORC1 signaling during palbociclib-induced G1 arrest is a potential liability for ER+ breast cancer cells, and suggest a strategy for novel drug combinations with palbociclib.
Assuntos
Neoplasias da Mama/tratamento farmacológico , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Senescência Celular/efeitos dos fármacos , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Piperazinas/farmacologia , Piridinas/farmacologia , Receptores de Estrogênio/metabolismo , Animais , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Quinase 4 Dependente de Ciclina/metabolismo , Quinase 6 Dependente de Ciclina/metabolismo , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Feminino , Humanos , Células MCF-7 , Camundongos , Transdução de Sinais/efeitos dos fármacosRESUMO
The aims of this study were to determine whether combination chemotherapeutics exhibit a synergistic effect on breast cancer cell metabolism. Palbociclib, is a selective inhibitor of cyclin-dependent kinases 4 and 6, and when patients are treated in combination with fulvestrant, an estrogen receptor antagonist, they have improved progression-free survival. The mechanisms for this survival advantage are not known. Therefore, we analyzed metabolic and transcriptomic changes in MCF-7 cells following single and combination chemotherapy to determine whether selective metabolic pathways are targeted during these different modes of treatment. Individually, the drugs caused metabolic disruption to the same metabolic pathways, however fulvestrant additionally attenuated the pentose phosphate pathway and the production of important coenzymes. A comprehensive effect was observed when the drugs were applied together, confirming the combinatory therapy's synergism in the cell model. This study also highlights the power of merging high-dimensional datasets to unravel mechanisms involved in cancer metabolism and therapy.
RESUMO
Acute myeloid leukemia (AML) therapy involves compounds that are cytotoxic to both normal and cancer cells, and relapsed AML is resistant to subsequent chemotherapy. Thus, agents are needed that selectively kill AML cells with minimal toxicity. Here, we report that AML is dependent on DDX5 and that inhibiting DDX5 expression slows AML cell proliferation in vitro and AML progression in vivo but is not toxic to cells from normal bone marrow. Inhibition of DDX5 expression in AML cells induces apoptosis via induction of reactive oxygen species (ROS). This apoptotic response can be blocked either by BCL2 overexpression or treatment with the ROS scavenger N-acetyl-L-cysteine. Combining DDX5 knockdown with a BCL2 family inhibitor cooperates to induce cell death in AML cells. By inhibiting DDX5 expression in vivo, we show that DDX5 is dispensable for normal hematopoiesis and tissue homeostasis. These results validate DDX5 as a potential target for blocking AML.
Assuntos
RNA Helicases DEAD-box/metabolismo , Leucemia Mieloide Aguda/enzimologia , Idoso , Animais , Apoptose/fisiologia , Linhagem Celular Tumoral , Proliferação de Células/fisiologia , RNA Helicases DEAD-box/antagonistas & inibidores , Progressão da Doença , Inibidores Enzimáticos/farmacologia , Humanos , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/patologia , Camundongos , Camundongos Transgênicos , Espécies Reativas de Oxigênio/metabolismoRESUMO
UNLABELLED: Understanding factors required for DNA replication will enrich our knowledge of this important process and potentially identify vulnerabilities that can be exploited in cancer therapy. We applied an assay that measures the stability of maintenance of an episomal plasmid in human tissue culture cells to screen for new DNA replication factors. We identify an important role for DDX5 in G(1)-S-phase progression where it directly regulates DNA replication factor expression by promoting the recruitment of RNA polymerase II to E2F-regulated gene promoters. We find that the DDX5 locus is frequently amplified in breast cancer and that breast cancer-derived cells with amplification of DDX5 are much more sensitive to its depletion than breast cancer cells and a breast epithelial cell line that lacks DDX5 amplification. Our results show a novel role for DDX5 in cancer cell proliferation and suggest DDX5 as a therapeutic target in breast cancer treatment. SIGNIFICANCE: DDX5 is required for cell proliferation by controlling the transcription of genes expressing DNA replication proteins in cancer cells in which the DDX5 locus is amplified, and this has uncovered a dependence on DDX5 for cell proliferation. Given the high frequency of DDX5 amplification in breast cancer, our results highlight DDX5 as a promising candidate for targeted therapy of breast tumors with DDX5 amplification, and indeed we show that DDX5 inhibition sensitizes a subset of breast cancer cells to trastuzumab.
Assuntos
Neoplasias da Mama/genética , RNA Helicases DEAD-box/genética , Replicação do DNA , DNA de Neoplasias/biossíntese , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Processos de Crescimento Celular/genética , Linhagem Celular Tumoral , RNA Helicases DEAD-box/metabolismo , DNA de Neoplasias/genética , Feminino , Amplificação de Genes , Regulação Neoplásica da Expressão Gênica , Células HCT116 , Humanos , Terapia de Alvo Molecular , Plasmídeos/genética , Regiões Promotoras Genéticas , RNA Polimerase II/metabolismo , Fase S/genéticaRESUMO
Numerous DNA mismatches and lesions activate MutS homologue (MSH) ATPase activity that is essential for mismatch repair (MMR). We have found that a mismatch embedded in a nearest-neighbor sequence context containing symmetric 3'-purines (2 x 3'-purines) enhanced, whereas symmetric 3'-pyrimidines (2 x 3'-pyrimidines) reduced, hMSH2-hMSH6 ATPase activation. The 3'-purine/pyrimidine effect was most evident for G-containing mispairs. A similar trend pervaded mismatch binding (K(D)) and the melting of unbound oligonucleotides (T(m); DeltaG). However, these latter measures did not accurately predict the hierarchy of MSH ATPase activation. NMR studies of imino proton lifetime, solvent accessibility, and NOE connectivity suggest that sequence contexts that provoke improved MSH-activation displayed enhanced localized DNA flexibility: a dynamic DNA signature that may account for the wide range of lesions that activate MSH functions.
Assuntos
Pareamento Incorreto de Bases , Proteínas de Ligação a DNA/metabolismo , Proteína 2 Homóloga a MutS/metabolismo , Adenosina Trifosfatases/metabolismo , Sequência de Bases , Reparo do DNA , Ativação Enzimática , Humanos , Espectroscopia de Ressonância Magnética , Conformação de Ácido Nucleico , Purinas/química , Pirimidinas/químicaRESUMO
Previous studies from our laboratory indicated that expression of the MLH1 DNA mismatch repair (MMR) gene was necessary to restore cytotoxicity and an efficient G(2) arrest in HCT116 human colon cancer cells, as well as Mlh1(-/-) murine embryonic fibroblasts, after treatment with 5-fluoro-2'-deoxyuridine (FdUrd). Here, we show that an identical phenomenon occurred when expression of MSH2, the other major MMR gene, was restored in HEC59 human endometrial carcinoma cells or was present in adenovirus E1A-immortalized Msh2(+/+) (compared with isogenic Msh2(-/-)) murine embryonic stem cells. Because MMR status had little effect on cellular responses (i.e. G(2) arrest and lethality) to the thymidylate synthase inhibitor, Tomudex, and a greater level of [(3)H]FdUrd incorporation into DNA was found in MMR-deficient cells, we concluded that the differential FdUrd cytotoxicity between MMR-competent and MMR-deficient cells was mediated at the level of DNA incorporation. Analyses of ATPase activation suggested that the hMSH2-hMSH6 heterodimer only recognized FdUrd moieties (as the base 5-fluorouracil (FU) in DNA) when mispaired with guanine, but not paired with adenine. Furthermore, analyses of incorporated FdUrd using methyl-CpG-binding domain 4 glycosylase indicated that there was more misincorporated FU:Gua in the DNA of MMR-deficient HCT116 cells. Our data provide the first demonstration that MMR specifically detects FU:Gua (in the first round of DNA replication), signaling a sustained G(2) arrest and lethality.
Assuntos
Pareamento Incorreto de Bases/genética , Dano ao DNA/efeitos dos fármacos , Reparo do DNA , Pirimidinas/farmacologia , Adenosina Trifosfatases/metabolismo , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , DNA/genética , DNA/metabolismo , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Ativação Enzimática/efeitos dos fármacos , Fase G2/efeitos dos fármacos , Humanos , Proteína 2 Homóloga a MutS , Proteína 3 Homóloga a MutS , Proteínas Proto-Oncogênicas/deficiência , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Quinazolinas/farmacologia , Tiofenos/farmacologiaRESUMO
Mutations in the human mismatch repair (MMR) gene hMSH2 have been linked to approximately 40% of hereditary nonpolyposis colorectal cancers (HNPCC). While the consequences of deletion or truncating mutations of hMSH2 would appear clear, the detailed functional defects associated with missense alterations are unknown. We have examined the effect of seven single amino acid substitutions associated with HNPCC that cover the structural subdomains of the hMSH2 protein. We show that alterations which produced a known cancer-causing phenotype affected the mismatch-dependent molecular switch function of the biologically relevant hMSH2-hMSH6 heterodimer. Our observations demonstrate that amino acid substitutions within hMSH2 that are distant from known functional regions significantly alter biochemical activity and the ability of hMSH2-hMSH6 to form a sliding clamp.
Assuntos
Neoplasias Colorretais Hereditárias sem Polipose/genética , Proteínas de Ligação a DNA/genética , Proteínas Proto-Oncogênicas/genética , Difosfato de Adenosina/metabolismo , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Pareamento Incorreto de Bases/genética , Sítios de Ligação/genética , DNA/metabolismo , Reparo do DNA/genética , Dimerização , Ensaio de Desvio de Mobilidade Eletroforética , Humanos , Hidrólise , Proteína 2 Homóloga a MutS , Mutagênese/genética , Mutação de Sentido Incorreto/genética , Ligação Proteica/genéticaRESUMO
The DNA lesion 8-oxo-guanine (8-oxo-G) is a highly mutagenic product of the interaction between reactive oxygen species and DNA. To maintain genomic integrity, cells have evolved mechanisms capable of removing this frequently arising oxidative lesion. Mismatch repair (MMR) appears to be one pathway associated with the repair of 8-oxo-G lesions (DeWeese, T. L., Shipman, J. M., Larrier, N. A., Buckley, N. M., Kidd, L. R., Groopman, J. D., Cutler, R. G., te Riele, H., and Nelson, W. G. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 11915-11920; Ni, T. T., Marsischky, G. T., and Kolodner, R. D. (1999) Mol. Cell 4, 439-444). Here we report the effect of double-stranded DNA oligonucleotides containing a single 8-oxo-G on the DNA binding affinity, ATPase, and ADP right arrow ATP exchange activities of hMSH2-hMSH6 and hMSH2-hMSH3. We found that hMSH2-hMSH6 binds the oligonucleotide DNA substrates with the following affinities: 8-oxo-G/T > 8-oxo-G/G > 8-oxo-G/A > 8-oxo-G/C approximately G/C. A similar trend was observed for DNA-stimulated ATPase and ADP --> ATP exchange activities of hMSH2-hMSH6. In contrast, hMSH2-hMSH3 did not appear to bind any of the 8-oxo-G containing DNA substrates nor was there enhanced ATPase or ADP --> ATP exchange activities. These results suggest that only hMSH2-hMSH6 is activated by recognition of 8-oxo-G lesions. Our data are consistent with the notion that post-replication MMR only participates in the repair of mismatched 8-oxo-G lesions.