Project description:In a 3D coculture with stroma cells derived from breast cancer patients’ brain metastasis, HER2+ breast cancer cells were protected from HER2-targeted therapies, particularly the EGFR/HER2 small molecule inhibitor neratinib. To get insight into how this protection arises, ATAC-seq on coculture cells with or without neratinib as performed.
Project description:Activated HER2 and EGFR stimulate the Ras small GTPases, which in turn primarily activate the MAPK, PI3K-Akt and RalGEF-Ral pathways. While activation of the MAPK and PI3K-Akt pathways downstream of HER2 and EGFR promote mammary tumorigenesis, little is known regarding the role of the RalGEF-Ral pathway. RalGEFs convert the small GTPases RalA and RalB to an active GTP-bound state. Of the two proteins, only activated RalA is transforming, while RalB is more important for cell motility, and hence we investigated the role of RalA in HER2-overexpressing and EGFR-positive breast cancer. We now report that shRNA-mediated knockdown of RalA reduced the in vitro transformed growth and in vivo tumorigenic growth of MDA-MB-231 human breast cancer cells, while knockdown of RalB reduced migration and invasion. Lastly, we demonstrate that expression of activated HER2 increases RalA-GTP levels, and that a number of genes associated with activated RalA are elevated in tumor compared to normal mammary tissue. Taken together, these results suggest a possible role for RalA in mammary tumorigenesis. Four independent cultures of HEK-HT cells stably infected with a retrovirus confirmed to expressed RalAQ72L and four independent cultures of HEK-HT cells stably infected with a control retrovirus RalA activation expression analysis
Project description:In a 3D coculture with stroma cells derived from breast cancer patients’ brain metastasis, HER2+ breast cancer cells were protected from HER2-targeted therapies, particularly the EGFR/HER2 small molecule inhibitor neratinib. To get insight into how this protection arises, a Synthetic Notch (SynNotch) reporter model allowed to study the effect of direct contact between stroma and cancer cells.
Project description:Recent studies suggested that crosstalk between ERα and EGFR/HER2 pathways plays a critical role in mediating endocrine therapy resistance. Several targeting EGFR/HER2 signaling inhibitors including FDA-approved lapatinib and gefitinib as well as a novel dual tyrosine kinase inhibitor (TKI) sapitnib showed greater inhibitory efficacies. However, how a 3D chromatin landscape of the response to the inhibition to EGFR/HER2 pathway remains to be elucidated. In this study, we conducted in situ Hi-C and RNA-seq in two ERα+ breast cancer cell systems, tamoxifen-sensitive MCF7 and T47D and tamoxifen-resistant MCF7TR and T47DTR before and after the treatment of sapitnib. We identified differential response of topologically associated domains (TADs), looping genes and expressed genes. Interestingly, we found that many differential TADs and looping genes are reversible, indicating that EGFR/HER2 signaling may play a role in reshaping and rewiring the high order genome organization. We further examined and recapitulated the reversible looping genes in 3D spheroids of breast cancer cells. Our data provides a rich resource for further evaluating chromatin structural response to anti-EGFR/HER2 targeted therapies in endocrine-resistant breast cancer.
Project description:Recent studies suggested that crosstalk between ERα and EGFR/HER2 pathways plays a critical role in mediating endocrine therapy resistance. Several targeting EGFR/HER2 signaling inhibitors including FDA-approved lapatinib and gefitinib as well as a novel dual tyrosine kinase inhibitor (TKI) sapitnib showed greater inhibitory efficacies. However, how a 3D chromatin landscape of the response to the inhibition to EGFR/HER2 pathway remains to be elucidated. In this study, we conducted in situ Hi-C and RNA-seq in two ERα+ breast cancer cell systems, tamoxifen-sensitive MCF7 and T47D and tamoxifen-resistant MCF7TR and T47DTR before and after the treatment of sapitnib. We identified differential response of topologically associated domains (TADs), looping genes and expressed genes. Interestingly, we found that many differential TADs and looping genes are reversible, indicating that EGFR/HER2 signaling may play a role in reshaping and rewiring the high order genome organization. We further examined and recapitulated the reversible looping genes in 3D spheroids of breast cancer cells. Our data provides a rich resource for further evaluating chromatin structural response to anti-EGFR/HER2 targeted therapies in endocrine-resistant breast cancer.
Project description:Activated HER2 and EGFR stimulate the Ras small GTPases, which in turn primarily activate the MAPK, PI3K-Akt and RalGEF-Ral pathways. While activation of the MAPK and PI3K-Akt pathways downstream of HER2 and EGFR promote mammary tumorigenesis, little is known regarding the role of the RalGEF-Ral pathway. RalGEFs convert the small GTPases RalA and RalB to an active GTP-bound state. Of the two proteins, only activated RalA is transforming, while RalB is more important for cell motility, and hence we investigated the role of RalA in HER2-overexpressing and EGFR-positive breast cancer. We now report that shRNA-mediated knockdown of RalA reduced the in vitro transformed growth and in vivo tumorigenic growth of MDA-MB-231 human breast cancer cells, while knockdown of RalB reduced migration and invasion. Lastly, we demonstrate that expression of activated HER2 increases RalA-GTP levels, and that a number of genes associated with activated RalA are elevated in tumor compared to normal mammary tissue. Taken together, these results suggest a possible role for RalA in mammary tumorigenesis.
Project description:To combine inhibition of EGFR/HER2 and targeting of the cytosolic roles of PCNA using the APIM-peptide, and study the anti-cancer effects of this combinatory therapy in in vitro and in vivo breast cancer models.
Project description:Why breast cancers become resistant to tamoxifen despite continued expression of the estrogen receptor alpha (ERα) and what factors are responsible for high HER2 expression in these tumors remains an enigma. HOXB7 ChIP analysis followed by validation showed that HOXB7 physically interacts with ERα, and that the HOXB7-ERα complex enhances transcription of many ERα target genes including HER2. Investigating strategies for controlling HOXB7, our studies revealed that MYC, stabilized via phosphorylation mediated by EGFR-HER2 signaling, inhibits transcription of miRNA-196a, a HOXB7 repressor. This leads to increased expression of HOXB7, ER-target genes and HER2. Repressing MYC using small molecule inhibitors reverses these events, and causes regression of breast cancer xenografts. The MYC-HOXB7-HER2 signaling pathway is eminently targetable in endocrine-resistant breast cancer. MCF7 cell lines stably transduced with either vector control of HOXB7. Array ran in duplicates.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.