Lysine acetyltransferase 5 in EGFR mutated non-small cell lung cancer

Histone modifications are crucial in activities such as transcriptional activation, gene silencing, and epigenetic cellular memory. In particular, lysine acetylation via lysine (K) acetyltransferases (KATs) has been implicated in cancer development. Interestingly, KAT5, also known as Tip60 (tat-interactive protein-60kDa), has been reported to possess both tumor promoting and tumor suppressing properties depending on the context of malignancy. Herein we report that KAT5 contributes to tumorigenesis in epidermal growth factor receptor (EGFR) mutated lung cancer, and Kat5-knockout mice models demonstrate significantly reduced lung tumor burden. To probe the aberrant modification of KAT5, we demonstrated that KAT5 binds to and is phosphorylated by oncogenic EGFR in co-immunoprecipitation experiments. Next, to investigate whether KAT5 is involved in cell proliferation and survival, H1975 cells harboring L858R-T790M double-activating mutations were transfected with doxycycline inducible short helical RNA (shRNA) targeting KAT5 (shKAT5). Following treatment, shKAT5 cells were observed to have suppressed proliferation rates. Pharmacological inhibition using TH1834, a known KAT5 inhibitor, also suppressed proliferation rates in shKAT5 cells; in contrast BEAS2B cells, an immortalized normal human bronchial cell line, surprisingly exhibited increased viability compared to transformed human lung H1975 cells. This finding supports KAT5’s context-dependent role in in normal and abnormal cell homeostasis. To further investigate KAT5 in lung tumorigenesis in vivo, we generated EGFR-mutant conditional Kat5 knockout mice using a tetracycline-induced Cre/loxP system. Following doxycycline treatment for 10 weeks, isolated mice lungs for EGFRTL/CCSP-rtTA/Cre/Kat5F/F possessed significantly lower tumor volume compared to EGFRTL/CCSP-rtTA/Cre/Kat5wt/F and EGFRTL/CCSP-rtTA/Cre/Kat5wt/wt mice lungs. Hemotoxylin and eosin staining showed no evident hyperproliferation in lungs isolated from EGFRTL/CCSP-rtTA/Cre/Kat5F/F mice whereas lungs isolated from EGFRTL/CCSP-rtTA/Cre/Kat5wt/wt and EGFRTL/CCSP-rtTA/Cre/Kat5wt/F did, signifying that KAT5 has a potential regulatory role in cellular proliferation. RNA-Seq analysis of shKAT5 H1975 cells identified downstream targets involved in tumorigenic pathways. Subsequent quantitative polymerase chain reaction (PCR) of shKAT5 cells served to validate the reported targets. Taken together, these data offer insight into a KAT5 mediated oncogenic pathway that can provide novel therapeutic approaches in treating lung cancer

Improved single-chain transactivators of the Tet-On gene expression system

BACKGROUND: The Tet-Off (tTA) and Tet-On (rtTA) regulatory systems are widely applied to control gene expression in eukaryotes. Both systems are based on the Tet repressor (TetR) from transposon Tn10, a dimeric DNA-binding protein that binds to specific operator sequences (tetO). To allow the independent regulation of multiple genes, novel Tet systems are being developed that respond to different effectors and bind to different tetO sites. To prevent heterodimerization when multiple Tet systems are expressed in the same cell, single-chain variants of the transactivators have been constructed. Unfortunately, the activity of the single-chain rtTA (sc-rtTA) is reduced when compared with the regular rtTA, which might limit its application. RESULTS: We recently identified amino acid substitutions in rtTA that greatly improved the transcriptional activity and doxycycline-sensitivity of the protein. To test whether we can similarly improve other TetR-based gene regulation systems, we introduced these mutations into tTA and sc-rtTA. Whereas none of the tested mutations improved tTA activity, they did significantly enhance sc-rtTA activity. We thus generated a novel sc-rtTA variant that is almost as active and dox-sensitive as the regular dimeric rtTA. This variant was also less sensitive to interference by co-expressed TetR-based tTS repressor protein and may therefore be more suitable for applications where multiple TetR-based regulatory systems are used. CONCLUSION: We developed an improved sc-rtTA variant that may replace regular rtTA in applications where multiple TetR-based regulatory systems are used

Cartilage on the Move: Cartilage Lineage Tracing During Tadpole Metamorphosis

The reorganization of cranial cartilages during tadpole metamorphosis is a set of complex processes. The fates of larval cartilage-forming cells (chondrocytes) and sources of adult chondrocytes are largely unknown. Individual larval cranial cartilages may either degenerate or remodel, while many adult cartilages appear to form de novo during metamorphosis. Determining the extent to which adult chondrocytes/cartilages are derived from larval chondrocytes during metamorphosis requires new techniques in chondrocyte lineage tracing. We have developed two transgenic systems to label cartilage cells throughout the body with fluorescent proteins. One system strongly labels early tadpole cartilages only. The other system inducibly labels forming cartilages at any developmental stage. We examined cartilages of the skull (viscero- and neurocranium), and identified larval cartilages that either resorb or remodel into adult cartilages. Our data show that the adult otic capsules, tecti anterius and posterius, hyale, and portions of Meckel\u27s cartilage are derived from larval chondrocytes. Our data also suggest that most adult cartilages form de novo, though we cannot rule out the potential for extreme larval chondrocyte proliferation or de- and re-differentiation, which could dilute our fluorescent protein signal. The transgenic lineage tracing strategies developed here are the first examples of inducible, skeleton-specific, lineage tracing in Xenopus

Comparison of single regulated lentiviral vectors with rtTA expression driven by an autoregulatory loop or a constitutive promoter

Regulated expression of a therapeutic gene is crucial for safe and efficacious gene therapy. Many inducible regulatory systems use a constitutive promoter to express a regulatory protein, such as rtTA in the Tet-On system, which may restrict their use because of cytotoxicity and immunogenicity. Autoregulatory expression of rtTA provides extremely low levels of rtTA when transgene expression is off, with rapid transgene induction upon addition of doxycycline. Lentiviral vectors efficiently transfer genes to dividing and non-dividing cells with long-term gene expression both in vitro and in vivo. We compared regulatory function in a single lentiviral vector where rtTA was either expressed from a constitutive promoter or placed in an autoregulatory loop. Autoregulatory expression of rtTA was superior to constitutive promoter expression, resulting in higher viral titers, undetectable levels of both rtTA and transgene expression in the absence of doxycycline, improved induction kinetics and increased induction levels in all cells tested. We further expanded the utility of the autoregulatory vector by using an improved rtTA variant with an increased sensitivity to doxycycline. This lentiviral vector with doxycycline-regulated transgene expression may be useful for gene therapy applications and in experimental settings where strict temporal expression of a transgene is required

Gateway vectors for efficient artificial gene assembly in vitro and expression in yeast Saccharomyces cerevisiae

Peer reviewedPublisher PD

A Novel Tetracycline-Responsive Transgenic Mouse Strain for Skeletal Muscle-Specific Gene Expression

Background: The tetracycline-responsive system (Tet-ON/OFF) has proven to be a valuable tool for manipulating gene expression in an inducible, temporal, and tissue-specific manner. The purpose of this study was to create and characterize a new transgenic mouse strain utilizing the human skeletal muscle α-actin (HSA) promoter to drive skeletal muscle-specific expression of the reverse tetracycline transactivator (rtTA) gene which we have designated as the HSA-rtTA mouse. Methods: To confirm the HSA-rtTA mouse was capable of driving skeletal muscle-specific expression, we crossed the HSA-rtTA mouse with the tetracycline-responsive histone H2B-green fluorescent protein (H2B-GFP) transgenic mouse in order to label myonuclei. Results: Reverse transcription-PCR confirmed skeletal muscle-specific expression of rtTA mRNA, while single-fiber analysis showed highly effective GFP labeling of myonuclei in both fast- and slow-twitch skeletal muscles. Pax7 immunohistochemistry of skeletal muscle cross-sections revealed no appreciable GFP expression in satellite cells. Conclusions: The HSA-rtTA transgenic mouse allows for robust, specific, and inducible gene expression across muscles of different fiber types. The HSA-rtTA mouse provides a powerful tool to manipulate gene expression in skeletal muscle

Modification of the Tet-On regulatory system prevents the conditional-live HIV-1 variant from losing doxycycline-control

BACKGROUND: We have previously constructed a doxycycline (dox)-dependent HIV-1 variant by incorporating the Tet-On gene regulatory system into the viral genome. Replication of this HIV-rtTA virus is driven by the dox-inducible transactivator protein rtTA, and can be switched on and off at will. We proposed this conditional-live virus as a novel vaccine approach against HIV-1. Upon vaccination, replication of HIV-rtTA can be temporarily activated by transient dox administration and controlled to the extent needed for optimal induction of the immune system. However, subsequent dox-withdrawal may impose a selection for virus variants with reduced dox-dependence. RESULTS: We simulated this on/off switching of virus replication in multiple, independent cultures and could indeed select for HIV-rtTA variants that replicated without dox. Nearly all evolved variants had acquired a typical amino acid substitution at position 56 in the rtTA protein. We developed a novel rtTA variant that blocks this undesired evolutionary route and thus prevents HIV-rtTA from losing dox-control. CONCLUSION: The loss of dox-control observed upon evolution of the dox-dependent HIV-1 variant was effectively blocked by modification of the Tet-On regulatory system

Vascular endothelial growth factor restores delayed tumor progression in tumors depleted of macrophages

Genetic depletion of macrophages in Polyoma Middle T oncoprotein (PyMT)‐induced mammary tumors in mice delayed the angiogenic switch and the progression to malignancy. To determine whether vascular endothelial growth factor A (VEGF‐A) produced by tumor‐associated macrophages regulated the onset of the angiogenic switch, a genetic approach was used to restore expression of VEGF‐A into tumors at the benign stages. This stimulated formation of a high‐density vessel network and in macrophage‐depleted mice, was followed by accelerated tumor progression. The expression of VEGF‐A led to a massive infiltration into the tumor of leukocytes that were mostly macrophages. This study suggests that macrophage‐produced VEGF regulates malignant progression through stimulating tumor angiogenesis, leukocytic infiltration and tumor cell invasion

Transthyretin Stimulates Tumor Growth through Regulation of Tumor, Immune, and Endothelial Cells

Early detection of lung cancer offers an important opportunity to decrease mortality while it is still treatable and curable. Thirteen secretory proteins that are Stat3 downstream gene products were identified as a panel of biomarkers for lung cancer detection in human sera. This panel of biomarkers potentially differentiates different types of lung cancer for classification. Among them, the transthyretin (TTR) concentration was highly increased in human serum of lung cancer patients. TTR concentration was also induced in the serum, bronchoalveolar lavage fluid, alveolar type II epithelial cells, and alveolar myeloid cells of the CCSP-rtTA/(tetO)7-Stat3C lung tumor mouse model. Recombinant TTR stimulated lung tumor cell proliferation and growth, which were mediated by activation of mitogenic and oncogenic molecules. TTR possesses cytokine functions to stimulate myeloid cell differentiation, which are known to play roles in tumor environment. Further analyses showed that TTR treatment enhanced the reactive oxygen species production in myeloid cells and enabled them to become functional myeloid-derived suppressive cells. TTR demonstrated a great influence on a wide spectrum of endothelial cell functions to control tumor and immune cell migration and infiltration. TTR-treated endothelial cells suppressed T cell proliferation. Taken together, these 13 Stat3 downstream inducible secretory protein biomarkers potentially can be used for lung cancer diagnosis, classification, and as clinical targets for lung cancer personalized treatment if their expression levels are increased in a given lung cancer patient in the blood