BIBW2992, an irreversible EGFR/HER2 inhibitor highly effective in preclinical lung cancer models

Genetic alterations in the kinase domain of the epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) patients are associated with sensitivity to treatment with small molecule tyrosine kinase inhibitors. Although first-generation reversible, ATP-competitive inhibitors showed encouraging clinical responses in lung adenocarcinoma tumors harboring such EGFR mutations, almost all patients developed resistance to these inhibitors over time. Such resistance to first-generation EGFR inhibitors was frequently linked to an acquired T790M point mutation in the kinase domain of EGFR, or upregulation of signaling pathways downstream of HER3. Overcoming these mechanisms of resistance, as well as primary resistance to reversible EGFR inhibitors driven by a subset of EGFR mutations, will be necessary for development of an effective targeted therapy regimen. Here, we show that BIBW2992, an anilino-quinazoline designed to irreversibly bind EGFR and HER2, potently suppresses the kinase activity of wild-type and activated EGFR and HER2 mutants, including erlotinib-resistant isoforms. Consistent with this activity, BIBW2992 suppresses transformation in isogenic cell-based assays, inhibits survival of cancer cell lines and induces tumor regression in xenograft and transgenic lung cancer models, with superior activity over erlotinib. These findings encourage further testing of BIBW2992 in lung cancer patients harboring EGFR or HER2 oncogenes.

Adjacent tissues (cartilage, bone) affect the functional integration of engineered calf cartilage in vitro

OBJECTIVE

An in vitro model was used to test the hypothesis that culture time and adjacent tissue structure and composition affected chondrogenesis and integrative repair in engineered cartilage.

METHOD

Engineered constructs made of bovine calf chondrocytes and hyaluronan benzyl ester non-woven mesh were press-fitted into adjacent tissue rings made of articular cartilage (AC), devitalized bone (DB), or vital bone (VB) and cultured in rotating bioreactors for up to 8 weeks. Structure (light and electron microscopy), biomechanical properties (interfacial adhesive strength, construct compressive modulus), biochemical composition (construct glycosaminoglycans (GAG), collagen, and cells), and adjacent tissue diffusivity were assessed.

RESULTS

Engineered constructs were comprised predominately of hyaline cartilage, and appeared either closely apposed to adjacent cartilage or functionally interdigitated with adjacent bone due to interfacial deposition of extracellular matrix. An increase in culture time significantly improved construct adhesive strength (P<0.001), modulus (P=0.02), GAG (P=0.04) and cellularity (P<0.001). The type of adjacent tissue significantly affected construct adhesion (P<0.001), modulus (P<0.001), GAG (P<0.001) and collagen (P<0.001). For constructs cultured in rings of cartilage, negative correlations were observed between ring GAG content (log transformed) and construct adhesion (R2=0.66, P<0.005), modulus (R2=0.49, P<0.05) and GAG (R2=0.44, P<0.05). Integrative repair was better for constructs cultured adjacent to bone than cartilage, in association with its solid architectural structure and high GAG content, and best for constructs cultured adjacent to DB, in association with its high diffusivity.

CONCLUSIONS

Chondrogenesis and integrative repair in engineered cartilage improved with time and depended on adjacent tissue architecture, composition, and transport properties.

Systemic delivery of human growth hormone using genetically modified tissue-engineered microvascular networks: prolonged delivery and endothelial survival with inclusion of nonendothelial cells

Endothelial cells have the potential to provide efficient long-term delivery of therapeutic proteins to the circulation if a sufficient number of genetically modified endothelial cells can be incorporated into the host vasculature and if these cells persist for an adequate period of time. Here we describe the ability of nonendothelial cells to modulate the survival of implanted endothelial cells and their incorporation into host vasculature. Bovine aortic endothelial cells (BAECs) suspended in Matrigel and cultured in vitro remained spherical and decreased in number over time. Subcutaneous implantation of gels containing BAECs secreting human growth hormone (hGH) in mice initially resulted in detectable plasma hGH levels, which were undetectable after 2 weeks. When mixed with fibroblasts and suspended in Matrigel, hGH-secreting BAECs formed microvascular networks in vitro. Implantation of these gels resulted in plasma hGH levels that decreased slightly over 2 weeks and then remained stable for at least 6 weeks. BAECs incorporated into blood vessels within both the implant and fibrous capsule that surrounded and invaded implants. Within implants containing BAECs and fibroblasts, viable BAECs were present for at least 6 weeks at a higher density than in implants containing BAECs alone at 3 weeks. These results indicate that implanted BAECs can incorporate into host blood vessels and that inclusion of fibroblasts in this system prolongs BAEC survival and hGH delivery.

Integration of engineered cartilage

The structure and function of cartilaginous constructs, engineered in vitro using bovine articular chondrocytes, biodegradable scaffolds and bioreactors, can be modulated by the conditions and duration of tissue cultivation. We hypothesized that the integrative properties of engineered cartilage depend on developmental stage of the construct and the extracellular matrix content of adjacent cartilage, and that some aspects of integration can be studied under controlled in vitro conditions. Disc-shaped constructs (cultured for 5+/-1 days or 5+/-1 weeks) or explants (untreated or trypsin treated cartilage) were sutured into ring-shaped explants (untreated or trypsin treated cartilage) to form composites that were cultured for an additional 1-8 weeks in bioreactors and evaluated biochemically, histologically and mechanically (compressive stiffness of the central disk, adhesive strength of the integration interface). Immature constructs had poorer mechanical properties but integrated better than either more mature constructs or cartilage explants. Integration of immature constructs involved cell proliferation and the progressive formation of cartilaginous tissue, in contrast to the integration of more mature constructs or native cartilage which involved only the secretion of extracellular matrix components. Integration patterns correlated with the adhesive strength of the disc-ring interface, which was markedly higher for immature constructs than for either more mature constructs or cartilage explants. Trypsin treatment of the adjacent cartilage further enhanced the integration of immature constructs.

Selective differentiation of mammalian bone marrow stromal cells cultured on three-dimensional polymer foams

Bone marrow stromal cells (BMSC) are pluripotent progenitor cells that can regenerate different skeletal tissues in response to environmental signals. In this study, we used highly porous, structurally stable three-dimensional polymer foams in conjunction with specific regulatory molecules to selectively differentiate mammalian BMSC into either cartilaginous or bone-like tissues. Bovine BMSC were expanded in monolayers and cultured on 5-mm-diameter, 2-mm-thick foams made of poly(lactic-co-glycolic acid) and poly(ethylene glycol). Constructs maintained their original size and shape for up to 4 weeks of culture and supported BMSC growth and production of extracellular matrix (ECM). By proper use of chondrogenic (dexamethasone, insulin, transforming growth factor-beta1) or osteogenic (dexamethasone, beta-glycerophosphate) medium supplements, we could control whether the generated ECM was cartilaginous (containing collagen type II and sulfated glycosaminoglycans) or bone-like (containing osteocalcin, osteonectin, and mineralized foci). After 4 weeks of cultivation, cartilaginous and bone-like ECM were uniformly distributed throughout the construct volume and respectively represented 34.2 +/- 9.3% and 12.6 +/- 3.2% of the total available area. BMSC culture on poly(lactic-co-glycolic acid)/poly(ethylene glycol) foams provides a three-dimensional model system to study the development of mesenchymal tissues in vitro and has potential applications in engineering autologous grafts for skeletal tissue repair.

In vitro generation of osteochondral composites

Osteochondral repair involves the regeneration of articular cartilage and underlying bone, and the development of a well-defined tissue-to-tissue interface. We investigated tissue engineering of three-dimensional cartilage/bone composites based on biodegradable polymer scaffolds, chondrogenic and osteogenic cells. Cartilage constructs were created by cultivating primary bovine calf articular chondrocytes on polyglycolic acid meshes; bone-like constructs were created by cultivating expanded bovine calf periosteal cells on foams made of a blend of poly-lactic-co-glycolic acid and polyethylene glycol. Pairs of constructs were sutured together after 1 or 4 weeks of isolated culture, and the resulting composites were cultured for an additional 4 weeks. All composites were structurally stable and consisted of well-defined cartilaginous and bone-like tissues. The fraction of glycosaminoglycan in the cartilaginous regions increased with time, both in isolated and composite cultures. In contrast, the mineralization in bone-like regions increased during isolated culture, but remained approximately constant during the subsequent composite culture. The integration at the cartilage/bone interface was generally better for composites consisting of immature (1-week) than mature (4-week) constructs. This study demonstrates that osteochondral tissue composites for potential use in osteochondral repair can be engineered in vitro by culturing mammalian chondrocytes and periosteal cells on appropriate polymer scaffolds.

A novel biotinylated degradable polymer for cell-interactive applications

We describe the development of a novel biodegradable polymer designed to present bioactive motifs at the surfaces of materials of any architecture. The polymer is a block copolymer of biotinylated poly(ethylene glycol) (PEG) with poly(lactic acid) (PLA); it utilizes the high-affinity coupling of the biotin-avidin system to undergo postfabrication surface engineering. We show, using surface plasmon resonance analysis (SPR) and confocal microscopy that surface engineering can be achieved under aqueous conditions in short time periods. These surfaces interact with cell surface molecules and generate beneficial responses as demonstrated by the model study of integrin-mediated spreading of endothelial cells on polymer surfaces presenting RGD peptide adhesion sequences.

In vitro differentiation of chick embryo bone marrow stromal cells into cartilaginous and bone-like tissues

Bone marrow stromal cells, progenitor cells involved in repair of bone and cartilage, can potentially provide a source for autologous skeletal tissue engineering. We investigated which factors were required to induce in vitro differentiation of avian bone marrow stromal cells into three-dimensional cartilaginous and bone-like tissues. Bone marrow stromal cells from embryonic chicks were expanded in monolayers, seeded onto biodegradable polyglycolic acid scaffolds, and cultured for 4 weeks in orbitally mixed Petri dishes. Cell-polymer constructs developed an organized extracellular matrix containing glycosaminoglycans and collagen, whereas control bone marrow stromal cell pellet cultures were smaller and consisted predominantly of fibrous tissue. Bone marrow stromal cells expanded with fibroblast growth factor-2 and seeded onto polymer scaffolds formed highly homogeneous three-dimensional tissues that contained cartilage-specific molecular markers and had biochemical compositions comparable with avian epiphyseal cartilage. When cell-polymer constructs were cultured in the presence of beta-glycerophosphate and dexamethasone, the extracellular matrix mineralized and bone-specific proteins were expressed. Our work shows that cell expansion in the presence of fibroblast growth factor-2 and cultivation on a three-dimensional polymer scaffold allows differentiation of chick bone marrow stromal cells into three-dimensional cartilaginous tissues. In the in vitro system studied, the same population could be selectively induced to regenerate either cartilaginous or bone-like tissue.

Time course of membrane microarchitecture-driven neovascularization

The host response to a microporous material that induces neovascularization at the material-tissue interface was studied in terms of the number and types of cells invading the membrane, the degree of vascularization at the material-tissue interface, and the characteristics of the surrounding connective tissue as a function of time following implantation. Millipore-MF mixed esters of cellulose membranes with a nominal pore diameter of 8.0 microns were implanted subcutaneously into male Sprague-Dawley rats and explanted at 3, 5, 7, 10, 21 and 329 days post-implantation. Two samples from each of two devices at each implantation time were embedded in paraffin, sectioned to a thickness of 5 microns, and stained with haematoxylin and eosin for light microscopic observation. The density of cells in the membrane increased up to 7 days following implantation, then remained roughly constant through 21 days and decreased at the 329 day time point. The vascularity of the material-tissue interface increased up to 10 days and remained at this level even at 329 days post-implantation. The connective tissue was disorganized, loose and avascular at 3 days, resembled granulation tissue at 5 days, and underwent fibrous capsule formation and maturation starting at 7 days following implantation.