The emergence of drug resistance is a primary concern in any cancer treatment, including with targeted kinase inhibitors as exemplified by the appearance of Bcr-Abl point mutations in chronic myeloid leukemia (CML) patients treated with imatinib. In vitro approaches to identify resistance mutations in Bcr-Abl have yielded mutation spectra that faithfully recapitulated clinical observations. To predict resistance mutations in the receptor tyrosine kinase MET that could emerge during inhibitor treatment in patients, we conducted a resistance screen in BaF3 TPR-MET cells using the novel selective MET inhibitor NVP-BVU972. The observed spectrum of mutations in resistant cells was dominated by substitutions of tyrosine 1230 but also included other missense mutations and partially overlapped with activating MET mutations that were previously described in cancer patients. Cocrystallization of the MET kinase domain in complex with NVP-BVU972 revealed a key role for Y1230 in binding of NVP-BVU972, as previously reported for multiple other selective MET inhibitors. A second resistance screen in the same format with the MET inhibitor AMG 458 yielded a distinct spectrum of mutations rich in F1200 alterations, which is consistent with a different predicted binding mode. Our findings suggest that amino acid substitutions in the MET kinase domain of cancer patients need to be carefully monitored before and during treatment with MET inhibitors, as resistance may preexist or emerge. Compounds binding in the same manner as NVP-BVU972 might be particularly susceptible to the development of resistance through mutations in Y1230, a condition that may be addressed by MET inhibitors with alternative binding modes. Cancer Res; 71(15); 5255-64. Ó2011 AACR.

Growth and Differentiation Factor 5 (GDF5) is a secreted growth factor that belongs to the Bone Morphogenetic Protein (BMP) family and plays a pivotal role during limb development. GDF5 is a susceptibility gene for osteoarthritis (OA) and mutations in GDF5 are associated with a wide variety of skeletal malformations ranging from complex syndromes such as acromesomelic chondrodysplasias to isolated forms of brachydactylies or multiple synostoses syndrome 2 (SYNS2). Here, we report on a family with an autosomal dominant inherited combination of SYNS2 and additional brachydactyly type A1 (BDA1) caused by a single point mutation in GDF5 (p.W414R). Functional studies, including chondrogenesis assays with primary mesenchymal cells, luciferase reporter gene assays and Surface Plasmon Resonance analysis, of the GDF5W414R variant in comparison to other GDF5 mutations associated with isolated BDA1 (p.R399C) or SYNS2 (p.E491K) revealed a dual pathomechanism characterized by a gain- and loss-of-function at the same time. On the one hand insensitivity to the main GDF5 antagonist NOGGIN (NOG) leads to a GDF5 gain of function and subsequent SYNS2 phenotype. Whereas on the other hand, a reduced signaling activity, specifically via the BMP receptor type IA (BMPR1A), is likely responsible for the BDA1 phenotype. These results demonstrate that one mutation in the overlapping interface of antagonist and receptor binding site in GDF5 can lead to a GDF5 variant with pathophysiological relevance for both, BDA1 and SYNS2 development. Consequently, our study assembles another part of the molecular puzzle of how loss and gain of function mutations in GDF5 affect bone development in hands and feet resulting in specific types of brachydactyly and SYNS2. These novel insights into the biology of GDF5 might also provide further clues on the pathophysiology of OA.

MicroRNAs play important roles during cell reprogramming and differentiation. In this study, we identified the miR-497$195 cluster, a member of the miR-15 family, as strongly upregulated with age of postnatal bone development in vivo and late differentiation stages of primary osteoblasts cultured in vitro. Early expression of miR-195-5p inhibits differentiation and mineralization. Microarray analyses along with quantitative PCR demonstrate that miR-195-5p alters the gene regulatory network of osteoblast differentiation and impairs the induction of bone morphogenetic protein (BMP) responsive genes. Applying reporter gene and Western blot assays, we show that miR-195-5p interferes with the BMP/Smad-pathway in a dose-dependent manner. Systematically comparing the changes in mRNA levels in response to miR-195-5p overexpression with the changes observed in the natural course of osteoblast differentiation, we demonstrate that microRNAs of the miR-15 family affect several target genes involved in BMP signaling. Predicted targets including Furin, a protease that cleaves pro-forms, genes encoding receptors such as Acvr2a, Bmp1a, Dies1, and Tgfbr3, molecules within the cascade like Smad5, transcriptional regulators like Ski and Zfp423 as well as Mapk3 and Smurf1 were validated by quantitative PCR. Taken together, our data strongly suggest that miR-497$195 cluster microRNAs act as intracellular antagonists of BMP signaling in bone cells.

Multiple synostoses syndrome 2 (SYNS2) is a rare genetic disease characterized by multiple fusions of the joints of the extremities, like phalangeal joints, carpal and tarsal joints or the knee and elbows. SYNS2 is caused by point mutations in the Growth and Differentiation Factor 5 (GDF5), which plays an essential role during skeletal development and regeneration. We selected one of the SYNS2-causing GDF5 mutations, p.N445T, which is known to destabilize the interaction with the Bone Morphogenetic Protein (BMP) antagonist NOGGIN (NOG), in order to generate the superagonistic GDF5 variant GDF5(N445T). In this study, we tested its capacity to support regeneration in a rat critical-sized defect model in vivo. MicroCT and histological analyses indicate that GDF5(N445T)-treated defects show faster and more efficient healing compared to GDF5 wild type (GDF5(wt))-treated defects. Microarray-based gene expression and quantitative PCR analyses from callus tissue point to a specific acceleration of the early phases of bone healing, comprising the inflammation and chondrogenesis phase. These results support the concept that disease-deduced growth factor variants are promising lead structures for novel therapeutics with improved clinical activities.

e17075 Background: Real-world evidence is urgently needed to monitor the translation of new treatment approaches into routine clinical practice as well as to improve cancer treatment and survivorship care. Methods: PAZOREAL is a prospective, multicenter, non-interventional study to evaluate effectiveness, tolerability, safety, and quality of life (QoL) in patients (pts) with advanced or metastatic renal cell carcinoma (mRCC) treated with 1st-line pazopanib (PAZO) followed by 2nd-line nivolumab (NIVO). The primary variable was time on drug (TD) in the respective treatment (Tx) lines. Other endpoints include overall survival (OS), safety and QoL evaluated by EQ-5D-5L. Results: Between December 2015 and September 2017, 414 pts were enrolled and 388 pts started first-line PAZO Tx, 136 pts subsequently received NIVO as second-line Tx. At time of data-cut (30 Sep 2019) median TD was 6.5 months (95%CI 5.7-7.6) for 1st-line PAZO and 4.6 months (95%CI 3.3-6.0) for 2nd-line NIVO. 9.0% of 1st-line PAZO pts and 5.9% of 2nd-line NIVO pts achieved a complete response and disease control rate was 58.0% (95% CI 53.0-62.8) and 44.9% (95% CI 36.8-53.2) for PAZO or NIVO, respectively. Median OS was 32.6 months (95% CI 28.0-38.9) for all pts, 32.6 months (95%CI 28.2-NA) for pts with 2nd-line NIVO and 32.3 months (95%CI 18.8-NA) for pts with other 2nd-line Tx. The most commonly reported treatment emergent AEs were diarrhea (37.2%), nausea (21.7%) and fatigue (19.1%) for PAZO Tx and diarrhea (8.8%), peripheral edema (5.9%) and dyspnea, fatigue, nausea, rash, vomiting (5.1% each) for NIVO. 66 pts (17.1%) discontinued PAZO and 7 pts (5.1%) discontinued NIVO due to related TEAEs. During 1st-line PAZO Tx, mean EQ-5D-5L utility scores initially decreased slightly by time, returned to baseline level and remained stable afterwards. During 2nd-line NIVO Tx the utility scores initially increased by time and remained stable thereafter. Similar tendencies were reported for mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Conclusions: The interim results of the PAZOREAL study confirm favorable clinical trial outcomes, the good benefit-risk profile and the sustained QoL in pts with mRCC in a real-world setting. The sequential treatment with PAZO followed by NIVO is effective and well tolerated. Clinical trial information: NIS-Nr.: 6687.

No abstract

More than 40 years after the discovery of Bone Morphogenetic Proteins (BMPs) as bone inducers, a whole protein family of growth factors connected to a wide variety of functions in embryonic development, homeostasis, and regeneration has been characterized. Today, BMP2 and BMP7 are already used in the clinic to promote vertebral fusions and restoration of non-union fractures. Besides describing present clinical applications, the authors review ongoing trials highlighting the future possibilities of BMPs in medicine. Apparently, the physiological roles of BMPs have expanded their range from bone growth induction and connective tissue regeneration to cancer diagnosis/treatment and cardiovascular disease prevention.

Supplementary Figures 1-2, Tables 1-4, Methods from A Drug Resistance Screen Using a Selective MET Inhibitor Reveals a Spectrum of Mutations That Partially Overlap with Activating Mutations Found in Cancer Patients