Developing bone morphogenetic receptor II inhibitors for the treatment of cancer

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Lung cancer is the leading cause of cancer deaths in the United States and despite advances in medical care, 85% of patients diagnosed with lung cancer will die from the disease. The bone morphogenetic protein 2 (BMP-2), which is part of the transforming growth factor β (TGFβ) superfamily, is an essential morphogen that is aberrantly over-expressed in 98% of lung cancers. There is now significant evidence demonstrating that the BMP signaling cascade promotes tumorigenesis in many carcinomas. BMP signaling regulates proliferation, migration, angiogenesis, and survival of cancer cells. BMP regulation of survival involves the potent anti- apoptotic proteins XIAP, TAK1, and Id1. Our recent studies show that suppression of BMP type I and type II receptors with small molecules causes a rapid and sustained increase in cytosolic and mitochondrial Ca2+ concentrations, which appears to be an early cell death mechanism. The increase in intracellular Ca2+ is followed by an increase in mitochondrial permeability (MMP), DNA double strand breaks (DSB), and cell death. BMP inhibitors that only target the type I receptors do not induce sustained intracellular Ca2+ levels and cause far less cell death then BMPRII/RI inhibitors. BMPRII receptors are constitutively active and are required for the activation of type I receptors. The BMPRII receptor also has a longer cytoplasmic tail that mediates transcription independent mechanisms including the regulation of XIAP and Src, which increases intracellular Ca2+ levels. We hypothesize that inhibition of BMPRII will induce more death mechanisms leading to an increase in MMP and DNA DSB than BMPRI specific inhibitors. The majority of BMP inhibitors have little inhibition of BMPRII receptors; therefore we predict a specific BMPRII inhibitor would be more potent than existing inhibitors. The vast number of BMP analogs has been designed from pyrazolo [1,5-a] pyrimidine core (PyPy), the majority of which are metabolically unstable. We used X-ray crystallography to design a novel core molecule that targets BMPRII. Our most advanced novel analog inhibits the BMP type II receptor, decreases BMP signaling, and induces death of lung cancer cells. Furthermore, we show that this novel class of compounds is more metabolically stable than PyPy analogs. We are now in position to design potent and specific BMPRII inhibitors and utilize cell based assays and xenograft mouse models to examine the mechanisms by which BMP inhibition leads to cell death of cancer cells. We have the expertise in medicinal chemistry, computational biology, X-ray crystallography, humanized mice models, veterinarian pathologist, and BMP biology to optimize and study these lead BMPRII inhibitors. For this grant proposal, we aim to (1) Design and synthesize more potent and selective BMPRII inhibitors from our novel core. (2) Evaluate in vitro structure activity relationships and compare BMPRII to BMPRI inhibitors in their ability induce BMP mediated cell death mechanisms in lung cancer cell lines. (3) Compare efficacy of BMPRII and BMPRI probes in mouse tumor xenograft models.