Inhibitors of the kinase mammalian target of rapamycin (mTOR) have shown sporadic activity in cancer trials, leading to confusion about the appropriate clinical setting for their use. Here we show that loss of the Von Hippel-Lindau tumor suppressor gene (VHL) sensitizes kidney cancer cells to the mTOR inhibitor CCI-779 in vitro and in mouse models. Growth arrest caused by CCI-779 correlates with a block in translation of mRNA encoding hypoxia-inducible factor (HIF1A), and is rescued by expression of a VHL-resistant HIF1A cDNA lacking the 5' untranslated region. VHL-deficient tumors show increased uptake of the positron emission tomography (PET) tracer fluorodeoxyglucose (FDG) in an mTOR-dependent manner. Our findings provide preclinical rationale for prospective, biomarker-driven clinical studies of mTOR inhibitors in kidney cancer and suggest that FDG-PET scans may have use as a pharmacodynamic marker in this setting.

Most colorectal cancers (CRC) are initiated by mutations of APC, leading to increased b-catenin-mediated signaling. However, continued requirement of Wnt/b-catenin signaling for tumor progression in the context of acquired KRAS and other mutations is less well-established. To attenuate Wnt/b-catenin signaling in tumors, we have developed potent and specific small-molecule tankyrase inhibitors, G007-LK and G244-LM, that reduce Wnt/b-catenin signaling by preventing poly(ADP-ribosyl)ation-dependent AXIN degradation, thereby promoting b-catenin destabilization. We show that novel tankyrase inhibitors completely block ligand-driven Wnt/b-catenin signaling in cell culture and display approximately 50% inhibition of APC mutation-driven signaling in most CRC cell lines. It was previously unknown whether the level of AXIN protein stabilization by tankyrase inhibition is sufficient to impact tumor growth in the absence of normal APC activity. Compound G007-LK displays favorable pharmacokinetic properties and inhibits in vivo tumor growth in a subset of APC-mutant CRC xenograft models. In the xenograft model most sensitive to tankyrase inhibitor, COLO-320DM, G007-LK inhibits cell-cycle progression, reduces colony formation, and induces differentiation, suggesting that b-catenin-dependent maintenance of an undifferentiated state may be blocked by tankyrase inhibition. The full potential of the antitumor activity of G007-LK may be limited by intestinal toxicity associated with inhibition of Wnt/b-catenin signaling and cell proliferation in intestinal crypts. These results establish proof-of-concept antitumor efficacy for tankyrase inhibitors in APC-mutant CRC models and uncover potential diagnostic and safety concerns to be overcome as tankyrase inhibitors are advanced into the clinic. Cancer Res; 73(10); 3132-44. Ó2013 AACR.

No abstract

Polymorph detection, identification, and quantitation in crystalline materials are of great importance to the pharmaceutical industry. Vibrational spectroscopic techniques used for this purpose include Fourier transform mid-infrared (FT-MIR) spectroscopy, Fourier transform near-infrared (FT-NIR) spectroscopy, Raman spectroscopy, and terahertz (THz) and far-infrared (FIR) spectroscopy. Typically, the fundamental molecular vibrations accessed using high-frequency Raman and MIR spectroscopy or the overtone and combination of bands in the NIR spectra are used to monitor the solid-state forms of active pharmaceutical ingredients (APIs). The local environmental sensitivity of the fundamental molecular vibrations provides an indirect probe of the long-range order in molecular crystals. However, low-frequency vibrational spectroscopy provides access to the lattice vibrations of molecular crystals and, hence, has the potential to more directly probe intermolecular interactions in the solid state. Recent advances in filter technology enable high-quality, low-frequency Raman spectra to be acquired using a single-stage spectrograph. This innovation enables the cost-effective collection of high-quality Raman spectra in the 200-10 cm(-1) region. In this study, we demonstrate the potential of low-frequency Raman spectroscopy for the polymorphic characterization of APIs. This approach provides several benefits over existing techniques, including ease of sampling and more intense, information-rich band structures that can potentially discriminate among crystalline forms. An improved understanding of the relationship between the crystalline structure and the low-frequency vibrational spectrum is needed for the more widespread use of the technique.

Trimorphic paracetamol, one of the most commonly used analgesic and antipyretic drugs, has been a model system for studying transformations among phases of molecular crystalline materials. During crystallization from the melt and the glass above 0 °C, three new polymorphs of paracetamol (N-acetyl-para-aminophenol or acetaminophen) were discovered, doubling the number of known ambient forms. The crystal structure of one new form was solved using a combination of powder X-ray diffraction and computational techniques. Growth kinetics became anomalous near the glass transition: as temperature decreased, growth rate increased; this rare and poorly understood phenomenon is commonly identified as the glass-to-crystal (GC) growth mode. In addition, two polymorphs displayed optical evidence of helicoidal morphologies, a characteristic of at least 25% of molecular crystals, that has been resistant to a universal explanation.