Decoupling the effects of surface chemistry and humidity on solid-state hydrolysis of aspirin in the presence of dicalcium phosphate dihydrate.

Atomic force microscopy (AFM) cantilevers were functionalized with particles of dicalcium phosphate dihydrate (DCP), and AFM, in force-displacement mode, was used to bring these probes into contact with aspirin (100) and (001) surfaces in order to investigate the effect of aspirin surface chemistry on the interaction between the two materials as a function of relative humidity (RH). The force of adhesion measurements showed a strong dependence on RH for the interactions between DCP and the aspirin (100) surface, with stronger interactions occurring at higher humudities. Relatively much weaker interactions were measured between DCP and the aspirin (001) surface under all RH conditions. Topographic imaging showed that contact between DCP and the aspirin (100) surface at high RH led to localised development of etch pits and, in some cases, growth normal to the surface. The methodology allows for the creation of a localised solid-solid interface between pharmaceutically relevant materials, providing a means of studying solid-state excipient-active ingredient decomposition reactions.

Identification of biomarkers in human head and neck tumor cell lines that predict for in vitro sensitivity to gefitinib.

Potential biomarkers were identified for in vitro sensitivity to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib in head and neck cancer. Gefitinib sensitivity was determined in cell lines, followed by transcript profiling coupled with a novel pathway analysis approach. Eleven cell lines were highly sensitive to gefitinib (inhibitor concentration required to give 50% growth inhibition [GI(50)] < 1 microM), three had intermediate sensitivity (GI(50) 1-7 microM), and six were resistant (GI(50) > 7 microM); an exploratory principal component analysis revealed a separation between the genomic profiles of sensitive and resistant cell lines. Subsequently, a hypothesis-driven analysis of Affymetrix data (Affymetrix, Inc., Santa Clara, CA, USA) revealed higher mRNA levels for E-cadherin (CDH1); transforming growth factor, alpha (TGF-alpha); amphiregulin (AREG); FLJ22662; EGFR; p21-activated kinase 6 (PAK6); glutathione S-transferase Pi (GSTP1); and ATP-binding cassette, subfamily C, member 5 (ABCC5) in sensitive versus resistant cell lines. A hypothesis-free analysis identified 46 gene transcripts that were strongly differentiated, seven of which had a known association with EGFR and head and neck cancer (human EGF receptor 3 [HER3], TGF-alpha, CDH1, EGFR, keratin 16 [KRT16], fibroblast growth factor 2 [FGF2], and cortactin [CTTN]). Polymerase chain reaction (PCR) and enzyme-linked immunoabsorbant assay analysis confirmed Affymetrix data, and EGFR gene mutation, amplification, and genomic gain correlated strongly with gefitinib sensitivity. We identified biomarkers that predict for in vitro responsiveness to gefitinib, seven of which have known association with EGFR and head and neck cancer. These in vitro predictive biomarkers may have potential utility in the clinic and warrant further investigation.