Faculty Bibliography

Activating mutations in the tyrosine kinase domain of receptor tyrosine kinases (RTKs) cause cancer and skeletal disorders. Comparison of the crystal structures of unphosphorylated and phosphorylated wild-type FGFR2 kinase domains with those of seven unphosphorylated pathogenic mutants reveals an autoinhibitory 'molecular brake' mediated by a triad of residues in the kinase hinge region of all FGFRs. Structural analysis shows that many other RTKs, including PDGFRs, VEGFRs, KIT, CSF1R, FLT3, TEK, and TIE, are also subject to regulation by this brake. Pathogenic mutations activate FGFRs and other RTKs by disengaging the brake either directly or indirectly

Tricyclic antidepressants exert their pharmacological effect-inhibiting the reuptake of serotonin, norepinephrine, and dopamine-by directly blocking neurotransmitter transporters (SERT, NET, and DAT, respectively) in the presynaptic membrane. The drug-binding site and the mechanism of this inhibition are poorly understood. We determined the crystal structure at 2.9 A of the bacterial leucine transporter (LeuT), a homolog of SERT, NET, and DAT, in complex with leucine and the antidepressant desipramine. Desipramine binds at the inner end of the extracellular cavity of the transporter and is held in place by a hairpin loop and by a salt bridge. This binding site is separated from the leucine-binding site by the extracellular gate of the transporter. By directly locking the gate, desipramine prevents conformational changes and blocks substrate transport. Mutagenesis experiments on human SERT and DAT indicate that both the desipramine-binding site and its inhibition mechanism are probably conserved in the human neurotransmitter transporters

Although human papillomavirus (HPV) infections are the primary cause of cervical cancer, the molecular mechanism by which HPV induces cervical cancer remains largely unclear. We used two-dimensional electrophoresis with mass spectrometry to study protein expression profiling between HPV16-positive cervical mucosa epithelial H8 cells and cervical cancer Caski cells to identify 18 differentially expressed proteins. Among them, retinoblastoma-binding protein 4 (RbAp48) was selected and its differentiation expression verified with both additional cervical cancer-derived cell lines and human tissues of cervical intraepithelial neoplasia and cervical cancer. Suppression of RbAp48 using siRNA approach in H8 cells significantly stimulated cell proliferation and colony formation and inhibited senescence-like phenotype. Remarkably, H8 cells acquired transforming activity if RpAp48 was suppressed, since H8 cells stably transfected with RbAp48 siRNA led to tumor formation in nude mice. In addition, overexpression of RbAp48 significantly inhibited cell growth and tumor formation. This RbAp48-mediated transformation of HPV16 is probably due to the regulation by RbAp48 of tumor suppressors Rb and p53, apoptosis-related enzymes caspase-3 and caspase-8, and oncogenic genes, including cyclin D1 and c-myc. In brief, RbAp48, previously unknown in cervical carcinogenesis, was isolated in a global screen and identified as a critical mediator controlling the transforming activity of HPV16 in cervical cancer

CONTEXT: The main pancreatic duct can form a fistulous communication with another epithelium in the setting of prolonged inflammation, operative manipulation, or direct trauma. We present a rare complication of a pancreaticoureteral fistula following a trauma nephrectomy. CASE REPORT: A 17-year-old male who sustained a gunshot wound to the back arrived to our Emergency Room hyopotensive, tachycardic, and with free intraperitoneal fluid on focused assessment sonography for trauma (FAST) exam. He was taken to the operating room for an exploratory laporatomy where a left nephrectomy was performed to control active bleeding from the left renal hilum. Significant bleeding was also encountered at the portal venous confluence. After packing and damage control laparotomy, the periportal/pancreatic bleeding was controlled during a second procedure 6 hours later. After one month in the Intensive Care Unit with an open abdomen, a computed tomography (CT) scan revealed a fluid collection in the splenic fossa which was drained by catheter. Persistent drainage revealed a high amylase concentration (greater than 50,000 U/L). A fistulogram revealed interruption of the main pancreatic duct, and a fluid collection by the tail of the pancreas that was in communication with the left ureter. The patient's urine amylase was also elevated. The patient was treated non-operatively given the healing open abdomen and controlled fistula. He had an otherwise uncomplicated recovery. CONCLUSIONS: This is the second report of a pancreaticoureteral fistula in the literature. Treatment of this communication should be similar to that of other pancreatic fistulae

IFI16 is a member of the interferon-inducible p200-protein family, capable of modulating cell proliferation, and cellular senescence. In this study, these effects of IFI16 were studied in tumor cells derived from bone and cartilage. The level of IFI16 was markedly lower in human osteosarcomas as compared with its level in normal bone. Overexpression of functional IFI16 in human osteosarcoma and chondrosarcoma cell lines markedly inhibited colony formation, and significantly inhibited cell growth, an effect that could be reversed by introduction of gene specific siRNA into tumor cells. These inhibitory effects of IFI16 were associated with upregulation of p21 and inhibition of cyclin E, cyclin D1, c-Myc and Ras. In addition, ectopic expression of IFI16 in tumor cells increased senescence-associated beta-galactosidase and induced a senescence-like phenotype. In view of such effects, IFI16 might be a suitable target for therapeutic intervention in osteosarcoma and chondrosarcoma.

NAD(P)H:quinone oxidoreductase 1(-/-) (NQO1(-/-)), NQO1(+/-) along with NRH:quinone oxidoreductase 2(-/-) (NQO2(-/-)), and wild-type (WT) mice were exposed to five once weekly doses of mitomycin C. The mice were euthanized 15 weeks after the first dose. Blood cell counts and histologic analyses were done. WT and NQO2(-/-) mice showed hypocellularity and a significant increase in adipocytes in bone marrow. They also showed anemia because of the loss of RBC and hemoglobin. The neutrophils and platelets were reduced, whereas other blood cell types and tissues were normal. Interestingly, NQO1(-/-) mice showed a complete resistance to mitomycin C-induced bone marrow cytotoxicity and reduction in RBC, hemoglobin, and neutrophils. NQO1(+/-) mice also showed limited resistance to mitomycin C-induced bone marrow cytotoxicity. These data show a major in vivo role of NQO1 in metabolic activation of mitomycin C with implications in mitomycin C chemotherapy.