@article{HausmannBrandtKoecheletal.2015,
  author    = {Hausmann, Stefan and Brandt, Evelyn and K{\"o}chel, Carolin and Einsele, Hermann and Bargou, Ralf C. and Seggewiss-Bernhardt, Ruth and St{\"u}hmer, Thorsten},
  title     = {Loss of serum and glucocorticoid-regulated kinase 3 (SGK3) does not affect proliferation and survival of multiple myeloma cell lines},
  series = {PLoS ONE},
  volume    = {10},
  journal   = {PLoS ONE},
  number    = {4},
  doi       = {10.1371/journal.pone.0122689},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148708},
  pages     = {e0122689},
  year      = {2015},
  abstract  = {Multiple myeloma (MM) is a generally fatal plasma cell cancer that often shows activation of the phosphoinositide 3-kinase/Akt (PI3K/Akt) pathway. Targeted pharmacologic therapies, however, have not yet progressed beyond the clinical trial stage, and given the complexity of the PI3K/Akt signalling system (e.g. multiple protein isoforms, diverse feedback regulation mechanisms, strong variability between patients) it is mandatory to characterise its ramifications in order to better guide informed decisions about the best therapeutic approaches. Here we explore whether serum and glucocorticoid-regulated kinase 3 (SGK3), a potential downstream effector of PI3K, plays a role in oncogenic signalling in MM cells-either in concert with or independent of Akt. SGK3 was expressed in all MM cell lines and in all primary MM samples tested. Four MM cell lines representing a broad range of intrinsic Akt activation (very strong: MM. 1s, moderate: L 363 and JJN-3, absent: AMO-1) were chosen to test the effects of transient SGK3 knockdown alone and in combination with pharmacological inhibition of Akt, PI3K-p110\(\alpha\), or in the context of serum starvation. Although the electroporation protocol led to strong SGK3 depletion for at least 5 days its absence had no substantial effect on the activation status of potential downstream substrates, or on the survival, viability or proliferation of MM cells in all experimental contexts tested. We conclude that it is unlikely that SGK3 plays a significant role for oncogenic signalling in multiple myeloma.},
  language  = {en}
}
@article{EhrenschwenderBittnerSeiboldetal.2014,
  author    = {Ehrenschwender, M. and Bittner, S. and Seibold, K. and Wajant, H.},
  title     = {XIAP-targeting drugs re-sensitize PIK3CA-mutated colorectal cancer cells for death receptor-induced apoptosis},
  series = {Cell Death \& Disease},
  volume    = {5},
  journal   = {Cell Death \& Disease},
  issn      = {2041-4889},
  doi       = {10.1038/cddis.2014.534},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-114374},
  pages     = {e1570},
  year      = {2014},
  abstract  = {Mutations in the oncogenic PIK3CA gene are found in 10-20\% of colorectal cancers (CRCs) and are associated with poor prognosis. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and agonistic TRAIL death receptor antibodies emerged as promising anti-neoplastic therapeutics, but to date failed to prove their capability in the clinical setting as especially primary tumors exhibit high rates of TRAIL resistance. In our study, we investigated the molecular mechanisms underlying TRAIL resistance in CRC cells with a mutant PIK3CA (PIK3CA-mut) gene. We show that inhibition of the constitutively active phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway only partially overcame TRAIL resistance in PIK3CA-mut-protected HCT116 cells, although synergistic effects of TRAIL plus PI3K, Akt or cyclin-dependent kinase (CDK) inhibitors could be noted. In sharp contrast, TRAIL triggered full-blown cell death induction in HCT116 PIK3CA-mut cells treated with proteasome inhibitors such as bortezomib and MG132. At the molecular level, resistance of HCT116 PIK3CA-mut cells against TRAIL was reflected by impaired caspase-3 activation and we provide evidence for a crucial involvement of the E3-ligase X-linked inhibitor of apoptosis protein (XIAP) therein. Drugs interfering with the activity and/or the expression of XIAP, such as the second mitochondria-derived activator of caspase mimetic BV6 and mithramycin-A, completely restored TRAIL sensitivity in PIK3CA-mut-protected HCT116 cells independent of a functional mitochondrial cell death pathway. Importantly, proteasome inhibitors and XIAP-targeting agents also sensitized other CRC cell lines with mutated PIK3CA for TRAIL-induced cell death. Together, our data suggest that proteasome-or XIAP-targeting drugs offer a novel therapeutic approach to overcome TRAIL resistance in PIK3CA-mutated CRC.},
  language  = {en}
}